[HN Gopher] What no one has seen before: gravitational waveforms...
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What no one has seen before: gravitational waveforms from warp
drive collapse
Author : raattgift
Score : 101 points
Date : 2024-06-05 13:29 UTC (9 hours ago)
(HTM) web link (arxiv.org)
(TXT) w3m dump (arxiv.org)
| gorkish wrote:
| Funny that the sci-fi got it backwards.
|
| It seems rather obvious in hindsight that should it even be
| possible, we will clearly be able to detect warp signatures far
| before we would be able to build a machine capable of producing
| them.
| sparky_ wrote:
| True, although the Fermi Paradox still sort of applies here,
| e.g., even if the galaxy were teeming with aliens zipping all
| over the galaxy in their warp-capable spacecraft, the odds of
| them charting a course right past our fairly uninteresting
| solar system seem low.
|
| This is likely not helped by the fact that we are more than
| halfway out to the edge of the galaxy, in one of the Milky
| Way's spiral arms; since we're not near the galactic centre,
| there are less possible travel paths that pass by us (if we
| just assume arbitrary random travel between any two points.)
|
| So even if it is happening right now in abundance, and even if
| we can detect its occurrence, are any of those paths close
| enough to us to be detected?
| JumpCrisscross wrote:
| > _we will clearly be able to detect warp signatures far before
| we would be able to build a machine capable of producing them_
|
| We're in the crystal-radio stage of gravitometrics.
| nico wrote:
| Excuse my ignorance about the term, what does "crystal-radio
| stage of gravitometrics" mean in this context?
| AnimalMuppet wrote:
| Primitive. (Primitive radios used a crystal for tuning. We
| have since gotten a _lot_ better at tuning radios...)
| ElevenLathe wrote:
| To be pedantic, the crystal is the rectifier in a crystal
| radio. Tuning was (or is, since there are still people
| out there playing with these things) still usually done
| via a normal tuned LC circuit.
|
| But yeah, we've gotten a lot better at rectifying too.
| rini17 wrote:
| Not even that, spark gaps and coherers :)
|
| And we can't really detect radio signatures yet, not farther
| than closest stars. Perhaps when we get solar gravitational
| lens telescopes.
| kelseyfrog wrote:
| Except now the dark forest hypothesis precludes the development
| and use of warp drives with detectable collapse signatures.
| kragen wrote:
| so if we detect them we know it's false; that's very
| significant
| kelseyfrog wrote:
| It would be, but we still have to keep in mind that
| P(ETs|warp signatures) != P(warp signatures|ETs) and
| there's also the issue of the Schelling point of never
| being the first.
| kragen wrote:
| agreed
| joe_the_user wrote:
| I don't think warp drives would be different from other kinds
| of waves expanding in space - their strength would normally
| decrease at least the square of the distance simply because
| their energy wouldn't have a direction. And if the energy did
| have a direction, the odds of it being aimed at earth would be
| small.
|
| For that reason, only warp drive harnessing star-equivalent
| energy levels would be visible at distance of stars and so-on.
| I mean, Fermi's observation comes down to "there's no
| intelligent-being signature at the star-levels of energy we can
| see". But that could be because: intelligent beings are rare
| _or_ because harnessing star-levels of energy is hard or
| impossible no matter how advanced a society gets _or_ advanced
| societies have no need for such harnessing _or_ because
| advanced societies follow the paranoid "dark forest" logic.
| dheera wrote:
| Another theory I have is that truly sufficiently advanced
| societies stop giving a shit. They figured out how to be in
| equilibrium with their resources and are capable of being
| happy that way.
|
| Giving shits about things is one of the big reasons we have
| wars and other potentially civilization-ending possibilities.
|
| Even if we are able to put 100 humans on a spacecraft for 100
| years hurtling across the galaxy I'm pretty sure they'll
| start fighting among each other after 2 years. It's one of
| the reasons that I think we'll need to make embodied AGIs
| that are less prone to fighting to continue the legacy of
| civilization long term.
| jiveturkey wrote:
| > Our work highlights the importance of exploring strange new
| spacetimes, to (boldly) simulate what no one has seen before.
|
| cute
| SoftTalker wrote:
| It's fun that people can get paid to do this.
