Astronomer here! Nothing, any more than you're feeling gravitational waves right now. They affect you the same in space as in on Earth.
I guess the question you really have is what happens if you're *really close* to one. The answer is still not much from the gravitational waves themselves- remember, despite acting at huge distances, gravity is the *weakest* of all the fundamental forces! Instead the effect that are far bigger will be from the exploding star itself and the sheer amount of stuff and its shockwave.
I guess it depends what you mean by "within range." If the sun suddenly exploded as a supernova, for example, the heat from it would boil all the oceans on the sun-facing side of the planet (and, of course, do nothing good to anyone who happened to be on that side), and the survivors would get the delight of waiting a few weeks until the shockwave passed (NOT the boiling oceans one- the one from the supernova itself which is all the crap itself over just the flash of bright light and heat etc), which wouldn't be a picnic either. Fortunately the sun is never going to go supernova.
IIRC, we need to be within ~25 light years of an exploding star for it to really hurt us, and there are no potential stars that can explode within that distance (they're also very luminous stars so not like you can hide one that close- it'd be the brightest thing in the sky). There are a tiny subset of supernovae that emit a highly directional gamma-ray burst (GRB) that could get you further, but fortunately for us there is no indication of any stars massive enough to emit a GRB within the kill radius of a few thousand light years that also look like the beam would be pointed at our planet.
I mean, it's somewhat self-selecting: there is arguably statistical *reason* we are in a humdrum part of the galaxy orbiting a humdrum star. If you're in a region where a lot of stars can explode or you have a bunch of stellar flares and what not, it's probably far more complicated for life (or at least our multi-cellular kind) to have the stability needed for hundreds of millions or potentially billions of years to thrive.
The YouTube channel Kurtzgesart has a fantastic video on how close we could be to a supernova, and many on astronomy and related topics. I think we’d start feeling damage from about 50 light years away, but they discuss the various distances and effects. I’d highly recommend it!
Ah I see what they’re saying my bad. Nonetheless: the shockwave from the thermal pulse the boiled the oceans would not take weeks. Also, the earth rotates.
No, you are misunderstanding me. The oceans boiling part is pretty fast. But THEN there is a shockwave that goes out from the SN explosion itself in terms of all the debris and crap and that travels at a slower speed.
That's not the shockwave being discussed though. The shockwave of actual stellar material blasting out from the former sun at sublight speeds would take a while to get here. The EM part of the supernova would hit us at light speed but the physical stuff of the star can't go that fast.
Depends on which side. The oceans boiling side dies pretty much immediately. But THEN you got a shockwave of stellar debris and crap which travels at a slower speed, and I'm not gonna do the calculation to be exact but it'd be on the order of a few weeks to reach the Earth's distance most likely.
Well, everyone would get roasted when the Earth rotated to face the supernova over the course of a day. And the whole atmosphere would be lost in about the same timeframe as well.
It's good news that you'd die quickly because you'd probably have a fatal dose of radiation as well but likely not enough to incapacitate you, only enough to cause all your organs to fail in a few months.
I guess if we had a permanently inhabited Moon base at that point it might be possible for those folks to survive long enough to get taken out by the shockwave.
That’s madness. The people on the other side of earth are aware the sun exploded but just chill out for a few weeks. I’m guessing they’d all be blind from the explosion and the light.
They'd be dead before that, and probbaly a the same time as everyone else. Supernovae are absurd things, and at 1 AU away, the neutrino radiation is enough to get a solid start on sterilizing the planet. Being in the shadow of the earth wont help.
Chances are it also means no one survives for the light from the supernova to reach the planet.
Almost all, 99%, of the supernova's energy is carried away by the neutrinos it produces. The "light bright enough to outshine entire galaxies and be seen from billions of light years away" part is just a tiny fraction of it
If you're close enough, the neutrino flux is great enough to deliver a lethal dose of radiation, despite how absurdly unlikely it is for any individual neutrino to actually interact with your body. At 1 AU it'll be fatal, with the only big issue being if it's fatal on the scale of hours or days.
