[HN Gopher] Gravitational waves should permanently distort space...
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Gravitational waves should permanently distort space-time
Author : theafh
Score : 105 points
Date : 2021-12-08 15:22 UTC (7 hours ago)
(HTM) web link (www.quantamagazine.org)
(TXT) w3m dump (www.quantamagazine.org)
| mikewarot wrote:
| The detectors we have are just sensitive enough to detect the
| spin down when two objects 50+ times the size of the sun merge
| into a single new object. The gravity in the direction of the
| objects decreases permanently by the delta of the mass expended
| creating gravity waves, which is shift too small to measure.
|
| I expect it may be possible in the future to confirm this, very
| small, persistent shift in spacetime, but not in my lifetime.
| cobaltoxide wrote:
| Gravitational wave detectors can only detect oscillatory
| signals, not static ones.
| tejtm wrote:
| Would not be surprised if this cues some
| Expansion of the universe due to gravity lost in waves.
|
| headlines.
|
| But the distance scales and force magnitudes are so far out of
| my experience that even with the help of math I would be hard
| pressed to be convinced one way or another.
| nsxwolf wrote:
| Could this mean the possibility of stable wormholes that don't
| require any "exotic matter" to keep them from collapsing?
| eli_gottlieb wrote:
| How can you change space-time? It's already got a time dimension,
| so you'd need _another_ time dimension with respect to which to
| take the derivative. Or is the real claim here that gravitational
| waves distort space as part of their temporal dynamics?
| LegitShady wrote:
| We already know that spacetime has local curvature, so it's
| possible that spacetimes curvature isn't static. How this
| affects or interacts with time isn't clear, since we don't
| really understand what spacetime is or how it comes to be.
| codingclaws wrote:
| I've had that theory. Gravity wells remain for a time after the
| responsible mass has moved on. Maybe that explains dark
| matter/energy.
| edgan wrote:
| I like your theory, but it doesn't explain galaxies that don't
| seem to have any dark matter.
| ststephen88 wrote:
| This is clear evidence, these are angels, be not afraid.
| kevinconroy wrote:
| Cue "Three Body Problem" trilogy references
| ASalazarMX wrote:
| Gravitational waves in the series are only mentioned briefly,
| as a telecommunication medium. IMO communicating with gravity
| waves is excessive, and they're not faster than electromagnetic
| radiation.
| bigodbiel wrote:
| Obviously not the graviational waves, but I was also thinking
| abouth the warp bubbles used in FTL travelling (and its
| abuse) distorting space time forever
| ASalazarMX wrote:
| But all space travel in "The Three Body Problem" is
| subluminical? I can't even recall a single Liu Cixin story
| with FTL space travel.
|
| The closest situation I can think of is ST TNG "Force of
| Nature", where warp travel was damaging subspace.
| SavantIdiot wrote:
| I read that whole article and all I came away with was,
| "Gravitational waves bend space time a little in a phenomenon
| called gravitational memory." I still have no idea by what
| mechanism though, other than guesses at some deeper super
| symmetry.
|
| Can anyone dumb this down a little more for me? What holds on to
| the deformation? If spacetime can be deformed by a gravitational
| wave, then how can its original be entirely decided by the amount
| of and the arrangement of matter nearby. Meaning: if a wave
| passes by, unless it impacts the arrangement of matter in the
| locality, then what "holds" the deformation?
| T-A wrote:
| Here's another (better, I think) attempt to explain it in plain
| language, from a few years ago:
|
| https://nautil.us/issue/69/patterns/how-the-universe-remembe...
| bopbeepboop wrote:
| Space time curvature is defined by the _energy_ nearby -- ie,
| photons contribute too. And so do gravitational waves!
|
| So the thing to remember is that the gravitational wave (having
| energy) interacts with space time -- and can create more
| gravitational waves!
|
| So the intuition here is that a wave passing an otherwise
| smooth area of space time leaves a permanent turbulence due to
| the nature of how space time waves propagate -- because the
| gravitational wave is interacting with space time and itself as
| it propagates.
|
| Space time is a tiny bit permanently mixed up because a space
| time wave passed through it.
| goohle wrote:
| Spacetime is just 4D array: [x,y,z;t]. "Bending of spacetime"
| means that you need to apply a shader to this array.
|
| If you want to talk about physics of the process, then you need
| to pick up a physical medium first, not an array of
| measurements.