| dylan604 wrote:
| Why not? People get paid to play video games and any other
| vast number of examples that break the traditional concept of
| "job"
| SoftTalker wrote:
| I was being genuine. It would be great to have that kind of
| a job.
| fghorow wrote:
| I Dinnae Hae Lang The Engines Can Take It, Cap'n! </Scotty>
| wrycoder wrote:
| What no one had _modeled_ before.
| largbae wrote:
| This is excellent. Like the Dyson sphere, predicting signals for
| technologies that we can imagine but not yet construct seems like
| a great way to guide our search for other life.
|
| Now we need a team of smart folks to identify tearing or other
| processing anomalies in universe-scale simulations.
| ganzuul wrote:
| If you like spooky stuff there is lots of fun things to think
| about.
|
| Just off the cuff; We are predicting a soul upload technology
| with Neuralink etc. So an alien technosignature could look
| like: https://en.wikipedia.org/wiki/21_grams_experiment
|
| This one is not rigorous but there are lots of other
| possibilities of this pattern.
| cydodon wrote:
| If measurement of the soul's weight gave 21, that can only be
| half of the answer[0], right?
|
| [0] https://en.m.wikipedia.org/wiki/Phrases_from_The_Hitchhik
| er%...
| x3n0ph3n3 wrote:
| That experiment was so poorly performed that it can be
| completely discounted.
| causality0 wrote:
| At absolute best, it would be soul copying, not uploading.
| bluGill wrote:
| Advanced life. There is no particular reason to think there is
| life out there (if there is or not - both are extraordinary).
| If there is, there is no particular reason it is advanced - vs
| just some plants and animals living a life but not doing
| anything different from the first members of the species. (that
| is not advancing to where they might get a house)
| perihelions wrote:
| Huh, so you _can_ hear things explode in space, after all. If you
| 're close enough to a warp field doing funny things, the
| gravitational wave strain would create audible-frequency
| artifacts, as it wiggles your eardrums at frequencies close
| enough to the audible.
|
| They derive an equation for estimated strain as a function of
| distance from the warp bubble collapse. How does strain translate
| to sound intensity, in the situation where a gravitational wave
| is driving sound pressure waves, and/or directly wiggling
| eardrums?
| WJW wrote:
| Would it even wiggle the eardrums relatively to the rest of
| your head? Intuitively it seems that would only happen if the
| wavelength is exactly right, but at that wavelength the
| frequency would be inaudible because the speed of light is so
| high.
| rini17 wrote:
| It can move soft tissues relatively to the skull bone,
| resulting in changes of pressure detectable by eardrums.
| amelius wrote:
| So those whooshing sounds of spaceships in sci-fi
| movies/series were real after all ...
| hedora wrote:
| I imagine the sound of the hull + everything else shuddering
| would probably dominate the perceived sound from eardrums or
| direct excitation of the air.
| dotancohen wrote:
| The hull is in a vacuum, and so are the eardrums.
| krunck wrote:
| That ringing in your ears you get once in a while... ?
| wayvey wrote:
| I'm curious about this, sometimes also when one ear suddenly
| sounds different for a short time.
| plasticeagle wrote:
| That's one of the little hairs in your ear dying. You're
| literally hearing the sound of your hearing deteriorating.
| doktrin wrote:
| Well, that or earwax.
| ben_w wrote:
| One of the reasons I no longer ask questions on Physics stack
| exchange:
|
| 1. I asked "how powerful" such waves would have to be to be
| audible.
|
| 2. I directly linked to another question whose accepted answer
| said "these waves can wiggle your ear drum"
|
| 3. Got my question closed as a duplicate but the link was to
| different question that only asked "is it possible" (and
| accepted the answer "yes") without there being any answer to
| the "how powerful" part.
|
| 4. Got an answer which said "no, never".
|
| Of course, I can now get an infinite supply of confusing
| contradictions from ChatGPT, and because I ask questions from a
| position of ignorant curiosity, I'm equally incapable of
| discerning which of the mutually incompatible responses I get
| is definitely incorrect regardless of if it comes from an LLM
| or a trained physicist.
| jvanderbot wrote:
| The moderation on SE is abysmal, but it's the best moderation
| around for such a large, universally accessible, user-
| submitted knowledge store.
| chownie wrote:
| A better form of moderation exists in the form of whatever
| they were doing before, when you could ask a question and
| get an answer.
