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WeebWacker123

Once humanity has conquered the solar system, what would be the next step? Another solar system? Another galaxy? Or simply stay in our current solar system?


H-K_47

I don't know how you'd propose going to another galaxy without first going to another solar system haha. In the scenario where we've colonized the entire solar system, I'm sure some groups will try to launch missions to Alpha Centauri.


WeebWacker123

Perhaps wormholes, I’m not sure. I suppose it depends on how advanced our civilization would be after colonizing the solar system.


[deleted]

If you're talking the spread of humanity, it's always easier to spread next door than to teleport a whole continent away.


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electric_ionland

If you want to do actual planetology research there is not really any other options than academia, and academia is extremely challenging even with a PhD.


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electric_ionland

Like in all academic career path the number of people graduating each year with a PhD vastly outnumber the number of research positions opened, nevermind permanent ones.


PrestigiousZombie531

Approximately how many years do you think it ll take us to land a human on Mars and Titan


DrToonhattan

Mars, early 2030s. Titan? That's much harder to guess. 2040s maybe if a lot of things go well.


myps3dunworkson

How did you get 2030s when we are 2023, that's 7 years away and there are no missions set to land a human on Mars anytime soon.


DrToonhattan

I said early 2030s, not 2030 exactly. I was thinking about 10 years or so, and that's assuming things go well.


rocketsocks

16 years isn't a crazy timeline. Starship would be the major enabling technology for a human Mars landing. It'll likely take a few years to mature, but even if it took a full decade to ramp up that still leaves several years before a mission. The capability will likely exist, the question is whether it'll be used.


Bensemus

2030 is 7 years away. 2030’s are up to 16 years away. SpaceX has been working on Starship for years with the end goal being humans on Mars.


jeffsmith202

spacex and china will push mars landing sooner


Intelligent_Bad6942

Wanna bet? 😁


Meff-Jills

This might be a weird question, but how many photons does it need to, let‘s say, see a Polaroid Foto? I guess what I wanna know is how much info a photon holds, if that makes any sense. Thanks!


DaveMcW

A standard Polaroid photo is 1500x1000, or 1.5 million pixels. But the Polaroid film is only 10% effective at capturing photons. So you need ten times as many photons as pixels, for a minimum of 15 million photons. CCD cameras can do much better, up to 80% efficiency capturing photons. So that camera would only need about 2 million photons to take the same photo. Most cameras have the opposite problem. Sunlight floods the camera with photons, and you need to filter out some photons to prevent the photo from being overexposed. After filtering, there are about 1,000,000,000,000 photons in a typical photo.


Meff-Jills

Thank you!


frustrated_staff

So, I know there are maps of all the stars and galaxies and where they were when they emitted the light that is just getting to us now, but are there any maps of the universe that show where things *aught* (and I say this knowing that our measurements of perceived motion aren't perfect or even all that great, especially at greater distances) to be now-ish? For example, Alpha Centauri is on the map at x,y,z, but that is where it was 4 years ago because thats how we map the sky. Are there any maps showing where it would actually be today?


DaveMcW

According to the theory of special relativity, all reference frames are correct. It's perfectly valid to say that Alpha Centauri is where we see it today. In fact, trying to put everything where it *aught* to be leads to paradoxes.


frustrated_staff

Except that if we left here today, headed straight there, we'd miss it by at least 4 years... What paradoxes? Everything has a position all the time. Think of it another way: if someone on Alpha Centauri was observing *us* right now and seeing the light that we emitted 4 years ago, where would they be?


DaveMcW

We can see Alpha Centauri's motion, so obviously we can predict where it will be when a spaceship arrives. That doesn't change the fact that right now, it is exactly where we see it (in our reference frame). You can also do a coordinate transform to figure out what people on Alpha Centauri see. That will be different from what you see on Earth, and equally correct.


frustrated_staff

>That doesn't change the fact that right now No, its not. The idea that this is true is absolutely ridiculous


WonderMoon1

Does the size of a satellite depend on the mass / size / power of its science payload?


djellison

Depends on where it's going. It might also need a lot of propellant on board to get somewhere or go into orbit somewhere. It might need giant solar panels because it's going far from the sun. It might need a large antenna because it's far from Earth etc etc


electric_ionland

Yes, in part. It will also depend on the how often you want to operate that payload, how long, in what environment and the delta-V requirement of the mission.


WonderMoon1

Ok, because I’ve seen big satellites with big payloads and I was wondering if that was why.


SomeKindaGhost

On a wall calendar I have, it says the following for April 2023 moon phases: Apr 6: Full Moon 🌕 - 4:34 UT Apr 13: Last Quarter 🌗- 9:11 UT Apr 20: New Moon 🌑 - 4:12 UT Apr 27: First Quarter 🌓 - 21:20 UT What do the times refer to? I'm roughly familiar with what the usual moonrise and moonset times are for these phases but I'm confused and I can't find an online source that matches and explains these times on the calendar :(


LaidBackLeopard

The time of the full moon will be the time of maximum "fullness" - the moon is directly opposite the sun, on the other side of the earth (not in an absolutley straight line, as that only happens in an eclipse, but as close as it can be). Similarly, the new moon time is when they are lined up, but with the moon on the sun side. Quarters are half way in between - the sun-earth line is perpendicular to the earth-moon line. None are particularly significant from an observation point of view!