| jcun4128 wrote:
| I don't get in many depictions they show this planet/ball
| over a grid that's deforming downwards. I can understand how
| another mass would want to "fall" into that but is it
| actually that shape (has up/down) or it some kind of sphere.
| I also believe with regard to mass clumping, gravity is
| strongest near the surface of the Earth vs. inside where you
| could say it's equal/0 except the oblique part.
| ben_w wrote:
| The rubber sheet analogy is criticised for this exact
| reason. Here's a different visualisation that starts with
| what's wrong with the rubber sheet:
| https://youtu.be/wrwgIjBUYVc
| pomian wrote:
| That's an amazing little video. thanks for posting.
| (Maybe that should go on to the main page, at some point)
| rdtsc wrote:
| Great video. Another one I like is "Why Gravity is NOT a
| Force" from Veritasium
| https://www.youtube.com/watch?v=XRr1kaXKBsU
| drran wrote:
| It uses gravity force to demonstrate that gravity force
| is not a force. ;-)
| jcun4128 wrote:
| Oh yeah I can see the 3D sinking inwards
|
| that's a neat video haven't seen that slicing idea before
| leephillips wrote:
| That's the best visualization of gravitation I've ever
| seen. Well done. I recommend it to anyone who's been
| misled by the ubiquitous rubber sheet picture.
| akomtu wrote:
| That's clever. I'd suggest an improvement. When a sat has
| initial speed, show its small local reference frame, so
| we'd see that it always moves forward in its own
| reference frame, but the frame happens to be pulled to
| Earth.
| SavantIdiot wrote:
| That's a great video. 7:50 is the important twist for me,
| and 10:25 really drives it home. I'll never forget that
| video now and it explains so much.
|
| THere's still one "flaw" with this video: explaining that
| the grid "moves" is a little confusing. It doesn't move
| per-se, it .. evolves? ... over time. That's weird. I
| keep wanting to think the curves are static, but from
| t0->tn the grid pinches up. Yes, that's why they call it
| spacetime, but I have to stop and reset myself because
| how can the grid keep pinching up indefinitely but it
| doesn't it is just a concept. That is a stumbling block.
| 35 years after my last physics class...lol.
| nybsop wrote:
| So were talking about magnetic monopoles except with gravity this
| time?
| mrkramer wrote:
| Just like sea waves which are permanently changing(shaping) the
| structure of rocks they are hitting[0].
|
| [0] https://en.wikipedia.org/wiki/Wave_pounding
| andrewflnr wrote:
| More like the sea itself doesn't go completely flat after the
| wave passes. If the water is space, a rock is more like a break
| in space.
| LegitShady wrote:
| I'm not sure that's a good analogy. Spacetime isn't necessarily
| pounding anything - it could be Spacetime itself that is
| distorted and curved by such a phenomonon. If spacetime is the
| medium of the waves, why are these waves hitting anything, and
| what?
| mrkramer wrote:
| >If spacetime is the medium of the waves, why are these waves
| hitting anything, and what?
|
| "Gravitational waves are disturbances in the curvature of
| spacetime, generated by accelerated masses, that propagate as
| waves outward from their source at the speed of light." [0]
|
| They are hitting everything what is on their way just like
| sea waves are.
|
| [0] https://en.wikipedia.org/wiki/Gravitational_wave
| LegitShady wrote:
| It depends what "everything" is though. We exist in
| spacetime, so we are as much the medium of the wave as
| everything else is. What are the 'rocks' in the analogy?
| What's 'wearing' like the rocks? We don't know enough about
| the spacetime or what's out of spacetime to say.
| jjk166 wrote:
| We, and everything else, are stuff floating in the sea of
| spacetime. Just as a ship would bob up and down as an
| ocean wave passed along but is not itself part of the
| wave, so too are we affected by gravitational waves as
| the pass through spacetime. The difference is instead of
| up and down motion, the distance between two points in
| space and time expands and contracts.
| mrkramer wrote:
| >We, and everything else, are stuff floating in the sea
| of spacetime. Just as a ship would bob up and down as an
| ocean wave passed along but is not itself part of the
| wave, so too are we affected by gravitational waves as
| the pass through spacetime.
|
| Exactly it's called Frame-dragging[0]: "Frame-dragging is
| an effect on spacetime, predicted by Albert Einstein's
| general theory of relativity, that is due to non-static
| stationary distributions of mass-energy. A stationary
| field is one that is in a steady state, but the masses
| causing that field may be non-static -rotating, for
| instance."
