Gravity Waves Detected

[chris_leyson]

Gravity Waves have been detected by the LIGO interferometers
http://www.bbc.co.uk/news/science-environment-35524440
http://www.bbc.co.uk/news/science-environment-35553549

Amazing if you think that this event occured 1.3 billion light years away, I guess that is 1.3E9 and only lasted 2 seconds.
Two binary black holes each 30 times the mass of the sun colliding would release E = mc² = 60*2E30*(3E8)²
about 10⁴⁹ Joules.

[sarepairman2]

[ataradov]

Don't those light photons move in the same space that is being stretched and contracted? Why their movement is not affected by this deformation?

I don't really expect to get a good answer for this, because the only people who understand this are probably drinking right now

But in general, it is pretty awesome that such experiment is even possible.

[TheAmmoniacal]

Original announcement, starting 27:10

[Zero999]

Don't those light photons move in the same space that is being stretched and contracted? Why their movement is not affected by this deformation?

I wouldn't have thought so. There will be peeks and troughs in the waves which should cancel one another out.

[JacquesBBB]

Don't those light photons move in the same space that is being stretched and contracted? Why their movement is not affected by this deformation?

The photon path is affected by the gravity wave. It is already affected by the presence of any massive object that deform the space-time. This is actually the essence of General Relativity.

[han]

I haven't learn about the detail. So is there any confirmation about the gravity speed?
Is it have same speed as light?

[chris_leyson]

Wow thanks TheAmmoniacal I loved that, and they even played the chirp. History in the making. Interesting times ahead for gravitational wave astronomy.

[JacquesBBB]

I haven't learn about the detail. So is there any confirmation about the gravity speed?
Is it have same speed as light?

I dont think they can get any information on the speed of the gravity wave with this experiment with only two detectors, as there is no way to find he direction of the source. Maybe it will be possible when more detectors will be recording the same event. Virgo and KAGRA will be soon working...

[dannyf]

"It's the first time the Universe has spoken to us through gravitational waves. Up until now, we've been deaf."

The first statement is definitive wrong: gravitational waves, if right, happen every second of every day. So the universes always spoken.

The 2nd statement is correct.

[welterde]

"It's the first time the Universe has spoken to us through gravitational waves. Up until now, we've been deaf."

The first statement is definitive wrong: gravitational waves, if right, happen every second of every day. So the universes always spoken.

The 2nd statement is correct.

I wouldn't say deaf per se.
If there had been an event more close by then VIRGO/GEO600/LIGO would have been able to hear it years ago.

[dannyf]

Well, I guess we thought we heard gravitational waves before but we were wrong. So there is still a chance that we are still deaf -> we just don't know yet.

[dannyf]

If there had been an event more close by then VIRGO/GEO600/LIGO would have been able to hear it years ago.

A big part of the detection is limited by geography: the detectors are so close to each other (4km?) that it can only detect "shorter" gravitational waves -> from smaller mass, astronomically speaking.

I suspect that long/longer gravitational waves are fairly abundant, if they really exist, but its detection requires sensors so far apart, on the scales of our solar system, or our galaxy, that it is practically impossible (at least now).

BTW, because of the duality, graviton must exist and we should be able to detect its spins. That's still unproven at this point.

Some people would use that as basis to dispute relativity as "unscientific theory",

[mikerj]

The most incredible for me thing was discovering the sensitivity of the interferometric sensors; they can detect a change in length of one part in 10²¹ which is just mind blowing.  That's the equivalent to the size of a nucleus in a 1750km length.

[miguelvp]

They had major upgrades of sensors and dampeners that affected the readings, so until then even a car approaching the parking lot would affect the readings.

That work was done sometime in 2014, that's why it wasn't extremely useful 'till they work out the kinks.

[PointyOintment]

Gravity Waves

Gravitational waves. A gravity wave is a wave in a fluid caused by gravity (e.g. wind pushes water, gravity pulls back => oscillation).

[JacquesBBB]

You are right !

[bills]

Original announcement, starting 27:10

Thank you for posting the video.
I was wondering what does it mean?
after reading and watching I believe we are going to see some MAJOR advances in our  understanding of the universe.
Kudos to LSU and all that worked on this project.
BTW I am convinced that I have almost zero knowledge on the math and science involved BUT I am trying to understand.

[Zero999]

Don't those light photons move in the same space that is being stretched and contracted? Why their movement is not affected by this deformation?

The photon path is affected by the gravity wave. It is already affected by the presence of any massive object that deform the space-time. This is actually the essence of General Relativity.

That will happen irrespective of whether the massive object is radiating gravity waves or not.

[profany]

can somebody tell me what is the speed of gravity.

[T3sl4co1l]

can somebody tell me what is the speed of gravity.

Gravity waves are just like light waves, except the charge is different (mass, not electric), there are no known negative charges, the sources have much lower frequencies, and they are harder to measure.  The propagation speed is identical (the speed of causality), and the quantum particle is a boson.

Tim

[AlessandroAU]

can somebody tell me what is the speed of gravity.

Gravity waves are just like light waves, except the charge is different (mass, not electric), there are no known negative charges, the sources have much lower frequencies, and they are harder to measure.  The propagation speed is identical (the speed of causality), and the quantum particle is a boson.

Tim

It is still not known if the hypothetical graviton actually exists!

[T3sl4co1l]

It will be rather difficult to observe; the quanta from black hole mergers peak in the ueV range, and we have a hard enough time measuring macroscopic superpositions of them (i.e., classical waves)!

Or, likewise, at extremely high energies and densities, where quantum gravity becomes inevitable, and presumably, gravitons of comparable eV (we're talking 10^20+ here..) become detectable.

But such is the matter of cutting-edge physics.  It's not obvious at this time whether a "graviton" will remain a suitable explanation, but there's absolutely no doubt that, whatever theory evolves, all currently known physics (QCD and electroweak, GR) are contained within it, as a low-energy limit (just as E&M is a low-energy case of electroweak, and Newtonian mechanics is a low-energy case of GR).  Perhaps by then, we will have a more satisfactory explanation of our current theory of gravity, perhaps using a graviton, perhaps using something altogether more elegant.

Tim

[apis]

This is really cool, as far as I can understand the problem preventing detection earlier was noise from local sources, i.e. trucks driving by outside. It would be interesting to know how they managed to suppress the noise enough.

First time humanity detect anything from space other than electromagnetic waves! Does anyone know if they could determine the direction to the origin of the signal with this machine? I assume that could be done by linking several interferometers and keeping track of the delay between signals.

[ataradov]

Does anyone know if they could determine the direction to the origin of the signal with this machine? I assume that could be done by linking several interferometers and keeping track of the delay between signals.

They only had two locations working, so they were able to detect hemisphere, but not accurate direction.