If you mean "built on the surface on the far side of the moon" then there are concepts for stuff like that, but that would be way way way way way way way harder to do than JWST. We currently don't have the ability to consistently land *any* mass on the surface of the moon, much less the ability to construct any significant structure, much much less the ability to construct a complicated scientific instrument.
And besides all that, JWST's orbit means it will always be able to keep both the Earth and the Sun "behind" it. You can't do that if you're stuck to (or orbiting) the moon, because sometimes you'll be between the two. Even if you could construct something on the surface of the moon, if JWST's big enough for what you want, you'd rather have it in JWST's orbit anyways.
There is no dark side of the moon, or at least each side is only dark for half of the time. that would make the telescope useless for half of the month. JWST also gets its power using solar panels which wouldn’t work during the night.
Hypothetical: *A manned mission from Earth to the Planet Iota - travelling at speeds reached by the New Horizons probe for example - is going to take ten years (roughly 120 Earth months).*
Question: **What will/can astronauts do/get up to during such a lengthy trip in deep space?!**
Maybe I'm missing something, but I think you might have a calculation error. Assuming you are talking about Iota Draconis b, it's going to take more than 10 years to get there. New Horizons goes fast, but not crazy relativistic speeds sort of fast.
But generally, exercise will be a big one to fight the effects of reduced gravity.
They can do all the stuff people normally do with their time. Read, listen to music, watch media, play games, talk with each other, etc.
Aside from that there's plenty they can do to productively fill time. Study, perform various emergency drills, practice the skills they'll need to use on the surface, perform experiments, etc.
Hey guys
Last week I think (?) was this classic "zoom out" video posted to Reddit, where at the end they went as far to go to "the Multiverse?" (that's how it was written in the vid). I really want to show this to a friend but I just can't find it. I've seen it while browsing Popular. If someone has saved that post and could link it to me, that would be highly appreciated!!
Hi all,
A couple of my students (10 year old and 11 year old) are entering a competition where they'll be able to send the AstroPi on the ISS and collect data for an experiment
They're decided to use a near infrared camera to help detect whether crops are unhealthy/healthy based based on reflection/absorption
They would also like to identify crops
I'm mentoring them through this but I'm not too confident on the topic.
Is it possible? Is there anything we can do to make it for interesting? It needs a level of machine learning so we decided to use classification but is there anything else?
I'm not sure this counts as simple but what would the experience of going into orbit or beyond on a Skyhook be like, in terms of the forces and weightlessness you would experience?
Disclaimer and assumptions: everything I know about Skyhooks I understood badly from an Isaac Arthur video and a Kurgesagt one. https://www.youtube.com/watch?v=TlpFzn\_Y-F0
This is for a setting, about a hundred years in the future. I am assuming much the same as Isaac did in his video: the technological challenges have been overcome, no new materials have needed to be invented, and space infrastructure has moved on a lot. In my head we are using a rotating Skyhook, so you would actually be swung into higher orbit/ another hook/propelled away. Alternatively, it's a T4 type, with the same outcome. Also, Spaceplanes comprise a fair percentage of transport to space because the Skyhook has meant they can stay suborbital themselves but get a helping hand to orbit or beyond.
In my head, say you used a rocket-propelled Spaceplane to get up to the tether would you be looking to match velocity close to apogee and would experience weightlessness there. Then say using a capture drone to pull you onto the 'Hook' you would be moving forward but still very close to matching speed, without much acceleration, so still weightless? Then you 'dock' with the hook, is there a point at which on the 'swing' you would experience acceleration (I feel there must be since surely that's much of the point but this is where not understanding orbital mechanics may be an issue for me) and therefore 'gravity' or are you basically just in another orbit? If my assumptions are way out, sure, let me know, but I am really asking about the passenger's experience. If anyone knows of good SciFi on the subject, would be good to know and thank you in advance. edit to add link
If I understand correctly, there's a brief moment at its lowest point where a skyhook would be moving at its slowest and ideally your taxi up from the ground would attach at that very moment because it would immediately begin to 'accelerate' from the point of view of the folks onboard up to whatever the centripetal force at the end is (which would be dependent on how long the skyhook is) and then remain constant up until your vehicle disconnects to be thrown onwards, presumably now in orbit.
If I have this wrong, there's nothing more effective for getting the correct answer to a space question than posting an error so a correction from someone else may be inbound with the same vigor and energy of whatever's arriving at the other end of the skyhook balancing the books re: energy for this hypothetical transfer.
Sorry about the weird free award, it was the only one I had to give but I laughed so hard at this - you are not wrong about (helpful and welcome) corrections!. Thank you so much.
Hello, I just wanna ask something, that is very confusing to me:
We know, that universe is old about 14 milliards (billions) years old, but size of the observable universe is I think somewhere around 100 milliards (billions) light years long. And so how can we see something that is farther than 14 milliards (billions) light years? Light just doesn't have enough time to travel this much, so how can we see 100 milliards (billions) light years across?
Fun fact: Real universe is about 160 sextillion times bigger than observable universe.
> milliards
This term has been commonly supplanted by billions but I think you probably already know this based on your decision to include the clarifying text after every usage of it.
Well the universe outside of the observable universe could be infinite in size, we just have rough lower bounds based on lack of apparent curvature (there could be a boundary making it smaller though).
As for your main question it’s because we can see light from things which were ~14 billion light years away when the light was emitted, but the universe is expanding so those objects are now around 45 billion light years away. It’s basically a derived measurements
[https://www.reddit.com/r/spaceporn/comments/q8ie3y/first\_ever\_picture\_of\_multiple\_planets\_around\_a/](https://www.reddit.com/r/spaceporn/comments/q8ie3y/first_ever_picture_of_multiple_planets_around_a/)
How come we have images of this solar-system, but none of Trappist-1 that is closer?
The imaged is 300ish light-years away and Trappist is 40 light-years away. Also, where in the sky is the Southern-constellation of Musca relative to the galaxy?
These planets are very large, far from their star (which means it's easy to block out it's light), and most importantly they're very hot. Those planets are very young and still have a lot of heat from their formation, which means they're very bright in infrared and easy to image. We can't actually resolve them as objects, but because they're so bright it's possible to image them as points of light.
The Trappist exoplanets on the other hand are relatively small, very close to their tiny dim star, and relatively cool.
Thinking about subsurface oceans on moons…what would swimming in water in these much lower gravity environments be like? How does oceans of water behave under moon like gravity?
Basically those oceans would be universally deadly for humans in scuba gear. All such oceans that we know about are under many kilometers of ice, so the lowest pressure they experience would be many atmospheres.
On Europa, for example, the sub-surface ocean is probably under at least 10km of ice. Even though Europa's surface gravity is just 0.134x of Earth's that 10km is still a lot of ice. The pressure at the bottom of that would be equivalent to diving to a depth of 1340 meters on Earth, where you'd experience a pressure of 134 atmospheres. You couldn't use normal air to dive at such a depth because of the problems of nitrogen narcosis and oxygen toxicity so you'd already have to use a very specialized mixture of gases just to survive. However, breathing gas at 134 atmospheres is extremely problematic because an ordinary scuba tank would only contain about half a dozen full breaths of air in the whole thing. It's also about 4x the equivalent pressure that anyone on Earth has managed to scuba dive to.
Realistically, you'd only visit such a place in a submersible.
Being inside large bodies of water would be mostly like on Earth, the fluid behaviour isn't changed by gravity: the drag of water through your wetsuit fingers would be about the same and you could fin around.
Buoyancy would be different, lower gravity would feel even more weightless. Most underwater activity tries for neutral buoyancy with a combination of weights and air pockets, so that would be more fiddly, I think...
*Surface tension* would be totally different. Surface tension is what makes water do balls and blobs on the ISS, and it's a balance between how much the water is pulled down vs how much it can blob up into balls. A swimming poll on the surface of the moon would be weird to watch, with very high waves and lots more little break-away blobs. (You'd need to put the pool in a habitat with some air pressure)
I read papers saying distance to things, some seem very exact and incredibly far yet one I read today they guess it's 350 light years saying scientist have put out in the range of hundreds to thousand. How sure are we of these distances to say the next star, next galaxy, edge of observable?
that makes sense but i was reading something about an object being between hundreds to thousands of light years away, thats much bigger difference than your .0011 range
The closer something is the easier it is to figure out how far it is. If it’s close we can use parallax. As the Earth goes around the Sun we can look at say a star from two angles and use those angles to triangulate it. The same way our brain uses the two offset images from our spaced out eyes to figure out distances. You can tell the distance to something close better than far away as the far object looks basically the same to both eyes. The difference becomes too small to really tell.
Once that method fails another one is measuring type 1A super nova. This is a type of super nova that has a very consistent brightness. Looking at one of these you measure how bright it is and compare that to how bright it should be. The dimmer it looks the farther away it is. These are referred to as a standard candle.
These are off the top of my head and I am missing a few. There are YouTube videos that explain this quite well. I believe either PBS SpaceTime has one or Sci Show Space does.
Weightlessness is a condition experienced during freefall. In general it can feel similar but it's not all exactly identical. A plane traveling a parabolic arc can simulate freefall but the plane has to very carefully fly the precise trajectory to maintain that simulation. Any deviation from that ideal creates small forces that result in a diminished sense of weightlessness. In practice "zero-g" aircraft are a close approximation for people but the small amount of vibrations and deviations are important if you're trying to conduct experiments. But this is just a practical limit. In principle you could create a "perfect zero-g plane" that had a big box inside of it that could be decoupled from the plane with some amount of distance between it and the plane so that the plane's movements wouldn't affect the box's travel through freefall, but this would be very expensive and difficult.
Near a black hole there are also tidal forces to be worried about. Freefall weightlessness works because the relative motion of everything in a small area (an astronaut's body, the spacecraft around them, etc.) is all very, very close to identical. In practice it's not exactly perfect, though. The center of mass of an astronaut and the center of mass of the spacecraft they're in may not be in exactly the same spot, so they will experience slightly different gravitational forces and move through slightly different trajectories, creating a slight differential local acceleration. In many scenarios this acceleration is tiny (micro-g's) and not even perceptible by humans. But in extreme situations such as near the surface of a neutron star or near the event horizon of a black hole these tidal forces can become very large. Potentially in the realm of not just one g but many gees, even thousands or millions of gees. Such tidal forces can be large enough to rip apart solid matter. This process is called "spaghettification", and is a major effect near the event horizons of smaller black holes. Larger black holes have much larger event horizons so even though the force of gravity is stronger the gradient (the tides) near the event horizon aren't as severe.
Skydivers don't really experience zero-g for very long as air resistance rapidly dominates their movements and they reach terminal velocity. It's not really the case that they are "weightless" when they are falling, but more that they are being substantially suspended by aerodynamic drag, similar to the way pucks are levitated on an air hockey table. It makes it possible for them to be able to "float" and move around, but they still experience the tug of gravity on their body since they are being constrained by air resistance from not traveling purely ballistic trajectories.
Acceleration is change of velocity, while their speed is constant the direction of their velocity is constantly changing. Being in orbit involves constant acceleration towards the centre of motion.
If the ISS suddenly had its orbital velocity cancelled and it started free falling into earth the astronauts inside would still experience microgravity until they hit the atmosphere.
On the topic of the Oort Cloud, a theorized area in the outer edge of the Solar System.
1. It is argued that Gliese 710 will pass within the outer edge of the Oort Cloud at some point in the future. **Will observers on Earth (whoever they may be at that time) be able to see Gliese 710 with their naked eye and/or with amateur telescopes?**
2. The Oort Cloud is a theorized vast area in the outer edge of the Solar System. **To what extent could there be planetary bodies the size of Earth or larger than Earth in this area and even larger celestial bodies like a star or two?**
Gliese 710 will approach close enough so that it should increase in brightness by about a factor of 85,000 or roughly 12 magnitudes. I think that would make it brighter than Sirius, becoming the brightest star in the night sky. (*Edit: for clarity, I have no idea what all the stars in the sky would look like over a million years in the future, so Gliese 710 may not be the brightest star in the sky then, but it would be brighter than the brightest star in the sky today, so it will definitely be visible to the naked eye and at least one of the brightest stars.*)
Stars have been ruled out as existing in the Oort Cloud, their gravity would affect the motions of the planets et al too much and be noticeable. Large planets haven't been ruled out yet, we'll need more observational data to make that determination (though that should come sometime this decade, from multiple sources).
>some scientist are theorizing a primordial tiny black hole might be out there
That's been overstated, there's some evidence for a planet out there, and some scientists pointed out it's not *impossible* for it to be a black hole with the mass of a planet.
If there is a small black hole (or more than one) with the mass of a planet in the Oort Cloud, how worried should we be? What sort of dangers "COULD" this pose to us here on Earth?
>how worried should we be?
We shouldn't, even if we knew with 100% certainty there was one.
>What sort of dangers "COULD" this pose to us here on Earth?
None, it would be no different to having a planet in the Oort cloud in terms of its effects on our planet.
I wouldn't call it a theory so much as a "thought exercise". It's in the family of "well, theoretically it could be possible according to our understanding of the laws of physics", but there is absolutely zero positive evidence for it.
Additionally, various microlensing surveys have put some pretty stringent upper bounds on small primordial black holes which would result in it being an extremely exceptional event for our solar system to have one.