|
| [0] https://en.wikipedia.org/wiki/Frame-dragging
| akomtu wrote:
| I'll make a guess that matter is like bubbles in
| spacetime. For some reason the bubbles remain stable and
| due to cleverness of equations governing spacetime, it
| allows to form stable complex structures around those
| bubbles. This is even a verifyable hypothesis: check what
| happens with GR equations in topologies with tiny
| spherical holes.
| drran wrote:
| Bubbles + thermal noise. Noise causes vibration,
| vibration makes bubbles stable. Vibration also causes
| bubbles to stick together due to Casimir effect.
| mrkramer wrote:
| I'm not a physicist but it doesn't seem hard to
| understand: "Water waves, sound waves, and
| electromagnetic waves are able to carry energy, momentum,
| and angular momentum and by doing so they carry those
| away from the source. Gravitational waves perform the
| same function[0]."
|
| So as water wave is hitting rock or any other
| object(mass/energy) on its way gravitational waves should
| hit also everything and anything on their way until they
| lose energy and collapse.
|
| "Gravitational waves are constantly passing Earth;
| however, even the strongest have a minuscule effect and
| their sources are generally at a great distance. For
| example, the waves given off by the cataclysmic final
| merger of GW150914 reached Earth after travelling over a
| billion light-years, as a ripple in spacetime that
| changed the length of a 4 km LIGO* arm by a thousandth of
| the width of a proton, proportionally equivalent to
| changing the distance to the nearest star outside the
| Solar System by one hair's width[0]."
|
| Gravitational waves are all around us but they have
| minimal impact whatsoever unless I suppose some large
| event(source) propagates strong gravitational waves near
| us.
|
| *Laser Interferometer Gravitational-Wave Observatory
|
| [0] https://en.wikipedia.org/wiki/Gravitational_wave
| galaxyLogic wrote:
| When we have a sound-wave it means air-pressure changes
| along the peaks and troughs of the wave.
|
| When we have a gravitational wave what measurable
| quantity changes?
| jjk166 wrote:
| Gravitational waves change the definition of length and
| time. If you have some baseline pressure in a room, a
| pressure wave causes a small region to be briefly higher
| or lower pressure. If you have a meterstick and a
| stopwatch, a gravitational wave causes the meter to grow
| bigger or smaller and the stopwatch to run fast or slow.
| It's as if you are briefly closer to some immense object
| like a black hole which causes time dilation - indeed
| that's exactly what it is. No matter how ridiculously far
| away they are, as two celestial objects orbit each other
| they are continually moving closer and then further away
| from you, and while gravity drops off with distance it
| never goes to zero. You are feeling the gravitational
| pull of that celestial object on the other side of the
| universe getting infinitesimally stronger and weaker as
| the distance between you and it shrinks and grows, or
| more accurately as the distance between you and where it
| was all those millions of years ago when the waves were
| first emitted shrinks and grows.
| mrkramer wrote:
| Ask a physicist but as far as I understood gravitational
| waves are dents in spacetime[0] and as they travel their
| energy, momentum, and angular momentum change over time
| because of interaction and collision with other "stuff"
| in space. Idk how you can measure any of that.
|
| [0]https://www.esa.int/Science_Exploration/Space_Science/
| Gravit...
| LegitShady wrote:
| >So as water wave is hitting rock or any other
| object(mass/energy) on its way gravitational waves should
| hit also everything and anything on their way until they
| lose energy and collapse.
|
| Gravitational waves are vibrations in spacetime. They
| interact very weakly with matter. They travel at more or
| less the speed of light without 'hitting' any rocks. The
| question is what are the 'rocks' - since gravitational
| waves don't really interact with matter significantly,
| and we don't really understand the makeup or source of
| spacetime.
|
| That was my original question to you, and the answer
| isn't obvious, because we don't actually know.
| mrkramer wrote:
| >Gravitational waves are vibrations in spacetime. They
| interact very weakly with matter. They travel at more or
| less the speed of light without 'hitting' any rocks. The
| question is what are the 'rocks' - since gravitational
| waves don't really interact with matter significantly,
| and we don't really understand the makeup or source of
| spacetime.
|
| They can have big impact: "The waves can also carry off
| linear momentum, a possibility that has some interesting
| implications for astrophysics. After two supermassive
| black holes coalesce, emission of linear momentum can
| produce a "kick" with amplitude as large as 4000 km/s.