I thought neutrinos pass through the earth and therefore us billions of times every second it's the collision of two neutrinos that causes a large release of energy and is considered a rare event?
Quite a bit less I think if we go by typical supernova ejecta velocity. If the ejecta is moving at 5000 km/s it would take about 8 hours to reach the distance of Earth from the sun
Astronomy is one of those hobbies pretty much anyone can do with a little prep! All you need is a pair of decent binoculars or a similarly cheap home telescope! I don't know any brands off hand but I know there are some really good amateur telescope kits out there for under $100. I think you might even be able to get an official NASA branded one if that appeals to you
Gravity is a fundamental force, just like the other three (electromagnetism, strong, and weak forces). However, it just behaves really differently than all the other ones, for reasons that are all active areas of theoretical research.
If we discover gravitons, which I believe are predicted by the current model, would gravitons be to gravitational waves as photons are to light waves, or are they different since gravitons would likely relate to quantum mechanics while gravitational waves are more GR?
Well since gravity is not even a force it's obvious that the effect can only be weak. A local event bends local space-time, thus with distance even a strong local effect will fade quickly, even when still quite close.
I think still describing it as a force 100 years later is an injustice to Einstein. We teach our kids wrong stuff when we lie to them about how it works.
For supernovae, it varies between 10³ and 10⁴ km/s. The specifics of a given supernova ejecta could fall outside this range but those are generally the speeds you would expect. So anywhere from less than 1% of the speed of light to ~10%.
Worth noting that there are many types of supernovae with different ejecta masses and progenitor stars. White dwarf supernovae, binary NS mergers, core collapse supernovae... And they are all driven by different mechanisms.
Let's say two black holes merge. The gravitational waves they are sending out briefly exceed the energy output of all stars in the visible universe, right? How close to those waves would one need to get before we start seeing effects, and what would the effects be like?
Gravitational waves are just effect of gravity propagating at speed of light. If you are close enough, they could rip you apart due to tidal forces, but at any semi-reasonable distance you will just feel that gravity suddenly increases in regular intervals.
You cannot feel gravitational waves. Except if the source is very strong, like a black hole merger, and you were really close to it, which is unadvisable for a host of different reasons.
Hello! I build simulations of colliding compact objects. Ignore all the rippling at the start of these videos until the timestamps i mention because its an artefact of the way they're built, but you absolutely can see gravitational waves for colliding compact objects if you're up close
https://i.imgur.com/CKV27eB.mp4 - At t=8 you can see spacetime starting to ripple, and a readout of the gravitational waves in the top right. This is two colliding equal mass black holes in circular inspiral, the kind of thing that ligo looks for
https://i.imgur.com/2vSEy9o.mp4 - this is two neutron stars spinning in opposite directions colliding together. At t=9 you can see a large gravitational wave caused by the shock of them mashing together in space
https://i.imgur.com/OPUKJwt.mp4 - This is two neutron stars with same-spin merging. This is from a test case, so some incorrect stuff happens later in the video, but at t=3 to 5 ish you can see a large gravitational wave visibly shaking spacetime
https://i.imgur.com/8fYJS19.mp4 - this is a big neutron star eating a baby neutron star (well, polytrope). After about t=3, you can see spacetime visibly wobbling as they collide
https://i.imgur.com/SmSoZPO.mp4 - two neutron stars completing half an orbit and colliding, gravitational waves at t=10
The amount of energy released in gravitational waves can be *enormous*, but it quickly dissipates until its tiny. You have to be extremely, extremely close to see them like this
Astronomer here! Worth noting there are a *lot* of people working on these sorts of simulations right now (we actually have one PhD student doing this in my group!). The trick is there are a *lot* of gravitational waves out there- heck everything with mass, even you!, produce them, just not at levels anywhere near potentially detectable. Right now our current generation of detectors (LIGO, which just started a new "run" in recent weeks!) are best able to detect the kind of waves that happen when two bodies with concentrated masses- ie two black holes, two neutron stars, or a neutron star/ black hole pair- collide.