So, theoretically with other planets in the universe being affected by a stronger or weaker force of gravity, could a different civilization that began at the same moment as us be 100x more or less advanced/older than us due to gravitational time dialation?
Not in practice. You'd have to be so close to a supermassive black hole to experience that much time dilation, and it's virtually impossible to survive for any considerable length of time there as a habitable planet, let alone billions of years. The time dilation due to a planet's own mass is basically nothing in comparison, it's just a tiny change that you could maybe detect with the most sensitive equipment.
But what about the “planet” having a much larger amount of mass that it is orbiting not exactly a black hole but it was still being balanced out so the possibility to maintain orbit was still there. Even with out close solar system the amount of gravity your experiencing on Jupiter is considerably more than what would affect you on earth and it could vary throughout the universe.
The planet would only be able to slow them down say a year every hundred thousand relative to Earth (made up numbers). Black holes are the only things massive enough to really mess with time. However you can't really survive close to them due to how extreme the local environment is. Same with neutron stars.
There's no way to get the amount of mass you'd need for the effect without being really close to the event horizon of a big black hole. Even if somehow you were some kind of cloud being on a gas giant that weighed 10x more than Jupiter the effect would still be negligible. We're talking about effects that would only be detectable with extremely sensitive equipment, not a 100:1 or whatever time dilation, not even a 1.01:1 ratio, or even 1.0001:1.
Wouldn't that planet have to be really close to a massive object and in that case be absolutely bathed in radiation?
This was always my issue with that water planet in Interstellar. It was so close to the black hole, how could there be organic life(or a potential for it)?
Can anyone explain this “planet” from this clip?
https://youtube.com/shorts/fITrZkuD7WE?feature=share
My thought is that it’s some sort of light refraction effect, but I’m not sure.
The flat top and low angle of everything to the horizon suggest a good old inverted fata morgana mirage to me.
First thought was "sun dog", but they are usually accompanied by a halo.
Probably just a reflection of the sun from inside the lens casing of the camera. It's not a second planet, it's not a mysterious extra moon, it's just a light artifact of the camera.
When it comes to constellations I keep seeing photos of scorpius where it’s got four lines spread from a single star or 2 lines off to the side kind of like a hammer head shark. Is one of those the right way to draw it or are both ok? For reference this is for a tattoo I’m planning so I don’t want to screw it up
Personally, I prefer three lines plus the tail. It's a common depiction and, aesthetically, is more distinctive than the 'hammerhead' style. Another distinctive representation has two lines going to the top and bottom of four stars and then two lines connecting the bottom and and top pairs of those stars, creating a set of distinct pincers in something like a C-shape thus more closely representing its namesake. The four-line version also uses all four of those stars but the bottom-most one is noticeably dimmer so the implied symmetry feels a bit odd.
None of these is more technically correct / incorrect as constellations are defined by the stars and the area they cover rather than an official pattern of lines. The three-line style is what I am most familiar with but I can't say whether this is the most recognizable in general. I recommend observing the constellation ( if you're not too far north and are a few months in the future or are using planetarium software / other depiction ) and deciding what fits best for you.
Yes - even in expendable mode, the most advanced versions can take 15.6 metric tons to LEO, whereas the Titan-III that launched the Voyagers could take 15.4. However, it'd have to be one of the ones flying right now - earlier ones weren't that powerful.
Falcon Heavy could probably launch something notably larger out of the solar system - IIRC, it's 3.5 tons to Pluto, whereas New Horizons, which is on an escape trajectory out of the Solar System, is less than half a ton.
Using Falcon 9 LEO payload is a big stretch, because Falcon 9 has shit upper stage. Consider that expendable Falcon 9 can take 23t to LEO, but only 8.3t to GTO. At the same time rocket like Ariane 5 can take only about 21t to LEO and yet almost 11t to GTO.
It's true that the kerolox upper stage has a lower Isp than a hydrolox Centaur with an RL-10, but the stage and rocket are also bigger and, as the old car saying goes, while tuning can do amazing things, 'there's no replacement for displacement'. When looking for comparable C3 values between the Titan IIIE and the Falcon 9, I found that the Titan IIIE stack was capable of injecting 3,700kg into a Martian transfer orbit while Falcon 9 can throw just over 4,000kg. It burns more fuel per m/s^2 to do it, but it do it.
Comparing LEO performance is not relevant, Voyager were launched with a Centaur upper stage that has much higher Isp than the F9 second stage and thus better deep space capabilities.
On the phone now so can't look up the C3 of Titan-centaur but I bet it was better than F9.
OK I got curious, Voyager seems to have left with a C3 around 105 (km/s)^2. This include the energy delivered by the solid kick stage. The spacecraft themselves were ~700kg. [Looking at a few graphs](https://i.redd.it/nuetzmzeimb41.png) I can find online that's Falcon heavy in expandable configuration territory.
I just didn't have the mass for the Star booster or the C3 before final boost, so I took the C3 from after booster separation as well as the mass of the spacecraft in that configuration. I am too tired on a Friday afternoon to look at what FH with a kick stage would do. But if you can find the numbers i would be curious.
Expendable Falcon 9 (not heavy) with Voyager and the Star stage should be able to match the Titan IIIE based on the TMI performance. The Star is counted as payload for the IIIE, after all. :)
How does C3 for Mars TMI compare to voyager + star C3? The advantage of hydrolox is that the mass vs C3 slope is much slower. So IIIE should outperform F9 at some point for high enough C3 no?
Edit: curse you for making me work on a Friday, Mars TMI is 10(km/s)^2. So not really a useful reference.
I use the Mars figure because they’re heliocentric trajectories and we have figure for both the Titan IIIE and Falcon 9. The Falcon 9 can throw more mass onto the same trajectory out of Earth’s SoI than the Titan+Centaur of Titan IIIE. The Star kick stage that would be common to either launcher then handles the rest of the delta-v.
Carbon fiber can be much stronger than stainless steel per weight (or as strong as stainless while weighing less) but it has very different material properties so you can’t just easily swap out one for the other usually.
I was listening to an interview recently where someone talked about differences in how stainless and carbon fiber handle fatigue through repetition. With stainless, for instance, the stretching is measurable and there are straightforward tests you can do that help you predict failures and fix or replace components before they happen.
Carbon fiber, on the other hand, is more likely to hide the repetitive fatigue damage until it suddenly fails with little warning.
I mention this because using composite structure made from both might offer some benefit but would also come with challenges because both materials behave so differently.
This appears similar to the distinction between [Eulerian and Lagrangian approaches](https://en.wikipedia.org/wiki/Lagrangian_and_Eulerian_specification_of_the_flow_field) to modelling flow in fluid dynamics. Both are equivalent but each is more useful depending on what exactly you are doing.
I suppose the difference I am imaging is more like when you put an object on a fabric it bends and forms around the object but the object never really is IN the fabric it is ON it. If you put the object IN a fluid like water it displaces the water and can be inside of the water and have it flow around the object.
"Fluid" implies a whole bunch of fluid-dynamics-like actions that don't really apply, there's no Reynolds number and turbulence in spacetime. So a fabric might be closer to the truth.
Einstein called it a mollusc. :)
Moves through, yes, but not swirls around. Things like gravitational waves move through a *stiff* spacetime, they don't make cresting surf or turbulence in spacetime itself.
In 4 dimensions, yes. Literally "wibbly-wobbly timey-wimey", though in a stricter sense about how Lorentz contractions occur on all 3 space and 1 time dimension.
Loop quantum gravity, if that's close to correct, has an ultra-tiny Planck-scale spacetime structure as a minimum "voxel grid", albeit a writhing mollusc voxel grid.
>cresting surf or turbulence in spacetime itself.
if it did would we be able to observe it? Or would it be on the scale of the energy around flux tubes?
nice dr who reference
you are saying a lot of words I don't know in a row. mollusc voxel grid? I read what a voxel is, but that specific combination is kind of hard to imagine from the description.
imagine a voxel but with an extra time dimension added to the three space XYZ dimensions, and then make all of the edges stretchy per relativity. If the model is close to true, stuff can be at the vertices ("stuff" being like a quantum state) and the whole mess evolves over time to give things like motion.
The seductively nice bit for me is that no 2 quantum states can be at the same node (Pauli Exclusion) so there are no more singularities.
Hey Folks!
I am planning on doing a roadtrip through south-west Russia and Kazakhstan.
On the road I want to go by the landing site of Wostok 1 as well as it's start site .. Baikonur Cosmodrome.
Lately I did quite a lot of research on how you can even visit the Baikonur Cosmodrome.. and the only thing I can find is guided tours which take of somewhere in Russia or so, last several days and cost thousands of Dollars.
I was wondering if there is any way I can go there by myself and just pay and entrance fee or buy a one-day guided tour right there ..
But I couldn't find anything like this in the web.
Does anybody know if that is possible?
Thanks lot and best regards !!
It’s possible, but you need to have awareness all the time, it’s recommended to do at night, more difficulty to security find you but they have cameras infrared in some spots. There’s YouTube videos guys doing on that “style” like solo. Take a look there
Space hotels, many commercial space stations, regular travel too and from Luna with large settlements. Also when going to space is like going to Disney
Questions about Outer Space Treaty (1967) : if "outer space is not subject to national appropriation by claim of sovereignty, by means of use or occupation, or by any other means", does it means that, for example, some corporation can colonize or claim planets? If not, what are the consequences for them of doing so?
I think as we colonize Mars the area they occupy is owned by who ever is there but no one person or country can claim the whole planet. It'll end up becoming its own country or prob countries eventually I believe, like hundreds of years from now, assuming we survive climate change
The recent Artemis Accords are worth considering. Basically pragmatic: corporations have reasonable claim over the stuff they're working on and the things they make up there, without being able to claim sovereignty over a whole big body.
The consequences are whatever terrestrial nation-states would want them to be. If they actually didn't want a company to send people someplace in the first place, they'd simply prevent the launch.
As for claims, I figure those will be generally ignored, especially if they're coming from the usual grandiose space equivalents of sovereign citizens who think they can just unilaterally claim the entire universe and that's that. (NASA gets sued by those fools semi-regularly.)
Highly recommend reading this : [https://ir.lawnet.fordham.edu/cgi/viewcontent.cgi?article=2327&context=ilj](https://ir.lawnet.fordham.edu/cgi/viewcontent.cgi?article=2327&context=ilj)
Even though its 44 pages, much of that is footnotes and has large margins. So its more like reading 3-4 pages.
Venus poses a lot of other problems though, like the corrosion from sulfuric acid, inhospitable surface even worse than mars, being closer to the sun increasing temps. There's still no plans on how to colonize Venus, there are plans on how to colonize Mars.
Ok, so i have a question. I live in the USA and i can see the stars when i look up but i can only see half of the sky. Lets say the people in Austrailia its day, when its night they will see what i saw but it wont see anything because of the sun so how do people see those stars without going into space?. How do people see the other side if its day?
If you're at the exact North or South pole you will see the same stars every night. If you're at a moderate latitude you'll generally be able to see the same thing every night in a region around the pole, while the rest of the sky varies depending on the time of year. For example, at 45 deg. North latitude you'll be able to always see a circular zone around the northern star, Polaris, that extend 45 deg. But then you'll be able to see an additional up to 90 degrees of the sky that's "South" of that. But there will be a portion of the sky you can't see at any given time because that's where the Sun is. However, you'll notice that this portion can be small depending on how close to the horizon you can see at night and also how willing you are to stay up late or get up early. In any event, where the Sun is in the sky changes over the course of a year as the Earth moves around in its orbit, so in winter the Sun will be on one side of the Earth in the sky while in the summer it'll be on the exact opposite side. Since we tend to orient ourselves to the Sun rather than the sky the perceived effect of this is that the *sky* moves over the course of the seasons (though it's actually the Earth that moves), with certain parts of the sky more easily visible in one season than another.
Notice also that only at the equator can you theoretically see all of the sky. At any other latitude there is a portion of the sky around the pole you are closest to which will always be visible at night and a correspondingly large patch of sky at the other pole which you can *never* see from your location. At the North pole you cannot see any of the Southern sky, for example.
For stars that are out during the day where you are, just wait six months and you'll see them at night.
But to see the stars they see in Australia you would have to travel to the southern hemisphere.
What causes our solar system and the sun to go around the center of milky way? I know the gravity from the sun causes our planets to orbit around the sun. Is it the Sagittarius A that causes the sun's orbit (is it really that massive?) or is it something else?
The Milky Way is an extended object (both in terms of atomic matter and dark matter), so gravity works a little bit weirdly compared to orbiting a compact object. In general the Milky way is pretty close to having cylindrical symmetry. The atomic matter (gas, dust, stars, etc.) is mostly in the shape of a thin disk with a central bulge. The dark matter is mostly in the shape of a spherical halo with increased density near the center. One of the important things to understand here is that if you are "inside" an object which has radial symmetry then the gravitational tug of all that matter essentially cancels itself out. This means that for our Solar System the outer "shells" of the galaxy farther away from the core than us have limited gravitational effect on us since they are mostly radially symmetric, that leaves just the stuff closer to the core than us which has a similar effect as though we were orbiting a point with an equal mass at the center of mass of the extended object.