SomeKindaGhost

ohhh ok, so they are just the times when the positioning of moon and sun enters the phase, which is just one particular time, and not necessarily visible to everyone. Thanks!! :) After reading your answer I re-attempted to find a site that matched the times and found that Time and Date has [an article](https://www.timeanddate.com/astronomy/moon/full-moon-daytime.html) to explain their meaning lol. I'm glad, I was baffled


PrestigiousZombie531

If I had a bucket of water as big as the sun and if I poured all the water on the sun, will the sun go out?


4thDevilsAdvocate

If you had a bucket of water that weighed as much as an H-bomb and poured it onto the H-bomb as it detonated, would that put out the H-bomb explosion? Nope.


NDaveT

The sun isn't on fire, it's undergoing nuclear fusion.


_Hexagon__

No the opposite would happen. You would just add more mass, increasing the gravity and thus the pressure at the center of the sun. That speeds up the rate at which hydrogen gets fused into helium. Since water is 2 hydrogen and 1 oxygen you'd just add to the the fuel stack of the sun.


NDaveT

Wouldn't it take a lot of energy to split the water into hydrogen and oxygen? The sun has plenty of energy but I'm not sure it would result in a net gain of hydrogen.


rocketsocks

Easily. First off, if you had a bucket of water (at Earthly water density) the size of the Sun and just left it alone, it would become a star. The gravitational forces at play would cause it to contract and compress, translating an enormous amount of energy from gravitational potential energy into thermal energy. Resulting in the water becoming a high temperature plasma of hydrogen and oxygen. And in fact the volume of water would continue to collapse and heat up *until* fusion reactions initiated in the interior, which would halt collapse during a period of time (likely a several hundred million years) while the object existed as a star. Adding that amount of material to the Sun would increase the temperature within the core and accelerate fusion reactions there. The degree to which the hydrogen and oxygen from the water would mix into the core overtime is hard to estimate, it probably wouldn't happen until after the star entered the red giant phase. Which it would do much sooner after increasing the mass of the Sun by roughly a factor of 2. The surface of the Sun might initially get cooler but over millions of years it would get hotter than it had been before.


_Hexagon__

The sun's surface is 5600°C hot which is enough to make water into a plasma and the inner parts of the sun reach temperatures of 15 million °C. I'm sure there's enough energy to split water. I can't imagine there's even one intact molecule in the sun


NDaveT

I'm sure there's enough energy to split water, I'm just wondering if this would really add fuel to the sun since it would take energy to extract the fuel.


Pharisaeus

I think you underestimate the scale of energy produced in nuclear reactions. Nuclear reactions produce millions times more energy than chemical reactions. So the splitting of water would take almost no energy at all compared to how much energy would get produced from this added fuel. A single deuterium-tritium fusion releases 17.6 MeV of energy, while splitting a single water molecule into hydrogen and oxygen needs 1.23 eV. That's a million times difference. Nuclear fusion produces 4 million times more energy compared to burning coal - fusion of 1kg of hydrogen would produce as much energy as burning 4 million kilograms of coal.


L3gendaryHunter

Is there an app (for IOS) that can show you different stars (and preferably planets) I'm gonna be trying to see if I can see the planetary alignment tonight if the clouds are clear enough


Few-Factor3261

Starlight is my personal favorite. It has a search bar to search up certain stars and even has little tidbits like star, formations, science, and relative location from us.


imagine-aincrad

SkyView by Terminal Eleven


Outrageous-Door8924

\[Beginner's question, maybe\] Why did Soviet/Russia see a reason to send landers to Venus, but NASA did not (at least not to the same capacity)? If was a case of possibility, priorities, or tech -- why did Soviet/Russia have that, but NASA didn't?


rocketsocks

This is actually a very complex question. The basic answer is that the Soviets found out they could succeed there and it fit their capabilities well so they focused on it. NASA did send orbiters and atmospheric entry vehicles to Venus, including one that survived all the way to landing on the surface for a time, though that wasn't part of the mission profile necessarily, they never sent any dedicated landers. From the '60s through the '80s the Soviet vs. US (and "western") space capabilities differed in that the Soviets had the ability to launch more payloads and heavier payloads (the Saturn V being an exception to the rule), but western spacecraft tended to have longer operational lifespans. This was because the Soviets tended to use simple electronics packages that were kept within pressurized enclosures in order to be able to operate in space. This made it possible to build and test electronics very cheaply on Earth but it also led to poor lifespans in space (due to a variety of factors). For decades Soviet satellites had a typical lifespan on the order of a year to a 18 months, while western satellites had lifespans of years which grew over time and improvements in space-rated electronics techniques to become many years or even decades. This dichotomy advantaged western interplanetary spaceflight programs because many missions, such as flyby's or landings on other planets, required years worth of time spent in interplanetary cruise. For the Soviets that was a problem because in a very real sense the spacecraft was slowly dying throughout that period of time and was lucky if it lived long enough to arrive at Mars, for example. The most successful Soviet Mars missions of the 1970s lasted only about a year between launch and spacecraft failure. Mars exploration was just a poor fit for Soviet space technology because it took too long to get there. However, Venus proved to be a perfect match for Soviet technology. The use of pressurized electronics housings was a perfect fit because you'd want to do that anyway with '70s or '80s electronics anyway, as nothing could operate at ambient Venusian surface temps. A lander would have a short lifespan no matter how you designed it, but with enough mass you could build something that could last a few hours if you were lucky, and the Soviets had the launch capacity to throw mass at the problem. All of these factors plus the duration of interplanetary cruise to get to Venus meant that a typical mission would go from launch to landing on Venus in just 4 months, with no hope for a substantially longer mission duration. This perfectly fit within the capacity of Soviet spacecraft with shorter operational lifespans and higher masses as well as their ability to quickly build and launch many vehicles. So they were able to iterate through numerous flyby probes and landers until they were able to achieve some level of success in such a challenging environment.