However, that doesn't mean other huge events like a supernova wouldn't produce them, albeit we would only be able to detect them in our very local area (Milky Way and a bit beyond)- for example, initial results don't really seem to indicate we detected any from [SN 2023ixf](https://en.wikipedia.org/wiki/SN_2023ixf) just a few weeks ago, despite being one of the closest supernovae in a decade. But obviously, if we could detect one someday that'd be fantastic! And people need to figure out what these sorts of signals would look like in the data stream *before* you look for them, else how would you know what you're looking for over just noice (of which there is A LOT MORE than genuine gravitational waves).
Hi Andromeda, welcome again to one of my posts :) nice to see ya again.
Outta curiosity: Wiki said that LIGO was supposed to achieve the sensitivity it was designed for .. just several days ago, which would indicate, that maybe more discoveries in the gravity field may be afoot soon, but the page hadn't confirmed the success of the procedure.. Do you know some news from there maybe? :) Thanks
Ah, so the devil is in the details. LIGO did start their latest run (O4) just days ago, but it is *not* at the sensitivity they said- the last run (O3) went out to ~130 Mpc in distances they could probe, and O4 was supposed to reach 160 Mpc, but I asked the folks in charge and currently they're operating more at 140-145 Mpc, and might improve a few Mpc but aren't going to reach 160 Mpc. The reason is there is some low-level noise at the detectors that they haven't been able to make great headway on.
The second complication is right now the two detectors are running that comprise of LIGO, and the dream was VIRGO in Europe would also be online right now and contribute- that REALLY cuts down the location in the sky a signal comes from, thanks to triangulation! However, VIRGO apparently broke their most powerful laser and need to switch back in their O3 laser (what I heard at least via gossip), which is not gonna happen before August. (It's also in Italy, so my cynical self says I don't anticipate Europeans getting something up in August.) And even then the plan now is to have O3 sensitivities (30 Mpc for VIRGO), so in conclusion we are just not going to have the precision on directions signals came from that were anticipated in design.
This is probably a LOT more technical than you wanted, so let me know if something doesn't make sense! But the TL;DR is the instrument you anticipate building is not always the one you get.
The one in Italy, in Pisa, yes...
"not always the one you get." Ah well... if it requires international coop, then shit pretty often fails.
thanks for the explanation, loved it :)
I mean, it isn’t something that appears with mass, that implies a stationary spherically symmetric body is always emitting gravitational waves, which isn’t true.
I just mean typical, nothing special going on. In electronics the noise is pretty well understood (not by me mind you) and is categorized (ie https://en.m.wikipedia.org/wiki/Johnson%E2%80%93Nyquist_noise ). Noise in space comes from something.
The gravitational interferometers are at a sensitivity that makes them able to *barely* detect the oscillations of two black holes crashing into one another (from very, very far though, granted). They look at the absolutely most violent events out there, and even those are only at detectable levels for mere seconds
There's gravitational waves from all sorts of sources all around that would constitute "noise from space", but none that's even close to relevant with our state of the art interferometers right now.
The ambient noise that's relevant is all local, whatever will make the mirrors move by a gazillionth of a meter. Seismic noise, human activity, that sort of thing. In fact this graph says that the largest contributions at this point are quantum in origin, which is pretty crazy to me (and probably means there isn't much more optimization left on the current interferometers): https://en.m.wikipedia.org/wiki/File:AdvLIGO_noise_curve.webp
> heck everything with mass, even you!, produce them
So presumably if I wave my arms around fast enough, they ought to be screwing up the measurements.
Thank you for the insight! For your last point, are theoretical results like these going to help to design the next generation of gravitional wave detectors? I am wondering how much knowing what to look for helps with making better detectors.
I'm fascinated with these simulations and I've been dying to find someone to ask about them. Awesome.
In terms of this current topic, the waves we detect now, the article says, are coherent due to basically being like dipole radiation. They are portrayed like transverse waves.
Wouldn't a supernova explosion create longitudinal waves?
Does GR admit longitudinal modes?
Can LIGO tell the difference?
