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Monster gravitational waves spotted for first time
- 0xfai 3y agoThinking about how gravitational waves pass through us all the time stretching us out and squishing us and changing how time passes has for some reason been one of the most comforting realizations I've ever had. I still don't quite have the right words for why, but to me it kind of answers questions like if we are in a simulation (my hunch is no) and weird head trip questions that can be depersonalizing like that from my perspective last Tuesday I started hallucinating all of this including everything I think is my history. Not that I think that, just something about the foam of turbulent gravity washing over all of us invisibly. Yeah, comforting.
- ComputerGuru 3y agoMore reporting, for a more pedestrian overview: In a major discovery, scientists say space-time churns like a choppy sea https://www.washingtonpost.com/science/2023/06/28/gravitational-wave-background-nanograv/ https://www.washingtonpost.com/science/2023/06/28/gravitatio... (Archived: https://archive.is/AmRvg https://archive.is/AmRvg)
- deleted 3y ago[deleted]
- TechBro8615 3y agoThat WaPo article was also discussed [0] on HN yesterday (although most of the comments were about the garbage quality of the reporting). [0] https://news.ycombinator.com/item?id=36514521 https://news.ycombinator.com/item?id=36514521
- ComputerGuru 3y agoThanks for the link. I had issues with the WaPo article, but that tongue-in-cheek joke with dead-pan delivery wasn't one of them. Fortunately another commenter called it out as a joke as well.
- sslayer 3y agoImagine if we could take advantage of the time-space potential/differences between gravitational areas to "skip" large parts of space. We would have to have a very precise gravity map, but could also get huge gravity potential boost!
- nomel 3y agoCould we? Is there math that supports this? Wouldn't this require taking some, and then not losing it when the wave passes? I don't see much happening with the earth, as it's experiencing them, so I assume the "extraction" process would be significant and unique.
- anonym29 3y agoEDIT as a commenter below has kindly pointed out, our current models indicate that the answer to this question is "no", per https://www.youtube.com/watch?v=QMFLcmsjOBg https://www.youtube.com/watch?v=QMFLcmsjOBg ------ This is all firmly outside my technical discipline, but aren't there some theories that faster-than-light travel might be achieved by bending spacetime around a spacecraft, as opposed to trying to propel the spacecraft through space? I really want to emphasize that this is entirely speculation, but is it possible that these gravitational waves could be the "ripples" produced in the wake of such faster-than-light travel, the same way a boat travelling through a body of water leaves ripples in the water behind it?
- sidcool 3y agoTheoretically it's impossible to travel through space at or more than speed of light. But space itself can move faster than light speed, and a warp drive would help something similar that you mentioned. That is possible theoretically. But the amount of energy or mass it needs is very high and no current technology (or in foreseeable future) can achieve it. So FTL remains a dream. My hunch based on nothing is that we will achieve FTL no earlier than 2250.
- SketchySeaBeast 3y ago> My hunch based on nothing is that we will achieve FTL no earlier than 2250. I see you too have been forced to give PMs estimates when you don't understand the problem.
- actionfromafar 3y agoAnd without a later bound, so a very reasonable estimation too.
- anonym29 3y ago"Did I say 2250? Sorry, I meant 22,500. Yeah, you know, with all the extra time needed to compile and everything..."
- Zoadian 3y agoare g-waves causing the Galactic filaments?
- notaustinpowers 3y agoNo, they are not caused by the galactic filaments. We don't know exactly yet what all is causing gravitational wave background (GWB), but a theory is that it could be caused by supermassive black holes, or primordial black holes from the early universe, etc.
- Zoadian 3y agoI asked the reverse. If the filaments are caused by gravitational waves.
- notaustinpowers 3y agoNo to that as well. The galactic filaments are just aggregations of gravitationally-massive objects in space.
- MeteorMarc 3y agoSee also Quanta Magazine: https://www.quantamagazine.org/an-enormous-gravity-hum-moves-through-the-universe-20230628/ https://www.quantamagazine.org/an-enormous-gravity-hum-moves...
- r721 3y agoAnother discussion: https://news.ycombinator.com/item?id=36514521 https://news.ycombinator.com/item?id=36514521
- derefr 3y agoWhat do these waves look like as they pass through us? Acoustic-like compression and expansion of particles as molecules temporarily reorient toward a “down” that is ever-so-slightly off from the Center of mass of the Earth? Also, I assume that these waves are very gentle sinusoids? Could the opposite — a high-amplitude gravitational square wave — be possible? What would it do to the things it passes through?