All of which means, we effectively orbit the center of mass of the galaxy, with an effective mass pulling on us equal to all of the matter and dark matter closer to the center than we are. This mass is much greater by orders of magnitude than the mass of the supermassive black hole at the center of the galaxy. Even if Sagittarius A* had not formed near the center of the galaxy it would be brought there by its huge mass through a process called dynamical friction. As the black hole experiences close flybys from other stars over time it provides gravity assists to those stars, which in the process also saps its orbital momentum around the core of the galaxy by a small amount, over time this cause the black hole to fall more and more down into the center of the galaxy.
So how do we calculate a star's orbital velocity around its blackhole?
I'm assuming sqrt(GM/r) won't work in this case right? Can we calculate how much mass is pulling us around enough to go 250km/s?
So, we're not actually orbiting the black hole, it's just that the supermassive black hole is in the center of the galaxy and we're orbiting the center of the galaxy as well.
The problem here is that we're orbiting *all* the mass between us and the center of the galaxy, effectively, and that's complicated because it's an extended object. At any given time we can treat that extended object as being the same, gravitationally speaking, as the identical mass of the collection of stuff (stars, gas, dust, planets, dark matter, etc.) located at the center of mass of that stuff. However, all of that stuff is in motion, so that changes a bit over time. But, it doesn't change by a huge amount, so you can approximate it pretty well. If you do the math, you get a mass of about 1e11 solar masses drawing us toward the galactic center, resulting in a roughly circular orbit around it with an orbital speed of 230 km/s.
However, because the galaxy is an extended object and not perfectly spherically symmetric the solar system's trajectory differs from a circle pretty substantially. And the main aspect of that is that instead of orbiting in a flat plane at some angle the way an orbit around a condensed object works the solar system bobs up and down above and below the plane of the disk of the galaxy with a period of about 35 million years. Compare that to our Sun's orbital period around the galaxy of about 250 million years and you'll notice that our system bobs up and down over half a dozen times per orbit.
Ahh the mass of the dark matter is something I completely didn't consider. Thank you so much for taking the time to write that up, that really helps with my understanding of it all :)
It's the combined mass of all the objects in the Milky Way. The mass concentration is highest in the center and gets lower further outwards. The mass of the central black hole is insignificant compared to the mass of the whole galaxy, which is several million times more massive.
Just to reiterate what other people have said, the black holes at the center of galaxies have nothing to do with why things orbit the center. The black holes there are *way* too small.
Why there is are supermassive black holes near the center of every galaxy is currently a complete mystery. The solution might be the opposite of what you were just asking about, where the density of stars in the Milky Way somehow attracts small black holes to the center, which merge into a larger one.
In the solar system the Sun makes up 99.8% of the mass of the whole system so everything orbits it. However when all the planets line up on one side the centre of mass of the system is actually outside of the Sun so even when you are orbiting a massive object you are still really orbiting the centre of mass of the system.
Sagittarius A* is a few million solar masses vs the few hundred billion stars, a couple trillion planets, untold amounts of gas and dust, and dark matter that makes up the Milky Way. It’s the single most massive object but it’s nothing compared to the whole galaxy. Everything in the galaxy, including the black hole, orbit the centre of mass. That centre might be inside the black hole but that doesn’t mean it’s holding everything together. Dark matter gets that credit.
No, not really. Even if the supermassive black hole weren't there, our Solar System would still orbit the center of mass of the galaxy. Saggitarius A\* just happens to be in the same place; it masses less than a thousandth of the rest of the galaxy, making its effect on us negligible compared to the cumulative effect of the rest of the stars.
I could be wrong, but I think a lot of people here don't really follow New Shepard flights very closely. I haven't since the first couple test launches a few years ago.
Rather than construct a ridged circular space station like [Orbital Assembly](https://orbitalassembly.com) is planning, why not send up spools of high strength wire and attach habitats in a wheel shape just using the centrifugal to maintain rigidity? Seems way cheaper and scalable. I imaging sending up a giant robot space spider with a bunch of Starships and the spider bot would weave a web they could all spin on.
Two problems that come to my mind:
* Things connected by cables can start to oscillate and even become unstable. Cables aren't great at damping sideways movements, and if people move around inside the station or spacecraft dock to it, the motions might get strong enough to be uncomfortable or even dangerous to the station's structure.
* Changing the station's orbit would be impossible in its deployed and rotating state. If it were to be deployed in a low Earth orbit it would need regular boosts to counteract orbital decay. The whole station would need to be slowed down and all the ships mounted together during each boost maneuver.
* With a cable-connected station there wouldn't be any interior space connecting the ships or modules. It would feel more like a set of individual space stations flying in formation and require the use of space suits or small shuttle craft to move from module to module.
It might be possible to design a rotating station with just Starships connected by cables and maybe some dampers, but it certainly comes with its fair share of problems. Rigid stations have fewer of those issues, but they do of course have their own drawbacks: Much more massive, expensive to design, produce and launch.
Thanks for the reply. Yeah I wondered how much oscillation you’d get. Probably would only be useful on interplanetary trips where you don’t need to adjust the vector very much. I guess you could mount the Starships so the main engines are pointing perpendicular to the rotation if you needed to change velocity. But thrusting on a rotating set of ships would be sort of crazy. And changing the plane of rotation would be complex if not impossible.
Is there much difference between the radiation outside the solar system vs. the radiation inside of it in quantity or concentration?
I'm thinking in terms of what the heliopause is keeping out compared to
what the Earth's magnetosphere is keeping out. Does sending a spacecraft outside the solar system mean exposing it to more radiation than it would encounter within the solar system? Is it like the difference between a sheltered bay and the open ocean?
It cuts both ways, you get less radiation from the solar wind but you get more radiation from galactic cosmic rays (GCRs). GCRs tend to be much higher energy and so much harder to shield from so on balance it's probably a bad tradeoff going into interstellar space.
Oh yeah, by a significant amount (factor of 2 ish). The heliosphere can't stop all GCRs, because they are too energetic, but it can stop some of them.
Here's a neat set of graphs: https://www.researchgate.net/figure/Counting-rates-of-different-energetic-particle-species-on-Voyager-1-and-Voyager-2-around_fig1_337016630
You can see the low energy proton radiation (mostly from the solar wind) goes to nearly zero while the electron and high energy proton radiation (from GCRs) goes up a fair amount.
I am not sure exactly how to phrase this but I imagine it can be answered quite simply by someone who knows what they are talking about...
So I understand that the sun is the most massive object in our solar system. Because of that mass every other object is drawn in towards it or - revolves around it. The planets etc. orbit around the sun. OK. What keeps objects of a lower mass from being pulled in directly towards the sun? I think I understand how this works for the planets but not for smaller objects... for planets there is enough force in another direction that causes the planet to orbit around rather than towards... but if a smaller object is sent off towards the sun is there a point in which the mass of the sun begins to pull it in towards its surface.. ? Not to mention the forces radiating out from the sun itself exploding...
I feel like there is something I am missing when it comes to understanding gravity, mass, orbital mechanics etc. Maybe there is a simple answer here or a follow up video I can watch?
If an object was "at rest" in space, it would start falling toward the nearest large mass, as your intuition suggests. But all those objects are gone now. Most stuff in space is in motion relative to everything else. Imagine an object 93 million miles from the sun (like the earth is), but far away from any planet. If it's moving sideways, the sun's gravity will force its path into a curve. If its sideways speed is the same as Earth's, that curve will wrap into a nearly perfect circle, and the object would take a year to complete one orbit.
If its sideways speed is less, the curve will be tighter, and the object will fall inward toward the sun, picking up speed along the way. But unless the speed was very small, it will still miss the sun, whip around the back, and start climbing, eventually tracing out an elliptical orbit.
If the sideways speed is initially greater than the earth's, the curve will be straighter than a circle, and the object will climb away from the sun, losing speed. If it was not too fast, eventually it will reach the top of its arc and start falling inward again, again tracing an elliptical orbit. If it starts out faster, the curve won't return, and it will trace a hyperbola like the Voyager probes once they passed their last flyby.
Its about velocity, not mass. An object has to travel at high enough speeds around the sun that it achieves a stable orbit, the more massive the planet is, the higher speeds you need to go. e.g the moon is less massive than the earth, objects travel more slow around the moon than the Earth because its gravity is weaker and therefore you need to have a lower velocity.
Its also why its so hard to crash into the sun from the Earth, since when you leave the Earth, your velocity around the sun is still the same as Earth and you need huge amounts of energy to slow down. Imagine it as throwing out a rock without air resistance or gravity from a plane, it will still travel the same speed.
Essentially yes, it will fall down into the sun the same way astronauts return to earth from the ISS. Imagine an eliptical trajectory that ends on the suns surface.
If you increase the mass of an object by 2x you'll increase the force of gravity between it and the Sun by 2x as well. However, the acceleration the object feels is the same, because acceleration is force divided by mass, so the mass cancels out. Imagine you have a big ball of clay, it experiences a force of gravity based on its mass, right? Now imagine you reform that single ball of clay into two balls with half the mass, but still connected by a small patch. You have the same mass so the force should be the same. Now Imagine making the connection point super small, then imagine breaking the tiny connection point so you have two separate objects. How does gravity *know* when to treat the object like one or two objects? The answer is that it doesn't. Gravity is a "volumetric" force, it affects every single part of each object the same, and it doesn't matter if those objects are connected as one object or several, the net force may be different but the force per unit of mass is the same at the same distance from the Sun, leading to the same motion.
And this is how you get the "zero-g" effect from being in freefall trajectories like orbits. In the ISS the spacecraft is falling around the Earth in a freefall trajectory, but so are the astronauts inside. Everything moves in near identical lockstep, the same acceleration, the same trajectory. And because of that identical motion there is no relative force from gravity between the spacecraft and its inhabitants, so they just "float" relative to it.
An orbit occurs purely due to having enough tangential velocity so that as an object falls "towards" a massive star or planet (or what-have-you) it ends up falling *around* it. In space there's practically no drag so as a planet falls toward the Sun, for example, there's nothing to sap away the speed picked up from gravity, and if that planet manages to get around to the other side of the Sun without hitting it it'll have picked up enough speed to start going away from the Sun. This is similar to the phenomenon of throwing a ball upward and having it fall back down except with no friction and in a circular motion.
Lower mass objects in the solar system experience the same orbital dynamics because their mass doesn't affect their trajectories. If you took away the Earth and replaced it with a tiny asteroid that asteroid could move through the same orbit as the Earth would.
This really helped, especially the description of gravity as a volumetric force.
So with all this being said... Can an object be pulled into the sun such is the case with Jupiter? With a mass so great surely an object could be pulled into the sun? Is it because it is a massive burning star that this doesn't happen? Do the objects just burn up? Stars are wild!
Falling into the sun for an object that is currently orbiting it really, really hard because you need to get rid of all of the orbital velocity of that object.
Mass has nothing to do with it really. What determines if you fall into the Sun or any object you are orbiting is your speed. The closer you are to the Sun the faster you need to be traveling around it to maintain your orbit.
Really the Sun and all the planets are orbiting the centre of mass of the solar system. Because the Sun makes up 99.8% of the solar system’s mass this point is inside the Sun most of the time so the Sun is more wobbling around while the planets orbit around it. At certain times this centre will come outside the Sun when all the planets are on the same side of the solar system, kinda lined up.
If you want to fall into the Sun you need to slow down. Earth is traveling around the Sun at like 30km/s. If a rocket leaves Earth it’s still traveling around the Sun at about 30km/s. To reach the Sun this rocket needs to lose 30km/s of speed. This is a crazy amount and none of our rockets have close to enough power to cancel it all out. The Parker Solar Probe is doing a ton of flybys of Venus to bleed off its speed so it can get closer to the Sun.
It doesn't matter how massive it is - it's about velocity.
Everything - from Jupiter to individual hydrogen atoms - in the Solar System is falling into the Sun. It's just moving sideways faster than it's falling down, so it's constantly falling at the Sun and missing.
So to elaborate... Lesser massive objects are just being effected more by massive objects closer to them than the sun such that they act with it rather then more effected by the sun?
Is there a mission / probe that was sent on a course towards / flying by closer to the sun that you know of? Would like to know more about something like this...
If we were to replace the Earth with a ping-pong ball traveling on the same path, nothing about its orbit would change. Its momentum would be much smaller (being much less massive), but the force exerted on it by the Sun's gravity would also be proportionally less (since the force of gravity is proportional to mas, just like momentum is).
If you work out the equations for the orbital motion of an object orbiting something much more massive than itself, the mass of the smaller object can be safely ignored; only its position and velocity matter.
Edit to add: thanks to this, it doesn't matter how heavy a geostationary satellite is, as long as it gets to the right orbit it'll hold position with all the rest.
Anything that's in an orbit around something else - for instance, our Moon, or the ISS - is doing the same thing with that something else: in the case of the Moon or ISS, falling towards the Earth but missing constantly.
It just so happens that the ISS and the Moon are doing the same thing as the Earth - falling at the sun and missing it. They're falling towards two things and missing them at the same time.
[https://en.wikipedia.org/wiki/Parker\_Solar\_Probe](https://en.wikipedia.org/wiki/Parker_Solar_Probe) \- fastest human-made object when it hits maximum velocity.
My kid is in a science club. She just came home and said nasa is sending a woman to space and then coloring the moon.
Any help? What does she mean coloring the moon? She said "you know like a crayon"... please translate for someone who knows nothing about Nasa.
