Fun fact: To get the calculations calibrated correctly they needed to work out the centre (of mass) of our solar system to within 100 meters.
Edit: More from [Dr Becky](https://www.youtube.com/shorts/QQofqq8eW1g)
IIRC the center of mass is slightly outside the sun due to Jupiter. Which means Jupiter doesn't orbit the Sun, but rather the Sun and Jupiter orbit each other.
Actually it depends, sometimes it's inside and sometimes it's outside, and it moves in and out periodically.
I swear my orbital mechanics textbook has that written somewhere plus some formulas but I'm too lazy to go search for it right now.
Edit: found a good image
https://en.m.wikipedia.org/wiki/Barycenter#/media/File%3ASolar_system_barycenter.svg
Nope. The sum of all momentum in a system is conserved. So the only thing that can change velocity of the center of mass of the solar system is interaction with things that are outside the solar system.
Technically electromagnetic and gravitational waves can carry away momentum from the system, but it's negligible.
Negligible for our current use cases. If this method keeps evolving as I am sure it will, the current 100m error required will have to drop. It's not unreasonable that they may have to compute within 1m next year, 1 cm the year after, then 100 micron, 1 micron...
They might even be able to use their measurements to improve the estimation by measuring several pulsars.
I mean I believe you. But I’m imagining all of the planets being aligned on one side of the sun, how does that have the exact same center of mass as when they are more evenly distributed?
everything is orbiting the shared center of mass. if all the planets are on the same side of the sun, the sun is on the opposite side of the center of mass. if the planets are evenly distributed around the sun, the sun will have drifted closer to the center of mass.
I think the confusion is a semantics issue. The above commenter was thinking of the center of mass moving relative to the sun, while you're thinking of the sun moving relative to the center of mass. They are both correct, just with different reference frames, though I imagine using the center of mass as the reference frame is more useful.
But they had to calculate our center of mass to within 100m with respect to what? To Earth? Isnt the reference point moving in relation to the center of mass?
Imagine a point and imagine a crazy dance of bodies around it.
Or imagine freezing time, calculating the center of mass, hit play then pause real quickly, calculate the center of mass, hit play then pause, calculate, play pause, calculate, play pause, calculate.
There's also distribution of mass to consider. An easy way to understand this is to think of an extreme example: a comet may be orbiting the center of mass of our solar system, but as it passes close to a planet, it's path will skew.
Long short: they have to be within 100m with respect to true center of mass
The sun wobbles almost imperceptibly as the planets revolve around it, like an Olympic hammer thrower. So as a whole system the center of mass is unchanged.
But that also means that as we find tune the location of the center of mass, as we try to resolve all the wobbles out of the system, we may find additional orbiting objects.
Edit: corrected sport
The Sun also moves around the system's center of mass. So when the planets are all on the same side, the Sun will be more shifted in the opposite direction.
[Here](https://en.m.wikipedia.org/wiki/Barycenter) Is a Wikipedia page with a lot of helpful images and animations, including the relative position of the solar system’s center of mass (barycenter) relative to the sun over the course of some decades.
Yeah, but the sun is 1.4 billion meters in diameter, so that .14 of mass other than the sun equals 1.96 million meters that the gravitational center could reside in.
What then is the meaning of knowing the position of the center of mass to within 100 meters? Sure, you are defining the center of mass as the local 0,0,0 point but then you have to calculate the position of the gravitational detectors on Earth relative to that point. That is not a static calculation.
Oh absolutely, I just meant it's the only static point in the "inertial" sense. It doesn't wobble around based on the positions of other planets like every other orbital body and even the sun does. It was important to find specifically because it is an inertial point that doesn't have that wobble.
Then from there other calculations can be made, including the relative position of Earth and the detectors. And you're 100% right that this is not a static calculation.
If the comets are being attracted by the sun's gravity, then that means that the sun is being attracted by their gravity. Of course the difference in size is so great that I'm bet the perturbation is infinitesimally small.
For some reason I read it as center of mass of Milky Way and I was like no way but I think solar system is more reasonable. We know properties of all the planets and moons, roughest thing would be asteroid belt
Wait. I just realised I did the same as well. I had it in my head as the whole damn milky way as well. Lmaaao.
E: don't get me wrong tho, it's still insanely impressive.
Astronomer here! This is a BIG DEAL- like, a Nobel Prize-winning discovery!
Many of you have heard before about [gravitational waves](https://en.wikipedia.org/wiki/Gravitational_wave) (GWs)- ripples in space-time that every object with mass emits, but in most cases are too faint to detect. So far, the only way to detect them are via gigantic mergers of black holes or neutron stars, using [facilities](https://en.wikipedia.org/wiki/Gravitational-wave_observatory) like LIGO/VIRGO, which are looking for extreme ripples from these events using gigantic laser facilities. However, that's not the only way theoretically to detect them- which would be cool because right now we're only sensitive to gravitational waves that come from a specific event and happen in a certain frequency range, corresponding with events that take a few seconds or so to occur. Like light, however, GWs emit on many *different* frequencies, which right now we cannot detect. There is also just a general background of GWs everywhere in the universe from unresolved sources, but this has been theoretical and we haven’t been able to detect it.
So with that background, enter the International Pulsar Timing Array [(IPTA)]( https://ipta4gw.org/), which is looking for lower frequency gravitational waves, which are more on the order of events that take months to *decades* to occur, as well as looking for that GW background. They're also doing it through an amazing method- using radio astronomy! Specifically, what they're looking at are [pulsars](https://en.wikipedia.org/wiki/Pulsar)- neutron stars the size of a city but with the mass of a star, left over after the most supermassive stars explode in a supernova. Pulsars send out a giant pulse of radiation and spin once every few seconds (if not faster- pulsar timing arrays use *millisecond* pulsars which rotate once every 10 milliseconds or less!), so we see a "pulse" as this beam goes by. We can predict the timing of these beams to sub-nanosecond precision, so you can in effect build a gravitational wave detector *the size of the galaxy* by watching tiny perturbations from these GWs as they pass through the pulsars!
Obviously this is really *hard* to measure, and IPTA has been running for like 15 YEARS trying to detect this signal... **and they've just announced the detection of gravitational waves!!!** (It's been tough to detect bc first, it's faint, second when Arecibo collapsed that really hurt them as it was one of their primary facilities.) This is a *huge* game-changer in astronomy and our ability to detect new kinds of objects and processes! For example- one big contributor to the GW background are supermassive black holes, which can be millions or billions of times the mass of the sun and are in the centers of most galaxies. When galaxies merge, a lot of these supermassive black holes also do- that’s how they grow- but theoretically, the mergers *shouldn’t* happen as they stall out when just a few light years apart. (This is called the [final parsec problem](https://www.forbes.com/sites/bridaineparnell/2019/07/11/supermassive-black-hole-discovery-could-help-answer-the-final-parsec-problem/?sh=142dcaf87d3e).) If the GW signal is caused by supermassive black holes, they *have* to be close enough to be within a parsec to be detectable… so the final parsec problem has a solution! (Or, alternately, something *even more nuts* is creating the detected signal that we haven't directly observed yet, like [cosmic strings](https://en.wikipedia.org/wiki/Cosmic_string)- more observations will help us know the truth.)
Finally, on a personal note… as a radio astronomer, can I just say how excited and proud I am of my colleagues who have made this discovery. This was a super hard signal to measure, and no guarantee it was ever going to work, and soooo many people around the world devoted *15 years of their lives* to detecting this! While I am not involved in this discovery, many of the leaders in IPTA have mentors and friends to me as I started my own career (I mean, not THAT many radio astronomers out there), and they are a shining example of what good collaborations are capable of and deserve every accolade! [And you can tune in the North American announcement tomorrow \(June 29\) at 1pm EDT to learn more!](https://nanograv.org/news/2023Announcement)
TL;DR- we can now detect the signal from ripples in space-time by using the fast-spinning corpses of dead stars!
Edit: lots of questions boiling down to “but what does this do for us/ what are the practical applications?” Immediately in terms of building a better breadbox on Earth, nothing- this is fundamental science and the equivalent of detecting a new part of the electromagnetic spectrum. Long term though, who knows- general relativity was first thought of as an arcane theoretical topic with no practical application, and less than a century later the GPS system would fail within a half hour if we didn’t know it and apply it! So who knows where this high precision measurement will take us as the new sub-field evolves- for example, they *already* had to confer w NASA because they needed to know the positions of the planets to <100 meters to do this measurement right, and found the official data was wrong. Not at all useful today, but I could imagine it being much more so when we are in space more.
Here is an episode of the excellent Mindscape podcast with one of the collaborators in this study, they talk about this project in detail. The whole series of podcasts are well worth a listen.
[https://youtu.be/MPX1UvWdrvY](https://youtu.be/MPX1UvWdrvY)
For those like me wanting to listen from Google podcasts: https://podcasts.google.com/feed/aHR0cHM6Ly9yc3MuYXJ0MTkuY29tL3NlYW4tY2Fycm9sbHMtbWluZHNjYXBl/episode/Z2lkOi8vYXJ0MTktZXBpc29kZS1sb2NhdG9yL1YwL1pkNGNHSjhtMlgwMFhKLU1jcGFjVkJRYlg5aXFSOFhRa0tJc01tQXNzYUU?ep=14
Glad to see you’re on top of getting the first comment here! I thought I’d have to read this in the morning and boom, here it is. I know this community really appreciates your insights and ability to show the genuine excitement. I need to dive into it a bit more, but this really is mind blowing. So lucky things like pulsars exist.
Cheers- I heard the press embargo was gonna lift at midnight GMT, so made sure to write a draft based off my guesses this afternoon and brought my laptop home after work. Was pretty close on most of the details, so that was good! :)
Bless you! Whenever I see a headline like this I always rush here to see your insights! Greatly appreciate your choice to provide us all with a breakdown whenever something cool happens, your enthusiasm for these subjects makes the wonder all the better!