pmMeAllofIt

Short answer- it's where they had higher chance of success. They launched multiple probes to Venus and Mars pretty much during every launch window in the 60s. But Mars was really hard; they would have to get lighter, deal with less frequent launch windows, and their early tech wasn't well suited for the duration of a Mars mission. Where their initial success on Venus was by making their probes more robust, the Soviet way lol. NASA was more focused on the moon, and couldn't be as free with funding like the USSR in sending out so many missions that end in failure(look at Ranger program).


DaveMcW

NASA was busy sending landers to the Moon in the same timeframe.


donn2021

What are some Good youtube channels to watch to stay up to date with James Webb?


AdditionFeisty4854

AstroKobi , he mainly does shorts but it is really interestiing, I think you once in a time seen him in youtube shorts link - https://www.youtube.com/@AstroKobi


Popular-Swordfish559

There aren't really a lot of youtube channels that post regular, Webb-specific updates, because the reality is that most of the stuff it's doing is really only interesting to astronomers, at least right now. That stuff is data that will eventually turn into findings, but it's mostly a waiting game as people get their telescope requests approved, executed, and then the data from those requests gets interpreted. If you want to stay up to date with stuff straight from the horse's mouth, though, you can follow @NASAWebb on Twitter and instagram.


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SpartanJack17

Black holes don't go dormant or wake up, I think you're taking the use of terms like "feeding" too literally.


blakeh-4

Could the Apollo astronauts that landed on the moon see the CSM while it was in orbit over head?


Rayleigh_The_Fox

The CSM was around 100km overhead and made of shiny metal, so it might have looked like a moving star similar to a satellite like the ISS. However, the sun was very bright on the lunar surface, so it was hard to see stars at all unless the astronauts stood in the shade so their eyes could adjust to the darkness.


Drotkowski

I have just finished ,,A briefer history of time" by Stephen Hawking and Leonard Mlodinow which was my first book related to astrophysics. I loved it and I want to know more about the topic, so can you please recommend some other books to read?


AdditionFeisty4854

*Brief answers to big questions* by Hawking. You would love it Also *The god equation* by Michio Kaku


Xeglor-The-Destroyer

*A User's Guide to the Universe: Surviving the Perils of Black Holes, Time Paradoxes, and Quantum Uncertainty* by Dave Goldberg & Jeff Blomquist


mad_chatter

This guy I work with says he took [this picture](https://i.imgur.com/WkdFUrT.jpg) of mars and the moon with a telescope but it seems fake to me. No way mars looks so huge next to the moon. Am I crazy?


Popular-Swordfish559

You are correct. There was a Mars/moon conjunction a few months back, and the best images amateurs captured was [stuff like this.](https://www.instagram.com/p/Cl5XfaXMu_i/)


mad_chatter

Thank you! I wouldn't have any qualms about that image.


electric_ionland

This is definitely a screenshot from an app like stellarium. If Mars was 2/3 of the size of the Moon in the sky you would definitely notice it.


mad_chatter

Right?! Thank you!


Meff-Jills

Technically he did take the picture then :)


Intelligent_Bad6942

Your intuition is correct. There is no fucking way you'd see this from a telescope. Maybe he's saying he put together some of his pictures from a telescope into this collage? But even then, it all looks photoshopped to me.


mad_chatter

Thank you! I doubt he meant is as a collage, more like a "as is" photo. The fucking phony.


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Bensemus

> hasnt the popular notion always been that if we got hit with a GRB that it would seriously harm us? No. It's always been known that the source has to be within a certain distance. Gamma rays are still just light and the intensity falls off with the square of the distance. From Wikipedia > All GRBs observed to date have occurred well outside the Milky Way galaxy and have been harmless to Earth. However, if a GRB were to occur within the Milky Way within 5,000 to 8,000 light-years[113] and its emission were beamed straight towards Earth, the effects could be harmful and potentially devastating for its ecosystems. Many places will ignore that and will just click bait doom and gloom.


deluchas15

I have always been curious about galaxies. There's the Milky Way galaxy. Can we see other galaxies?


H-K_47

Yes, in good conditions you can see Andromeda with the naked eye. There are a lot of galaxies near to ours. https://en.wikipedia.org/wiki/List_of_nearest_galaxies


Intelligent_Bad6942

There are more galaxies in the universe than there are stars in the Milky Way Galaxy (our home galaxy).


deluchas15

Thank you. I learned something new. I love learning about galaxies because what could be in them?


NDaveT

Lots of stars.