- readams 3y agoIt's not so much that you see a slightly different "down," but that space itself is changing such that the distance between e.g. your head and feet is (very) slightly altered.
- jessriedel 3y agoThe two descriptions are equivalent. By the equivalence principle, the wave looks locally like neighboring bodies see different directions of down (and also slightly different strengths of the force of gravity in that direction).
- truculent 3y agoDumb, but earnest question: if space itself changes, how can the distance change? What is the distance a measure of, if not space itself? What's the yardstick, speed of light?
- ISL 3y agoThe yardstick is indeed the light-travel time. Gravitational waves really do change the time it takes for light to travel between two points. We use light travel-times to measure distances, thus we say that the distance between the points has changed. If it feels counterintuitive for spacetime to be changing, that's good. It is outside our human experience and perception. The strongest gravitational waves ever observed by scientists passed through everyone who was alive in 2015. None of those people noticed before the instruments registered a detection.
- peterlk 3y agoHey dang! There are a ton of these threads showing up right now. Any chance we could get them merged or pinned in a comment?
- FollowingTheDao 3y agoIf the distance between the earth and these stars can change, then we can change the distance between the earth and these stars.
- pedro_hab 3y agoMathematically yes, actually probably not. I'd suggest looking into Alcubierre Warp Drive, cool story on why the guy came up with it and shows how to wrap spacetime around a spaceship to make it go faster than light. The ship wouldn't go faster than light because it wouldn't move at all, the spacetime around it would. The channel below has quite a few other videos on the subject. I love it. https://www.youtube.com/watch?v=94ed4v_T6YM https://www.youtube.com/watch?v=94ed4v_T6YM
- tannhaeuser 3y agoAlso, The second data release from the European Pulsar Timing Array I - The dataset and timing analysis [1] was published just today. [1]: https://arxiv.org/abs/2306.16224 https://arxiv.org/abs/2306.16224
- rkagerer 3y agoCould one devise similar detectors for time dilation and expansion?
- domrally 3y agoThese waves were discovered in spacetime, so these detectors are already for both space and time dilation and expansion.
- deleted 3y ago[deleted]
- TechBro8615 3y agoI understand the gist of this research: pulsars emit radio waves at regular frequencies, so by monitoring radio waves received from pulsars in the sphere surrounding us, we can measure correlated anomalies in their frequencies and infer that they were caused by large gravitational waves that effectively changed the shape of the transmission medium. That makes sense. But this is not measuring the gravitational wave itself. It's measuring the change in trajectory of the radio signals that are "riding" the wave. In the ocean analogy, it would be as if we were surrounded by a circle of floating turrets that each emitted floating darts at regular intervals in all directions. Then we would measure the time it took the darts to reach us, and from that we could infer the size of the waves the darts encountered along the way. But we never actually see the waves, only the darts. So my question is: how can we tell the difference between one really big wave, and many really small waves that would sum to the same effect? In other words, we know there is some waveform(s) that changed the velocity vector of the radio signal. But if there are multiple arrangements of waves that would produce the same change in signal, how do we pick the right arrangement?
- rkagerer 3y agoThe timing of a single pulsar would not be reliable enough to detect gravitational waves. Instead, each collaboration monitors an array of dozens. As a result, they have found a signature called the Hellings–Downs curve, which predicts how, in the presence of gravitational waves coming from all possible directions, the correlation between pairs of pulsars varies as a function of their separation in the sky. Not sure it answers your question but my impression is they simulate results of all possible effects and then see which one(s) the data correlates with. So if there are multiple causes that could produce identical effects then I doubt they could distinguish between them.
- TechBro8615 3y agoThat makes intuitive sense. So I guess the more pulsars we measure, the more accurately we can disambiguate between different possible waveforms. It reminds me of EEG (brain wave) measurement: a hairnet with 256 electrodes will have higher resolution than one with 128 electrodes (ignoring all the issues with interference of the skull).
- theonlybutlet 3y agoA great non-technical explanation https://www.reddit.com/r/space/comments/14lpjnx/scientists_have_finally_heard_the_chorus_of/jpxitgq?utm_source=share&utm_medium=android_app&utm_name=androidcss&utm_term=1&utm_content=share_button https://www.reddit.com/r/space/comments/14lpjnx/scientists_h...
- bilsbie 3y agoDumb question but why can a gravity wave escape a black hole but not a light wave?