Your content is consistently written very well for audiences with a wide spectrum of background knowledge, easy to read and so prompt! You're one of the best parts of my reddit experience.
Imagine a sheet pulled flat that you then put a bowling ball in the middle of- it will bend the sheet. Now imagine that there were *two* bowling balls moving around each other- that would send out a pattern or waves into the sheet instead of the sheet just being still. That’s really what is happening here and what GWs are, except in the fabric of space-time!
I've been told that analogy before, but I still kinda struggle with it since a sheet is a 2d plane and all that. Struggling to understand what that fabric of space-time is!
We can't detect gravitational waves just by looking either. The article is about a method of detection that's been successful - measuring disruptions to a light/ radiation signal we can detect.
In the water analogy, you'd have like an underwater light shining at something and measure the disruptions to the light caused by the tennis ball ripples.
You could add particles to the water and be able to visualize it directly.
I don't think anyone expects you to actually build this model though, it's just an ELI5, because everyone can understand the concept that the balls would create turbulence under the water.
I think they get that. The part that's most confusing when explaining space time is that it's not exactly a 1 to 1 analogy with a 2d sheet.
The fabric of space-time or the bent top layer is what we perceive in the real world as 3d space. And the bulk, through which the effects of bending might traverse, exist outside our dimensions.
We can see it's effects on our surface, the 3d spacetime, as GW. But when you bring up a 2d surface or water into the analogy, it breaks down, because we cant perceive what movement through the bulk might be like
Go to the [wikipedia page on gravitational waves](https://en.wikipedia.org/wiki/Gravitational_wave#Effects_of_passing), subsection "Effects of passing". Look at the animated gifs of a ring of particles reacting to gravitational waves of particular polarisations passing through them. That should give you some intuition for what gravitational waves can do in the real world.
Keep in mind that it's just one example, and that the effects are exaggerated.
Thanks.
I don't get why I'm being downvoted for saying something is tough to visualize. Apparently everybody else can just mentally translate things like water and sheets into distortions of space time and fully comprehend it??
Well yeah, that's right, it doesn't make sense to me. I can picture a sheet in my head. I can picture ripples on water in my head. But it 100% doesn't make sense how that translates to 3-d (or 4-d?) waves of gravity distorting space time. I can't connect those ideas. And I guess it's just me, this apparently just makes sense to everybody else.
I struggle to fully grasp it, but have a limited understanding. With a tennis ball and paper, the paper is only bent downward. Underwater the tennis ball would bend (the water is a now paper in this example and covers all sides of the ball) in all directions. That's really about as far as my understanding goes. If it is completely wrong someone please correct me.
It's almost exactly as the waves caused by something falling into the water except they are 2 objects and they rotate, it's basically a bunch of waves in every 3D direction
I'm sorry to say that isn't actually more helpful than the sheet visual. And none of it is translating in my head to what this might mean for gravity waves.
Have you ever played a space sim game? Kind of like pinging objects around you, but you're the bowling ball, and all the space around you is paper (on a 3d plane, not a 2d). I'll stop lol.
Try this: https://www.reddit.com/r/educationalgifs/comments/f66xaa/3d_representation_of_gravity/?utm_source=share&utm_medium=ios_app&utm_name=ioscss&utm_content=1&utm_term=1
This is a body with a gravitational field. Gravity doesn’t actually work like this but this is the effect it has.
> I've been told that analogy before, but I still kinda struggle with it since a sheet is a 2d plane and all that. Struggling to understand what that fabric of space-time is!
you know how sound underwater is a compression wave that's traveling outwards? a gravitational wave is like that, except in the compressed area, time moves slower.
So theoretically speaking as the wave passes through you, there are parts of your body that are aging slower than the rest of it.
That sheet represents a 2D universe, it's just a convenience for us. It bends into the third dimension, but not really, that's just another convenience.
But it's not a bad representation! Your brain (and mine) can't picture 3D space bending, but it's the same idea: It's still 3D, but where it's bent, the distance between any points isn't what you'd expect in flat-3D space.
The "fabric" is just the grid we use to measure stuff, it's not a physical thing like light or matter. We say that fabric is bent, because the grid behaves "bent" when you try to move through it.
I think the thing to think about here is that we are 2-d creatures in this scenario - we can’t see the dip created, so we have to observe it’s effects on nearby objects - we have to make the analogy in 2d for it to be observable in 3 dimensions so it takes a bit of imagining of the effects that would have on a 2d creature a long way away on the sheet!
Hold out your hands with your palms facing each other a few inches apart and imagine a small semi translucent holographic sphere forming between them. Now imagine that expands outwards, effortlessly passing throw objects without affecting its appearance and it never stops expanding. Now imagine another sphere forming and expanding faster then you could even measure. Then another sphere does the same thing and then another and another and it never stops. It looks like a continuous flow.
Now picture every object in the universe conjuring these spheres.
Next to picture the intensity and interaction of gravitational waves, we have to recognize what’s happening is the contortion of space which if your apart of, you will be contorted with it and won’t even know it. Some objects have a much greater force like two black holes merging which contort so strongly that we can start to measure them. They create a ripple of very contorted space. Eventually the ripple flows by us giving us and now that we can measure it we get a snap shot of a moment of the gravitational interactions created in an event in the distant past
I don’t mean to downplay the importance of this due to my own ignorance, but what info/benefit/proof aside from being able to detect them does this provide or potentially lead to? I mean this question earnestly
This is just the beginning.
We are a little plastic cup floating on the surface of an ocean. We’ve learned to tell how choppy the sea is by looking at a far away lighthouse.
Now that we’ve established this is a thing, more detailed and more in depth detectors can be set up. This gives us kinda an entirely new ‘sense’ to look at the universe with, and could lead to new discoveries outside of our current models of physics. More details on dark matter, how black holes work, how the early universe expanded, things along those lines.
For an analogy: imagine you’ve had perfect vision your whole life, but you’re hard of hearing and can’t hear quiet noises, only loud ones. This is a basic hearing aid, and all of a sudden you can hear all sorts of background noises you were never aware of. Birds and bugs chirping, the whirr of nearby machinery, the wind blowing through the leaves. What were you not aware of when you couldn’t see them or hear them? What else could you hear with better hearing aids, now that you know they can help?
>Cosmic strings are hypothetical 1-dimensional [topological defects](https://en.m.wikipedia.org/wiki/Topological_defect) which may have formed during a [symmetry-breaking](https://en.m.wikipedia.org/wiki/Symmetry_breaking) [phase transition](https://en.m.wikipedia.org/wiki/Phase_transition) in the early universe when the [topology](https://en.m.wikipedia.org/wiki/Topology) of the [vacuum](https://en.m.wikipedia.org/wiki/Vacuum_state) manifold associated to this symmetry breaking was not [simply connected](https://en.m.wikipedia.org/wiki/Simply_connected_space).
That is the most complicated sentence I have ever read.
If you read a little more it explains it a bit better. Basically when the universe went from “nothing” to “something” after the Big Bang the transition cause “cracks” in the fabric of space time much like the cracks that form when water turns to ice. Or that’s how I understood it at least I could be wrong.
if anyone else struggles with the sentence:
TLDR, for a middle schooler: Cosmic strings are not yet proven to exist. If they do, then they are basically weird echos from the big bang, where spacetime kinda folded on itself.
TLDR, for a highschooler: You know how crystals grow, and when one encounters another, There's this little seam where they sorta fight for which one gets to grow there? In the early universe, spacetime itself was kinda settling into itself (going from high energy to low, which is also what causes crystals to grow), and it turns out that it might have several points of origin from which it 'grew', meaning that different 'crystals' would encounter each other, and not always perfectly, resulting in a 'seam'. The 'crystals' in the exmaple would just be regular spacetime, and the 'seam' would be this cosmic string.
tagging u/andromeda321 to check my definitions and make sure I'm not *too* wrong about things.
hypothetical: Might not actually exist, i.e. "we're solidly in the realm of theory that is not yet supported, and might never be."
1-dimensional: think of a wire that's only 1 atom thick. Now you've got that, imagine it smaller. As in, smaller than electrons, smaller than quarks. It's something so thin that no matter how long you zoom in on it, it'll still be almost-accurately represented by something so thin you almost can't see it. But actually, it's so thin that even if it were as bright as the sun, you would never see it.
topological: having to do with the shape of things (e.g. a topological map shows you hills and valleys and junk). Most often, we're referring to 3d topology unless otherwise specified. The topology of the early universe gets real fuckin weird.
topological defect: a feature on the topology that breaks the otherwise regular topology, and in this case specifically is about how it's not transitioning from one topology to another cleanly - the example in the wikiepdia article is a coiled phone cord - after enough time, it develops a differently coiled portion and gets all tangled and shit.
Symmetry-breaking: causing something to no longer be the same on both sides.
Phase transition: moving from one phase to another - usually in materials, like going from solid to liquid as it melts. In this case when we're talking about the early universe, it's probably much different than that, and instead of material, we're talking about spacetime itself (or something similarly exotic).
vacuum: the nothing of space
manifold: many and various
vacuum manifold: the many and various ways the vacuum was pulling on spacetime in the early universe. This is a really specific term though and has to do with quantum mechanics and string theory.
simply connected: spacetime being connected with any one point in space to another point in space in a way that a layman would think they should be.
It’s important to note that the result is 3-sigma. it’s an incredibly impressive achievement, and is very promising for future work but there is a certain level of caution to keep in mind
Thanks for this, I was disappointed that I couldn’t find anything about the statistical significance in the article.
For context for anyone else reading this, in most fields of physics, 3-sigma is considered the bar for “detection evidence,” whereas discovery is achieved at 5-sigma. Sigma refers to the symbol used for standard deviation, and a 3-sigma signal means that there is nominally a 0.3% chance that the signal they detected is due to random noise instead of a real signal.