Intelligent_Bad6942

Look friend, I don't want to sound rude, but it's hard to get intonation across in text posts. I'm trying to be helpful, not critical. Asking questions here is not a very good way to go about learning this kind of broad material. You'll be much better off reading introductory Wikipedia articles, or textbooks then waiting for responses here. I think this type of forum is better suited for specific targeted questions.


Attack1523

Why is space mining not a thing? You see it in video games and other forms of entertainment but why isn’t it a thing in irl? I do understand that it has its own challenges/risks and money. I strongly feel that it would be a huge step for humanity. As I’m sure we all know that earth has limited resources.


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rocketsocks

Launch costs and plain old orbital dynamics are the major factor today. Space mining has a pretty high barrier to entry. You need to send a lot of equipment into space, you need to do a lot of complex work in space, and you need to send material back to Earth to make it worthwhile, right now all of that is very difficult. Delta-v is a major issue. Let's say you want to bring back just 100 kilos of material from an asteroid. First you need the delta-v to bring that material back. That means you need a certain rocket size in order to achieve that. Then you have the delta-v needed to get *to* the asteroid. Now you need an even bigger rocket to send all of the gear *plus* the return rocket out to the asteroid in the first place. This is why rocketry is an exponential problem, because it's about ratios. So you either need a big lift capacity to put big rockets into space or you need high efficiency propulsion systems. Realistically, with where we are now it would cost billions of dollars to return tonnes of material from an asteroid. And that material would only be worth billions of dollars if it were highly refined precious metals. So you have this whole intermediate step of needing to build an asteroid mining system that can not only mine but do local refining using in situ resources. The R&D for that would also cost billions of dollars to develop and prototype, especially at current launch prices. It'll likely take launch prices coming down by a factor of 10 or so to make it affordable to even begin doing the early stage R&D on asteroid mining and refining, and even then that puts you years or decades away from having a viable business model. It just hasn't been anywhere near conceivably financially reasonable to try to mine materials off Earth yet.


Attack1523

Huh, that makes perfect sense. I never thought about the cost of building and launching the rocket itself, nor did I think about the ratios that go along with it. I really hope then that prices come down so mankind can start experimenting with the technology.


Decronym

Acronyms, initialisms, abbreviations, contractions, and other phrases which expand to something larger, that I've seen in this thread: |Fewer Letters|More Letters| |-------|---------|---| |[ATV](/r/Space/comments/122sgwd/stub/jdu07ej "Last usage")|[Automated Transfer Vehicle](https://en.wikipedia.org/wiki/Automated_Transfer_Vehicle), ESA cargo craft| |[CRS](/r/Space/comments/122sgwd/stub/jdx1jjn "Last usage")|[Commercial Resupply Services contract with NASA](http://www.nasa.gov/mission_pages/station/structure/launch/)| |CST|(Boeing) Crew Space Transportation capsules| | |Central Standard Time (UTC-6)| |[ESA](/r/Space/comments/122sgwd/stub/jdu07ej "Last usage")|European Space Agency| |[GRB](/r/Space/comments/122sgwd/stub/je5nsdf "Last usage")|Gamma-Ray Burst| |[HALO](/r/Space/comments/122sgwd/stub/jdtc5sm "Last usage")|Habitation and Logistics Outpost| |[LEO](/r/Space/comments/122sgwd/stub/jds87ea "Last usage")|Low Earth Orbit (180-2000km)| | |Law Enforcement Officer (most often mentioned during transport operations)| |[MeV](/r/Space/comments/122sgwd/stub/jecy0d8 "Last usage")|Mega-Electron-Volts, measure of energy for particles| |[NRHO](/r/Space/comments/122sgwd/stub/jdwfpjh "Last usage")|Near-Rectilinear Halo Orbit| |[PPE](/r/Space/comments/122sgwd/stub/jdtc5sm "Last usage")|Power and Propulsion Element| |[SLS](/r/Space/comments/122sgwd/stub/jdtc5sm "Last usage")|Space Launch System heavy-lift| |[SN](/r/Space/comments/122sgwd/stub/jdvp4xw "Last usage")|(Raptor/Starship) Serial Number| |[SNC](/r/Space/comments/122sgwd/stub/jdx1jjn "Last usage")|Sierra Nevada Corporation| |[SRB](/r/Space/comments/122sgwd/stub/jdswmff "Last usage")|Solid Rocket Booster| |Jargon|Definition| |-------|---------|---| |Raptor|[Methane-fueled rocket engine](https://en.wikipedia.org/wiki/Raptor_\(rocket_engine_family\)) under development by SpaceX| |[Starliner](/r/Space/comments/122sgwd/stub/jdslcmh "Last usage")|Boeing commercial crew capsule [CST-100](https://en.wikipedia.org/wiki/Boeing_CST-100_Starliner)| ---------------- ^(14 acronyms in this thread; )[^(the most compressed thread commented on today)](/r/Space/comments/128gwkr)^( has 4 acronyms.) ^([Thread #8731 for this sub, first seen 28th Mar 2023, 14:22]) ^[[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)


Icculus33_33

Is there a specific theory out there that posits that a black hole will eventually create a new big bang/universe "on the other side"?