| This is fast enough to eject the coalesced black hole
| completely from its host galaxy. Even if the kick is too
| small to eject the black hole completely, it can remove
| it temporarily from the nucleus of the galaxy, after
| which it will oscillate about the center, eventually
| coming to rest. A kicked black hole can also carry a star
| cluster with it, forming a hyper-compact stellar system.
| Or it may carry gas, allowing the recoiling black hole to
| appear temporarily as a "naked quasar"[1].
|
| And idk what do you mean by "source of spacetime" you
| mean quantum origin[2]?
| https://knowablemagazine.org/article/physical-
| world/2019/qua...
|
| [1] https://en.wikipedia.org/wiki/Gravitational_wave
|
| [2] https://knowablemagazine.org/article/physical-
| world/2019/qua...
| pomian wrote:
| "I'm not a physicist but"... You should be. That was a
| nice postulation.
| goldenkey wrote:
| Correct, it's all just spacetime. This is what Einstein
| was after in the last years of his life - a unified
| geometric theory, where mass was not separate from the
| sheet, but rather, part of it - a deformation of it.
|
| [1] https://www.arxiv.org/pdf/0706.0190v2
|
| Water waves can crash into eachother. There's no reason
| that spacetime waves cannot either. You can get some hint
| of this if you look at the oscillations that comprise the
| Higgs field.
|
| The negative curvature of gravitation should be cancelled
| out by the positive curvature of matter and energy.
|
| https://en.wikipedia.org/wiki/Zero-energy_universe
| paulpauper wrote:
| It's interesting how two posts recently about Newton's Method
| went viral here. it shows how despite how Quanta Magazine focuses
| on the most cutting edge of theoretical math, that applied math
| is still very important.
| k2xl wrote:
| Could this prove/disprove whether there have been "prior"
| universes? In other words, the theory that after the heat death
| of the universe another universe will form... If gravitational
| waves permanently distort space time would that allow us to
| observe evidence of previous universes?
| mrfusion wrote:
| I never understood how gravity waves can go through anything and
| not be weakened?
|
| If the wave imparts energy on an object and makes it move, how is
| that energy still available for the next object the wave goes
| through?
| p1mrx wrote:
| It's possible to move an object, and return it to its original
| location, without expending energy. Ocean waves do this all the
| time.
|
| Based on conservation of energy, I would assume that friction
| can weaken a gravitational wave by turning some of its energy
| into heat.
|
| Though if we're talking about _permanently changing_ the
| location of an object, that theoretically requires a negligible
| amount of energy... reminds me of the magic drive in
| https://qntm.org/frontier
| neophyt3 wrote:
| I never understood how gravity waves propagate Mass causes
| gravity then what are these waves then? Is it dark matter thats
| not visible, not measurable and yet it has mass which causes
| ripple in space fabric
| thehappypm wrote:
| This is cool. Maybe it's an explanation for mass. When you're at
| rest (or at a constant velocity) you're constantly making a dent
| in spacetime, that closes up eventually behind you. Go faster,
| the dent grows, so you need a force to push through that initial
| resistance of making the dent bigger.
| p00tst00t wrote:
| Space-time doesn't exist. Space is innert. Counter-space however
| is another story. Matter is relative, it cares not for
| "spacetime"
| legohead wrote:
| So as I was trying to imagine this I came up with an example that
| I think fits, can someone confirm my thoughts?
|
| My idea is a square piece of fabric (space). You cut a single
| strand of fabric somewhere, which is the origin of the wave
| event. This affects the whole fabric as the destruction ripples
| throughout, and also results is a permanent scar/distortion on
| the fabric as a whole.
| TheOtherHobbes wrote:
| My understanding was more that spacetime isn't perfectly
| elastic, so when it's distorted by a gravitational wave it
| stores the equivalent of a gravitational charge - a bit like a
| piezoelectric crystal that stays very slightly permanently
| polarised after you stop squeezing it.
|
| This would be amazing if true because spacetime would be rough
| on very tiny scales because of all the waves that passed
| through it.
|
| Speculating wildly, this might even have observable quantum-
| level effects.
| akomtu wrote:
| Offtopic. This would be a precursor for the typical generator
| in the future: a stone on a rope inside a stone cavity that
| resonates with gravity waves, converts the piezoelectric
| tension of spacetime into vibration, heats up as a result and
| boils a rusty cup of water.
| denton-scratch wrote:
| > But a gravitational wave has a longer reach than the force of
| gravity.