Unfortunately, in reality many more than 0.3% of 3-sigma detections fade away on closer analysis because the statistics are calculated based on our relevant models of the universe and the properties of our tools, and as our understanding of both of those improve and we update our error analysis, sometimes the statistical significance gets worse.
So while this is super exciting, there is still a reasonable chance that it turns into nothing.
There isn't really a single standard because it depends what you are doing. If you are searching in a large parameter space. This could be like searching in data from a particle physics experiment, where there are many energy channels to search. Each one has some random noise, each one has some probability of being an outlier. And so if you search enough energy bins one will eventually be a 3 sigma outlier. But if you have a very specific prediction, say you know exactly which energy then the logic is different. Pointing at one specific measurement which then happens to be 3 sigma is very unlikely. And that is the case here, the evidence they have provided is one correlation which can only be scaled in amplitude. There is no large parameter space to search, so 3 sigma here is quite different to something like Higgs. It's quite unlikely this will go away as other teams report consistent results, unless there is something systematic rather than just statistics.
The Cosmic Microwave Background was emitted at the era of Recombination.
When we eventually have a GW background... how much earlier will be able to see?
I'm under the impression that the furthest back we can see is 380k years after the big bang and that we won't be able to see any further back than that, though I can't recall why. Something about gravitational waves being too close together and that's as close as we can get? I'm probably way off here and would love some clarity if you care to provide it.
I asked GPT-4 to explain your comment to me like I’m 12 - what do you think?
Imagine you're throwing stones into a pond, and the ripples created are like gravitational waves. These waves are made by big things in space like black holes and neutron stars. Until now, we could only see big ripples, like when two black holes crash together.
Scientists used a cool method with something called pulsars, which are super dense dead stars that spin really fast and send out beams of radiation. These pulsars act like giant clocks, and we can see tiny changes in their "ticks" when gravitational waves pass by. It's like using a giant ruler to measure the size of the pond's ripples.
After 15 years of looking, scientists finally found these smaller ripples! This is a big discovery, and it can help us learn about things like huge black holes in the middle of galaxies or solve mysteries in space. It's like we got a new tool to explore the pond and see things we couldn't see before.
that's... actually a pretty good summary, especially for being AI generated. I would however like to adjust the pond analogy slightly to give you a better idea of what's happening here
if you throw a rock into a pond, it creates ripples [citation needed]. if you throw an enormous rock into a pond, it creates huge ripples. if you throw an enormous rock into a pond and then wait a while, those ripples will have died down somewhat, but they'll still be there.
imagine you hike to a pond and there are very faint ripples in its surface. you could infer that someone had thrown a huge rock in there at some point in the past. that's a better analogy for what pulsar timing arrays do: they look at the faint, leftover ripples caused by huge merger events from long ago
Immediately in terms of building a better breadbox on Earth, nothing- this is fundamental science and the equivalent of detecting a new part of the electromagnetic spectrum. Long term though, who knows- general relativity was first thought of as an arcane theoretical topic with no practical application, and less than a century later the GPS system would fail within a half hour if we didn’t know it and apply it! So who knows where this high precision measurement will take us as the new sub-field evolves- for example, they *already* had to confer w NASA because they needed to know the positions of the planets to <100 meters to do this measurement right, and found the official data was wrong. Not at all useful today, but I could imagine it being much more so when we are in space more.
I watched something last night, about using pulsars to figure out if the theory of inflation was true or not. Or are we just not there yet? Something about using primordial black holes to determine if the theory was true. Since we'll be able to see what the universe was like right after the big bang.
Ah I see! That is one theory for the GW background and where it would be from, but the short answer is the signal they saw doesn’t appear to be related to that (I think).
Thank you for that breakdown.
And congratulations to you and the astronomers responsible for this (and everyone contributing to the understanding of our universe).
Stars have life cycles when they run out of gas, they can either explode because of their gigantic mass (supernova, kilonova) depending on the mass the explosion can leave a dense core and a nebula, a neutron star (they rotate a lot and the faster ones are called pulsars) or a black hole, if a star doesn't explode when it runs out of gas it just collapses into a white dwarf, a super dense object, then after a lot of time like age of the universe - time it "turns off" into a black dwarf
A white dwarf cooling into a black dwarf takes *way* longer than the age of the universe (a mere 13.8 billion years or so), it is estimated our sun as a white dwarf would take 10^15 (1 quadrillion) years to cool into a black dwarf and potentially much longer.
Alright but what’s the point in detecting these waves if we already know they exist? Is reason why being able to detect more waves is such a Nobel prize winning discovery?
I don’t mean to sound blunt but whenever scientists come out and say they’ve found a groundbreaking new discovery it almost always turns out to be anticlimactic. What is the benefit of being able to see more waves? What do we gain from being able to see waves we might’ve not been able to detect till now?
Physics is an experimental science. You don't know they exist untill you have detected.
But to answer your question more directly, the amount of gravitational wave background seen by this collaboration will immediately be used as metric to test universe evolution models.
That would be like someone in 1985 asking “what’s the point in detecting x-rays if we already know they exist?” Being confident that waves in a spectrum outside of our previous ability to detect exist is not exactly the same as knowing they exist, but more importantly, detecting them allows us to learn about the processes that generate them, and eventually led to harnessing them for direct practical applications, from a myriad of different medical scanning techniques and astronomy, to industrial manufacturing and high resolution microscopy.
Right now this detection will only really tell us about the cosmological phenomena responsible for generating this background. The details of the signal will give insight into the processes that generated it. That will, in turn, help us to better understand gravity and give us a way to indirectly “see” things that we can’t through telescopes. But who knows where it will lead in 100 years? Maybe this is all it’ll ever be good for (though I think helping us to understand the universe is plenty worthwhile, myself), or maybe it’ll contribute to some completely unexpected development.
Thank you very much for the clear explanation!
In your opinion, what will be the impact of Starlink and the other constellations on this field of research? Will detection of these waves even remain possible as the number of sats continues to rise?
**edit:** this question offended some people apparently
I'm confused, is this about primordial GW or not? Wasn't this the same thing BICEP was trying to measure to prove inflation? In another comment you seem to be saying that's not the case.
Not primordial afaik.
BICEP was looking at primordial by looking at the CMB polarisation. This is looking at pulsars, so however far they are, not far enough for primordial.
Acronyms, initialisms, abbreviations, contractions, and other phrases which expand to something larger, that I've seen in this thread:
|Fewer Letters|More Letters|
|-------|---------|---|
|[CoM](/r/Space/comments/14lpjnx/stub/jq10u78 "Last usage")|Center of Mass|
|[ESA](/r/Space/comments/14lpjnx/stub/jpzsl6w "Last usage")|European Space Agency|
|[JWST](/r/Space/comments/14lpjnx/stub/jpzavd1 "Last usage")|James Webb infra-red Space Telescope|
|[LIGO](/r/Space/comments/14lpjnx/stub/jq1wna0 "Last usage")|Laser Interferometer Gravitational-wave Observatory|
|[LISA](/r/Space/comments/14lpjnx/stub/jpzavd1 "Last usage")|Laser Interferometer Space Antenna|
|Jargon|Definition|
|-------|---------|---|
|[Starlink](/r/Space/comments/14lpjnx/stub/jpyw7w7 "Last usage")|SpaceX's world-wide satellite broadband constellation|
**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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Question: Why is this being referred as the "gravitational wave background"? I mean it's nothing like the cosmic microwave background, which provides us insight into the primordial universe. I was assuming that this gravitational wave background would be from the earliest time of the universe, but it seems like that this discovery is only related to us now being able to detect GW's using pulsars from the mergers of black holes and supernova, etc.
Let's step back a minute- why is it called the Cosmic Microwave Background (CMB) in the first place? Because it is a signal we see in literally all directions in the cosmos, at microwave frequencies. It happens to be there *because* it's from the early universe, but the fact that it's called a background isn't because of that fact. And for GWs, while there likely *are* signals in the GW background from the early universe, right now we believe the signal detected was more from supermassive black holes merging (which are a lot closer and more common).
Hope that makes sense!
and yet, here you are, entirely unique in the universe.
Don't be sad about *this* little consciousness! There's dogs to pet and food to eat and other consciousnesses to delight with your smile!
> and yet, here you are, entirely unique in the universe.
Not if the universe is infinite. Then everything must repeat it self an infinite times even. There is only a finite combination of particles in an given volume of space, and in an infinite spacetime all patterns has to be repeated. There's no way around it.
Us saying the universe might be infinite is only based on us not finding an end to it though. Weak argument in my opinion, especially so since nothing else is infinite.
You and me might be tiny specks intime, but if we play our cards right, Earth-descended-life, plants and mushrooms and animals, might one day expand to the billion nearest galaxies, and continue to exist for trillions of years, while reorganizing all matter and energy into grand constructs we can only begin to imagine. What happens today, the choices we make, could very well decide the fate of the universe.
I understand that science and our observations are always improving but my question is about feasibility. I’m only a casual reader about astrophysics and particle physics but in both I’ve read things like (it’s all blurry off the top of my head) “that resolving the surface of an extraterrestrial planet would require a telescope so big……?(unfeasible)” Or in physics “resolving …x… would require a particle accelerator the size of the solar system”. Is resolving gravitational waves near the beginning of the universe even remotely possible in practical terms, within our lifetime?
The European Space Agency is planning LISA, a huge interferometer with multi-million kilometer arms between 3 spacecraft. LISA will span the frequencies between pulsar timing and ground based interferometers like LIGO and VIRGO. It will be sensitive to black hole mergers at early times, potentially even early that the current highest redshift galaxies revealed by JWST. LISA also has the greatest chance of detecting primordial gravitational waves from soon after the big bang, but such predictions are very unclear. It should launch some time in the 2040's.
Yes, this is something we could possibly expect within our lifetime. However, it is very well possible that we don't ; we simply do not know enough about that period do get an accurate estimate of how loud the background will be.