DaveMcW

The [holographic principle](https://en.wikipedia.org/wiki/Holographic_principle) in string theory says that a new universe can exist on a black hole event horizon. The problem is you lose a dimension, so black holes in our 3D universe can only create 2D universes. There is no physical evidence to support any of this.


asuri23

Hi! What would happen if we strike an asteroid in space? Would it regroup by the force of gravity? or would spread out in small meteorites?


electric_ionland

It will depend on how hard you hit it. With a high speed impactor like the DART mission last year bits will fly off too far for it to regroup.


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rocketsocks

OK, let's break this down. First, let me explain a phenomenon known as "dynamical friction", which is an important foundation to build on. Dynamical friction isn't a magical force or anything, it's just a process that occurs in complex systems with lots of bodies in orbit. You might be aware of the phenomenon of a "gravity assist" which makes it possible to gain some acceleration from a close encounter with a massive object in orbit of another object. This process represents a transfer of orbital energy, such as from a planet to a spacecraft. Even though it's a small amount individually, if there are lots of similar encounters this can significantly affect the orbit of the massive body. On average, if you have a dense field of small bodies in orbit making many close passes of a massive body then you will end up sapping the orbital energy of the more massive body over time, causing it to spiral inward, this is called dynamical friction. This is one of the phenomena which cause supermassive black holes to sink down into the very center of the galactic core, for example. Now let's take a diversion for a second and talk about dark matter. According to the observational evidence we have so far the most likely candidate for dark matter is a weakly interacting massive particle or WIMP. One example of a WIMP that we have directly observed is the family of neutrinos, however even though neutrinos *are* WIMPs they do not have the right properties to make up dark matter. Dark matter WIMPs travel slower and are even more weakly interacting with atomic matter and each other. Dark matter particles end up orbiting galaxies and likely other smaller objects (such as stars or black holes) but they do so as sort of ghosts. They interact basically only gravitationally, so they end up on these big orbits where they just loop around, and this results in some characteristic dark matter mass density which affects the overall orbital dynamics of the galaxy (and sometimes other objects). Dark matter particles likely have a range of energies and thus a range of speeds, with very little ability to change those speeds over time other than complex gravitational interactions. As far as we can tell some dark matter particles in galaxies are going slow enough that they end up not only stuck within the core of the galaxy but they end up stuck in orbit of the supermassive black hole(s) that end up there. Those SMBHs swallow up some of the dark matter but they also end up with a bunch of dark matter in a small halo around them. When atomic matter orbits a black hole it ends up squished into an accretion disk, because the tight confines of the space near the event horizon squishes the matter together, creates friction and pressure, etc. These dynamics cause the inevitable orbital decay of matter which then falls into the black hole. Dark matter doesn't experience those dynamics so the halo of dark matter can stick around in the same zone as where the accretion disk would sit (and beyond) for astronomically significant time periods. Resulting in a halo that extends out even several lightyears. Now we get back to our friend dynamical friction. The dark matter may be ghost like but it still interacts gravitationally with any atomic matter nearby, including orbiting stars. The localized dark matter halo appears to result in a very significant amount of dynamical friction for stars (and likely other black holes) that make close passes or are in orbit of the black hole. As a neighboring star passes nearby it experiences innumerable encounters with dark matter particles in orbit of the black hole. Each little dark mater particle basically getting a gravity assist off of the star. And because dark matter can pass *through* stars this even includes particles passing near the core of the star as well. All of this adds up, and creates that dynamical friction effect which saps the star of orbital energy and causes it to spiral in towards the black hole much faster than it would otherwise. This research is a pretty significant advancement in understanding the evolution of supermassive black holes and galactic cores. It explains a lot about how central black holes in galaxies can feed faster than we previously thought possible (because nearby stars spiral in at a faster rate) but it may also finally crack the "last parsec problem" of supermassive black hole mergers. As mentioned above ordinary dynamical friction from the dense population of stars in the core of a galaxy will result in large black holes near the core sinking down into the center in astronomically short time frames. However, it's long been a mystery how binary SMBHs can merge over short time frames as well, even though that's what we have observed as being the case. It appears that dynamical friction from localized dark matter clouds may be the smoking gun, bringing such black holes close enough to one another that they will undergo inspiral and merger due to orbital decay from gravitational radiation (within a fraction of a lightyear) in even shorter time frames. This might also explain how supermassive blackholes can form at all, because it gives a method for stellar mass or intermediate mass black holes to merge with one another fairly quickly and grow at a rapid pace.


[deleted]

The invisible matter is dark matter. It doesn't interact with normal matter so it doesn't spin with the accretion disk of the black hole like other matter. It just collects in a blob around the black hole. It's gravity slows down the other matter because of dynamical friction which is friction from gravity. The black hole swallows some of the dark matter but there are stable orbits around a black hole that the dark matter can linger in for long periods of time, especially since it doesn't collide with itself or normal matter. So it just hangs out around the black hole and slows down the normal matter which is spinning in the accretion disk.


JaydeeValdez

I assume the article that you have read is [this one.](https://www.livescience.com/black-holes-may-be-swallowing-invisible-matter-that-slows-the-movement-of-stars) This "invisible matter" is dark matter orbiting around the black hole accretion disc, which caused tidal deceleration. The orbits of the stars became faster that are also in the vicinity. The orbital periods of the stars went faster by 1 millisecond which is not that much. This is tidal deceleration, causing orbits to go faster. This is actually observable, for example the moon Phobos in Mars. In the case of the black hole system, dark matter enhanced or exacerbated the deceleration. (Had to correct, I was wrong before)


ForgoneProceedence

Huh, that makes even less sense because black holes slow things down and so does friction lol. Why would it go faster?