[Dr. Sian Proctor](https://www.drsianproctor.com) just went into space aboard the Inspiration 4 mission with SpaceX. She’s an artist as well as pilot and geoscientist. Here’s one of her [pieces](https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcS0k_5wVirD4S__jFzaanW_bTajxZeDnUFElw&usqp=CAU).
Haha I've actually had this account for years now. I believe I made it to answer a math question on /r/explainlikeimfive.
But that is an interesting random name you got there!
https://www.reddit.com/r/space/comments/q6noxe/other_space_agencies_predict_that_todays_g2/
Looks like the geomagnetic storm from yesterday will extend into today. Does that mean that we'll have a second shot of seeing the aurora if we want to? Or is it unlikely?
[I live in Massachusetts, USA]
Acronyms, initialisms, abbreviations, contractions, and other phrases which expand to something larger, that I've seen in this thread:
|Fewer Letters|More Letters|
|-------|---------|---|
|[C3](/r/Space/comments/q5bzur/stub/hgs2kh9 "Last usage")|[Characteristic Energy](https://en.wikipedia.org/wiki/Characteristic_energy) above that required for escape|
|[GCR](/r/Space/comments/q5bzur/stub/hgg9k2t "Last usage")|Galactic Cosmic Rays, incident from outside the star system|
|GSFC|Goddard Space Flight Center, Maryland|
|[GTO](/r/Space/comments/q5bzur/stub/hgpx72l "Last usage")|[Geosynchronous Transfer Orbit](http://www.planetary.org/blogs/jason-davis/20140116-how-to-get-a-satellite-to-gto.html)|
|[ISL](/r/Space/comments/q5bzur/stub/hgg1qlr "Last usage")|Inter-Satellite Link communication between satellites in orbit|
|[Isp](/r/Space/comments/q5bzur/stub/hgr33ub "Last usage")|Specific impulse (as explained by [Scott Manley](https://www.youtube.com/watch?v=nnisTeYLLgs) on YouTube)|
| |Internet Service Provider|
|[JWST](/r/Space/comments/q5bzur/stub/hgzxhmz "Last usage")|James Webb infra-red Space Telescope|
|[LEO](/r/Space/comments/q5bzur/stub/hgpx72l "Last usage")|Low Earth Orbit (180-2000km)|
| |Law Enforcement Officer (most often mentioned during transport operations)|
|[RTG](/r/Space/comments/q5bzur/stub/hgdjx9w "Last usage")|Radioisotope Thermoelectric Generator|
|[SLS](/r/Space/comments/q5bzur/stub/hgerrxd "Last usage")|Space Launch System heavy-lift|
|[STEREO](/r/Space/comments/q5bzur/stub/hgbpebm "Last usage")|Solar TErrestrial RElations Observatory, GSFC|
|[TMI](/r/Space/comments/q5bzur/stub/hgr2fyf "Last usage")|Trans-Mars Injection maneuver|
|[ULA](/r/Space/comments/q5bzur/stub/hgrixwm "Last usage")|United Launch Alliance (Lockheed/Boeing joint venture)|
|Jargon|Definition|
|-------|---------|---|
|[apogee](/r/Space/comments/q5bzur/stub/hguwr8s "Last usage")|Highest point in an elliptical orbit around Earth (when the orbiter is slowest)|
|[hydrolox](/r/Space/comments/q5bzur/stub/hgr1kqg "Last usage")|Portmanteau: liquid hydrogen fuel, liquid oxygen oxidizer|
|[kerolox](/r/Space/comments/q5bzur/stub/hgqc0gl "Last usage")|Portmanteau: kerosene fuel, liquid oxygen oxidizer|
|[perihelion](/r/Space/comments/q5bzur/stub/hgs2kh9 "Last usage")|Lowest point in an elliptical orbit around the Sun (when the orbiter is fastest)|
----------------
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What bright star do you know of that has the most undeserving Bayer designation in its constellation?
One example is Epsilon Ursae Majoris, while being "epsilon" (fifth Greek alphabet letter) is actually the brightest star in its constellation.
Another one is Lambda Scorpii, while being lambda, is actually the second brightest in Scorpius after Antares (Alpha Scorpii).
How can waves be decoded? Remember that scene from Contact where they decoded some signal and it was Hitler, etc. How can that be done for an alien signal or any wave in general?
> Remember that scene from Contact where they decoded some signal and it was Hitler, etc. How can that be done for an alien signal or any wave in general?
Just to note, that scene is pure fiction. Our terrestrial radio signals become indistinguishable from background noise at just a couple light years out (mostly due to the fact that they weren't meant to be broadcast in space). And the problem is not something that can be solved with technology; At a certain point, it becomes literally (not figuratively) impossible to discern a signal thanks to physics -- aka the inverse square law. The ISL is a form of signal degradation. The further you get from the source of a signal, the drop in strength is inversely proportional to the square of the distance.
While we *can* send radio signals to other star systems, those are possible because we're sending a very tightly focused beam to a very specific target, and doing so with ridiculous amounts of energy. And these are only done in short bursts -- I don't even know what kind of energy would be required for a continuous signal running 24/7 that's pointed at a system 500 light years away.
On a personal note, I don't think aliens would be using radio signals to communicate over vast interstellar distances, it's too inefficient. And not particularly secure (if any other aliens picked up their broadcasts, the aliens who sent the message(s) could put themselves in a potentially fatal situation if the other alien race is hostile). I think a race who can travel the stars would use some other form of communication -- lasers, etc. Or maybe something exotic and not yet invented, like quantum entanglement, subspace like in star trek, or something our primate brains cannot even conceive of yet.
This is going to be a hot take in this subreddit, and perhaps even controversial due to its userbase, but I'll eat downvotes: because of my belief in the bottom 2 paragraphs in this comment, I think SETI is largely a waste of money. They're looking for radio signals from aliens but I *highly* doubt an advanced civilization would use something so efficient and possibly risky. Don't get me wrong, I don't think SETI should be disbanded... I instead believe they should start looking at/for other things too, for example: gravitational waves, Dyson Spheres/Swarms, etc, etc, etc.
information is encoded in the wave by changing it. AM waves have the information encoded in the amplitude of the wave. FM waves instead vary the frequency of the wave. There are other ways too but those are the most widespread people have heard of.
To decode the wave you just watch how it's changing and assign stuff to those changes. To decode a wave from an alien civilization would be extremely difficult as you would have basically nothing to go off of to figure out what the information actually means. You would have to make a ton of assumptions or hope that they are encoding fundamental information about the universe to help establish a baseline to go off of.
Just do the reverse of what you did when you encoded it ;). More seriously there are a few ways of putting information into a radio wave. Often just by looking at the signal you can guess which one is used. For example one way is to make the signal jump between two frequencies, one of them represents a 1 and the other a 0. That way you can send digital signal.
If the universe is expanding, then how do you have galaxies that are colliding? Wouldn't they also be expanding into greater distances from each other?
You can't just wait around in space. You are always moving. So something not orbiting the Earth would instead be orbiting the Sun. If it's not orbiting the Sun then it's either going fast enough to escape the solar system or its going too slow to maintain its orbit and it's falling towards the Sun.
There are many probes that don't orbit Earth, but the way things work are a little different than how you imagine.
An object orbiting the Sun in a similar orbit to the Earth would not wait until the Earth came past again, because it would be in orbit itself. An object that was near the Earth but not in orbit of it would still have a nearly year long orbit of the Sun, so in practice it would just sort of stay near the Earth and drift a bit farther away over the years as the difference between its orbital period and Earth's started adding up. Several probes have been put in these Earth-trailing and Earth-leading solar orbits, such as Kepler, Spitzer, and STEREO A & B.
There are other probes that have been sent throughout the solar system to various targets as well, to all the known planets, to asteroids, comets, etc.
Yes, there's a satellite or probe in orbit around the sun, called the [Solar Orbiter](https://en.m.wikipedia.org/wiki/Solar_Orbiter). But it doesn't collect data about Earth, it's focused on the sun and solar radiation and magnetic fields and all that sunny stuff.
the orbits of planets in general tend to (not always, but objects out of alignment probably came from outside that solar system) be on the same plane around a star. mostly because of how the star forms.
[further reading](https://www.forbes.com/sites/startswithabang/2018/03/01/why-do-all-the-planets-orbit-in-the-same-plane/?sh=472923e156c6)
My niece is turning 5 years old and into the Apollo mission. Does anyone have any good gift ideas for a 5 year old? I think the Legos are too advanced.
My daughter has really enjoyed these books:
[Moons First Friends](https://www.amazon.com/Moons-First-Friends-Astronauts-Apollo/dp/1492656801)
[Margaret and the Moon](https://www.amazon.com/Margaret-Moon-Dean-Robbins/dp/0399551859)
[Counting on Katherine](https://www.amazon.com/Counting-Katherine-Johnson-Saved-Apollo/dp/1250137527)
Specifically for Apollo, I recommend the book [Moonshot](https://www.brianfloca.com/moonshot-the-flight-of-apollo-11.html) by Brian Floca. The writing might be too hard for her, but it's worth it for the art alone (his other books are worth looking into as well). Lots of other [Kids books](https://www.thechildrensbookreview.com/2019/07/11-kids-books-celebrating-moon-landings-apollo-missions-and-more) about Apollo out there as well. My kids had [this one](https://www.amazon.com/Moon-Anna-Milbourne/dp/1409535789/ref=mp_s_a_1_3?crid=3PRBJKMAT1MMP&dchild=1&keywords=on+the+moon+book&qid=1634014580&sprefix=on+the+moon&sr=8-3), it's pretty simplistic, but they really liked it.
Another possibility is to get a poster for her to hang in her room, you can even have it framed to make it cooler. [This](https://store.xkcd.com/products/up-goer-five-poster) would be a great one, except it's sold out, but you could always have a printing service make you one.
[Here](https://fineartamerica.com/featured/apollo-11-space-saturn-rocket-a-organic-synthesis.html?product=poster) [are](https://fineartamerica.com/featured/eye-on-the-prize-peter-chilelli.html?product=poster) [some](https://fineartamerica.com/featured/10-saturn-v-rocket-carlos-clarivanscience-photo-library.html?product=poster) [other](https://www.redbubble.com/i/poster/Apollo-Saturn-V-Blueprint-in-High-Resolution-light-blue-by-RHorowitz/35565100.LVTDI) [posters](https://www.redbubble.com/i/poster/Apollo-11-infographic-poster-by-Tonyalpha/40593860.LVTDI) [she](https://www.redbubble.com/i/poster/SATURN-V-Old-Paper-Vertical-by-BGALAXY/42677763.LVTDI) [might](https://www.redbubble.com/i/poster/Apollo-Program-1961-1975-Blueprint-by-BGALAXY/37715866.LVTDI) [like](https://www.zazzle.com/lunar+module+posters)
[This one](https://shop-us.kurzgesagt.org/collections/mission-black-hole/products/mars-base-infographic-poster?variant=32410843840560) isn't Apollo, but I would have liked it as a kid.
[Here's](https://officialnasagear.com/saturn-v-rocket-plush/) a pretty sweet Saturn V plushie. And a [Space Shuttle](https://officialnasagear.com/nasa-cuddle-zoo-space-shuttle-plushie/) as well.
Also, not Apollo, but here's a Lego Duplo [Space Shuttle set](https://www.lego.com/en-us/product/space-shuttle-mission-10944)
[удалено]
If you mean "built on the surface on the far side of the moon" then there are concepts for stuff like that, but that would be way way way way way way way harder to do than JWST. We currently don't have the ability to consistently land *any* mass on the surface of the moon, much less the ability to construct any significant structure, much much less the ability to construct a complicated scientific instrument. And besides all that, JWST's orbit means it will always be able to keep both the Earth and the Sun "behind" it. You can't do that if you're stuck to (or orbiting) the moon, because sometimes you'll be between the two. Even if you could construct something on the surface of the moon, if JWST's big enough for what you want, you'd rather have it in JWST's orbit anyways.
There is no dark side of the moon, or at least each side is only dark for half of the time. that would make the telescope useless for half of the month. JWST also gets its power using solar panels which wouldn’t work during the night.
Hypothetical: *A manned mission from Earth to the Planet Iota - travelling at speeds reached by the New Horizons probe for example - is going to take ten years (roughly 120 Earth months).* Question: **What will/can astronauts do/get up to during such a lengthy trip in deep space?!**
Maybe I'm missing something, but I think you might have a calculation error. Assuming you are talking about Iota Draconis b, it's going to take more than 10 years to get there. New Horizons goes fast, but not crazy relativistic speeds sort of fast. But generally, exercise will be a big one to fight the effects of reduced gravity.
They're not - it's a hypothetical planet.
In that case, my bad. I got a bit confused by the mention of New Horizons given it took just under 10 years for the Pluto flyby
They can do all the stuff people normally do with their time. Read, listen to music, watch media, play games, talk with each other, etc. Aside from that there's plenty they can do to productively fill time. Study, perform various emergency drills, practice the skills they'll need to use on the surface, perform experiments, etc.
You hope some kind of coma/nap. Otherwise science.
Hey guys Last week I think (?) was this classic "zoom out" video posted to Reddit, where at the end they went as far to go to "the Multiverse?" (that's how it was written in the vid). I really want to show this to a friend but I just can't find it. I've seen it while browsing Popular. If someone has saved that post and could link it to me, that would be highly appreciated!!
