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Physicists Detect Gravitational Waves, Proving Einstein Right

nytimes.com

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Re: Physicists Detect Gravitational Waves, Proving Einstein Right

#411

Post by codeplay »

hun-nemethpeter wrote: post #389

According to this paper ( https://dcc.ligo.org/LIGO-P150914/public ) they detected the signal first at Livingston, Louisiana and 6.9ms later in Hanford, Washington. The distance between them according to wikipedia ( https://en.wikipedia.org/wiki/LIGO ) is 3002km (Ok, the 3002 km distance is on the Earth). If the gravity wave travel at the speed of light they should detect 10ms later (300 000/3002 sec = 1/100 sec = 10…

I am just curious that is the speed of gravity wave travel at different speed in different medium?

Re: Physicists Detect Gravitational Waves, Proving Einstein Right

#412

Post by deciplex »

purpled_haze wrote: post #388
contravariant wrote: post #210

Earlier quoted context omitted.

Force carrying particles in general don't have mass. Except that some of them seem to do, which was rather puzzling for some time, but was solved using the Higgs mechanism. I can't think of an obvious reason the Higgs mechanism wouldn't work for gravitons, but I could be mistaken, it's not exactly the most intuitive area of physics. Also, keep in mind that the strong force transmits the force between colour charges w…

> Force carrying particles in general don't have mass. Massless particles don't have energy. Massless and energyless particles have no speed. I have no interest in massless and energyless particles that stand still.

This is an awfully confident-sounding post for being so off base.

Re: Physicists Detect Gravitational Waves, Proving Einstein Right

#413

Post by gus_massa »

kamaal wrote: post #123

Tangential question. With blackholes merging, can more and more merge some time in future, creating a net gravitational pull to slow down the expansion of the universe and then may be eventually cause the universe to collapse into that continually merging mega black hole.

The gravity pull of the new black hole is essentially equal to the sum of the gravity pull of the two isolated black holes, and it's essentially equal to the gravity pull of the two stars before they transformed into black holes. So merging black holes don't increase the pull.

Actually, in each transformation there is an explosion and part of the mass goes away (try to not be very close). So the total mass in the final black hole is smaller than the mass in the initial stars, the rest are debris forming a nebula or something around the black hole.

(And, as the other commenter said, gravity is too weak.)

Re: Physicists Detect Gravitational Waves, Proving Einstein Right

#415

Post by purpled_haze »

cyphar wrote: post #392
purpled_haze wrote: post #388

Earlier quoted context omitted.

> Force carrying particles in general don't have mass. Massless particles don't have energy. Massless and energyless particles have no speed. I have no interest in massless and energyless particles that stand still.

Photons are massless particles that have energy. All massless particles travel at the speed of light.

Protons are said to be massless, but a proton may have mass that is so small that we cannot measure it easily. We can't currently say with 100% certainty that it is massless- only that it is at most very, very small: < 1×10−18 eV/c2

Re: Physicists Detect Gravitational Waves, Proving Einstein Right

#416

Post by [deleted] »

deciplex wrote: post #412
purpled_haze wrote: post #388

Earlier quoted context omitted.

> Force carrying particles in general don't have mass. Massless particles don't have energy. Massless and energyless particles have no speed. I have no interest in massless and energyless particles that stand still.

This is an awfully confident-sounding post for being so off base.

[deleted]

Re: Physicists Detect Gravitational Waves, Proving Einstein Right

#419

Post by andrepd »

pbhjpbhj wrote: post #324
ScottBurson wrote: post #176

This made me wonder how far we are from being able to create and detect gravitons. The Wikipedia page on gravitons [0] addresses this question: Unambiguous detection of individual gravitons, though not prohibited by any fundamental law, is impossible with any physically reasonable detector. The reason is the extremely low cross section for the interaction of gravitons with matter. For example, a detector with the mas…

>how far we are from being able to create and detect gravitons // Surely we create gravitons whenever we move a mass just like we create photons whenever we move a body that interacts electromagnetically? Isn't the point that we're constantly exchanging gravitons with all matter as they mediate gravitational attraction.

Keyword here is detect. As the post says, even if we created them we would have no way of knowing because they are virtually impossible to detect.

Re: Physicists Detect Gravitational Waves, Proving Einstein Right

#420

Post by meganvito »

hoodoof wrote: post #410
glial wrote: post #409

Earlier quoted context omitted.

I think your calculation assumes that the waves are traveling parallel to the line connecting Livingston/Hanford. In the diagram below, 's' is the source of the waves. H-----L-------s If instead the waves are traveling perpendicularly to the line between those two cities, they should be detected at the same time. s /|\ / | \ L-----H Since the measured time difference is between 0ms and 10ms, the reality is probably s…

Weird, that's exactly what I was thinking.

the wave can come from two slits, one beam comes later maybe
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