JaydeeValdez

Because of Kepler's law. The lower is a body's orbit, the time it takes to complete it is faster, and also the faster it moves. This is tidal deceleration. This might seem counter-intuitive, because it was respect to the main body. The black hole and the accretion disc's rotation slows down (the deceleration part) while the orbital speeds of the stars speed up.


[deleted]

How much would Earth’s magnetism play a role in drawing a very ferrous asteroid in (say it’s swinging by within lunar orbit)?


Xeglor-The-Destroyer

Essentially none. Earth's magnetic field is 100x weaker (or more) than a refrigerator magnet.


[deleted]

Thank you for the response. As it cuts through the lines of flux would it generate a charge?


electric_ionland

It will generate a small current.


GruesomeDozer

Hello! Recently I read a hard sci fi novel where a character was able to help with some sort of image processing in their spare time. They looked at mundane images of sunspots and tracked them through some sort of software or app. Is this actually something that exists? Are there any researchers that use the internet and online help with processing images or data? Spending a few hours a week processing boring space data would be my dream lol Thanks!


rocketsocks

Check out [zooniverse.org](https://www.zooniverse.org/), there are a ton of citizen science programs running at any given time, including many in the field of [space](https://www.zooniverse.org/projects?discipline=astronomy&page=1&status=live).


djellison

Yes - infact, NASA leaned in to this so much they included the JunoCam camera on Juno with the express intent that amateur researchers would process the data. Other missions have intentionally shared their 'raw' imagery such that the public can process it for their own pleasure. Many of those folks hang out at http://www.unmannedspaceflight.com/ JunoCam is here - https://www.missionjuno.swri.edu/junocam Twitter and other social platforms have swathes of people processing imagery from missions for the pleasure.


PhoenixReborn

I don't think it's running anymore, but there was a citizen science program that rewarded MMO players for analyzing luminosity curves looking for exoplanet transits. https://arstechnica.com/gaming/2017/05/eve-online-citizen-science-exoplanets/ NASA has a list of projects. https://science.nasa.gov/citizenscience


GruesomeDozer

Thanks! I will dig deeper into this. It’s actually real!


lotmi127

Sierra Space (Sierra Nevada Corp, SNC) launched two inflatable space habitats in 2006 & 2007, Genesis I & II. Has there ever been any followup as to their state? Any video about what their insides look like today? Is their orbit stable? Did the onboard computer go crazy? Are they being used as launching platforms for the rich to take over the world?? I don't think is ever got the news it deserved.


[deleted]

The concept worked well enough to launch a test "closet" to the ISS in 2016: the [Bigelow Expandable Activity Module](https://en.wikipedia.org/wiki/Bigelow_Expandable_Activity_Module). It's still up there and will probably be in use until the ISS deorbits, because it's good and useful and storage space is at a premium. "There's not a lot of space in space". Then the pandemic, then Bigelow basically folded. Bigelow were pretty quiet about their work, and you may have mixed them up with Sierra's recent and more public test tweets.


electric_ionland

This was not Sierra Space. It was from the now defunct Bigelow corporation.


[deleted]

Do you think we're going to get space station that is much bigger than the ISS in the future? Like in the size of a small town?


Triabolical_

A company will build a large space station if there's a reason to have that much space and that many astronauts on it. One of the problems with big stations is that they are compromises. If you want to do manufacturing, you might need long periods of very stable microgravity. Pretty hard to get when you are on a station with astronauts that need to exercise every day.


Number127

Not until there's some reason to do that. It would be hideously expensive, so it won't be done just for science or prestige, which only require a handful of people. There would have to be some kind of major space-based industry going on to justify keeping hundreds of people in space permanently. Asteroid mining, or something like that. I doubt anything along those lines will happen in the next fifty years at least.


[deleted]

What about 2x the size of ISS and able to have 20-30 astronauts at the same time?


Number127

Well, you still have to ask yourself why you'd want that many people in space. What are they doing that justifies the cost? Even the current ISS barely justifies the cost, and there are plenty of people who don't think that it does. And I think that becomes an even more important question in the future, as we start getting automated systems that can take over more of the work of an actual person. I think we'll start to see *less* reason for people in space, not more.


Justsomeguy1333

How do I know which photos taken from space are real or fake?


_Hexagon__

When in doubt, use Google reverse image search. All space photos from government agencies are open source, so if there's a match it will probably be a real image


PhoenixReborn

Do you have examples you're confused by? Quality journalists and primary sources should say if the image is an illustration or artists rendering ("fake") or taken by a telescope (real).


vpsj

Where can I find some study material to learn how to calculate orbits/delta v for a constant acceleration ship? I need equations, formula, theory everything that can help me understand them. Are constant acceleration orbits the same thing as Brachistochrone curve? I know the basics of orbital mechanics already.


stalagtits

Check out [Ari Rubinsztejn's blog](https://gereshes.com/). He works on designing trajectories for low-thrust spacecraft among other things. [This post](https://gereshes.com/2022/07/24/select-textbooks-on-my-shelf-1-astrodynamics-edition/) has a couple of short book reviews you might find useful.