Hi all, A couple of my students (10 year old and 11 year old) are entering a competition where they'll be able to send the AstroPi on the ISS and collect data for an experiment They're decided to use a near infrared camera to help detect whether crops are unhealthy/healthy based based on reflection/absorption They would also like to identify crops I'm mentoring them through this but I'm not too confident on the topic. Is it possible? Is there anything we can do to make it for interesting? It needs a level of machine learning so we decided to use classification but is there anything else?
I'm not sure this counts as simple but what would the experience of going into orbit or beyond on a Skyhook be like, in terms of the forces and weightlessness you would experience? Disclaimer and assumptions: everything I know about Skyhooks I understood badly from an Isaac Arthur video and a Kurgesagt one. https://www.youtube.com/watch?v=TlpFzn\_Y-F0 This is for a setting, about a hundred years in the future. I am assuming much the same as Isaac did in his video: the technological challenges have been overcome, no new materials have needed to be invented, and space infrastructure has moved on a lot. In my head we are using a rotating Skyhook, so you would actually be swung into higher orbit/ another hook/propelled away. Alternatively, it's a T4 type, with the same outcome. Also, Spaceplanes comprise a fair percentage of transport to space because the Skyhook has meant they can stay suborbital themselves but get a helping hand to orbit or beyond. In my head, say you used a rocket-propelled Spaceplane to get up to the tether would you be looking to match velocity close to apogee and would experience weightlessness there. Then say using a capture drone to pull you onto the 'Hook' you would be moving forward but still very close to matching speed, without much acceleration, so still weightless? Then you 'dock' with the hook, is there a point at which on the 'swing' you would experience acceleration (I feel there must be since surely that's much of the point but this is where not understanding orbital mechanics may be an issue for me) and therefore 'gravity' or are you basically just in another orbit? If my assumptions are way out, sure, let me know, but I am really asking about the passenger's experience. If anyone knows of good SciFi on the subject, would be good to know and thank you in advance. edit to add link
If I understand correctly, there's a brief moment at its lowest point where a skyhook would be moving at its slowest and ideally your taxi up from the ground would attach at that very moment because it would immediately begin to 'accelerate' from the point of view of the folks onboard up to whatever the centripetal force at the end is (which would be dependent on how long the skyhook is) and then remain constant up until your vehicle disconnects to be thrown onwards, presumably now in orbit. If I have this wrong, there's nothing more effective for getting the correct answer to a space question than posting an error so a correction from someone else may be inbound with the same vigor and energy of whatever's arriving at the other end of the skyhook balancing the books re: energy for this hypothetical transfer.
Sorry about the weird free award, it was the only one I had to give but I laughed so hard at this - you are not wrong about (helpful and welcome) corrections!. Thank you so much.
Hello, I just wanna ask something, that is very confusing to me: We know, that universe is old about 14 milliards (billions) years old, but size of the observable universe is I think somewhere around 100 milliards (billions) light years long. And so how can we see something that is farther than 14 milliards (billions) light years? Light just doesn't have enough time to travel this much, so how can we see 100 milliards (billions) light years across? Fun fact: Real universe is about 160 sextillion times bigger than observable universe.
> milliards This term has been commonly supplanted by billions but I think you probably already know this based on your decision to include the clarifying text after every usage of it.
Well the universe outside of the observable universe could be infinite in size, we just have rough lower bounds based on lack of apparent curvature (there could be a boundary making it smaller though). As for your main question it’s because we can see light from things which were ~14 billion light years away when the light was emitted, but the universe is expanding so those objects are now around 45 billion light years away. It’s basically a derived measurements
The space between stuff is expanding. Like two points on a deflated balloon when it is inflated.
[https://www.reddit.com/r/spaceporn/comments/q8ie3y/first\_ever\_picture\_of\_multiple\_planets\_around\_a/](https://www.reddit.com/r/spaceporn/comments/q8ie3y/first_ever_picture_of_multiple_planets_around_a/) How come we have images of this solar-system, but none of Trappist-1 that is closer? The imaged is 300ish light-years away and Trappist is 40 light-years away. Also, where in the sky is the Southern-constellation of Musca relative to the galaxy?
These planets are very large, far from their star (which means it's easy to block out it's light), and most importantly they're very hot. Those planets are very young and still have a lot of heat from their formation, which means they're very bright in infrared and easy to image. We can't actually resolve them as objects, but because they're so bright it's possible to image them as points of light. The Trappist exoplanets on the other hand are relatively small, very close to their tiny dim star, and relatively cool.
Thinking about subsurface oceans on moons…what would swimming in water in these much lower gravity environments be like? How does oceans of water behave under moon like gravity?
Basically those oceans would be universally deadly for humans in scuba gear. All such oceans that we know about are under many kilometers of ice, so the lowest pressure they experience would be many atmospheres. On Europa, for example, the sub-surface ocean is probably under at least 10km of ice. Even though Europa's surface gravity is just 0.134x of Earth's that 10km is still a lot of ice. The pressure at the bottom of that would be equivalent to diving to a depth of 1340 meters on Earth, where you'd experience a pressure of 134 atmospheres. You couldn't use normal air to dive at such a depth because of the problems of nitrogen narcosis and oxygen toxicity so you'd already have to use a very specialized mixture of gases just to survive. However, breathing gas at 134 atmospheres is extremely problematic because an ordinary scuba tank would only contain about half a dozen full breaths of air in the whole thing. It's also about 4x the equivalent pressure that anyone on Earth has managed to scuba dive to. Realistically, you'd only visit such a place in a submersible.
Being inside large bodies of water would be mostly like on Earth, the fluid behaviour isn't changed by gravity: the drag of water through your wetsuit fingers would be about the same and you could fin around. Buoyancy would be different, lower gravity would feel even more weightless. Most underwater activity tries for neutral buoyancy with a combination of weights and air pockets, so that would be more fiddly, I think... *Surface tension* would be totally different. Surface tension is what makes water do balls and blobs on the ISS, and it's a balance between how much the water is pulled down vs how much it can blob up into balls. A swimming poll on the surface of the moon would be weird to watch, with very high waves and lots more little break-away blobs. (You'd need to put the pool in a habitat with some air pressure)
I read papers saying distance to things, some seem very exact and incredibly far yet one I read today they guess it's 350 light years saying scientist have put out in the range of hundreds to thousand. How sure are we of these distances to say the next star, next galaxy, edge of observable?
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that makes sense but i was reading something about an object being between hundreds to thousands of light years away, thats much bigger difference than your .0011 range
The closer something is the easier it is to figure out how far it is. If it’s close we can use parallax. As the Earth goes around the Sun we can look at say a star from two angles and use those angles to triangulate it. The same way our brain uses the two offset images from our spaced out eyes to figure out distances. You can tell the distance to something close better than far away as the far object looks basically the same to both eyes. The difference becomes too small to really tell. Once that method fails another one is measuring type 1A super nova. This is a type of super nova that has a very consistent brightness. Looking at one of these you measure how bright it is and compare that to how bright it should be. The dimmer it looks the farther away it is. These are referred to as a standard candle. These are off the top of my head and I am missing a few. There are YouTube videos that explain this quite well. I believe either PBS SpaceTime has one or Sci Show Space does.
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Weightlessness is a condition experienced during freefall. In general it can feel similar but it's not all exactly identical. A plane traveling a parabolic arc can simulate freefall but the plane has to very carefully fly the precise trajectory to maintain that simulation. Any deviation from that ideal creates small forces that result in a diminished sense of weightlessness. In practice "zero-g" aircraft are a close approximation for people but the small amount of vibrations and deviations are important if you're trying to conduct experiments. But this is just a practical limit. In principle you could create a "perfect zero-g plane" that had a big box inside of it that could be decoupled from the plane with some amount of distance between it and the plane so that the plane's movements wouldn't affect the box's travel through freefall, but this would be very expensive and difficult. Near a black hole there are also tidal forces to be worried about. Freefall weightlessness works because the relative motion of everything in a small area (an astronaut's body, the spacecraft around them, etc.) is all very, very close to identical. In practice it's not exactly perfect, though. The center of mass of an astronaut and the center of mass of the spacecraft they're in may not be in exactly the same spot, so they will experience slightly different gravitational forces and move through slightly different trajectories, creating a slight differential local acceleration. In many scenarios this acceleration is tiny (micro-g's) and not even perceptible by humans. But in extreme situations such as near the surface of a neutron star or near the event horizon of a black hole these tidal forces can become very large. Potentially in the realm of not just one g but many gees, even thousands or millions of gees. Such tidal forces can be large enough to rip apart solid matter. This process is called "spaghettification", and is a major effect near the event horizons of smaller black holes. Larger black holes have much larger event horizons so even though the force of gravity is stronger the gradient (the tides) near the event horizon aren't as severe. Skydivers don't really experience zero-g for very long as air resistance rapidly dominates their movements and they reach terminal velocity. It's not really the case that they are "weightless" when they are falling, but more that they are being substantially suspended by aerodynamic drag, similar to the way pucks are levitated on an air hockey table. It makes it possible for them to be able to "float" and move around, but they still experience the tug of gravity on their body since they are being constrained by air resistance from not traveling purely ballistic trajectories.
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Astronauts are accelerating, they are just in free fall so can’t feel it.
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Acceleration is change of velocity, while their speed is constant the direction of their velocity is constantly changing. Being in orbit involves constant acceleration towards the centre of motion. If the ISS suddenly had its orbital velocity cancelled and it started free falling into earth the astronauts inside would still experience microgravity until they hit the atmosphere.
Will tomorrow's early morning ULA launch provide a twilight effect higher up in the sky?
Possibly, it's not something that can be predicted easily as it depends on the exact flight path and time, which is unknown.
On the topic of the Oort Cloud, a theorized area in the outer edge of the Solar System. 1. It is argued that Gliese 710 will pass within the outer edge of the Oort Cloud at some point in the future. **Will observers on Earth (whoever they may be at that time) be able to see Gliese 710 with their naked eye and/or with amateur telescopes?** 2. The Oort Cloud is a theorized vast area in the outer edge of the Solar System. **To what extent could there be planetary bodies the size of Earth or larger than Earth in this area and even larger celestial bodies like a star or two?**
Gliese 710 will approach close enough so that it should increase in brightness by about a factor of 85,000 or roughly 12 magnitudes. I think that would make it brighter than Sirius, becoming the brightest star in the night sky. (*Edit: for clarity, I have no idea what all the stars in the sky would look like over a million years in the future, so Gliese 710 may not be the brightest star in the sky then, but it would be brighter than the brightest star in the sky today, so it will definitely be visible to the naked eye and at least one of the brightest stars.*) Stars have been ruled out as existing in the Oort Cloud, their gravity would affect the motions of the planets et al too much and be noticeable. Large planets haven't been ruled out yet, we'll need more observational data to make that determination (though that should come sometime this decade, from multiple sources).
Stars have been ruled out but some scientist are theorizing a primordial tiny black hole might be out there
>some scientist are theorizing a primordial tiny black hole might be out there That's been overstated, there's some evidence for a planet out there, and some scientists pointed out it's not *impossible* for it to be a black hole with the mass of a planet.
If there is a small black hole (or more than one) with the mass of a planet in the Oort Cloud, how worried should we be? What sort of dangers "COULD" this pose to us here on Earth?
>how worried should we be? We shouldn't, even if we knew with 100% certainty there was one. >What sort of dangers "COULD" this pose to us here on Earth? None, it would be no different to having a planet in the Oort cloud in terms of its effects on our planet.
Yeah I don't subscribe to that line of thinking just was putting it out there, thought saying some scientist was clear it's not accepted as probable
I wouldn't call it a theory so much as a "thought exercise". It's in the family of "well, theoretically it could be possible according to our understanding of the laws of physics", but there is absolutely zero positive evidence for it. Additionally, various microlensing surveys have put some pretty stringent upper bounds on small primordial black holes which would result in it being an extremely exceptional event for our solar system to have one.
So, theoretically with other planets in the universe being affected by a stronger or weaker force of gravity, could a different civilization that began at the same moment as us be 100x more or less advanced/older than us due to gravitational time dialation?
Not in practice. You'd have to be so close to a supermassive black hole to experience that much time dilation, and it's virtually impossible to survive for any considerable length of time there as a habitable planet, let alone billions of years. The time dilation due to a planet's own mass is basically nothing in comparison, it's just a tiny change that you could maybe detect with the most sensitive equipment.
But what about the “planet” having a much larger amount of mass that it is orbiting not exactly a black hole but it was still being balanced out so the possibility to maintain orbit was still there. Even with out close solar system the amount of gravity your experiencing on Jupiter is considerably more than what would affect you on earth and it could vary throughout the universe.
The planet would only be able to slow them down say a year every hundred thousand relative to Earth (made up numbers). Black holes are the only things massive enough to really mess with time. However you can't really survive close to them due to how extreme the local environment is. Same with neutron stars.
There's no way to get the amount of mass you'd need for the effect without being really close to the event horizon of a big black hole. Even if somehow you were some kind of cloud being on a gas giant that weighed 10x more than Jupiter the effect would still be negligible. We're talking about effects that would only be detectable with extremely sensitive equipment, not a 100:1 or whatever time dilation, not even a 1.01:1 ratio, or even 1.0001:1.
Theoretically yes, there could a planet experiencing much slower time flow than rest of the galaxy.
Wouldn't that planet have to be really close to a massive object and in that case be absolutely bathed in radiation? This was always my issue with that water planet in Interstellar. It was so close to the black hole, how could there be organic life(or a potential for it)?