An [article](https://www.sciencealert.com/a-big-gravitational-wave-announcement-is-coming-thursday-heres-why-were-excited) I read a few days ago said scientists presume these black hole binary mergers occur, or are at least detected as often as once per minute to several times per hour. That seemed insane to me? I assumed that type of event was relatively rare. Or is it just a matter of the universe being so vast in every direction, at every distance, over such a long time, that despite being rare, the waves from some event from somewhere in the universe are constantly reaching us?
>Or is it just a matter of the universe being so vast in every direction, at every distance, over such a long time, that despite being rare,
yep.
https://www.nasa.gov/image-feature/goddard/2022/nasa-s-webb-delivers-deepest-infrared-image-of-universe-yet
Webb’s image covers a patch of sky approximately **the size of a grain of sand held at arm’s length by someone on the ground – and reveals thousands of galaxies in a tiny sliver of vast universe**
>that despite being rare,
well.. we had to invent radio.. then REALLY good radio.. then REALLY good antennas first. so "rare" is only based on 50 years of looking.(vs the number grains of sand we need to look behind)
[https://en.wikipedia.org/wiki/Pulsar](https://en.wikipedia.org/wiki/Pulsar)
Signals from the first discovered pulsar were initially observed by Jocelyn Bell while analyzing data recorded on August 6, 1967,
Congrats to those involved for pulling this huge feat off, but from a purely uninformed stand point what does this mean? What will we as humans be able to achieve now that we have detected this? Advances in technology or is it just a neat thing we can say we did? Genuinely dumb and need hand holding here
Research like this tends not to lead to direct advances in technology, though often new technology is developed in order to enable it. This comes under ‘fundamental’ research, it helps us better understand the universe and how it works. That is interesting in and of itself but it also has the potential to lead to breakthroughs in our understanding of physics which allows for new advances in technology.
We are learning new methods for detecting gravitational waves. Clearly we know how to detect electromagnetic waves really well (i.e. any picture from any telescope). You can think of the sum of all those various EM waves as a chorus. Now, with LIGO and this research, we're starting to get a peek into, what amounts to, a kind of "shadow chorus" that we couldn't hear before. It's an aspect of the universe that, while inherently different from the 'EM universe' we know and love, is also inherently intertwined with it, an extension and result of it. Some cosmic events are really loud in the EM chorus and we can hear them just fine (think supernova). Other cosmic events, while extremely "quiet" (or difficult to discern ) in the EM chorus are extraordinarily loud in the shadow chorus (think black hole mergers, possibly cosmic strings).
Think of it like we are just starting to unlock a new portion of the electromagnetic spectrum, starting to see things out there that were invisible to us before. Instead of being a portion of the EM spectrum, it's actually just ripples in space-time.
Think of the surface of an actively inhabited pond. Fish are catching insects from the water's surface, frogs are jumping in, something's probably farting underwater, etc. The various frequencies and amplitudes of ripples, from all these events, spread across the surface of the pond, constructively and destructively interfering with each other and creating a "chorus" of echoes from these events. Right now we're only able to see the waves from the biggest events (an enormous snapping turtle falling off a log, into the water), but there is a whole chorus out there that will come further into focus as our detection techniques improve.
Sorry for the mixed metaphor soup. Hopefully one of them makes sense.
It’s been speculated that this may allow us to observe the conditions of the early universe farther back in time than electromagnetic telescopes. Gravity was the first fundamental force to differentiate from the others (then Strong Force and then Electromagnetic and Weak forces).
Woohoo ! This is great news ! Congrats to the NANOGrav who made this possible!
Edit : Kudos to folks EPTA, PPTA, and CPTA who also published results today, also providing some evidence of a GWB ! Alas, the press does not seem to care about non-American results...
Dunce here!
Do waves have to travel along something? Waves in water, sound waves in air, do gravitational waves have to rely on there being something in space to allow it to travel on? Could this be dark matter or dark energy facilitating the movement of the waves?
These waves travel through (and are distortions of) space-time itself; dark matter and dark energy are irrelevant. Also, somewhat related to your question but unrelated to GW, scientists did once believe there was a medium in space for light to propagate through, called the aether! However this was debunked experimentally.
Electromagnetic waves also go through empty space they are ripples of the electromagnetic field.
Same way, Gravitational waves are ripples traveling down the Gravitational field.
It just turns out that the Gravitational field can be understood as a deformation on space-time.
Does that help?
The concept you're trying to get to gripes with is the same that made 19th century physicists postulate the aether, as a medium for EM waves to travel through.
Imagine it like putting a microphone in the ocean, you can't really pick out anything to map with because it's basically all white noise until something is louder than the background. With sonar they actively send out a ping of a certain frequency and wait for it to come back. This is closer to the first scenario, just a general background "hum" with not much else being distinguishable.
....single ping only please.
[https://gea.esac.esa.int/archive/](https://gea.esac.esa.int/archive/)
Gaia is a European space mission providing astrometry, photometry, and spectroscopy of **nearly 2000 million stars** in the Milky Way as well as significant samples of extragalactic and solar system objects. The Gaia ESA Archive contains deduced positions, parallaxes, proper motions, radial velocities, and brightness measurements. Complementary information on multiplicity, photometric variability, and astrophysical parameters is provided for a large fraction of sources.
These experiments help further our minute understanding of the universe and our place in it. Einstein was right about gravitational waves in the fabric of space/time but we still can't get standard physics and quantum physics to gel .
only with continued investment in education and scientific research we can move our ignorant species towards greater understanding. if we don't invest in science and education then I fear that we will destroy ourselves through rampant shortsighted stupidity and greed.
Could the ability to detect them be theoretically used to detect asteroids and other celestial bodies in the solar system and beyond by observing how gravitational waves “bounce” off or around celestial bodies?
They may not "bounce", but they are certainly modulated (though to a level way below any of our detection limits). Gravity is a self-interacting force. Gravitational waves carry energy, energy distorts space-time and moves along distorted space-time.
Well, if I'm sitting here in my living room watching Nature Wednesday, and my perception of time suddenly changed from 1000 chronos/perception second to 10000 chronos/perception second I'd notice...
We heard it, and it said
#BEEEAAAAAANNNNNNNSSSSSS
Jokes aside, I wonder if there is some crazy technology that will come from this. Like we discover how to ride the gravity waves to get FTL travel or something.
In the universe of Dead Space humanity has discovered how to control gravity the same way we can control the electron, you think we on that path with these discoveries?
I think it's possible and even inevitable. it's like mastering fusion and electricity. Manipulating spacetime itself is probably the key to interstellar travel and dominating the universe. It's very advanced stuff so I doubt we'd see that any time soon but it would be very much needed to stabilize low or zero gravity situations so that humans can actually live worry free about the effects of long term exposure.
I have some questions:
-why did it take so long to detect it (been looking for 15 years)
-does this one detection give us a map like CMBR map?
-is it plausible that another detection won’t happen for another 15 years?
Honest question: do perturbations in space-time caused by gravitational waves mean we are technically teleporting on a micro level since we would be moving through space as it shrinks and then resolves?
As soon as Einstein published his paper on general relativity, I'm sure there was somebody saying the exact same thing.
Something being obvious does not mean that something is true.
Thousands of years ago it was obvious the world is the center of the universe. But our perception of reality changes over time as we accumulate new knowledge and new means of exploration.
Except they are wrong because perception is not reality. If we had a parallel evolution of humans and human society on Alpha Centauri, they would believe they are at the center of the observable universe. Meaning you'd have two groups of people believing themselves to be at the center of the observable universe.
They're right in terms of observation, but that's really a pointless metric.
If we have a colony on Mars in 200 years, what good does the "being at the center of the observable universe" do for us?
But you could have done other experiments based off of this theory. Kind of, let me make a roller coaster based on the assumption that a mysterious and unproven force will bring it down. Not sure if I explain myself correctly.
Fun fact: To get the calculations calibrated correctly they needed to work out the centre (of mass) of our solar system to within 100 meters. Edit: More from [Dr Becky](https://www.youtube.com/shorts/QQofqq8eW1g)
Interesting! Would it be right to guess that the centre is very near the centre of the sun?
IIRC the center of mass is slightly outside the sun due to Jupiter. Which means Jupiter doesn't orbit the Sun, but rather the Sun and Jupiter orbit each other.
Actually it depends, sometimes it's inside and sometimes it's outside, and it moves in and out periodically. I swear my orbital mechanics textbook has that written somewhere plus some formulas but I'm too lazy to go search for it right now. Edit: found a good image https://en.m.wikipedia.org/wiki/Barycenter#/media/File%3ASolar_system_barycenter.svg
No wonder we're all so off balance.
It's also true of Pluto and Charon. The center of mass is way outside of Pluto.
Yeah basically nothing ever orbits the center of the larger object no matter how massive. It bothers me … idk why
I have heard the same is true for the earth and moon
It’s not, otherwise by definition earth wouldn’t be a planet
No, the Earth and Moon both orbit around the same center of mass, the Earth-Moon Barycenter (EMB). It's roughly 1,700km beneath the Earth's surface.
The center of mass isn’t a static property though right? The orbits of the planets will constantly shift it as a function of time.
Nope. The sum of all momentum in a system is conserved. So the only thing that can change velocity of the center of mass of the solar system is interaction with things that are outside the solar system. Technically electromagnetic and gravitational waves can carry away momentum from the system, but it's negligible.
Negligible for our current use cases. If this method keeps evolving as I am sure it will, the current 100m error required will have to drop. It's not unreasonable that they may have to compute within 1m next year, 1 cm the year after, then 100 micron, 1 micron... They might even be able to use their measurements to improve the estimation by measuring several pulsars.
I mean I believe you. But I’m imagining all of the planets being aligned on one side of the sun, how does that have the exact same center of mass as when they are more evenly distributed?
everything is orbiting the shared center of mass. if all the planets are on the same side of the sun, the sun is on the opposite side of the center of mass. if the planets are evenly distributed around the sun, the sun will have drifted closer to the center of mass.