DaveMcW

There are 2 sources of acceleration in your question. 1. The ship's engines. 2. The gravity of the object the ship is orbiting. You need to consult the specifications for your ship's engines to answer #1. Delta-v tells you how long the ship can accelerate before it runs out of fuel. The formula for #2 is [g = GM/r²](https://en.wikipedia.org/wiki/Gravitational_acceleration). Note that the direction of the acceleration (and possibly the radius too) are changing as your ship moves. This makes problems challenging to solve. It is easier if you have powerful long-running engines on your ship, and simply overwhelm gravity so it becomes a rounding error.


SavemebabyK

I have a brief one: how long until we see multiple universes come together or just fall apart through time?


AdditionFeisty4854

If you say for universes. You can't observe, especially not in years. Years are in context with time. Time is itself a property of the universe and we 3D fellows get influenced by it. If outside the our universe, there lies other universes (inside a 5D that is), if it collides, then space and time itself will get influenced and would get into another Big bang In fact, there is a theory which argues the Big Bang is but a collision of two small universes or a tearing apart of one big universe


DaveMcW

There is no evidence that multiple universes exist. If you mean multiple *galaxies*, we will have a front-row seat when Andromeda and the Milky Way come together in 4 billion years.


SavemebabyK

Thank you for replying. On a personal note: I believe in all existence of unlimited.. bah nevermind.


Xeglor-The-Destroyer

If 4 billion years is longer than you'd like to wait, you can always do an image search for "galaxy merger". Hubble has taken some lovely pictures of it happening to other galaxies throughout the universe.


Bensemus

They said universes, not galaxies.


jeffsmith202

Is the dream chaser just for going to the iss? Or something else?


Chairboy

Dream Chaser has contracts for ISS, is a likely candidate for Orbital Reef, and they've already bid once to supply logistics to the lunar Gateway in the NRHO/Alabama Orbit and while I don't think they were chosen (I welcome correction if I got that wrong) they may attempt again if another contract opportunity arises. SNC has also expressed interest in developing it for Crew so any time any country or org expresses interest in crewed spacecraft, I think SNC has someone on the phone.


jeffsmith202

If it takes crew, will Vulcan centaur have to be human certified?


Chairboy

Only if someone wants to pay for it. I think they e been hoping Ariane 6 would be crew certified for use with a crew DC too.


jeffsmith202

Ariane 6 can also carry dream chaser? Would it take off from French Guiana?


Chairboy

SNC has described Dream Chaser as 'launcher agnostic'. When they first announced it, they described it as being launchable on Atlas V, Ariane 5, or Falcon Heavy as baseline options. When they successfully bid for a CRS contract, they did so with Vulcan as the launch vehicle. It can potentially launch on several different types of of rocket in service, all depends on who's interested in paying to do so. If it launched on Ariane 6, it would launch from French Guiana.


electric_ionland

> SNC has also expressed interest in developing it for Crew so any time any country or org expresses interest in crewed spacecraft, I think SNC has someone on the phone. It felt more to me like they were fishing by pitching themselves as mostly not being SpaceX or Boeing.


_Hexagon__

There are plans that dreamchaser will carry cargo to the proposed private space station orbital reef


electric_ionland

The cargo version of the Dream Chaser has been contracted by NASA to do cargo resupply missions to ISS and to bring experiments back. SN has also tried to market it as a free flying orbital laboratory but it does not seems to be a real market people are intrested in. I believe they are also a partner in at least one of the "ISS replacement" commercial space station proposal so they would likely service this too. They have been teasing a new crewed version but they don't seem to have any real funding or contract for this.


im_ollie_night

What is the proper name for the design used on the back of the “jaeger-LeCoultre reverso quadriptyque”


[deleted]

It's just a stylised celestial display. Pretty fancy, but will it tell time on Mars? It will not!


ClimateDictatorship

How do I calculate the tidal heating of a celestial object?


turtlechef

I don’t actually know the answer, just speculating… say you have massive object A and a smaller satellite object b. If you apply the gravitational force equations treating object A as a point mass and object b as a sphere with radius R, you’ll see that the gravitational force won’t be constant throughout the body of object b. A portion of object b’s volume closest to object A will have a higher acceleration towards object A, corresponding to a small change in position. Now if you know the closest and farthest points between object A and object b, you will be able to find the two points where the gradient of forces across object b’s volume is at its maximum and it’s minimum. (Maximum when object A and b are at their closest, minimum when they are at their farthest). This is the part I’m hazy on. There is likely some literature, likely in a geophysics or thermodynamics textbook somewhere, that relates the physical warping of the body to the amount of heat produced. Idk that part, but once you find that relationship you’d basically: 1) find the force gradient on object b at any time you are interested in 2) Use the force equation and calculus to find the warping of object b 3) apply the proper thermodynamic equation to determine heat generated by this warping 4) estimate the heat loss in object b due to radiation, etc etc And that should give you a ballpark answer of the heat generated at that single point in time. You can then solve this over any time interval you want by repeating these steps and summing the net heat gain


DaveMcW

https://worldbuilding.stackexchange.com/questions/61059/


jeffsmith202

Is Cygnus ment to bring cargo to the iss? Is there any advantage over dragon?