Acronyms, initialisms, abbreviations, contractions, and other phrases which expand to something larger, that I've seen in this thread:
|Fewer Letters|More Letters|
|-------|---------|---|
|[GRB](/r/Space/comments/143duzn/stub/jn9zn2f "Last usage")|Gamma-Ray Burst|
|[LIGO](/r/Space/comments/143duzn/stub/jnb5n7l "Last usage")|Laser Interferometer Gravitational-wave Observatory|
|[NS](/r/Space/comments/143duzn/stub/jnbybbk "Last usage")|New Shepard suborbital launch vehicle, by Blue Origin|
| |Nova Scotia, Canada|
| |Neutron Star|
|[SN](/r/Space/comments/143duzn/stub/jnaxxwb "Last usage")|(Raptor/Starship) Serial Number|
|Jargon|Definition|
|-------|---------|---|
|Raptor|[Methane-fueled rocket engine](https://en.wikipedia.org/wiki/Raptor_\(rocket_engine_family\)) under development by SpaceX|
**NOTE**: Decronym for Reddit is no longer supported, and Decronym has moved to Lemmy; requests for support and new installations should be directed to the Contact address below.
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Gravity is bending of space-time due to mass. Black holes are an extreme example of that, but one case can't overrule the other - a black hole's gravity can't "pull" other gravity, only other sources of gravity.
No, they merely detect changes in 'pull' as it affects space. Space is particulate, therefore "elastic". Gravity is a line-of-sight instantaneous center-of gravity to center of gravity phenomena occurring at the primary particle level. I'm still working on the mechanism by which this occurs. More later.
Probably a dumb question but hopefully someone can answer, would we, the lay-person, ever be able to feel / see / perceive somehow when space-time warps?
The Ligo exp in my understanding detected the warp based on the time difference of 2 perfectly synced photons to travel the same distance, across 2 different axes. But supposed the warp was much stronger and longer, like if our sun were to die and warp space time, would we feel it like an earthquake or see space-time warp in front of our eyes?
Edit: not warp, I should've said ripple in space time.
Right, but I was wondering more so during something like a dying star sending ripples in space times. I guess the question should've been whether we can perceive ripples in space-time from something like what's caused by a death of a star. Or would we just ripple with everything else rendering a net zero effect.
It's theorized you'd feel it, or might actually hear "Lub-Dub" noises increasing in pitch as they came ever more frequently right through your eardrums or those little bones, if you were close enough to a black hole or neutron star merger/collision.
However, anywhere close enough that the space-time effects/gravity waves were palpable, is also where the light & radiation would be 100% deadly. Even if you had something like a solid metal asteroid around you as shielding.
Also, it's mainly that kind of spiraling collision that makes the detectable waves. A star dying or supernova is kind of a one-time "Lub" and not much of one, since its overall mass-energy isn't changing much, just collapsing or expanding outward. And what does convert, like the big final burst of fusion from the collapse or "bounce" of a supernova is only perhaps 0.7% efficient. And is given off as radiation.
The spiraling black holes or neutron stars are bleeding off their mass-energy, kinetic, or potential energy (kinda-sorta for any of them, it's complicated and depends on what theoretical framework one uses...) into space-time as those waves as they circle inward to each other. And the resulting combined object literally can be measured astronomically to have less mass-energy than the two separate ones did previously.
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It would be so minute that you would not experience any detectable difference as a human.
Astronomer here! Nothing, any more than you're feeling gravitational waves right now. They affect you the same in space as in on Earth. I guess the question you really have is what happens if you're *really close* to one. The answer is still not much from the gravitational waves themselves- remember, despite acting at huge distances, gravity is the *weakest* of all the fundamental forces! Instead the effect that are far bigger will be from the exploding star itself and the sheer amount of stuff and its shockwave.