- jessriedel 3y agoRoughly speaking, it's because the waves are emitted from the region outside the black holes, being created by the in-spiraling of two black holds before/during their merger. Once the black holes merge and settle down, they stop emitting gravitational waves. But that's just a cartoon. Strictly speaking, the picture of a wave traveling with respect to a fixed background spacetime is only an accurate approximation when the wave is very weak. In the immediate neighborhood of a black hole merger, the approximation breaks down, and you just have to look how the whole spacetime itself is evolving (usually through simulation).
- chorsestudios 3y agoThese ‘monster’ gravitational waves have supposedly been ‘spotted’ by calculating disparities in pulsar timings. The article didn’t have as much information as I was hoping - were any of these waves detected/confirmed by LIGO?
- gaoshan 3y agoIt's my understanding that LIGO is too small to be able to detect such waves, hence the use of pulsar timings.
- flqn 3y ago[dead]
- seventhson 3y agoThe wavelengths are too large for LIGO. The wave measurements were correlated with data collected from many pulsars. https://arstechnica.com/science/2023/06/nanograv-picks-up-signal-of-cosmic-choir-of-supermassive-black-holes/ https://arstechnica.com/science/2023/06/nanograv-picks-up-si...
- chorsestudios 3y agoThank you for this article link, I found it much more informative than the parent article. The video at the bottom was well made.
- bowsamic 3y agoAs others pointed out, LIGO is too small compared to the wavelength of the GW, but even if LIGO was extremely long, the technical noises (seismic, control system noises, gravity gradient noise, etc.) at such low frequencies are extremely high for ground-based detectors
- x3874 3y ago[flagged]
- beginning_end 3y agoI'm curious what the amplitude of these waves are: what's the (order of magnitude) change in the distance to a 1000 light year distant pulsar, as the gravitational wave passes through? Edit: Being told by @Dr_CMingarelli on twitter that it's 10 meters pr lightyear.
- lucgommans 3y agoYou mean in like meters? > Each observatory has two light storage arms that are 4 kilometers in length. [...] A passing gravitational wave will slightly stretch one arm as it shortens the other. [...] Even with such long arms, the strongest gravitational waves will only change the distance between the ends of the arms by at most roughly 10⁻¹⁸ m. With the nominal hair value being 75 µm, `apt install qalc` tells me that's > 75 µm / 10^-18 m (75 * micrometer) / ((10^-18) * meter) = 7.5E13 so a change in length 7'500'000'000'000 times smaller than the width of a hair https://en.wikipedia.org/wiki/Gravitational_wave https://en.wikipedia.org/wiki/Gravitational_wave , https://en.wikipedia.org/wiki/Hair%27s_breadth https://en.wikipedia.org/wiki/Hair%27s_breadth
- beginning_end 3y agoI was referring to the latest results using pulsars.
- kennywinker 3y agoThat's for the gravitational waves we can detect from LIGO. These new ones, as I understand it, are being detected by changes in pulsar frequency over 15 years of measurements - so they have a pretty different character than the ones wikipedia's talking about... I don't know how that translates to anything that makes any sense tho
- kennywinker 3y agoPer the wikipedia article: https://en.wikipedia.org/wiki/Gravitational_wave https://en.wikipedia.org/wiki/Gravitational_wave > Gravitational waves are not easily detectable. When they reach the Earth, they have a small amplitude with strain approximately 10^−21 "strain" being the unit-less measurement they use for gravitational wave. The ones we measured just now, if I'm reading this article right (https://iopscience.iop.org/article/10.3847/2041-8213/acdac6 https://iopscience.iop.org/article/10.3847/2041-8213/acdac6), are being reported as 2.4x10^-15. I can say that's a lot larger, but I can't tell you much else about what that means.
- 8lahaj 3y agoI was hoping they were gravitational waves from a monster, darn title getting my hopes up.
- ivanhoe 3y agoWhat's the value of amplitude of one such 'monster' g-wave?
- photochemsyn 3y agoAstronomy Picture of the Day has a nice graphic of this: https://apod.nasa.gov/apod/ap230629.html https://apod.nasa.gov/apod/ap230629.html Spacetime is incredibly resistant to deformation, hence the tiny displacements and the need for long-baseline laser interferometry to detect these waves. https://blogs.scientificamerican.com/life-unbounded/just-how-resilient-is-spacetime/ https://blogs.scientificamerican.com/life-unbounded/just-how...