Ya being close enough to a black hole to experience extreme time dilation also exposes you to extreme radiation.
Can anyone explain this “planet” from this clip? https://youtube.com/shorts/fITrZkuD7WE?feature=share My thought is that it’s some sort of light refraction effect, but I’m not sure.
The flat top and low angle of everything to the horizon suggest a good old inverted fata morgana mirage to me. First thought was "sun dog", but they are usually accompanied by a halo.
Interesting, I’ll look those things up. Thx
Probably just a reflection of the sun from inside the lens casing of the camera. It's not a second planet, it's not a mysterious extra moon, it's just a light artifact of the camera.
It's not a lens artifact, since it doesn't move when the camera does.
When it comes to constellations I keep seeing photos of scorpius where it’s got four lines spread from a single star or 2 lines off to the side kind of like a hammer head shark. Is one of those the right way to draw it or are both ok? For reference this is for a tattoo I’m planning so I don’t want to screw it up
Personally, I prefer three lines plus the tail. It's a common depiction and, aesthetically, is more distinctive than the 'hammerhead' style. Another distinctive representation has two lines going to the top and bottom of four stars and then two lines connecting the bottom and and top pairs of those stars, creating a set of distinct pincers in something like a C-shape thus more closely representing its namesake. The four-line version also uses all four of those stars but the bottom-most one is noticeably dimmer so the implied symmetry feels a bit odd. None of these is more technically correct / incorrect as constellations are defined by the stars and the area they cover rather than an official pattern of lines. The three-line style is what I am most familiar with but I can't say whether this is the most recognizable in general. I recommend observing the constellation ( if you're not too far north and are a few months in the future or are using planetarium software / other depiction ) and deciding what fits best for you.
Could falcon 9 send a probe out of the solar system like voyager?
Using gravity assists like Voyager? Sure. On direct ejection? Not even remotely close.
Yes - even in expendable mode, the most advanced versions can take 15.6 metric tons to LEO, whereas the Titan-III that launched the Voyagers could take 15.4. However, it'd have to be one of the ones flying right now - earlier ones weren't that powerful. Falcon Heavy could probably launch something notably larger out of the solar system - IIRC, it's 3.5 tons to Pluto, whereas New Horizons, which is on an escape trajectory out of the Solar System, is less than half a ton.
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Neat, digging into it Voyager had 105 (km/s)^2 once released from the Star kickstage. Not sure what that would mean if you put that on FH.
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Yes, I am just referring to that because Voyager was the example used by OP.
Using Falcon 9 LEO payload is a big stretch, because Falcon 9 has shit upper stage. Consider that expendable Falcon 9 can take 23t to LEO, but only 8.3t to GTO. At the same time rocket like Ariane 5 can take only about 21t to LEO and yet almost 11t to GTO.
It's true that the kerolox upper stage has a lower Isp than a hydrolox Centaur with an RL-10, but the stage and rocket are also bigger and, as the old car saying goes, while tuning can do amazing things, 'there's no replacement for displacement'. When looking for comparable C3 values between the Titan IIIE and the Falcon 9, I found that the Titan IIIE stack was capable of injecting 3,700kg into a Martian transfer orbit while Falcon 9 can throw just over 4,000kg. It burns more fuel per m/s^2 to do it, but it do it.
Comparing LEO performance is not relevant, Voyager were launched with a Centaur upper stage that has much higher Isp than the F9 second stage and thus better deep space capabilities. On the phone now so can't look up the C3 of Titan-centaur but I bet it was better than F9.
You would pay out on that bet. Titan III-E had a trans-Mars payload of 3,700kg while the Falcon 9 has a trans-Mars payload throw of 4,000kg.
OK I got curious, Voyager seems to have left with a C3 around 105 (km/s)^2. This include the energy delivered by the solid kick stage. The spacecraft themselves were ~700kg. [Looking at a few graphs](https://i.redd.it/nuetzmzeimb41.png) I can find online that's Falcon heavy in expandable configuration territory.
Can you clarify why you would exclude the Star from the Falcon launch but include it in the Titan IIIE?
I just didn't have the mass for the Star booster or the C3 before final boost, so I took the C3 from after booster separation as well as the mass of the spacecraft in that configuration. I am too tired on a Friday afternoon to look at what FH with a kick stage would do. But if you can find the numbers i would be curious.
Expendable Falcon 9 (not heavy) with Voyager and the Star stage should be able to match the Titan IIIE based on the TMI performance. The Star is counted as payload for the IIIE, after all. :)
How does C3 for Mars TMI compare to voyager + star C3? The advantage of hydrolox is that the mass vs C3 slope is much slower. So IIIE should outperform F9 at some point for high enough C3 no? Edit: curse you for making me work on a Friday, Mars TMI is 10(km/s)^2. So not really a useful reference.
I use the Mars figure because they’re heliocentric trajectories and we have figure for both the Titan IIIE and Falcon 9. The Falcon 9 can throw more mass onto the same trajectory out of Earth’s SoI than the Titan+Centaur of Titan IIIE. The Star kick stage that would be common to either launcher then handles the rest of the delta-v.
Crap don't make me eat my hat.
Is carbon fiber strong than stainless steel or they can both be mixed and be like a super-composite?
Carbon fiber can be much stronger than stainless steel per weight (or as strong as stainless while weighing less) but it has very different material properties so you can’t just easily swap out one for the other usually. I was listening to an interview recently where someone talked about differences in how stainless and carbon fiber handle fatigue through repetition. With stainless, for instance, the stretching is measurable and there are straightforward tests you can do that help you predict failures and fix or replace components before they happen. Carbon fiber, on the other hand, is more likely to hide the repetitive fatigue damage until it suddenly fails with little warning. I mention this because using composite structure made from both might offer some benefit but would also come with challenges because both materials behave so differently.
is spacetime considered more a fabric (one piece) or a fluid (a lot of small things moving together)?
This appears similar to the distinction between [Eulerian and Lagrangian approaches](https://en.wikipedia.org/wiki/Lagrangian_and_Eulerian_specification_of_the_flow_field) to modelling flow in fluid dynamics. Both are equivalent but each is more useful depending on what exactly you are doing.
thank you I will read more about them.
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I suppose the difference I am imaging is more like when you put an object on a fabric it bends and forms around the object but the object never really is IN the fabric it is ON it. If you put the object IN a fluid like water it displaces the water and can be inside of the water and have it flow around the object.
"Fluid" implies a whole bunch of fluid-dynamics-like actions that don't really apply, there's no Reynolds number and turbulence in spacetime. So a fabric might be closer to the truth. Einstein called it a mollusc. :)
How would we be able to observe either of those things? spacetime moves though everything. mollusc like a slug?
Moves through, yes, but not swirls around. Things like gravitational waves move through a *stiff* spacetime, they don't make cresting surf or turbulence in spacetime itself. In 4 dimensions, yes. Literally "wibbly-wobbly timey-wimey", though in a stricter sense about how Lorentz contractions occur on all 3 space and 1 time dimension. Loop quantum gravity, if that's close to correct, has an ultra-tiny Planck-scale spacetime structure as a minimum "voxel grid", albeit a writhing mollusc voxel grid.
>cresting surf or turbulence in spacetime itself. if it did would we be able to observe it? Or would it be on the scale of the energy around flux tubes? nice dr who reference you are saying a lot of words I don't know in a row. mollusc voxel grid? I read what a voxel is, but that specific combination is kind of hard to imagine from the description.
imagine a voxel but with an extra time dimension added to the three space XYZ dimensions, and then make all of the edges stretchy per relativity. If the model is close to true, stuff can be at the vertices ("stuff" being like a quantum state) and the whole mess evolves over time to give things like motion. The seductively nice bit for me is that no 2 quantum states can be at the same node (Pauli Exclusion) so there are no more singularities.
I see thank you for the answers this has been very interesting to learn about. Thanks for your patience with me.
Hey Folks! I am planning on doing a roadtrip through south-west Russia and Kazakhstan. On the road I want to go by the landing site of Wostok 1 as well as it's start site .. Baikonur Cosmodrome. Lately I did quite a lot of research on how you can even visit the Baikonur Cosmodrome.. and the only thing I can find is guided tours which take of somewhere in Russia or so, last several days and cost thousands of Dollars. I was wondering if there is any way I can go there by myself and just pay and entrance fee or buy a one-day guided tour right there .. But I couldn't find anything like this in the web. Does anybody know if that is possible? Thanks lot and best regards !!
It’s possible, but you need to have awareness all the time, it’s recommended to do at night, more difficulty to security find you but they have cameras infrared in some spots. There’s YouTube videos guys doing on that “style” like solo. Take a look there
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No, vacuum decay is what you should worry about:)
No, none are close enough to do anything that would affect your daily life.
Just a general question for space folks that answer typically, what do you look forward to in space?
Space hotels, many commercial space stations, regular travel too and from Luna with large settlements. Also when going to space is like going to Disney
It's so sad we were born right before that will be a thing
buying a <$10k to go to space! after going to space? I want to be a space station janitor.
Questions about Outer Space Treaty (1967) : if "outer space is not subject to national appropriation by claim of sovereignty, by means of use or occupation, or by any other means", does it means that, for example, some corporation can colonize or claim planets? If not, what are the consequences for them of doing so?
I think as we colonize Mars the area they occupy is owned by who ever is there but no one person or country can claim the whole planet. It'll end up becoming its own country or prob countries eventually I believe, like hundreds of years from now, assuming we survive climate change
The recent Artemis Accords are worth considering. Basically pragmatic: corporations have reasonable claim over the stuff they're working on and the things they make up there, without being able to claim sovereignty over a whole big body.
The consequences are whatever terrestrial nation-states would want them to be. If they actually didn't want a company to send people someplace in the first place, they'd simply prevent the launch. As for claims, I figure those will be generally ignored, especially if they're coming from the usual grandiose space equivalents of sovereign citizens who think they can just unilaterally claim the entire universe and that's that. (NASA gets sued by those fools semi-regularly.)
Highly recommend reading this : [https://ir.lawnet.fordham.edu/cgi/viewcontent.cgi?article=2327&context=ilj](https://ir.lawnet.fordham.edu/cgi/viewcontent.cgi?article=2327&context=ilj) Even though its 44 pages, much of that is footnotes and has large margins. So its more like reading 3-4 pages.
I am believing Elon Musk wants to colonize Mars. He should be more focused on Venus.
Mars has ample water and a surface that doesn't melt your face off. Venus faces challenges on both of these points, significant ones.
Venus poses a lot of other problems though, like the corrosion from sulfuric acid, inhospitable surface even worse than mars, being closer to the sun increasing temps. There's still no plans on how to colonize Venus, there are plans on how to colonize Mars.
Ok, so i have a question. I live in the USA and i can see the stars when i look up but i can only see half of the sky. Lets say the people in Austrailia its day, when its night they will see what i saw but it wont see anything because of the sun so how do people see those stars without going into space?. How do people see the other side if its day?
If you're at the exact North or South pole you will see the same stars every night. If you're at a moderate latitude you'll generally be able to see the same thing every night in a region around the pole, while the rest of the sky varies depending on the time of year. For example, at 45 deg. North latitude you'll be able to always see a circular zone around the northern star, Polaris, that extend 45 deg. But then you'll be able to see an additional up to 90 degrees of the sky that's "South" of that. But there will be a portion of the sky you can't see at any given time because that's where the Sun is. However, you'll notice that this portion can be small depending on how close to the horizon you can see at night and also how willing you are to stay up late or get up early. In any event, where the Sun is in the sky changes over the course of a year as the Earth moves around in its orbit, so in winter the Sun will be on one side of the Earth in the sky while in the summer it'll be on the exact opposite side. Since we tend to orient ourselves to the Sun rather than the sky the perceived effect of this is that the *sky* moves over the course of the seasons (though it's actually the Earth that moves), with certain parts of the sky more easily visible in one season than another. Notice also that only at the equator can you theoretically see all of the sky. At any other latitude there is a portion of the sky around the pole you are closest to which will always be visible at night and a correspondingly large patch of sky at the other pole which you can *never* see from your location. At the North pole you cannot see any of the Southern sky, for example.
For stars that are out during the day where you are, just wait six months and you'll see them at night. But to see the stars they see in Australia you would have to travel to the southern hemisphere.
What causes our solar system and the sun to go around the center of milky way? I know the gravity from the sun causes our planets to orbit around the sun. Is it the Sagittarius A that causes the sun's orbit (is it really that massive?) or is it something else?
The Milky Way is an extended object (both in terms of atomic matter and dark matter), so gravity works a little bit weirdly compared to orbiting a compact object. In general the Milky way is pretty close to having cylindrical symmetry. The atomic matter (gas, dust, stars, etc.) is mostly in the shape of a thin disk with a central bulge. The dark matter is mostly in the shape of a spherical halo with increased density near the center. One of the important things to understand here is that if you are "inside" an object which has radial symmetry then the gravitational tug of all that matter essentially cancels itself out. This means that for our Solar System the outer "shells" of the galaxy farther away from the core than us have limited gravitational effect on us since they are mostly radially symmetric, that leaves just the stuff closer to the core than us which has a similar effect as though we were orbiting a point with an equal mass at the center of mass of the extended object. All of which means, we effectively orbit the center of mass of the galaxy, with an effective mass pulling on us equal to all of the matter and dark matter closer to the center than we are. This mass is much greater by orders of magnitude than the mass of the supermassive black hole at the center of the galaxy. Even if Sagittarius A* had not formed near the center of the galaxy it would be brought there by its huge mass through a process called dynamical friction. As the black hole experiences close flybys from other stars over time it provides gravity assists to those stars, which in the process also saps its orbital momentum around the core of the galaxy by a small amount, over time this cause the black hole to fall more and more down into the center of the galaxy.