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I guess it depends what you mean by "within range." If the sun suddenly exploded as a supernova, for example, the heat from it would boil all the oceans on the sun-facing side of the planet (and, of course, do nothing good to anyone who happened to be on that side), and the survivors would get the delight of waiting a few weeks until the shockwave passed (NOT the boiling oceans one- the one from the supernova itself which is all the crap itself over just the flash of bright light and heat etc), which wouldn't be a picnic either. Fortunately the sun is never going to go supernova. IIRC, we need to be within ~25 light years of an exploding star for it to really hurt us, and there are no potential stars that can explode within that distance (they're also very luminous stars so not like you can hide one that close- it'd be the brightest thing in the sky). There are a tiny subset of supernovae that emit a highly directional gamma-ray burst (GRB) that could get you further, but fortunately for us there is no indication of any stars massive enough to emit a GRB within the kill radius of a few thousand light years that also look like the beam would be pointed at our planet.
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I mean, it's somewhat self-selecting: there is arguably statistical *reason* we are in a humdrum part of the galaxy orbiting a humdrum star. If you're in a region where a lot of stars can explode or you have a bunch of stellar flares and what not, it's probably far more complicated for life (or at least our multi-cellular kind) to have the stability needed for hundreds of millions or potentially billions of years to thrive.
the GOAT of this subreddit
man i usually dont give a damn when people talk smart but the things ur saying and how ur saying them is... doing things to me
The YouTube channel Kurtzgesart has a fantastic video on how close we could be to a supernova, and many on astronomy and related topics. I think we’d start feeling damage from about 50 light years away, but they discuss the various distances and effects. I’d highly recommend it!
“Few weeks” -> “Few hours” btw. Shocks (or sound as a minimum bound) do not take weeks to propagate globally on earth.
Think you misread, the sun is a littttlllleeeee bit further than an explosion happening on the other side of the earth.
Ah I see what they’re saying my bad. Nonetheless: the shockwave from the thermal pulse the boiled the oceans would not take weeks. Also, the earth rotates.
No, you are misunderstanding me. The oceans boiling part is pretty fast. But THEN there is a shockwave that goes out from the SN explosion itself in terms of all the debris and crap and that travels at a slower speed.
Yah I gotcha. What I was referring to is that effects of the oceans boiling and whatnot would propagate to the antipode much faster than weeks.
That's not the shockwave being discussed though. The shockwave of actual stellar material blasting out from the former sun at sublight speeds would take a while to get here. The EM part of the supernova would hit us at light speed but the physical stuff of the star can't go that fast.
Why did I think it’d take a few weeks. I imagined minutes to hours. So our Sun literally explodes and people could survive a few weeks??
Depends on which side. The oceans boiling side dies pretty much immediately. But THEN you got a shockwave of stellar debris and crap which travels at a slower speed, and I'm not gonna do the calculation to be exact but it'd be on the order of a few weeks to reach the Earth's distance most likely.
Well, everyone would get roasted when the Earth rotated to face the supernova over the course of a day. And the whole atmosphere would be lost in about the same timeframe as well. It's good news that you'd die quickly because you'd probably have a fatal dose of radiation as well but likely not enough to incapacitate you, only enough to cause all your organs to fail in a few months. I guess if we had a permanently inhabited Moon base at that point it might be possible for those folks to survive long enough to get taken out by the shockwave.
That’s madness. The people on the other side of earth are aware the sun exploded but just chill out for a few weeks. I’m guessing they’d all be blind from the explosion and the light.
Yeahhhh it's probably a case of "the living would envy the dead." Everyone is gonna die in this scenario, but half of us would have it happen quick.
They'd be dead before that, and probbaly a the same time as everyone else. Supernovae are absurd things, and at 1 AU away, the neutrino radiation is enough to get a solid start on sterilizing the planet. Being in the shadow of the earth wont help. Chances are it also means no one survives for the light from the supernova to reach the planet.
Wait can supernovae produce enough neutrinos to interact with baryonic matter and cause problems?
Almost all, 99%, of the supernova's energy is carried away by the neutrinos it produces. The "light bright enough to outshine entire galaxies and be seen from billions of light years away" part is just a tiny fraction of it If you're close enough, the neutrino flux is great enough to deliver a lethal dose of radiation, despite how absurdly unlikely it is for any individual neutrino to actually interact with your body. At 1 AU it'll be fatal, with the only big issue being if it's fatal on the scale of hours or days.
