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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

#121

Post by criddell »

derefr wrote: post #114
criddell wrote: post #112

Earlier quoted context omitted.

> the faster you go, the slower your proper time appears to an external observer From my perspective, it takes about 8 minutes for a photon from the sun to hit my eye. From the perspective of the photon, a little time has passed, no? Doesn't the atmosphere and passing through my glasses slow it down a wee bit? Can the photon "know" that its position has changed between emission and absorption? From the photons point…

It takes time for a photon to move in your reference frame, but time within the photon's own reference frame is not advancing at all during that. Within the photon's reference frame, the photon exists instantaneously, simultaneously, at its emitter and absorber. Its whole existence "brings together" the spacetime it was emitted from and the spacetime it is absorbed into, at a single 4D pinch-point. It's like the whol…

So from the photon's point of view, the entire universe is a single point?

Re: Monster gravitational waves spotted for first time

#122

Post by xattt »

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…

> Just as a child can swing their legs at the resonant frequency of a swing to pump up their sinusoidal amplitude, a very weak gravitational wave can pump up a ring oscillator if it's oscillating at the ring's resonant frequency.

So is it possible that a passing gravitational wave could initiate some natural process that otherwise might have not happened?

Re: Monster gravitational waves spotted for first time

#123

Post by ithkuil »

criddell wrote: post #121
derefr wrote: post #114

Earlier quoted context omitted.

It takes time for a photon to move in your reference frame, but time within the photon's own reference frame is not advancing at all during that. Within the photon's reference frame, the photon exists instantaneously, simultaneously, at its emitter and absorber. Its whole existence "brings together" the spacetime it was emitted from and the spacetime it is absorbed into, at a single 4D pinch-point. It's like the whol…

So from the photon's point of view, the entire universe is a single point?

No because a single photon doesn't *experience" the whole universe but only the points where it's emitted and absorbed and you could say all the points in between along the geodesic between the emission and absorption events

Re: Monster gravitational waves spotted for first time

#124

Post by staunton »

treeman79 wrote: post #89
cyberax wrote: post #83

Earlier quoted context omitted.

> Or is gravitational energy not dissipated into other forms of energy at all? Extremely weakly. The mechanism is similar to acoustic waves, but the coupling constant is so small, that the amount of dissipated power would be insignificantly small. In theory, you can use gravitational waves to extract energy. For example, you can wait for the "compression" part of the wave, and push a cart uphill during it. Then let i…

The earth going around the sun produces gravitational waves, and some of the energy is lost. If all of that energy could be harnessed; it would be sufficient to power a small toaster oven.

> If all of that energy could be harnessed; it would be sufficient to power a small toaster oven.

Do you have a source? Sounds like an interesting calculation.

Re: Monster gravitational waves spotted for first time

#127

Post by adgjlsfhk1 »

ben_w wrote: post #113
criddell wrote: post #112

Earlier quoted context omitted.

> the faster you go, the slower your proper time appears to an external observer From my perspective, it takes about 8 minutes for a photon from the sun to hit my eye. From the perspective of the photon, a little time has passed, no? Doesn't the atmosphere and passing through my glasses slow it down a wee bit? Can the photon "know" that its position has changed between emission and absorption? From the photons point…

Light does slow in a medium, the statement presumes the light is in a vacuum. From the point of view of the photon, "forwards" is, like time, a null[0] dimension. [0] I may be using that word imprecisely, but I can't think of a better one.

This isn't quite true. At a macro level, light slows down. At a micro level, photons travel at the speed of light, get absorbed and re-emitted, and change directions. These effects average out to looking like photons traveling slower.

Re: Monster gravitational waves spotted for first time

#128

Post by wes-k »

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…

Futurama had an episode about that!

"I understand how the engines work now. It came to me in a dream. The engines don't move the ship at all. The ship stays where it is and the engines move the universe around it." ―Cubert Farnsworth

https://futurama.fandom.com/wiki/Dark_Matter_Engine

https://www.youtube.com/watch?v=1RtMMupdOC4

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