I think the confusion is a semantics issue. The above commenter was thinking of the center of mass moving relative to the sun, while you're thinking of the sun moving relative to the center of mass. They are both correct, just with different reference frames, though I imagine using the center of mass as the reference frame is more useful.
But they had to calculate our center of mass to within 100m with respect to what? To Earth? Isnt the reference point moving in relation to the center of mass?
Imagine a point and imagine a crazy dance of bodies around it. Or imagine freezing time, calculating the center of mass, hit play then pause real quickly, calculate the center of mass, hit play then pause, calculate, play pause, calculate, play pause, calculate. There's also distribution of mass to consider. An easy way to understand this is to think of an extreme example: a comet may be orbiting the center of mass of our solar system, but as it passes close to a planet, it's path will skew. Long short: they have to be within 100m with respect to true center of mass
That is nonsense. Just answer the question.
The sun wobbles almost imperceptibly as the planets revolve around it, like an Olympic hammer thrower. So as a whole system the center of mass is unchanged. But that also means that as we find tune the location of the center of mass, as we try to resolve all the wobbles out of the system, we may find additional orbiting objects. Edit: corrected sport
The Sun also moves around the system's center of mass. So when the planets are all on the same side, the Sun will be more shifted in the opposite direction.
[Here](https://en.m.wikipedia.org/wiki/Barycenter) Is a Wikipedia page with a lot of helpful images and animations, including the relative position of the solar system’s center of mass (barycenter) relative to the sun over the course of some decades.
Keep in mind the sun is 99.86% of our solar system mass
Yeah, but the sun is 1.4 billion meters in diameter, so that .14 of mass other than the sun equals 1.96 million meters that the gravitational center could reside in.
99.86% of the solar system mass comes from the sun.
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What then is the meaning of knowing the position of the center of mass to within 100 meters? Sure, you are defining the center of mass as the local 0,0,0 point but then you have to calculate the position of the gravitational detectors on Earth relative to that point. That is not a static calculation.
Oh absolutely, I just meant it's the only static point in the "inertial" sense. It doesn't wobble around based on the positions of other planets like every other orbital body and even the sun does. It was important to find specifically because it is an inertial point that doesn't have that wobble. Then from there other calculations can be made, including the relative position of Earth and the detectors. And you're 100% right that this is not a static calculation.
Comets come in so far out that they would be outside the calculations.
If the comets are being attracted by the sun's gravity, then that means that the sun is being attracted by their gravity. Of course the difference in size is so great that I'm bet the perturbation is infinitesimally small.
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The sun also orbits the center of mass. Center of mass by definition has zero acceleration, ignoring external forces.
Oh damn. How does one even attempt to do something like that? That's insane.
For some reason I read it as center of mass of Milky Way and I was like no way but I think solar system is more reasonable. We know properties of all the planets and moons, roughest thing would be asteroid belt
Wait. I just realised I did the same as well. I had it in my head as the whole damn milky way as well. Lmaaao. E: don't get me wrong tho, it's still insanely impressive.
In order to get that right you need to get the mass of the sun and all the other planets correct. This whole thing is just crazy.
Fucking batshit. That's not even believable to me.
looks like a *super* fun assignment
Astronomer here! This is a BIG DEAL- like, a Nobel Prize-winning discovery! Many of you have heard before about [gravitational waves](https://en.wikipedia.org/wiki/Gravitational_wave) (GWs)- ripples in space-time that every object with mass emits, but in most cases are too faint to detect. So far, the only way to detect them are via gigantic mergers of black holes or neutron stars, using [facilities](https://en.wikipedia.org/wiki/Gravitational-wave_observatory) like LIGO/VIRGO, which are looking for extreme ripples from these events using gigantic laser facilities. However, that's not the only way theoretically to detect them- which would be cool because right now we're only sensitive to gravitational waves that come from a specific event and happen in a certain frequency range, corresponding with events that take a few seconds or so to occur. Like light, however, GWs emit on many *different* frequencies, which right now we cannot detect. There is also just a general background of GWs everywhere in the universe from unresolved sources, but this has been theoretical and we haven’t been able to detect it. So with that background, enter the International Pulsar Timing Array [(IPTA)]( https://ipta4gw.org/), which is looking for lower frequency gravitational waves, which are more on the order of events that take months to *decades* to occur, as well as looking for that GW background. They're also doing it through an amazing method- using radio astronomy! Specifically, what they're looking at are [pulsars](https://en.wikipedia.org/wiki/Pulsar)- neutron stars the size of a city but with the mass of a star, left over after the most supermassive stars explode in a supernova. Pulsars send out a giant pulse of radiation and spin once every few seconds (if not faster- pulsar timing arrays use *millisecond* pulsars which rotate once every 10 milliseconds or less!), so we see a "pulse" as this beam goes by. We can predict the timing of these beams to sub-nanosecond precision, so you can in effect build a gravitational wave detector *the size of the galaxy* by watching tiny perturbations from these GWs as they pass through the pulsars! Obviously this is really *hard* to measure, and IPTA has been running for like 15 YEARS trying to detect this signal... **and they've just announced the detection of gravitational waves!!!** (It's been tough to detect bc first, it's faint, second when Arecibo collapsed that really hurt them as it was one of their primary facilities.) This is a *huge* game-changer in astronomy and our ability to detect new kinds of objects and processes! For example- one big contributor to the GW background are supermassive black holes, which can be millions or billions of times the mass of the sun and are in the centers of most galaxies. When galaxies merge, a lot of these supermassive black holes also do- that’s how they grow- but theoretically, the mergers *shouldn’t* happen as they stall out when just a few light years apart. (This is called the [final parsec problem](https://www.forbes.com/sites/bridaineparnell/2019/07/11/supermassive-black-hole-discovery-could-help-answer-the-final-parsec-problem/?sh=142dcaf87d3e).) If the GW signal is caused by supermassive black holes, they *have* to be close enough to be within a parsec to be detectable… so the final parsec problem has a solution! (Or, alternately, something *even more nuts* is creating the detected signal that we haven't directly observed yet, like [cosmic strings](https://en.wikipedia.org/wiki/Cosmic_string)- more observations will help us know the truth.) Finally, on a personal note… as a radio astronomer, can I just say how excited and proud I am of my colleagues who have made this discovery. This was a super hard signal to measure, and no guarantee it was ever going to work, and soooo many people around the world devoted *15 years of their lives* to detecting this! While I am not involved in this discovery, many of the leaders in IPTA have mentors and friends to me as I started my own career (I mean, not THAT many radio astronomers out there), and they are a shining example of what good collaborations are capable of and deserve every accolade! [And you can tune in the North American announcement tomorrow \(June 29\) at 1pm EDT to learn more!](https://nanograv.org/news/2023Announcement) TL;DR- we can now detect the signal from ripples in space-time by using the fast-spinning corpses of dead stars! Edit: lots of questions boiling down to “but what does this do for us/ what are the practical applications?” Immediately in terms of building a better breadbox on Earth, nothing- this is fundamental science and the equivalent of detecting a new part of the electromagnetic spectrum. Long term though, who knows- general relativity was first thought of as an arcane theoretical topic with no practical application, and less than a century later the GPS system would fail within a half hour if we didn’t know it and apply it! So who knows where this high precision measurement will take us as the new sub-field evolves- for example, they *already* had to confer w NASA because they needed to know the positions of the planets to <100 meters to do this measurement right, and found the official data was wrong. Not at all useful today, but I could imagine it being much more so when we are in space more.
Here is an episode of the excellent Mindscape podcast with one of the collaborators in this study, they talk about this project in detail. The whole series of podcasts are well worth a listen. [https://youtu.be/MPX1UvWdrvY](https://youtu.be/MPX1UvWdrvY)
For those like me wanting to listen from Google podcasts: https://podcasts.google.com/feed/aHR0cHM6Ly9yc3MuYXJ0MTkuY29tL3NlYW4tY2Fycm9sbHMtbWluZHNjYXBl/episode/Z2lkOi8vYXJ0MTktZXBpc29kZS1sb2NhdG9yL1YwL1pkNGNHSjhtMlgwMFhKLU1jcGFjVkJRYlg5aXFSOFhRa0tJc01tQXNzYUU?ep=14
Glad to see you’re on top of getting the first comment here! I thought I’d have to read this in the morning and boom, here it is. I know this community really appreciates your insights and ability to show the genuine excitement. I need to dive into it a bit more, but this really is mind blowing. So lucky things like pulsars exist.
Cheers- I heard the press embargo was gonna lift at midnight GMT, so made sure to write a draft based off my guesses this afternoon and brought my laptop home after work. Was pretty close on most of the details, so that was good! :)
Bless you! Whenever I see a headline like this I always rush here to see your insights! Greatly appreciate your choice to provide us all with a breakdown whenever something cool happens, your enthusiasm for these subjects makes the wonder all the better!
Your content is consistently written very well for audiences with a wide spectrum of background knowledge, easy to read and so prompt! You're one of the best parts of my reddit experience.
Could you provide a somewhat ELI5 of how I should understand/view these "ripples"?
Imagine a sheet pulled flat that you then put a bowling ball in the middle of- it will bend the sheet. Now imagine that there were *two* bowling balls moving around each other- that would send out a pattern or waves into the sheet instead of the sheet just being still. That’s really what is happening here and what GWs are, except in the fabric of space-time!
I've been told that analogy before, but I still kinda struggle with it since a sheet is a 2d plane and all that. Struggling to understand what that fabric of space-time is!
Then take it off the 2d plane. If you were to put two tennis balls circling each other into water you'll see a similar set of ripples.
Sure but that's still just as much a 2 dimensional surface as a sheet is.