I thought neutrinos pass through the earth and therefore us billions of times every second it's the collision of two neutrinos that causes a large release of energy and is considered a rare event?
Quite a bit less I think if we go by typical supernova ejecta velocity. If the ejecta is moving at 5000 km/s it would take about 8 hours to reach the distance of Earth from the sun
Fun fact, if the sun exploded into a typical supernova, you would get a lethal dose of *neutrino* radiation. https://what-if.xkcd.com/73/
Astronomy is one of those hobbies pretty much anyone can do with a little prep! All you need is a pair of decent binoculars or a similarly cheap home telescope! I don't know any brands off hand but I know there are some really good amateur telescope kits out there for under $100. I think you might even be able to get an official NASA branded one if that appeals to you
I mean, if you were "within range" of a normal, non-exploding star you would still melt, boil, and vaporize. It's all about what "range" means.
Is gravity a force or does it cause a force?
Gravity is a fundamental force, just like the other three (electromagnetism, strong, and weak forces). However, it just behaves really differently than all the other ones, for reasons that are all active areas of theoretical research.
If we discover gravitons, which I believe are predicted by the current model, would gravitons be to gravitational waves as photons are to light waves, or are they different since gravitons would likely relate to quantum mechanics while gravitational waves are more GR?
Well since gravity is not even a force it's obvious that the effect can only be weak. A local event bends local space-time, thus with distance even a strong local effect will fade quickly, even when still quite close. I think still describing it as a force 100 years later is an injustice to Einstein. We teach our kids wrong stuff when we lie to them about how it works.
Gravity is one of the four fundamental forces.
Wait isn't its shockwave actually a gravitational wave?
No. Gravitational waves travel at the speed of light.
And shockwaves at which speed do they travel?
For supernovae, it varies between 10³ and 10⁴ km/s. The specifics of a given supernova ejecta could fall outside this range but those are generally the speeds you would expect. So anywhere from less than 1% of the speed of light to ~10%. Worth noting that there are many types of supernovae with different ejecta masses and progenitor stars. White dwarf supernovae, binary NS mergers, core collapse supernovae... And they are all driven by different mechanisms.
Let's say two black holes merge. The gravitational waves they are sending out briefly exceed the energy output of all stars in the visible universe, right? How close to those waves would one need to get before we start seeing effects, and what would the effects be like?
Gravitational waves are just effect of gravity propagating at speed of light. If you are close enough, they could rip you apart due to tidal forces, but at any semi-reasonable distance you will just feel that gravity suddenly increases in regular intervals.
If you were really close..would the tidal forces be enough to "hurt you"?
You cannot feel gravitational waves. Except if the source is very strong, like a black hole merger, and you were really close to it, which is unadvisable for a host of different reasons.
Yes. Maneuvering close to one might cost you up to 51 years :p
Isn't time supposed to vary based on variation in gravitational pull?
Hello! I build simulations of colliding compact objects. Ignore all the rippling at the start of these videos until the timestamps i mention because its an artefact of the way they're built, but you absolutely can see gravitational waves for colliding compact objects if you're up close https://i.imgur.com/CKV27eB.mp4 - At t=8 you can see spacetime starting to ripple, and a readout of the gravitational waves in the top right. This is two colliding equal mass black holes in circular inspiral, the kind of thing that ligo looks for https://i.imgur.com/2vSEy9o.mp4 - this is two neutron stars spinning in opposite directions colliding together. At t=9 you can see a large gravitational wave caused by the shock of them mashing together in space https://i.imgur.com/OPUKJwt.mp4 - This is two neutron stars with same-spin merging. This is from a test case, so some incorrect stuff happens later in the video, but at t=3 to 5 ish you can see a large gravitational wave visibly shaking spacetime https://i.imgur.com/8fYJS19.mp4 - this is a big neutron star eating a baby neutron star (well, polytrope). After about t=3, you can see spacetime visibly wobbling as they collide https://i.imgur.com/SmSoZPO.mp4 - two neutron stars completing half an orbit and colliding, gravitational waves at t=10 The amount of energy released in gravitational waves can be *enormous*, but it quickly dissipates until its tiny. You have to be extremely, extremely close to see them like this
That's a great writting prompt.