|
| That can't be right - surely the gravitational field permeates
| the whole of space; and surely the wave and the force are the
| same thing?
| vmception wrote:
| mmm haven't seen Apophysis fractal art in a long time!
| CoastalCoder wrote:
| Layman's question: are gravitational waves really "waves"?
|
| When I think of waves, I think of systems governed by the wave
| equation [0].
|
| But IIUC that requires a restoring force. I'm not sure what that
| would mean in the case of gravity.
|
| E.g., if the moon suddenly lurched towards the Earth, we'd
| perceive an increase in gravity between the two. But that would
| be a semi-permanent change in the strength of that attraction
| between the two objects; not what I'd think of as a wave-like
| fluctuation.
|
| [0] https://en.wikipedia.org/wiki/Wave_equation
| joe__f wrote:
| Yes, gravitational wave are governed by the wave equation. A
| standard way to treat them is as a small perturbation around a
| known spacetime geometry. Then the metric would be $g = g_0 +
| \epsilon h$, where $g_0$ is the background, $\epsilon$ is a
| small parameter and $h$ is the perturbation.
|
| In general Einstein's field equations govern the dynamics of
| $g$, and if you take the first order behaviour in $\epsilon$
| around $g_0$ as flat space, then you recover the wave equation
| for $h$ as in the article you linked, with propagation speed
| $c$ the speed of light. (There are some additional subtleties
| about choice of gauge, but this is not physical).
|
| I'm not sure what you mean with your moon example.
| CoastalCoder wrote:
| Thanks! I'm not ready to understand your explanation, but I
| can clarify the moon example at least.
|
| Suppose the gravitational attraction between the earth and
| moon is 2e20 Newtons.
|
| Now imagine something forces that attraction to strengthen
| from 2e20N to 3e20N. E.g. the Earth and moon get closer to
| each other, or the moon gets more massive somehow.
|
| When we talk about "detecting gravity waves", I understand
| that to mean that on Earth we've managed to detect that
| increase from 2e20N to 3e20N.
|
| My point was: perhaps that looks like the rising edge of a
| wave phenomenon, but it's not actually cyclic like I expect
| from a traditional "wave". So I couldn't understand why it's
| called a gravity _wave_.
| cobaltoxide wrote:
| Gravitational waves are waves of the metric tensor. Einstein's
| field equations provide the "restoring force."
|
| Importantly, gravitational waves are _not_ waves of Newtonian
| gravity. Gravitational waves _do not_ "push and pull" along the
| direction of propagation. They stretch and compress space along
| axes perpendicular to the direction of propagation.
|
| > E.g., if the moon suddenly lurched towards the Earth, we'd
| perceive an increase in gravity between the two. But that would
| be a semi-permanent change in the strength of that attraction
| between the two objects; not what I'd think of as a wave-like
| fluctuation.
|
| Indeed, gravitational waves do not work this way.
|
| Unfortunately it is hard to explain gravitational waves without
| significant math.
|
| In fairness, even Einstein himself waffled over whether
| gravitational waves would be a real effect predicted by the
| theory. Then it took nearly a century to detect them
| experimentally, and there were plenty of doubters along the
| way.
|
| The results one gets from intuition are generally incorrect in
| important ways. Here's a derivation of a wave equation from
| Einstein's field equations:
|
| https://en.wikipedia.org/wiki/Linearized_gravity
|
| A more helpful introduction for a layperson might be the paper
| titled "Gravitational Waves on the back of an envelope":
|
| https://aapt.scitation.org/doi/10.1119/1.13627
|
| But, infuriatingly, that paper does not seem to be open-access.
| Here's someone's scanned copy:
|
| https://www.ru.ac.za/media/rhodesuniversity/content/mathemat...
| fsflover wrote:
| > But, infuriatingly, that paper does not seem to be open-
| access.
|
| Try sci-hub.
| sildur wrote:
| > They stretch and compress space along axes perpendicular to
| the direction of propagation.
|
| Is it possible to compress space?
| drran wrote:
| (Not a native speaker).
|
| Space is a mathematical abstraction. You can do anything
| with, because it's just math. If you want to bend, curve,
| distort, rip space, or add more dimensions -- go for it.