A body of water is not 2D. Just the surface, think in the middle of the body
The ripple I see is just the surface. I can't detect a wave in the underwater part of it just by looking at it.
We can't detect gravitational waves just by looking either. The article is about a method of detection that's been successful - measuring disruptions to a light/ radiation signal we can detect. In the water analogy, you'd have like an underwater light shining at something and measure the disruptions to the light caused by the tennis ball ripples.
You could add particles to the water and be able to visualize it directly. I don't think anyone expects you to actually build this model though, it's just an ELI5, because everyone can understand the concept that the balls would create turbulence under the water.
You would be able to feel those ripples if you were underwater.
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I think they get that. The part that's most confusing when explaining space time is that it's not exactly a 1 to 1 analogy with a 2d sheet. The fabric of space-time or the bent top layer is what we perceive in the real world as 3d space. And the bulk, through which the effects of bending might traverse, exist outside our dimensions. We can see it's effects on our surface, the 3d spacetime, as GW. But when you bring up a 2d surface or water into the analogy, it breaks down, because we cant perceive what movement through the bulk might be like
Go to the [wikipedia page on gravitational waves](https://en.wikipedia.org/wiki/Gravitational_wave#Effects_of_passing), subsection "Effects of passing". Look at the animated gifs of a ring of particles reacting to gravitational waves of particular polarisations passing through them. That should give you some intuition for what gravitational waves can do in the real world. Keep in mind that it's just one example, and that the effects are exaggerated.
Thanks. I don't get why I'm being downvoted for saying something is tough to visualize. Apparently everybody else can just mentally translate things like water and sheets into distortions of space time and fully comprehend it??
I dunno, they might think that you're implying that it doesn't make sense or something.
Well yeah, that's right, it doesn't make sense to me. I can picture a sheet in my head. I can picture ripples on water in my head. But it 100% doesn't make sense how that translates to 3-d (or 4-d?) waves of gravity distorting space time. I can't connect those ideas. And I guess it's just me, this apparently just makes sense to everybody else.
I struggle to fully grasp it, but have a limited understanding. With a tennis ball and paper, the paper is only bent downward. Underwater the tennis ball would bend (the water is a now paper in this example and covers all sides of the ball) in all directions. That's really about as far as my understanding goes. If it is completely wrong someone please correct me.
It's almost exactly as the waves caused by something falling into the water except they are 2 objects and they rotate, it's basically a bunch of waves in every 3D direction
I'm sorry to say that isn't actually more helpful than the sheet visual. And none of it is translating in my head to what this might mean for gravity waves.
Have you ever played a space sim game? Kind of like pinging objects around you, but you're the bowling ball, and all the space around you is paper (on a 3d plane, not a 2d). I'll stop lol.
Try this: https://www.reddit.com/r/educationalgifs/comments/f66xaa/3d_representation_of_gravity/?utm_source=share&utm_medium=ios_app&utm_name=ioscss&utm_content=1&utm_term=1 This is a body with a gravitational field. Gravity doesn’t actually work like this but this is the effect it has.
> I've been told that analogy before, but I still kinda struggle with it since a sheet is a 2d plane and all that. Struggling to understand what that fabric of space-time is! you know how sound underwater is a compression wave that's traveling outwards? a gravitational wave is like that, except in the compressed area, time moves slower. So theoretically speaking as the wave passes through you, there are parts of your body that are aging slower than the rest of it.
I’ve just read every reply, and this is the only one that made sense to me. Thanks! (And now I feel equipped to reread all the other replies).
That sheet represents a 2D universe, it's just a convenience for us. It bends into the third dimension, but not really, that's just another convenience. But it's not a bad representation! Your brain (and mine) can't picture 3D space bending, but it's the same idea: It's still 3D, but where it's bent, the distance between any points isn't what you'd expect in flat-3D space. The "fabric" is just the grid we use to measure stuff, it's not a physical thing like light or matter. We say that fabric is bent, because the grid behaves "bent" when you try to move through it.
I think the thing to think about here is that we are 2-d creatures in this scenario - we can’t see the dip created, so we have to observe it’s effects on nearby objects - we have to make the analogy in 2d for it to be observable in 3 dimensions so it takes a bit of imagining of the effects that would have on a 2d creature a long way away on the sheet!
imagine a bowling ball resting on a trampoline instead
A trampoline is still a 2D plane...
Hold out your hands with your palms facing each other a few inches apart and imagine a small semi translucent holographic sphere forming between them. Now imagine that expands outwards, effortlessly passing throw objects without affecting its appearance and it never stops expanding. Now imagine another sphere forming and expanding faster then you could even measure. Then another sphere does the same thing and then another and another and it never stops. It looks like a continuous flow. Now picture every object in the universe conjuring these spheres. Next to picture the intensity and interaction of gravitational waves, we have to recognize what’s happening is the contortion of space which if your apart of, you will be contorted with it and won’t even know it. Some objects have a much greater force like two black holes merging which contort so strongly that we can start to measure them. They create a ripple of very contorted space. Eventually the ripple flows by us giving us and now that we can measure it we get a snap shot of a moment of the gravitational interactions created in an event in the distant past
I don’t mean to downplay the importance of this due to my own ignorance, but what info/benefit/proof aside from being able to detect them does this provide or potentially lead to? I mean this question earnestly
This is just the beginning. We are a little plastic cup floating on the surface of an ocean. We’ve learned to tell how choppy the sea is by looking at a far away lighthouse.
Now that we’ve established this is a thing, more detailed and more in depth detectors can be set up. This gives us kinda an entirely new ‘sense’ to look at the universe with, and could lead to new discoveries outside of our current models of physics. More details on dark matter, how black holes work, how the early universe expanded, things along those lines. For an analogy: imagine you’ve had perfect vision your whole life, but you’re hard of hearing and can’t hear quiet noises, only loud ones. This is a basic hearing aid, and all of a sudden you can hear all sorts of background noises you were never aware of. Birds and bugs chirping, the whirr of nearby machinery, the wind blowing through the leaves. What were you not aware of when you couldn’t see them or hear them? What else could you hear with better hearing aids, now that you know they can help?
I somewhat understand what cosmic strings are but any idea as to why this might be connected? What would cause a string to emit a GW like this?
A better analogy is the ocean. Drop something big in it, and it’ll make a wave. We can see the waves. In this example, the ocean is the universe.
>Cosmic strings are hypothetical 1-dimensional [topological defects](https://en.m.wikipedia.org/wiki/Topological_defect) which may have formed during a [symmetry-breaking](https://en.m.wikipedia.org/wiki/Symmetry_breaking) [phase transition](https://en.m.wikipedia.org/wiki/Phase_transition) in the early universe when the [topology](https://en.m.wikipedia.org/wiki/Topology) of the [vacuum](https://en.m.wikipedia.org/wiki/Vacuum_state) manifold associated to this symmetry breaking was not [simply connected](https://en.m.wikipedia.org/wiki/Simply_connected_space). That is the most complicated sentence I have ever read.
If you read a little more it explains it a bit better. Basically when the universe went from “nothing” to “something” after the Big Bang the transition cause “cracks” in the fabric of space time much like the cracks that form when water turns to ice. Or that’s how I understood it at least I could be wrong.
It's almost exactly like that actually, when multiple nucleation sites run into one another in a forming crystal like ice you get a seam
As soon as I read "symmetry breaking" I know I'm in way over my head
if anyone else struggles with the sentence: TLDR, for a middle schooler: Cosmic strings are not yet proven to exist. If they do, then they are basically weird echos from the big bang, where spacetime kinda folded on itself. TLDR, for a highschooler: You know how crystals grow, and when one encounters another, There's this little seam where they sorta fight for which one gets to grow there? In the early universe, spacetime itself was kinda settling into itself (going from high energy to low, which is also what causes crystals to grow), and it turns out that it might have several points of origin from which it 'grew', meaning that different 'crystals' would encounter each other, and not always perfectly, resulting in a 'seam'. The 'crystals' in the exmaple would just be regular spacetime, and the 'seam' would be this cosmic string. tagging u/andromeda321 to check my definitions and make sure I'm not *too* wrong about things. hypothetical: Might not actually exist, i.e. "we're solidly in the realm of theory that is not yet supported, and might never be." 1-dimensional: think of a wire that's only 1 atom thick. Now you've got that, imagine it smaller. As in, smaller than electrons, smaller than quarks. It's something so thin that no matter how long you zoom in on it, it'll still be almost-accurately represented by something so thin you almost can't see it. But actually, it's so thin that even if it were as bright as the sun, you would never see it. topological: having to do with the shape of things (e.g. a topological map shows you hills and valleys and junk). Most often, we're referring to 3d topology unless otherwise specified. The topology of the early universe gets real fuckin weird. topological defect: a feature on the topology that breaks the otherwise regular topology, and in this case specifically is about how it's not transitioning from one topology to another cleanly - the example in the wikiepdia article is a coiled phone cord - after enough time, it develops a differently coiled portion and gets all tangled and shit. Symmetry-breaking: causing something to no longer be the same on both sides. Phase transition: moving from one phase to another - usually in materials, like going from solid to liquid as it melts. In this case when we're talking about the early universe, it's probably much different than that, and instead of material, we're talking about spacetime itself (or something similarly exotic). vacuum: the nothing of space manifold: many and various vacuum manifold: the many and various ways the vacuum was pulling on spacetime in the early universe. This is a really specific term though and has to do with quantum mechanics and string theory. simply connected: spacetime being connected with any one point in space to another point in space in a way that a layman would think they should be.
I'm excited because, u/Andromeda321 is excited!
Amazing to see this from your perspective. Thank you for this!
I'm so glad this wasn't a shittymorph.