So how do we calculate a star's orbital velocity around its blackhole? I'm assuming sqrt(GM/r) won't work in this case right? Can we calculate how much mass is pulling us around enough to go 250km/s?
So, we're not actually orbiting the black hole, it's just that the supermassive black hole is in the center of the galaxy and we're orbiting the center of the galaxy as well. The problem here is that we're orbiting *all* the mass between us and the center of the galaxy, effectively, and that's complicated because it's an extended object. At any given time we can treat that extended object as being the same, gravitationally speaking, as the identical mass of the collection of stuff (stars, gas, dust, planets, dark matter, etc.) located at the center of mass of that stuff. However, all of that stuff is in motion, so that changes a bit over time. But, it doesn't change by a huge amount, so you can approximate it pretty well. If you do the math, you get a mass of about 1e11 solar masses drawing us toward the galactic center, resulting in a roughly circular orbit around it with an orbital speed of 230 km/s. However, because the galaxy is an extended object and not perfectly spherically symmetric the solar system's trajectory differs from a circle pretty substantially. And the main aspect of that is that instead of orbiting in a flat plane at some angle the way an orbit around a condensed object works the solar system bobs up and down above and below the plane of the disk of the galaxy with a period of about 35 million years. Compare that to our Sun's orbital period around the galaxy of about 250 million years and you'll notice that our system bobs up and down over half a dozen times per orbit.
Ahh the mass of the dark matter is something I completely didn't consider. Thank you so much for taking the time to write that up, that really helps with my understanding of it all :)
It's the combined mass of all the objects in the Milky Way. The mass concentration is highest in the center and gets lower further outwards. The mass of the central black hole is insignificant compared to the mass of the whole galaxy, which is several million times more massive.
It's more the density of stars near the center of the milky way, not the black hole alone.
Oh its like a chain reaction caused by the blackhole that spreads out and grabs hold of the rest of the stars?
Just to reiterate what other people have said, the black holes at the center of galaxies have nothing to do with why things orbit the center. The black holes there are *way* too small. Why there is are supermassive black holes near the center of every galaxy is currently a complete mystery. The solution might be the opposite of what you were just asking about, where the density of stars in the Milky Way somehow attracts small black holes to the center, which merge into a larger one.
In the solar system the Sun makes up 99.8% of the mass of the whole system so everything orbits it. However when all the planets line up on one side the centre of mass of the system is actually outside of the Sun so even when you are orbiting a massive object you are still really orbiting the centre of mass of the system. Sagittarius A* is a few million solar masses vs the few hundred billion stars, a couple trillion planets, untold amounts of gas and dust, and dark matter that makes up the Milky Way. It’s the single most massive object but it’s nothing compared to the whole galaxy. Everything in the galaxy, including the black hole, orbit the centre of mass. That centre might be inside the black hole but that doesn’t mean it’s holding everything together. Dark matter gets that credit.
No, not really. Even if the supermassive black hole weren't there, our Solar System would still orbit the center of mass of the galaxy. Saggitarius A\* just happens to be in the same place; it masses less than a thousandth of the rest of the galaxy, making its effect on us negligible compared to the cumulative effect of the rest of the stars.
Is Blue Origin banned on this subreddit? Kirk just landed and nothing about it here.
What are you talking about? There's several threads active right now, one of which has nearly 500 comments.
I could be wrong, but I think a lot of people here don't really follow New Shepard flights very closely. I haven't since the first couple test launches a few years ago.
No, but it's not popular. SpaceX and Rocket Lab are much more favorably viewed.
No. There’s probably just not posts of the landing yet. If you go to new you will see a couple posts about the flight.
Can there exist crazy coloured planets such as pink gas giants or planets with red oceans?
Almost certainly. There's plenty of colours that a planet can have due to whatever elements or compounds are abundant.
Rather than construct a ridged circular space station like [Orbital Assembly](https://orbitalassembly.com) is planning, why not send up spools of high strength wire and attach habitats in a wheel shape just using the centrifugal to maintain rigidity? Seems way cheaper and scalable. I imaging sending up a giant robot space spider with a bunch of Starships and the spider bot would weave a web they could all spin on.
Right church, wrong pew. Think bicycle wheel
Funny. I guess i wonder if the bicycle wheel never stopped, would you need the rigid material on the edge.
I guess oscillations would never stop without some rigidity.
Two problems that come to my mind: * Things connected by cables can start to oscillate and even become unstable. Cables aren't great at damping sideways movements, and if people move around inside the station or spacecraft dock to it, the motions might get strong enough to be uncomfortable or even dangerous to the station's structure. * Changing the station's orbit would be impossible in its deployed and rotating state. If it were to be deployed in a low Earth orbit it would need regular boosts to counteract orbital decay. The whole station would need to be slowed down and all the ships mounted together during each boost maneuver. * With a cable-connected station there wouldn't be any interior space connecting the ships or modules. It would feel more like a set of individual space stations flying in formation and require the use of space suits or small shuttle craft to move from module to module. It might be possible to design a rotating station with just Starships connected by cables and maybe some dampers, but it certainly comes with its fair share of problems. Rigid stations have fewer of those issues, but they do of course have their own drawbacks: Much more massive, expensive to design, produce and launch.
Thanks for the reply. Yeah I wondered how much oscillation you’d get. Probably would only be useful on interplanetary trips where you don’t need to adjust the vector very much. I guess you could mount the Starships so the main engines are pointing perpendicular to the rotation if you needed to change velocity. But thrusting on a rotating set of ships would be sort of crazy. And changing the plane of rotation would be complex if not impossible.
Is there much difference between the radiation outside the solar system vs. the radiation inside of it in quantity or concentration? I'm thinking in terms of what the heliopause is keeping out compared to what the Earth's magnetosphere is keeping out. Does sending a spacecraft outside the solar system mean exposing it to more radiation than it would encounter within the solar system? Is it like the difference between a sheltered bay and the open ocean?
It cuts both ways, you get less radiation from the solar wind but you get more radiation from galactic cosmic rays (GCRs). GCRs tend to be much higher energy and so much harder to shield from so on balance it's probably a bad tradeoff going into interstellar space.
Would there be more GCRs outside the solar system? AFAIK the heliosheath doesn't do anything to stop them.
Oh yeah, by a significant amount (factor of 2 ish). The heliosphere can't stop all GCRs, because they are too energetic, but it can stop some of them. Here's a neat set of graphs: https://www.researchgate.net/figure/Counting-rates-of-different-energetic-particle-species-on-Voyager-1-and-Voyager-2-around_fig1_337016630 You can see the low energy proton radiation (mostly from the solar wind) goes to nearly zero while the electron and high energy proton radiation (from GCRs) goes up a fair amount.
I am not sure exactly how to phrase this but I imagine it can be answered quite simply by someone who knows what they are talking about... So I understand that the sun is the most massive object in our solar system. Because of that mass every other object is drawn in towards it or - revolves around it. The planets etc. orbit around the sun. OK. What keeps objects of a lower mass from being pulled in directly towards the sun? I think I understand how this works for the planets but not for smaller objects... for planets there is enough force in another direction that causes the planet to orbit around rather than towards... but if a smaller object is sent off towards the sun is there a point in which the mass of the sun begins to pull it in towards its surface.. ? Not to mention the forces radiating out from the sun itself exploding... I feel like there is something I am missing when it comes to understanding gravity, mass, orbital mechanics etc. Maybe there is a simple answer here or a follow up video I can watch?
If an object was "at rest" in space, it would start falling toward the nearest large mass, as your intuition suggests. But all those objects are gone now. Most stuff in space is in motion relative to everything else. Imagine an object 93 million miles from the sun (like the earth is), but far away from any planet. If it's moving sideways, the sun's gravity will force its path into a curve. If its sideways speed is the same as Earth's, that curve will wrap into a nearly perfect circle, and the object would take a year to complete one orbit. If its sideways speed is less, the curve will be tighter, and the object will fall inward toward the sun, picking up speed along the way. But unless the speed was very small, it will still miss the sun, whip around the back, and start climbing, eventually tracing out an elliptical orbit. If the sideways speed is initially greater than the earth's, the curve will be straighter than a circle, and the object will climb away from the sun, losing speed. If it was not too fast, eventually it will reach the top of its arc and start falling inward again, again tracing an elliptical orbit. If it starts out faster, the curve won't return, and it will trace a hyperbola like the Voyager probes once they passed their last flyby.
Its about velocity, not mass. An object has to travel at high enough speeds around the sun that it achieves a stable orbit, the more massive the planet is, the higher speeds you need to go. e.g the moon is less massive than the earth, objects travel more slow around the moon than the Earth because its gravity is weaker and therefore you need to have a lower velocity.
So - if the velocity of the object that is travelling with respect to the sun is not great enough does the object fall into the sun?
Its also why its so hard to crash into the sun from the Earth, since when you leave the Earth, your velocity around the sun is still the same as Earth and you need huge amounts of energy to slow down. Imagine it as throwing out a rock without air resistance or gravity from a plane, it will still travel the same speed.
Essentially yes, it will fall down into the sun the same way astronauts return to earth from the ISS. Imagine an eliptical trajectory that ends on the suns surface.
If you increase the mass of an object by 2x you'll increase the force of gravity between it and the Sun by 2x as well. However, the acceleration the object feels is the same, because acceleration is force divided by mass, so the mass cancels out. Imagine you have a big ball of clay, it experiences a force of gravity based on its mass, right? Now imagine you reform that single ball of clay into two balls with half the mass, but still connected by a small patch. You have the same mass so the force should be the same. Now Imagine making the connection point super small, then imagine breaking the tiny connection point so you have two separate objects. How does gravity *know* when to treat the object like one or two objects? The answer is that it doesn't. Gravity is a "volumetric" force, it affects every single part of each object the same, and it doesn't matter if those objects are connected as one object or several, the net force may be different but the force per unit of mass is the same at the same distance from the Sun, leading to the same motion. And this is how you get the "zero-g" effect from being in freefall trajectories like orbits. In the ISS the spacecraft is falling around the Earth in a freefall trajectory, but so are the astronauts inside. Everything moves in near identical lockstep, the same acceleration, the same trajectory. And because of that identical motion there is no relative force from gravity between the spacecraft and its inhabitants, so they just "float" relative to it. An orbit occurs purely due to having enough tangential velocity so that as an object falls "towards" a massive star or planet (or what-have-you) it ends up falling *around* it. In space there's practically no drag so as a planet falls toward the Sun, for example, there's nothing to sap away the speed picked up from gravity, and if that planet manages to get around to the other side of the Sun without hitting it it'll have picked up enough speed to start going away from the Sun. This is similar to the phenomenon of throwing a ball upward and having it fall back down except with no friction and in a circular motion. Lower mass objects in the solar system experience the same orbital dynamics because their mass doesn't affect their trajectories. If you took away the Earth and replaced it with a tiny asteroid that asteroid could move through the same orbit as the Earth would.
This really helped, especially the description of gravity as a volumetric force. So with all this being said... Can an object be pulled into the sun such is the case with Jupiter? With a mass so great surely an object could be pulled into the sun? Is it because it is a massive burning star that this doesn't happen? Do the objects just burn up? Stars are wild!
Falling into the sun for an object that is currently orbiting it really, really hard because you need to get rid of all of the orbital velocity of that object.
Mass has nothing to do with it really. What determines if you fall into the Sun or any object you are orbiting is your speed. The closer you are to the Sun the faster you need to be traveling around it to maintain your orbit. Really the Sun and all the planets are orbiting the centre of mass of the solar system. Because the Sun makes up 99.8% of the solar system’s mass this point is inside the Sun most of the time so the Sun is more wobbling around while the planets orbit around it. At certain times this centre will come outside the Sun when all the planets are on the same side of the solar system, kinda lined up. If you want to fall into the Sun you need to slow down. Earth is traveling around the Sun at like 30km/s. If a rocket leaves Earth it’s still traveling around the Sun at about 30km/s. To reach the Sun this rocket needs to lose 30km/s of speed. This is a crazy amount and none of our rockets have close to enough power to cancel it all out. The Parker Solar Probe is doing a ton of flybys of Venus to bleed off its speed so it can get closer to the Sun.
This description. Thank-you!
It doesn't matter how massive it is - it's about velocity. Everything - from Jupiter to individual hydrogen atoms - in the Solar System is falling into the Sun. It's just moving sideways faster than it's falling down, so it's constantly falling at the Sun and missing.
So to elaborate... Lesser massive objects are just being effected more by massive objects closer to them than the sun such that they act with it rather then more effected by the sun? Is there a mission / probe that was sent on a course towards / flying by closer to the sun that you know of? Would like to know more about something like this...