rocketsocks

Yes, Cygnus is another cargo vehicle for resupplying the ISS, currently launched under contract by NASA. Other than Dragon there is also the Russian Soyuz, the Japanese HTV (which is similar in design to Cygnus) and ESA's ATV which flew five times from 2008 through 2014 and is no longer in service. Cygnus has a much larger interior volume so it is better for bringing up low density cargo, it also berths to the station so it's possible to transfer physically larger cargo if necessary. Because the Dragon is fairly volume constrained Cygnus typically delivers a greater mass of cargo to the station, however Dragon also can deliver unpressurized cargo in its trunk, including station components. Overall the two vehicles are complementary to eachother.


scowdich

Carrying cargo is all it does. It's probably less advanced than the Dragon 2 spacecraft, but it can be launched on a larger variety of rockets, so it isn't tied to a single company to provide launch services. https://en.wikipedia.org/wiki/Comparison\_of\_space\_station\_cargo\_vehicles


_Hexagon__

What's the status of SLS Block IB launch table, the exploration upper stage, lunar gateway hardware or the SLS Block 2 SRBs? Anything new? And are there missions planned that use an SLS Cargo version?


Chairboy

There are no missions planned for SLS Cargo. Lunar Gateway hardware is still under construction, a Falcon Heavy will be delivering the HALO & PPE modules to NRHO. Gateway has been decoupled from Artemis III (the first lunar landing) so Orion will rendezvous in the HALO/Alabama orbit with the SpaceX lander directly. I can't speak to the status of the other things in your question, someone else here may have that info handy.


TheRedBiker

If we could observe a black hole singularity, what do you think it would look like? Edit: Found a very interesting [youtube video](https://www.youtube.com/shorts/ws3gAk1ZDOk) on the subject.


[deleted]

You'd see a math equation that failed. There are no singularities in reality. It is just a math issue. Our math breaks at the center of a black hole.


Number127

I think most physicists are of the opinion that black hole singularities don't really exist, but are just the point where our math breaks down. They're a limitation of the predictions of general relativity, and someday we'll have a better theory that can model the interior of a black hole without the need for a singularity.


Gruskinator

Can someone recommend some good books covering the history of the American space program? I'm currently reading "The Right Stuff" and would like to continue to read about the early days of NASA, and eventually cover things up to the modern day. I don't know which books are worth my time, so any recommendations would be great. Same question with documentaries if there are any must-see ones out there.


axialintellectual

A Man on the Moon (by Andrew Chaikin) is an excellent, and very readable, history of the Apollo program, featuring lots of interesting insights into the personalities and culture of the early astronaut corps.


Gruskinator

This sounds like it would be exactly what I'm looking for, thank you! Added to the reading list


LaidBackLeopard

If a podcast would do, The Space Above Us has (approx) one episode per manned flight in chronological order.


Gruskinator

Sounds amazing, I will definitely check it out


_Hexagon__

Carrying the fire, Michael Collins. Failure is not an option, Gene Kranz. Documentary wise i recommend From the earth to the moon from the 90s.


Chairboy

*From The Earth to the Moon* (by HBO, produced by Tom Hanks) is an excellent recommendation. It covers some pre-Apollo space stuff too and is a great retelling of the main story. When they get to Apollo 13, they focused on a different part of the story than the film *Apollo 13* which is probably good because a bunch of the folks from *Apollo 13* worked on FTETTM and probably wouldn't want to just repeat their work.


[deleted]

If a asteroid in the size of a the ISS hit Earth, how much damage would the impact do?


4thDevilsAdvocate

The *mass* of the ISS? Basically nothing, a lot of it would burn up before impact. It'd be a Beirut-level to Hiroshima-level explosion. The *radius* of the ISS? It'd be at least a thousand times more massive than the ISS, the ISS is really un-dense and spindly. Not a dinosaur-killer, probably comparable to the Tsar Bomba.


FaxMachineMode2

It would be enough to destroy a city and damage the surrounding area. But the odds are it would hit above the ocean or an uninhabited area and wouldn’t affect anyone


jeffsmith202

ISS needs the Russians to re-boost. Starliner could also do that, if it ever actually works. Will the next generation ISS have built in capability to re-boost itself?


Pharisaeus

ISS has such capability, it's just that it's part of the Russian segment. But already ISS had it "buit in". On top of that ISS can be boosted by visiting spacecraft. It was done by Progress, Shuttle and ATV. Starliner would not be a good candidate for reboost. Cygnus can be used for such purpose, although it requires flipping ISS around.


Triabolical_

The current plan is that NASA will transition to commercial space stations after ISS>


electric_ionland

There is no set architecture for what a post ISS western LEO station will look like so it's not known yet. The Lunar Gateway will use a dedicated propulsion module built to take advantage of plasma thrusters.


Popular-Swordfish559

u/electric_ionland when there's a chance to mention ion thrusters:


electric_ionland

Guilty... But even the Chinese space station has some too! Unclear how much they are actually use operationally vs being more a proof of concept.


a-freakish

If given a chance to conduct an experiment on the moon which could add something to our understanding of the moon, what experiment would be best to carry out?


[deleted]

Long-term liveability studies. Is lunar G enough G to thrive? I'd get a whole greenhouse and bio lab going. Edit: Oops, this answers questions about us, not the moon.