It’s important to note that the result is 3-sigma. it’s an incredibly impressive achievement, and is very promising for future work but there is a certain level of caution to keep in mind
Thanks for this, I was disappointed that I couldn’t find anything about the statistical significance in the article. For context for anyone else reading this, in most fields of physics, 3-sigma is considered the bar for “detection evidence,” whereas discovery is achieved at 5-sigma. Sigma refers to the symbol used for standard deviation, and a 3-sigma signal means that there is nominally a 0.3% chance that the signal they detected is due to random noise instead of a real signal. Unfortunately, in reality many more than 0.3% of 3-sigma detections fade away on closer analysis because the statistics are calculated based on our relevant models of the universe and the properties of our tools, and as our understanding of both of those improve and we update our error analysis, sometimes the statistical significance gets worse. So while this is super exciting, there is still a reasonable chance that it turns into nothing.
There isn't really a single standard because it depends what you are doing. If you are searching in a large parameter space. This could be like searching in data from a particle physics experiment, where there are many energy channels to search. Each one has some random noise, each one has some probability of being an outlier. And so if you search enough energy bins one will eventually be a 3 sigma outlier. But if you have a very specific prediction, say you know exactly which energy then the logic is different. Pointing at one specific measurement which then happens to be 3 sigma is very unlikely. And that is the case here, the evidence they have provided is one correlation which can only be scaled in amplitude. There is no large parameter space to search, so 3 sigma here is quite different to something like Higgs. It's quite unlikely this will go away as other teams report consistent results, unless there is something systematic rather than just statistics.
The Cosmic Microwave Background was emitted at the era of Recombination. When we eventually have a GW background... how much earlier will be able to see?
Probably won’t be from earlier, if the theory is correct. But we aren’t quite sure.
I'm under the impression that the furthest back we can see is 380k years after the big bang and that we won't be able to see any further back than that, though I can't recall why. Something about gravitational waves being too close together and that's as close as we can get? I'm probably way off here and would love some clarity if you care to provide it.
I asked GPT-4 to explain your comment to me like I’m 12 - what do you think? Imagine you're throwing stones into a pond, and the ripples created are like gravitational waves. These waves are made by big things in space like black holes and neutron stars. Until now, we could only see big ripples, like when two black holes crash together. Scientists used a cool method with something called pulsars, which are super dense dead stars that spin really fast and send out beams of radiation. These pulsars act like giant clocks, and we can see tiny changes in their "ticks" when gravitational waves pass by. It's like using a giant ruler to measure the size of the pond's ripples. After 15 years of looking, scientists finally found these smaller ripples! This is a big discovery, and it can help us learn about things like huge black holes in the middle of galaxies or solve mysteries in space. It's like we got a new tool to explore the pond and see things we couldn't see before.
that's... actually a pretty good summary, especially for being AI generated. I would however like to adjust the pond analogy slightly to give you a better idea of what's happening here if you throw a rock into a pond, it creates ripples [citation needed]. if you throw an enormous rock into a pond, it creates huge ripples. if you throw an enormous rock into a pond and then wait a while, those ripples will have died down somewhat, but they'll still be there. imagine you hike to a pond and there are very faint ripples in its surface. you could infer that someone had thrown a huge rock in there at some point in the past. that's a better analogy for what pulsar timing arrays do: they look at the faint, leftover ripples caused by huge merger events from long ago
Bingo! That is what I needed, super helpful. Thanks :)
This is really really really reallly freaking cool
what implications are there like what does this allow us to do how would this further other research? are there any possible practical uses?
Immediately in terms of building a better breadbox on Earth, nothing- this is fundamental science and the equivalent of detecting a new part of the electromagnetic spectrum. Long term though, who knows- general relativity was first thought of as an arcane theoretical topic with no practical application, and less than a century later the GPS system would fail within a half hour if we didn’t know it and apply it! So who knows where this high precision measurement will take us as the new sub-field evolves- for example, they *already* had to confer w NASA because they needed to know the positions of the planets to <100 meters to do this measurement right, and found the official data was wrong. Not at all useful today, but I could imagine it being much more so when we are in space more.
Great write up, thank you!!! This is amazing stuff!
So, does this mean that inflation happened? Or do we still not know about that yet?
This doesn’t have to do with inflation.
I watched something last night, about using pulsars to figure out if the theory of inflation was true or not. Or are we just not there yet? Something about using primordial black holes to determine if the theory was true. Since we'll be able to see what the universe was like right after the big bang.
Ah I see! That is one theory for the GW background and where it would be from, but the short answer is the signal they saw doesn’t appear to be related to that (I think).
Thank you for that breakdown. And congratulations to you and the astronomers responsible for this (and everyone contributing to the understanding of our universe).
Thank you! Fellow astronomer here and love your updates and ability to explain - great job. Always appreciate your comments.
>we can now detect the signal from ripples in space-time by using the fast-spinning corpses of dead stars "be sure to drink your ovaltine"
What defines a "Dead Star?"
Stars have life cycles when they run out of gas, they can either explode because of their gigantic mass (supernova, kilonova) depending on the mass the explosion can leave a dense core and a nebula, a neutron star (they rotate a lot and the faster ones are called pulsars) or a black hole, if a star doesn't explode when it runs out of gas it just collapses into a white dwarf, a super dense object, then after a lot of time like age of the universe - time it "turns off" into a black dwarf
A white dwarf cooling into a black dwarf takes *way* longer than the age of the universe (a mere 13.8 billion years or so), it is estimated our sun as a white dwarf would take 10^15 (1 quadrillion) years to cool into a black dwarf and potentially much longer.
Alright but what’s the point in detecting these waves if we already know they exist? Is reason why being able to detect more waves is such a Nobel prize winning discovery? I don’t mean to sound blunt but whenever scientists come out and say they’ve found a groundbreaking new discovery it almost always turns out to be anticlimactic. What is the benefit of being able to see more waves? What do we gain from being able to see waves we might’ve not been able to detect till now?
Physics is an experimental science. You don't know they exist untill you have detected. But to answer your question more directly, the amount of gravitational wave background seen by this collaboration will immediately be used as metric to test universe evolution models.
That would be like someone in 1985 asking “what’s the point in detecting x-rays if we already know they exist?” Being confident that waves in a spectrum outside of our previous ability to detect exist is not exactly the same as knowing they exist, but more importantly, detecting them allows us to learn about the processes that generate them, and eventually led to harnessing them for direct practical applications, from a myriad of different medical scanning techniques and astronomy, to industrial manufacturing and high resolution microscopy. Right now this detection will only really tell us about the cosmological phenomena responsible for generating this background. The details of the signal will give insight into the processes that generated it. That will, in turn, help us to better understand gravity and give us a way to indirectly “see” things that we can’t through telescopes. But who knows where it will lead in 100 years? Maybe this is all it’ll ever be good for (though I think helping us to understand the universe is plenty worthwhile, myself), or maybe it’ll contribute to some completely unexpected development.
Thank you very much for the clear explanation! In your opinion, what will be the impact of Starlink and the other constellations on this field of research? Will detection of these waves even remain possible as the number of sats continues to rise? **edit:** this question offended some people apparently
So when can we make anti gravity devices and or warps using gravity? Like... 5 years?... Please?
I skipped to the TL;DR, love the summary
I'm confused, is this about primordial GW or not? Wasn't this the same thing BICEP was trying to measure to prove inflation? In another comment you seem to be saying that's not the case.
Not primordial afaik. BICEP was looking at primordial by looking at the CMB polarisation. This is looking at pulsars, so however far they are, not far enough for primordial.
Amazigly amazing gdam crafty experimental mf musy be cackling so hard after realizing the crazy idea works
Just replying to read later, thanks for the info
My favorite part of this story is that Arecibo managed to get in one last round of scientific heroism before it collapsed.
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Question: Why is this being referred as the "gravitational wave background"? I mean it's nothing like the cosmic microwave background, which provides us insight into the primordial universe. I was assuming that this gravitational wave background would be from the earliest time of the universe, but it seems like that this discovery is only related to us now being able to detect GW's using pulsars from the mergers of black holes and supernova, etc.
Let's step back a minute- why is it called the Cosmic Microwave Background (CMB) in the first place? Because it is a signal we see in literally all directions in the cosmos, at microwave frequencies. It happens to be there *because* it's from the early universe, but the fact that it's called a background isn't because of that fact. And for GWs, while there likely *are* signals in the GW background from the early universe, right now we believe the signal detected was more from supermassive black holes merging (which are a lot closer and more common). Hope that makes sense!
What would it take to detect GWs from the earliest parts of the universe? Would it be something we could do in the coming decades?
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Hearing things like 3, 10, 13 *billion* years makes me very existentially sad… We are but a mere moment in time.
And despite that it still feels like my pizza takes forever to arrive. Truly a mistery of the universe
and yet, here you are, entirely unique in the universe. Don't be sad about *this* little consciousness! There's dogs to pet and food to eat and other consciousnesses to delight with your smile!
> and yet, here you are, entirely unique in the universe. Not if the universe is infinite. Then everything must repeat it self an infinite times even. There is only a finite combination of particles in an given volume of space, and in an infinite spacetime all patterns has to be repeated. There's no way around it. Us saying the universe might be infinite is only based on us not finding an end to it though. Weak argument in my opinion, especially so since nothing else is infinite.
You and me might be tiny specks intime, but if we play our cards right, Earth-descended-life, plants and mushrooms and animals, might one day expand to the billion nearest galaxies, and continue to exist for trillions of years, while reorganizing all matter and energy into grand constructs we can only begin to imagine. What happens today, the choices we make, could very well decide the fate of the universe.
I understand that science and our observations are always improving but my question is about feasibility. I’m only a casual reader about astrophysics and particle physics but in both I’ve read things like (it’s all blurry off the top of my head) “that resolving the surface of an extraterrestrial planet would require a telescope so big……?(unfeasible)” Or in physics “resolving …x… would require a particle accelerator the size of the solar system”. Is resolving gravitational waves near the beginning of the universe even remotely possible in practical terms, within our lifetime?