|
| Physical medium should be compressible, like any other
| medium. Higgs <<field>> (let's call it Higgium --
| Higgs+Vacuum) is presented everywhere, because Higgs boson
| gives mass to every particle in the Visible Universe and
| beyond, so it should conduct gravitational waves. As
| demonstrated by LIGO/VIRGO, gravitational waves causes
| distortions in light travel. These distortions can be
| explained as changes of conductivity in Higgium, which can
| be caused by changes in density, so yes, it can be waves of
| compression.
| evanb wrote:
| I appreciate what you're trying to get at, but it's not
| right. Gravitational waves exist in GR even in theories
| with no matter / Higgs.
|
| The Higgs is a scalar field; gravitational waves are
| spin-2.
| [deleted]
| akomtu wrote:
| I'm hardly an expert in GR, but it seems to me that
| gravitational waves is a trivial consequence of limited speed
| of gravity propagation. It takes 8 mins for Sun's gravity to
| reach Earth. If Sun suddenly moves left and right, in 8 mins
| we'll feel a pull to the left and then to the right, so in
| effect gravity will feel like a couple waves passing thru us.
| The exact geometry of those waves is complex, but that hardly
| matters for intuitive understanding. The exact geometry of
| water ripples is also very complex, after all.
| jleahy wrote:
| Unfortunately that's not how they behave at all. See some of
| the references posted by others in other comments. Intuition
| doesn't really work at all here.
| [deleted]
| VLM wrote:
| Earth-Sun system should radiate about 200 watts of gravitational
| waves continuously. One 20th that should be 10 watts of permanent
| deformation.
|
| Bad news is 10 watts is not much, spread thru a large volume.
| Good news is its "easy" to measure the infra red radiation from
| Pioneer and Voyager space probes running less than a KW point
| source of energy.
|
| I wonder if the gravity probe A and B missions would show those
| permanent deformations in their data.
|
| Permanent deformation should be detected in large scale long term
| orbits, eventually?
| galaxyLogic wrote:
| What does this deformation mean physically? I thought matter
| makes space curve. Does the deformation mean the curvature get
| changed?
| errcorrectcode wrote:
| So I wonder if spacetime has a kind of "entropy" where it can be
| stretched-out but never put back exactly how it was. Possibly
| explaining inflation.
| xwolfi wrote:
| No inflation is very different, it's pervasive in every
| direction, it's not localized like your idea would mean.
|
| Plus, it's not like galaxies are temporarily pulling on a
| memory foam, before releasing the pressure, so I m not sure why
| you think inflation (such a bad name, people think balloon) is
| so close to that model.
| goohle wrote:
| It looks like Big Shrink (BS) theory is easier to understand:
| we are shrinking, our rulers are shrinking, so cosmic
| distances are looking bigger in every direction. It explains
| why our Universe is flat and why we cannot find a Universe-
| big source of energy for expanding of the Universe.
| jjk166 wrote:
| This doesn't make sense either - if I were shrinking and
| you were shrinking, then the distance between us would
| appear to be growing larger, but it's not. Gravitationally
| bound systems don't expand, only the galaxies themselves
| seem to be moving away from one another. Combined with no
| mechanism to explain the shrinking, nor any reason why the
| various other laws of physics don't seem to be affected and
| it doesn't seem any easier to understand at all.
| [deleted]
| msk-lywenn wrote:
| But what energy is making us shrink?
| klyrs wrote:
| From the article:
|
| > "The memory is nothing but the change in the
| gravitational potential," said Thorne, "but it's a
| relativistic gravitational potential." The energy of a
| passing gravitational wave creates a change in the
| gravitational potential; that change in potential
| distorts space-time, even after the wave has passed.
|
| Gravitational waves are that energy.
| Kerbonut wrote:
| I posit inflation is simply our perception of time dilation
| at scale.
| dokem wrote:
| Can we make memristors with this info?
| pdonis wrote:
| The Wikipedia page on gravitational memory effect [1] gives links
| to some actual papers, which might be more illuminating than the
| rather garbled description in this article.
|
| https://en.wikipedia.org/wiki/Gravitational_memory_effect
| p1mrx wrote:
| "persistent changes in the relative position of pairs of points
| in space due to the passing of a gravitational wave."
|
| So the idea isn't that space itself is storing information,
| just that a gravitational wave doesn't put everything back
| where it found it. Presumably if you cleared out all the stuff,
| there would be no memory left behind.
| pdonis wrote:
| That's my understanding, yes. So the "permanently distort
| spacetime" part in the article's title is misleading.
| kingcharles wrote:
| Wow, the citations in the article are bigger than the text.
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