- thallada 3y agoHow are we sure that pulsars are 100% consistent? How do we know the timing discrepancies are due to gravitational waves and not just tiny wobbles in the pulsar itself?
- pertymcpert 3y agoFTA: they don't just use a single pulsar.
- satellite2 3y ago[flagged]
- m3kw9 3y agoThis joke is probably the most this discovery will affect me in my lifetime
- swayvil 3y agoI hear that gravity is a contour in spacetime, or something like that. Does that mean that a gravity wave is a ripple in space or a travelling wave of pinched or stretched space? Also, assuming all that. I think we have 2 ways of squishing space this way : mass and acceleration. Are there any others?
- sam_goody 3y agoCan someone please ELI5: I was taught that all items fall at the same speed, due to the gravitational constant. With these waves, does that mean that items will fall at ever so slightly differing speeds, as depending on the size of the wave there is a pull in the other direction, and the constant is slightly off? And OT, but related: Since every item has a gravitational pull related to its mass, would a bigger item fall ever so slightly faster than a small one, as it is pulling itself to Earth in addition to Earth pulling it down.
- mpalczewski 3y agoGravitational waves warp space/time. so the distance between two points will be slightly longer/shorter.
- deleted 3y ago[deleted]
- pdonis 3y agoNo, gravitational waves do not affect the equivalence principle and do not change the gravitational constant. They are waves of change in the geometry of spacetime; freely falling objects show these spacetime geometry changes by changes in their relative motion.
- Lichtso 3y agoWell in both your questions it depends on how you define speed. It is commonly understood to be the first derivative of position, or the quotient of distance divided by a time-span. But how do you define and measure distance and time-spans? Which reference frame do you use? Also, the things falling in a vacuum at the same speed thing is a common misconception. The two arguments usually are that the mass of one body can be canceled out in both equations or that splitting a body into two won't make its halves fall slower. To answer the question: Given all bodies have the same size, a constant distance to and mass of the reference body (usually earth) and everything starting at rest with no relative speed heavy and light bodies do experience the same acceleration, but a heavy body will collide sooner than a light body. Did it "fall faster"?
- mtlmtlmtlmtl 3y agoModern physics(and engineering) is kind of absurd. And I mean that in a good way. LIGO? I didn't believe at all that it would ever work. Even when they got detections I kinda thought they were chasing their own tails. Now the evidence is pretty much rock solid that the data is real(multiple facilities, correlations with light observations for neutron star mergers, etc). Then I heard about LISA, which essentially is building this thing in fucking space(different geometry, but same basic concept), with probes somehow orbiting in unison and firing lasers at eachother over ridiculous distances(2.5 million kilometers!). I thought they were raving mad. But pathfinder, the POC, seemed to work, and now they're building the thing. Planned for 2037, but still. When I heard about this project in a spacetime video a few years ago IIRC, again I thought okay, this is too far. It's never gonna work, there'll be too much noise yadda yadda. And it now it looks they might have done it. At this point, if physicists say something is possible, I listen no matter how impossible it sounds.
- defrost 3y agoIt takes a while to build these things. My physics professor, David Blair, sketched out the design for LIGO and other detectors back ~1980 and the kinds of technology that would first need to be created in order to get there. The big money and the big builds tend to be in the US (for now, at least, but empires always shift centres over the long time periods) but the ideas come from all over the world. https://www.uwa.edu.au/Profile/David-Blair https://www.uwa.edu.au/Profile/David-Blair
- MichaelMoser123 3y agoso how comes they can't get this fusion thing to work?
- distant_hat 3y agoFusion is easy and you can set off a hydrogen bomb whenever you like, it is turning that energy into electricity that's the hard part.
- JumpCrisscross 3y ago
- mcpackieh 3y agoProbably a stupid question, but could you theoretically surf on gravitational waves? Obviously not on earth, but maybe near a binary black hole or something. If I imagine waves in a rubber-sheet mental model of gravity warping spacetime, it seems like surfing should be possible.
- jcarreiro 3y agoSadly, this is not possible, at least AFAIK. The basic problem is that a gravitational wave won't push against you, like a water wave would; the wave will pass through you. See https://worldbuilding.stackexchange.com/questions/36113/would-it-be-possible-to-ride-a-gravitational-wave https://worldbuilding.stackexchange.com/questions/36113/woul... for a more detailed explanation.
- kumarvvr 3y agoSo, this methods relies on detecting changes in distance between earth and distant pulsars. How can that be accurate enough to measure space-time ripples? Mind bending to think about it.