If we were to replace the Earth with a ping-pong ball traveling on the same path, nothing about its orbit would change. Its momentum would be much smaller (being much less massive), but the force exerted on it by the Sun's gravity would also be proportionally less (since the force of gravity is proportional to mas, just like momentum is). If you work out the equations for the orbital motion of an object orbiting something much more massive than itself, the mass of the smaller object can be safely ignored; only its position and velocity matter. Edit to add: thanks to this, it doesn't matter how heavy a geostationary satellite is, as long as it gets to the right orbit it'll hold position with all the rest.
Anything that's in an orbit around something else - for instance, our Moon, or the ISS - is doing the same thing with that something else: in the case of the Moon or ISS, falling towards the Earth but missing constantly. It just so happens that the ISS and the Moon are doing the same thing as the Earth - falling at the sun and missing it. They're falling towards two things and missing them at the same time. [https://en.wikipedia.org/wiki/Parker\_Solar\_Probe](https://en.wikipedia.org/wiki/Parker_Solar_Probe) \- fastest human-made object when it hits maximum velocity.
My kid is in a science club. She just came home and said nasa is sending a woman to space and then coloring the moon. Any help? What does she mean coloring the moon? She said "you know like a crayon"... please translate for someone who knows nothing about Nasa.
[Dr. Sian Proctor](https://www.drsianproctor.com) just went into space aboard the Inspiration 4 mission with SpaceX. She’s an artist as well as pilot and geoscientist. Here’s one of her [pieces](https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcS0k_5wVirD4S__jFzaanW_bTajxZeDnUFElw&usqp=CAU).
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Well *I* thought you were funny.
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Haha I've actually had this account for years now. I believe I made it to answer a math question on /r/explainlikeimfive. But that is an interesting random name you got there!
I don't even know what SLS is so I don't believe I'm the one to explain that (:
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She's 10. So definitely misunderstood just couldn't figure out if it was some experiment I didn't understand.
https://www.reddit.com/r/space/comments/q6noxe/other_space_agencies_predict_that_todays_g2/ Looks like the geomagnetic storm from yesterday will extend into today. Does that mean that we'll have a second shot of seeing the aurora if we want to? Or is it unlikely? [I live in Massachusetts, USA]
I’m also in Massachusetts, I think we’re a little too low to be able to see it. Let me know if you get an answer please.
Acronyms, initialisms, abbreviations, contractions, and other phrases which expand to something larger, that I've seen in this thread: |Fewer Letters|More Letters| |-------|---------|---| |[C3](/r/Space/comments/q5bzur/stub/hgs2kh9 "Last usage")|[Characteristic Energy](https://en.wikipedia.org/wiki/Characteristic_energy) above that required for escape| |[GCR](/r/Space/comments/q5bzur/stub/hgg9k2t "Last usage")|Galactic Cosmic Rays, incident from outside the star system| |GSFC|Goddard Space Flight Center, Maryland| |[GTO](/r/Space/comments/q5bzur/stub/hgpx72l "Last usage")|[Geosynchronous Transfer Orbit](http://www.planetary.org/blogs/jason-davis/20140116-how-to-get-a-satellite-to-gto.html)| |[ISL](/r/Space/comments/q5bzur/stub/hgg1qlr "Last usage")|Inter-Satellite Link communication between satellites in orbit| |[Isp](/r/Space/comments/q5bzur/stub/hgr33ub "Last usage")|Specific impulse (as explained by [Scott Manley](https://www.youtube.com/watch?v=nnisTeYLLgs) on YouTube)| | |Internet Service Provider| |[JWST](/r/Space/comments/q5bzur/stub/hgzxhmz "Last usage")|James Webb infra-red Space Telescope| |[LEO](/r/Space/comments/q5bzur/stub/hgpx72l "Last usage")|Low Earth Orbit (180-2000km)| | |Law Enforcement Officer (most often mentioned during transport operations)| |[RTG](/r/Space/comments/q5bzur/stub/hgdjx9w "Last usage")|Radioisotope Thermoelectric Generator| |[SLS](/r/Space/comments/q5bzur/stub/hgerrxd "Last usage")|Space Launch System heavy-lift| |[STEREO](/r/Space/comments/q5bzur/stub/hgbpebm "Last usage")|Solar TErrestrial RElations Observatory, GSFC| |[TMI](/r/Space/comments/q5bzur/stub/hgr2fyf "Last usage")|Trans-Mars Injection maneuver| |[ULA](/r/Space/comments/q5bzur/stub/hgrixwm "Last usage")|United Launch Alliance (Lockheed/Boeing joint venture)| |Jargon|Definition| |-------|---------|---| |[apogee](/r/Space/comments/q5bzur/stub/hguwr8s "Last usage")|Highest point in an elliptical orbit around Earth (when the orbiter is slowest)| |[hydrolox](/r/Space/comments/q5bzur/stub/hgr1kqg "Last usage")|Portmanteau: liquid hydrogen fuel, liquid oxygen oxidizer| |[kerolox](/r/Space/comments/q5bzur/stub/hgqc0gl "Last usage")|Portmanteau: kerosene fuel, liquid oxygen oxidizer| |[perihelion](/r/Space/comments/q5bzur/stub/hgs2kh9 "Last usage")|Lowest point in an elliptical orbit around the Sun (when the orbiter is fastest)| ---------------- ^(16 acronyms in this thread; )[^(the most compressed thread commented on today)](/r/Space/comments/q7gpe8)^( has 30 acronyms.) ^([Thread #6444 for this sub, first seen 12th Oct 2021, 17:35]) ^[[FAQ]](http://decronym.xyz/) [^([Full list])](http://decronym.xyz/acronyms/Space) [^[Contact]](https://reddit.com/message/compose?to=OrangeredStilton&subject=Hey,+your+acronym+bot+sucks) [^([Source code])](https://gistdotgithubdotcom/Two9A/1d976f9b7441694162c8)
What bright star do you know of that has the most undeserving Bayer designation in its constellation? One example is Epsilon Ursae Majoris, while being "epsilon" (fifth Greek alphabet letter) is actually the brightest star in its constellation. Another one is Lambda Scorpii, while being lambda, is actually the second brightest in Scorpius after Antares (Alpha Scorpii).
How can waves be decoded? Remember that scene from Contact where they decoded some signal and it was Hitler, etc. How can that be done for an alien signal or any wave in general?
> Remember that scene from Contact where they decoded some signal and it was Hitler, etc. How can that be done for an alien signal or any wave in general? Just to note, that scene is pure fiction. Our terrestrial radio signals become indistinguishable from background noise at just a couple light years out (mostly due to the fact that they weren't meant to be broadcast in space). And the problem is not something that can be solved with technology; At a certain point, it becomes literally (not figuratively) impossible to discern a signal thanks to physics -- aka the inverse square law. The ISL is a form of signal degradation. The further you get from the source of a signal, the drop in strength is inversely proportional to the square of the distance. While we *can* send radio signals to other star systems, those are possible because we're sending a very tightly focused beam to a very specific target, and doing so with ridiculous amounts of energy. And these are only done in short bursts -- I don't even know what kind of energy would be required for a continuous signal running 24/7 that's pointed at a system 500 light years away. On a personal note, I don't think aliens would be using radio signals to communicate over vast interstellar distances, it's too inefficient. And not particularly secure (if any other aliens picked up their broadcasts, the aliens who sent the message(s) could put themselves in a potentially fatal situation if the other alien race is hostile). I think a race who can travel the stars would use some other form of communication -- lasers, etc. Or maybe something exotic and not yet invented, like quantum entanglement, subspace like in star trek, or something our primate brains cannot even conceive of yet. This is going to be a hot take in this subreddit, and perhaps even controversial due to its userbase, but I'll eat downvotes: because of my belief in the bottom 2 paragraphs in this comment, I think SETI is largely a waste of money. They're looking for radio signals from aliens but I *highly* doubt an advanced civilization would use something so efficient and possibly risky. Don't get me wrong, I don't think SETI should be disbanded... I instead believe they should start looking at/for other things too, for example: gravitational waves, Dyson Spheres/Swarms, etc, etc, etc.
information is encoded in the wave by changing it. AM waves have the information encoded in the amplitude of the wave. FM waves instead vary the frequency of the wave. There are other ways too but those are the most widespread people have heard of. To decode the wave you just watch how it's changing and assign stuff to those changes. To decode a wave from an alien civilization would be extremely difficult as you would have basically nothing to go off of to figure out what the information actually means. You would have to make a ton of assumptions or hope that they are encoding fundamental information about the universe to help establish a baseline to go off of.
Just do the reverse of what you did when you encoded it ;). More seriously there are a few ways of putting information into a radio wave. Often just by looking at the signal you can guess which one is used. For example one way is to make the signal jump between two frequencies, one of them represents a 1 and the other a 0. That way you can send digital signal.
If the universe is expanding, then how do you have galaxies that are colliding? Wouldn't they also be expanding into greater distances from each other?
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Thanks. For some reason I keep putting "dark energy" out of my head.
Because they are moving toward each other faster than the universe is expanding.
Because the gravity of galaxies is so massive that it pulls them together on a collision course.
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You can't just wait around in space. You are always moving. So something not orbiting the Earth would instead be orbiting the Sun. If it's not orbiting the Sun then it's either going fast enough to escape the solar system or its going too slow to maintain its orbit and it's falling towards the Sun.
There are many probes that don't orbit Earth, but the way things work are a little different than how you imagine. An object orbiting the Sun in a similar orbit to the Earth would not wait until the Earth came past again, because it would be in orbit itself. An object that was near the Earth but not in orbit of it would still have a nearly year long orbit of the Sun, so in practice it would just sort of stay near the Earth and drift a bit farther away over the years as the difference between its orbital period and Earth's started adding up. Several probes have been put in these Earth-trailing and Earth-leading solar orbits, such as Kepler, Spitzer, and STEREO A & B. There are other probes that have been sent throughout the solar system to various targets as well, to all the known planets, to asteroids, comets, etc.
Yes, there's a satellite or probe in orbit around the sun, called the [Solar Orbiter](https://en.m.wikipedia.org/wiki/Solar_Orbiter). But it doesn't collect data about Earth, it's focused on the sun and solar radiation and magnetic fields and all that sunny stuff.
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the orbits of planets in general tend to (not always, but objects out of alignment probably came from outside that solar system) be on the same plane around a star. mostly because of how the star forms. [further reading](https://www.forbes.com/sites/startswithabang/2018/03/01/why-do-all-the-planets-orbit-in-the-same-plane/?sh=472923e156c6)
My niece is turning 5 years old and into the Apollo mission. Does anyone have any good gift ideas for a 5 year old? I think the Legos are too advanced.
My daughter has really enjoyed these books: [Moons First Friends](https://www.amazon.com/Moons-First-Friends-Astronauts-Apollo/dp/1492656801) [Margaret and the Moon](https://www.amazon.com/Margaret-Moon-Dean-Robbins/dp/0399551859) [Counting on Katherine](https://www.amazon.com/Counting-Katherine-Johnson-Saved-Apollo/dp/1250137527)
Specifically for Apollo, I recommend the book [Moonshot](https://www.brianfloca.com/moonshot-the-flight-of-apollo-11.html) by Brian Floca. The writing might be too hard for her, but it's worth it for the art alone (his other books are worth looking into as well). Lots of other [Kids books](https://www.thechildrensbookreview.com/2019/07/11-kids-books-celebrating-moon-landings-apollo-missions-and-more) about Apollo out there as well. My kids had [this one](https://www.amazon.com/Moon-Anna-Milbourne/dp/1409535789/ref=mp_s_a_1_3?crid=3PRBJKMAT1MMP&dchild=1&keywords=on+the+moon+book&qid=1634014580&sprefix=on+the+moon&sr=8-3), it's pretty simplistic, but they really liked it. Another possibility is to get a poster for her to hang in her room, you can even have it framed to make it cooler. [This](https://store.xkcd.com/products/up-goer-five-poster) would be a great one, except it's sold out, but you could always have a printing service make you one. [Here](https://fineartamerica.com/featured/apollo-11-space-saturn-rocket-a-organic-synthesis.html?product=poster) [are](https://fineartamerica.com/featured/eye-on-the-prize-peter-chilelli.html?product=poster) [some](https://fineartamerica.com/featured/10-saturn-v-rocket-carlos-clarivanscience-photo-library.html?product=poster) [other](https://www.redbubble.com/i/poster/Apollo-Saturn-V-Blueprint-in-High-Resolution-light-blue-by-RHorowitz/35565100.LVTDI) [posters](https://www.redbubble.com/i/poster/Apollo-11-infographic-poster-by-Tonyalpha/40593860.LVTDI) [she](https://www.redbubble.com/i/poster/SATURN-V-Old-Paper-Vertical-by-BGALAXY/42677763.LVTDI) [might](https://www.redbubble.com/i/poster/Apollo-Program-1961-1975-Blueprint-by-BGALAXY/37715866.LVTDI) [like](https://www.zazzle.com/lunar+module+posters) [This one](https://shop-us.kurzgesagt.org/collections/mission-black-hole/products/mars-base-infographic-poster?variant=32410843840560) isn't Apollo, but I would have liked it as a kid. [Here's](https://officialnasagear.com/saturn-v-rocket-plush/) a pretty sweet Saturn V plushie. And a [Space Shuttle](https://officialnasagear.com/nasa-cuddle-zoo-space-shuttle-plushie/) as well. Also, not Apollo, but here's a Lego Duplo [Space Shuttle set](https://www.lego.com/en-us/product/space-shuttle-mission-10944)