|
| At one point SE was my most used resource. As of now I
| haven't used SE _at all_ for I think four years. Why would
| you, when so much of the site 's content is outdated and
| the moderators enforce that situation?
| Filligree wrote:
| That's for sure. It's been... five, six years? Since last
| time I visited any of those sites and found relevant
| information. Not for lack of trying, but it's all
| outdated or incomplete.
| digging wrote:
| I find that weird, so maybe we're in different spaces. SO
| often comes up with relevant answers to my queries, and
| I'll click them if they seem helpful. They aren't always
| available and when they are they aren't always useful,
| but I still end up on it at least once or twice a month.
| StableAlkyne wrote:
| "Marked as a duplicate of an outdated post" has been a
| common complaint since the 2000s, the only "before" was
| when the site was brand new.
|
| I even checked to make sure I wasn't misremembering
| things - here's someone complaining about the same thing
| in 2011: https://old.reddit.com/r/programming/comments/cm
| 02a/you_cant...
| rachofsunshine wrote:
| I worked this out once!
|
| Gravitational waves obey the inverse-square law much like
| most radiation does (and subject to some constraints about
| weird spatial geometry, but most of their propagation is
| going on in open flat-ish space, so we can ignore that).
|
| GW150914, the first gravitational wave observed, had an
| amplitude of about 4 times 10^-22 [1], i.e., differences
| changed by a factor of about that. Typical sound displaces
| the eardrum by on the order of half a micron or so [2], with
| the threshold of hearing at about 100 nm. The inner ear's
| shape is curved, but linear length is on the order of 10 mm
| [3] (it curves around so the total length is longer, but the
| gravitational wave would be transverse along its length).
|
| A 100 nm displacement on a 10 mm length is a relative change
| of (100 x 10^-9) / (10 x 10^-3) = 10^-7, that is, 4 times
| 10^-17 times larger than the gravitational wave detected.
| That gravitational wave was emitted at a distance of about
| 410 Mpc [1], and so we can solve:
|
| (d / 410 Mpc)^2 = 4 x 10^-17
|
| d^2 = 4 x 10^-17 * (410 Mpc)^2
|
| d = 2 parsec.
|
| Granted, this is at the limit of hearing for a very brief
| sound (the sound was only in the human audible range for
| about a tenth of a second). You'd need to be perhaps 10 times
| closer - about 20,000 AU - for it to be a loud sound under
| these assumptions.
|
| Of course you wouldn't be around to hear it for very long
| because you're 20,000 AU from one of the most energetic
| events in the cosmos, but hey, you'd hear a brief "click".
| Totally worth being vaporized.
|
| [1] https://en.wikipedia.org/wiki/First_observation_of_gravit
| ati... [2]
| https://biology.stackexchange.com/questions/79963/how-far-
| do... [3] https://www.verywellhealth.com/inner-ear-
| anatomy-5094399
| colanderman wrote:
| 4 times 10^-17 doesn't sound right... 2.5 times 10^14 I
| think?
| spankalee wrote:
| Why would you ever consider asking an LLM a question like
| this though? They just make plausible-sounding things up,
| even if sometimes they're correct.
| bongodongobob wrote:
| If you tell it to use wolframalpha it could probably do
| some ballpark spherical cow physics.
| powersnail wrote:
| This is stretching my imagination to a point where I don't have
| any practical understanding of the physics behind it.
|
| Would the eardrum be "wiggled" in the same way as a normal
| mechanical wave? Does the gravitational wave apply force on the
| eardrum?
|
| Can I touch a gravitational wave and feel it?
| thriftwy wrote:
| Imagine how much ridicule would a SF author in the XX century
| will get for suggesting his characters "hearing" FTL ships
| arriving into their solar system.
| xg15 wrote:
| Only if the characters take it for granted.
|
| That's one of the few situations where some good expospeak
| can make things better. If it's established the FTL travel is
| specifically audible in that universe because of some
| gravitational eardrum-wiggling snenanigans, it would just be
| a perfectly valid, probably quite interesting mechanic in
| that universe.
| wizardforhire wrote:
| Still waiting for the complete lack of gravitational waves as
| result of Omega particles
| Optimal_Persona wrote:
| Good thing it runs on negative energy - there's no shortage of
| bad vibes in the world today!
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