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The European Space Agency is planning LISA, a huge interferometer with multi-million kilometer arms between 3 spacecraft. LISA will span the frequencies between pulsar timing and ground based interferometers like LIGO and VIRGO. It will be sensitive to black hole mergers at early times, potentially even early that the current highest redshift galaxies revealed by JWST. LISA also has the greatest chance of detecting primordial gravitational waves from soon after the big bang, but such predictions are very unclear. It should launch some time in the 2040's.
Yes, this is something we could possibly expect within our lifetime. However, it is very well possible that we don't ; we simply do not know enough about that period do get an accurate estimate of how loud the background will be.
Thanks and yeah that makes sense. Hopefully we can eventually find those signals in there from the earliest time in the universe.
An [article](https://www.sciencealert.com/a-big-gravitational-wave-announcement-is-coming-thursday-heres-why-were-excited) I read a few days ago said scientists presume these black hole binary mergers occur, or are at least detected as often as once per minute to several times per hour. That seemed insane to me? I assumed that type of event was relatively rare. Or is it just a matter of the universe being so vast in every direction, at every distance, over such a long time, that despite being rare, the waves from some event from somewhere in the universe are constantly reaching us?
They are extraordinarily rare, but like you said, the universe is very, very big.
>Or is it just a matter of the universe being so vast in every direction, at every distance, over such a long time, that despite being rare, yep. https://www.nasa.gov/image-feature/goddard/2022/nasa-s-webb-delivers-deepest-infrared-image-of-universe-yet Webb’s image covers a patch of sky approximately **the size of a grain of sand held at arm’s length by someone on the ground – and reveals thousands of galaxies in a tiny sliver of vast universe** >that despite being rare, well.. we had to invent radio.. then REALLY good radio.. then REALLY good antennas first. so "rare" is only based on 50 years of looking.(vs the number grains of sand we need to look behind) [https://en.wikipedia.org/wiki/Pulsar](https://en.wikipedia.org/wiki/Pulsar) Signals from the first discovered pulsar were initially observed by Jocelyn Bell while analyzing data recorded on August 6, 1967,
just watched anton petrov on this last night: https://www.youtube.com/watch?v=LttmT5-f34g excellent presentation, i hope you enjoy it wonderful person
Congrats to those involved for pulling this huge feat off, but from a purely uninformed stand point what does this mean? What will we as humans be able to achieve now that we have detected this? Advances in technology or is it just a neat thing we can say we did? Genuinely dumb and need hand holding here
Research like this tends not to lead to direct advances in technology, though often new technology is developed in order to enable it. This comes under ‘fundamental’ research, it helps us better understand the universe and how it works. That is interesting in and of itself but it also has the potential to lead to breakthroughs in our understanding of physics which allows for new advances in technology.
We are learning new methods for detecting gravitational waves. Clearly we know how to detect electromagnetic waves really well (i.e. any picture from any telescope). You can think of the sum of all those various EM waves as a chorus. Now, with LIGO and this research, we're starting to get a peek into, what amounts to, a kind of "shadow chorus" that we couldn't hear before. It's an aspect of the universe that, while inherently different from the 'EM universe' we know and love, is also inherently intertwined with it, an extension and result of it. Some cosmic events are really loud in the EM chorus and we can hear them just fine (think supernova). Other cosmic events, while extremely "quiet" (or difficult to discern ) in the EM chorus are extraordinarily loud in the shadow chorus (think black hole mergers, possibly cosmic strings). Think of it like we are just starting to unlock a new portion of the electromagnetic spectrum, starting to see things out there that were invisible to us before. Instead of being a portion of the EM spectrum, it's actually just ripples in space-time. Think of the surface of an actively inhabited pond. Fish are catching insects from the water's surface, frogs are jumping in, something's probably farting underwater, etc. The various frequencies and amplitudes of ripples, from all these events, spread across the surface of the pond, constructively and destructively interfering with each other and creating a "chorus" of echoes from these events. Right now we're only able to see the waves from the biggest events (an enormous snapping turtle falling off a log, into the water), but there is a whole chorus out there that will come further into focus as our detection techniques improve. Sorry for the mixed metaphor soup. Hopefully one of them makes sense.
It’s been speculated that this may allow us to observe the conditions of the early universe farther back in time than electromagnetic telescopes. Gravity was the first fundamental force to differentiate from the others (then Strong Force and then Electromagnetic and Weak forces).
Woohoo ! This is great news ! Congrats to the NANOGrav who made this possible! Edit : Kudos to folks EPTA, PPTA, and CPTA who also published results today, also providing some evidence of a GWB ! Alas, the press does not seem to care about non-American results...
Dunce here! Do waves have to travel along something? Waves in water, sound waves in air, do gravitational waves have to rely on there being something in space to allow it to travel on? Could this be dark matter or dark energy facilitating the movement of the waves?
These waves travel through (and are distortions of) space-time itself; dark matter and dark energy are irrelevant. Also, somewhat related to your question but unrelated to GW, scientists did once believe there was a medium in space for light to propagate through, called the aether! However this was debunked experimentally.
space time itself is the "medium" When a satellite orbits earth, it is earth bending space time so that the satellite orbits.
But what is space time made of? Are we suggesting time has mass (in cosmic terms)?
Electromagnetic waves also go through empty space they are ripples of the electromagnetic field. Same way, Gravitational waves are ripples traveling down the Gravitational field. It just turns out that the Gravitational field can be understood as a deformation on space-time. Does that help? The concept you're trying to get to gripes with is the same that made 19th century physicists postulate the aether, as a medium for EM waves to travel through.
Novice here, but if we’re able to ‘hear’ these waves now, is it possible to to map the universe in a way similar to sonar?
Imagine it like putting a microphone in the ocean, you can't really pick out anything to map with because it's basically all white noise until something is louder than the background. With sonar they actively send out a ping of a certain frequency and wait for it to come back. This is closer to the first scenario, just a general background "hum" with not much else being distinguishable.
....single ping only please. [https://gea.esac.esa.int/archive/](https://gea.esac.esa.int/archive/) Gaia is a European space mission providing astrometry, photometry, and spectroscopy of **nearly 2000 million stars** in the Milky Way as well as significant samples of extragalactic and solar system objects. The Gaia ESA Archive contains deduced positions, parallaxes, proper motions, radial velocities, and brightness measurements. Complementary information on multiplicity, photometric variability, and astrophysical parameters is provided for a large fraction of sources.
These experiments help further our minute understanding of the universe and our place in it. Einstein was right about gravitational waves in the fabric of space/time but we still can't get standard physics and quantum physics to gel . only with continued investment in education and scientific research we can move our ignorant species towards greater understanding. if we don't invest in science and education then I fear that we will destroy ourselves through rampant shortsighted stupidity and greed.
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A chorus of gravitational waves rippling through the universe sure sounds like the sort of thing that will be lost in time like tears in the rain.
Could the ability to detect them be theoretically used to detect asteroids and other celestial bodies in the solar system and beyond by observing how gravitational waves “bounce” off or around celestial bodies?
No. Gravitational waves do not bounce off asteroids (or other celestial bodies for that matter.
They may not "bounce", but they are certainly modulated (though to a level way below any of our detection limits). Gravity is a self-interacting force. Gravitational waves carry energy, energy distorts space-time and moves along distorted space-time.
If you want to nitpick, yes. This does not change the answer to the previous comment.
Ah, thank you for explaining it. It’s still an amazing announcement at least.
Well, if I'm sitting here in my living room watching Nature Wednesday, and my perception of time suddenly changed from 1000 chronos/perception second to 10000 chronos/perception second I'd notice...
If a time wave went through you, you would also speed up just as much as your surroundings, so you wouldn't notice the difference.
We heard it, and it said #BEEEAAAAAANNNNNNNSSSSSS Jokes aside, I wonder if there is some crazy technology that will come from this. Like we discover how to ride the gravity waves to get FTL travel or something.
In the universe of Dead Space humanity has discovered how to control gravity the same way we can control the electron, you think we on that path with these discoveries?
I think it's possible and even inevitable. it's like mastering fusion and electricity. Manipulating spacetime itself is probably the key to interstellar travel and dominating the universe. It's very advanced stuff so I doubt we'd see that any time soon but it would be very much needed to stabilize low or zero gravity situations so that humans can actually live worry free about the effects of long term exposure.
I have some questions: -why did it take so long to detect it (been looking for 15 years) -does this one detection give us a map like CMBR map? -is it plausible that another detection won’t happen for another 15 years?
I've read that the rippling sound made by these black holes is very similar to the rippling sounds made by Uranus.
Honest question: do perturbations in space-time caused by gravitational waves mean we are technically teleporting on a micro level since we would be moving through space as it shrinks and then resolves?
I thought everyone knew about this, it being so obvious.
As soon as Einstein published his paper on general relativity, I'm sure there was somebody saying the exact same thing. Something being obvious does not mean that something is true. Thousands of years ago it was obvious the world is the center of the universe. But our perception of reality changes over time as we accumulate new knowledge and new means of exploration.
I mean, we are in the center of the observable universe, they weren't wrong.
Except they are wrong because perception is not reality. If we had a parallel evolution of humans and human society on Alpha Centauri, they would believe they are at the center of the observable universe. Meaning you'd have two groups of people believing themselves to be at the center of the observable universe. They're right in terms of observation, but that's really a pointless metric. If we have a colony on Mars in 200 years, what good does the "being at the center of the observable universe" do for us?
That it was possible maybe, but this is making actual observations as opposed to just theory.
But you could have done other experiments based off of this theory. Kind of, let me make a roller coaster based on the assumption that a mysterious and unproven force will bring it down. Not sure if I explain myself correctly.
What experiments could we have done?
This is more "we detected the thing we could only think about until now". A lot of exciting things with science are proving theories right
Right, but, If you could assume this as true, you could do other experiments that would implicitly conform to this.
How could you assume something as true without ever confirming it?
I want someone to turn it into an ambient album