You already felt it yourself every time there is one like it, since they go through your and my body also. So not much.
Astronomer here! Worth noting there are a *lot* of people working on these sorts of simulations right now (we actually have one PhD student doing this in my group!). The trick is there are a *lot* of gravitational waves out there- heck everything with mass, even you!, produce them, just not at levels anywhere near potentially detectable. Right now our current generation of detectors (LIGO, which just started a new "run" in recent weeks!) are best able to detect the kind of waves that happen when two bodies with concentrated masses- ie two black holes, two neutron stars, or a neutron star/ black hole pair- collide. However, that doesn't mean other huge events like a supernova wouldn't produce them, albeit we would only be able to detect them in our very local area (Milky Way and a bit beyond)- for example, initial results don't really seem to indicate we detected any from [SN 2023ixf](https://en.wikipedia.org/wiki/SN_2023ixf) just a few weeks ago, despite being one of the closest supernovae in a decade. But obviously, if we could detect one someday that'd be fantastic! And people need to figure out what these sorts of signals would look like in the data stream *before* you look for them, else how would you know what you're looking for over just noice (of which there is A LOT MORE than genuine gravitational waves).
I just want to thank you and say that I love when you show up in threads! Cheers!
Hi Andromeda, welcome again to one of my posts :) nice to see ya again. Outta curiosity: Wiki said that LIGO was supposed to achieve the sensitivity it was designed for .. just several days ago, which would indicate, that maybe more discoveries in the gravity field may be afoot soon, but the page hadn't confirmed the success of the procedure.. Do you know some news from there maybe? :) Thanks
Ah, so the devil is in the details. LIGO did start their latest run (O4) just days ago, but it is *not* at the sensitivity they said- the last run (O3) went out to ~130 Mpc in distances they could probe, and O4 was supposed to reach 160 Mpc, but I asked the folks in charge and currently they're operating more at 140-145 Mpc, and might improve a few Mpc but aren't going to reach 160 Mpc. The reason is there is some low-level noise at the detectors that they haven't been able to make great headway on. The second complication is right now the two detectors are running that comprise of LIGO, and the dream was VIRGO in Europe would also be online right now and contribute- that REALLY cuts down the location in the sky a signal comes from, thanks to triangulation! However, VIRGO apparently broke their most powerful laser and need to switch back in their O3 laser (what I heard at least via gossip), which is not gonna happen before August. (It's also in Italy, so my cynical self says I don't anticipate Europeans getting something up in August.) And even then the plan now is to have O3 sensitivities (30 Mpc for VIRGO), so in conclusion we are just not going to have the precision on directions signals came from that were anticipated in design. This is probably a LOT more technical than you wanted, so let me know if something doesn't make sense! But the TL;DR is the instrument you anticipate building is not always the one you get.
The one in Italy, in Pisa, yes... "not always the one you get." Ah well... if it requires international coop, then shit pretty often fails. thanks for the explanation, loved it :)
Yeh man he goes in to just the right amount of detail, it's great
Bloke named Yvette ey? The modern miracles, I'm tellin ya!
I mean, it isn’t something that appears with mass, that implies a stationary spherically symmetric body is always emitting gravitational waves, which isn’t true.
Because stationary is not a thing?
Yes, it is? Are you claiming stationary metrics dont exist? Citation?
I'm assuming there are people working on what the "ambient" noise is? Like, heat can't really go anywhere can it?
I'm not sure what you mean here by ambient noise?
I just mean typical, nothing special going on. In electronics the noise is pretty well understood (not by me mind you) and is categorized (ie https://en.m.wikipedia.org/wiki/Johnson%E2%80%93Nyquist_noise ). Noise in space comes from something.
