Gravity Waves Detected - Page 1
Forum section: electronics / general

author: chris_leyson
author_rank: Super Contributor
timestamp: February 12, 2016, 02:08:07 am
content: Gravity Waves have been detected by the LIGO interferometershttp://www.bbc.co.uk/news/science-environment-35524440http://www.bbc.co.uk/news/science-environment-35553549Amazing 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)2about 1049Joules.

author: ataradov
author_rank: Super Contributor
timestamp: February 12, 2016, 06:05:46 am
content: 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 nowBut in general, it is pretty awesome that such experiment is even possible.

author: TheAmmoniacal
author_rank: Unknown
timestamp: February 12, 2016, 06:07:40 am
content: Original announcement, starting 27:10

author: Zero999
author_rank: Super Contributor
timestamp: February 12, 2016, 08:42:34 am
content: Quote from: ataradov on February 12, 2016, 06:05:46 amI wouldn't have thought so. There will be peeks and troughs in the waves which should cancel one another out.

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: February 12, 2016, 09:01:08 am
content: Quote from: ataradov on February 12, 2016, 06:05:46 amThe 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.

author: han
author_rank: Frequent Contributor
timestamp: February 12, 2016, 09:07:17 am
content: I haven't learn about the detail. So is there any confirmation about the gravity speed?Is it have same speed as light?

author: chris_leyson
author_rank: Super Contributor
timestamp: February 12, 2016, 09:09:16 am
content: Wow thanks TheAmmoniacal I loved that, and they even played the chirp. History in the making. Interesting times ahead for gravitational wave astronomy.

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: February 12, 2016, 10:09:07 am
content: Quote from: han on February 12, 2016, 09:07:17 amI 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...

author: dannyf
author_rank: Super Contributor
timestamp: February 12, 2016, 11:37:16 am
content: "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.

author: welterde
author_rank: Contributor
timestamp: February 12, 2016, 12:02:31 pm
content: Quote from: dannyf on February 12, 2016, 11:37:16 amI 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.

author: dannyf
author_rank: Super Contributor
timestamp: February 12, 2016, 12:12:35 pm
content: 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.

author: dannyf
author_rank: Super Contributor
timestamp: February 12, 2016, 01:47:22 pm
content: QuoteA 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",

author: mikerj
author_rank: Super Contributor
timestamp: February 12, 2016, 05:43:25 pm
content: 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 1021which is just mind blowing. That's the equivalent to the size of a nucleus in a 1750km length.

author: miguelvp
author_rank: Super Contributor
timestamp: February 12, 2016, 06:19:56 pm
content: 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.

author: PointyOintment
author_rank: Frequent Contributor
timestamp: February 12, 2016, 09:43:53 pm
content: QuoteGravitationalwaves.Agravity waveis a wave in a fluid caused by gravity (e.g. wind pushes water, gravity pulls back => oscillation).

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: February 12, 2016, 10:16:17 pm
content: You are right !

author: bills
author_rank: Frequent Contributor
timestamp: February 12, 2016, 11:27:16 pm
content: Quote from: TheAmmoniacal on February 12, 2016, 06:07:40 amThank 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.

author: Zero999
author_rank: Super Contributor
timestamp: February 13, 2016, 06:23:04 pm
content: Quote from: JacquesBBB on February 12, 2016, 09:01:08 amThat will happen irrespective of whether the massive object is radiating gravity waves or not.

author: profany
author_rank: Contributor
timestamp: March 06, 2016, 07:27:45 pm
content: can somebody tell me what is the speed of gravity.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: March 06, 2016, 07:48:42 pm
content: Quote from: profany on March 06, 2016, 07:27:45 pmGravity 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

author: AlessandroAU
author_rank: Regular Contributor
timestamp: March 06, 2016, 10:18:43 pm
content: Quote from: T3sl4co1l on March 06, 2016, 07:48:42 pmIt is still not known if the hypothetical graviton actually exists!

author: T3sl4co1l
author_rank: Super Contributor
timestamp: March 06, 2016, 10:57:46 pm
content: 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

author: apis
author_rank: Super Contributor
timestamp: March 06, 2016, 11:24:07 pm
content: 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.

author: ataradov
author_rank: Super Contributor
timestamp: March 06, 2016, 11:27:15 pm
content: Quote from: apis on March 06, 2016, 11:24:07 pmThey only had two locations working, so they were able to detect hemisphere, but not accurate direction.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: March 06, 2016, 11:36:45 pm
content: Quote from: apis on March 06, 2016, 11:24:07 pmI made an interesting comment about that, on a recent hangout stream:I think, towards the end. I'd love to see the designs they've used. Suffice it to say, this would be impossible by something like 20 orders of magnitude if they didn't have many-axis dampeners/isolators to account for everything from seismic movement to... people walking around.Tim

author: hopski
author_rank: Regular Contributor
timestamp: March 06, 2016, 11:42:58 pm
content: Quote from: ataradov on March 06, 2016, 11:27:15 pmThat's right only the two detectors at Hanford, Washinton and Liivingston Louisiana were working at the time and they were the only ones with the sensitivity to detect the event anyway, so getting a precise direction was not possible.

author: apis
author_rank: Super Contributor
timestamp: March 07, 2016, 12:47:50 am
content: I assume that will be possible eventually, when more detectors get online?Quote from: T3sl4co1l on March 06, 2016, 11:36:45 pmThanks, there is a comment about it at around 38 minutes (but not as much details as one might hope for unfortunately). Interesting video though.

author: 3roomlab
author_rank: Frequent Contributor
timestamp: January 08, 2018, 02:26:18 pm
content: I caught this video while scouring around about LIGO/VIRGO. it appears NASA already has a gravity sensor satellite since 2002and the satellite measures gravity variations via a 200km+ laser distance measurement. fascinating !

author: Kleinstein
author_rank: Super Contributor
timestamp: January 08, 2018, 04:25:55 pm
content: Those gravity mapping satellites are way less sensitive than detecting gravity waves. The Grace satellites look for the deviation of the earth from a perfect sphere - thus detecting mountains under water and changes in the crust density. The not so even earth makes is necessary to move the satellites for gravitational wave detection further away from the earth - so they may not actually be satellites in the strict sense.