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Monster gravitational waves spotted for first time

nature.com

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Re: Monster gravitational waves spotted for first time

#101

Post by nyrikki »

sunshinerag wrote: post #97
nyrikki wrote: post #90

Earlier quoted context omitted.

Hard or impossible to visualize, but as the temporal dimension is so much larger, most of the deformity is in the time dimension. But yes, spacetime itself is jiggly like Jell-O. As we can't visualize 4d spacetime, most analogies will be wrong. But as photons don't experience time themselves, thinking about the geodesic path is probably less error prone than thinking of it as squishing physical objects. Objects being…

what does "photos don't experience time themselves.." mean? why not?

Nothing that travels at light speed experiences time. For a photon, emission and absorption is a single event.

Re: Monster gravitational waves spotted for first time

#103

Post by asdff »

jessriedel wrote: post #53
derefr wrote: post #31

What 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?

Yes, that's basically right. The gravitational way has a direction (say, z) in which its propagating. Within the plane perpendicular to that direction (x-y), a circular ring of particles will at at one moment experience squeezing in one direction (x) and stretching the perpendicular direction (y). As the wave passes through and you move from the peak of the wave to the trough, the directions reverse, so the first dir…

Could you set up massive pendulums to convert this gravitational wave energy into mechanical energy? Would such a device diminish the strength of the wave downstream?

Re: Monster gravitational waves spotted for first time

#104

Post by Retric »

akiselev wrote: post #27
edgyquant wrote: post #20

Earlier quoted context omitted.

Are not the energies required for a theoretical warp drive also stupendous?

The original Alcubierre paper came up with the energy equivalent of the entire mass of Jupiter, if I remember correctly.

Which as shocking as it sounds still small compared to large gravitational waves.

The merger of black holes radiate something like 10% of that mass as gravitational waves. Start talking 2.5+ million solar masses black holes and ~500,000 solar mass worth of energy in gravitational waves seems plausible though obviously rare.

Re: Monster gravitational waves spotted for first time

#106

Post by AdamH12113 »

dangond wrote: post #86
pantulis wrote: post #72

Earlier quoted context omitted.

Space itself means the metric of spacetime: how you measure distances. Locally, if there was no gravity, you could think of space as a plain reticule where distances would be calculated through eucledian geometry: that means cartesian distances, parallel lines would be parallel and the angles of a triangle would sum 180, and the shortest path between two points is the straight line. General Relativity successfully es…

Out of curiosity, from someone who has never worked with non-euclidean geometry, what does it mean for a path to be curved in non-Euclidean space? My outsider understanding of curvature is that the inside of a curve is shorter than the outside of the curve, whereas a line has the same length on either side (assuming we give these curves and lines some thickness). But, if the shortest path can be curved, what do we me…

I've found it's easier to think about this stuff in two dimensions. The surface of a sphere (or the Earth!) has non-Euclidean geometry.

Imagine two people standing some distance apart from each other at the equator. They both begin walking in straight-line paths due south. At first, their paths are parallel. But as they move toward the south pole, they begin to drift closer to each other, as though their paths were curving towards each other. When they reach the south pole, they bump into each other. But they were both walking straight forward following the shortest path to the south pole the whole time. The curvature of the surface causes their initially-parallel paths to converge.[1]

On a plane (which has Euclidean geometry), initially-parallel paths never converge.

[1] Don't take this too literally; the real planet Earth is three-dimensional, and its gravity keeps us on the surface. But mathematically, it's possible to describe a curved two-dimensional space without referring to any higher dimensions. When I talk about "the surface of a sphere", that's what I mean -- the surface is the entire 2D space.

Re: Monster gravitational waves spotted for first time

#107

Post by TechBro8615 »

rkagerer wrote: post #54
TechBro8615 wrote: post #49

I 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 it…

The 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…

That 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).

Re: Monster gravitational waves spotted for first time

#108

Post by thatcherc »

asdff wrote: post #103
jessriedel wrote: post #53

Earlier quoted context omitted.

Yes, that's basically right. The gravitational way has a direction (say, z) in which its propagating. Within the plane perpendicular to that direction (x-y), a circular ring of particles will at at one moment experience squeezing in one direction (x) and stretching the perpendicular direction (y). As the wave passes through and you move from the peak of the wave to the trough, the directions reverse, so the first dir…

Could you set up massive pendulums to convert this gravitational wave energy into mechanical energy? Would such a device diminish the strength of the wave downstream?

Yes! In principle at least, and only miniscule/undetectable amounts of energy. The first gravitational wave detectors build were these "Weber bars" [1] - big block of aluminum that were supposed to resonant mechanically (like a bell) when a gravitation wave of the right frequency passed through them.

Looks like these things haven't detected a real gravitational wave, but if a strong enough one at the right frequency came through, they might start ringing like (very quiet) bells!

[1] - https://en.wikipedia.org/wiki/Weber_bar

Re: Monster gravitational waves spotted for first time

#109

Post by sslayer »

ComputerGuru wrote: post #2

More 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/gravitatio... (Archived: https://archive.is/AmRvg )

Imagine 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!

Re: Monster gravitational waves spotted for first time

#110

Post by UncleSlacky »

zackmorris wrote: post #80
anonym29 wrote: post #3

EDIT 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 ------ 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 wa…

This video might help understand where mass comes from and how to potentially modulate it, because mass can be thought of as bound energy creating voids in the gluon field: https://m.youtube.com/watch?v=Ztc6QPNUqls The Higgs mechanism affects electrons, not quarks, and is only responsible for about 1% of matter's mass. Most mass comes from the binding energy between quarks, which creates flux tubes between quark-anti…

You should join us at APEC: https://www.altpropulsion.com/
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