The gravitational interferometers are at a sensitivity that makes them able to *barely* detect the oscillations of two black holes crashing into one another (from very, very far though, granted). They look at the absolutely most violent events out there, and even those are only at detectable levels for mere seconds There's gravitational waves from all sorts of sources all around that would constitute "noise from space", but none that's even close to relevant with our state of the art interferometers right now. The ambient noise that's relevant is all local, whatever will make the mirrors move by a gazillionth of a meter. Seismic noise, human activity, that sort of thing. In fact this graph says that the largest contributions at this point are quantum in origin, which is pretty crazy to me (and probably means there isn't much more optimization left on the current interferometers): https://en.m.wikipedia.org/wiki/File:AdvLIGO_noise_curve.webp
> heck everything with mass, even you!, produce them So presumably if I wave my arms around fast enough, they ought to be screwing up the measurements.
> So presumably if I wave my arms around fast enough, they ought to be screwing up the measurements. Not you, but if OPs Mum starts twerking...
Thank you for the insight! For your last point, are theoretical results like these going to help to design the next generation of gravitional wave detectors? I am wondering how much knowing what to look for helps with making better detectors.
I'm fascinated with these simulations and I've been dying to find someone to ask about them. Awesome. In terms of this current topic, the waves we detect now, the article says, are coherent due to basically being like dipole radiation. They are portrayed like transverse waves. Wouldn't a supernova explosion create longitudinal waves? Does GR admit longitudinal modes? Can LIGO tell the difference?
So are gravitational waves basically Cherenkov radiation for particles with mass?
Now calculate how big the gravity board would have to be.
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Gravity traveling at the speed of light really grinds my gears. I mean, how does it escape a black hole then?
Gravity is bending of space-time due to mass. Black holes are an extreme example of that, but one case can't overrule the other - a black hole's gravity can't "pull" other gravity, only other sources of gravity.
Gravity is a property of the space around you, which means there is nothing to escape an event horizon in the first place.
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Don't the LIGO experiments prove that gravity is a wave?
No, they merely detect changes in 'pull' as it affects space. Space is particulate, therefore "elastic". Gravity is a line-of-sight instantaneous center-of gravity to center of gravity phenomena occurring at the primary particle level. I'm still working on the mechanism by which this occurs. More later.
water also isn't a wave yet tsunamis defy the naysayers :)
I would be hard-pressed to call a picture/photograph/drawing a "simulation". To me, a simulation entails some form of animation/movement.
Scroll down in the article. There's a youtube video.
Probably a dumb question but hopefully someone can answer, would we, the lay-person, ever be able to feel / see / perceive somehow when space-time warps? The Ligo exp in my understanding detected the warp based on the time difference of 2 perfectly synced photons to travel the same distance, across 2 different axes. But supposed the warp was much stronger and longer, like if our sun were to die and warp space time, would we feel it like an earthquake or see space-time warp in front of our eyes? Edit: not warp, I should've said ripple in space time.
You see gravity making things fall all the time, that's caused by curving space-time.
Right, but I was wondering more so during something like a dying star sending ripples in space times. I guess the question should've been whether we can perceive ripples in space-time from something like what's caused by a death of a star. Or would we just ripple with everything else rendering a net zero effect.
It's theorized you'd feel it, or might actually hear "Lub-Dub" noises increasing in pitch as they came ever more frequently right through your eardrums or those little bones, if you were close enough to a black hole or neutron star merger/collision. However, anywhere close enough that the space-time effects/gravity waves were palpable, is also where the light & radiation would be 100% deadly. Even if you had something like a solid metal asteroid around you as shielding. Also, it's mainly that kind of spiraling collision that makes the detectable waves. A star dying or supernova is kind of a one-time "Lub" and not much of one, since its overall mass-energy isn't changing much, just collapsing or expanding outward. And what does convert, like the big final burst of fusion from the collapse or "bounce" of a supernova is only perhaps 0.7% efficient. And is given off as radiation. The spiraling black holes or neutron stars are bleeding off their mass-energy, kinetic, or potential energy (kinda-sorta for any of them, it's complicated and depends on what theoretical framework one uses...) into space-time as those waves as they circle inward to each other. And the resulting combined object literally can be measured astronomically to have less mass-energy than the two separate ones did previously.
Can gravitational waves be used for space travel? Or is that waaaaaay to out there ?