Brace yourselves for gravitational waves

[Excited Penguin]

Interesting news.  I wish I understood more of it.

If you ask me I can ramble on about it at will

Please, please do.

[Excited Penguin]

https://www.youtube.com/watch?v=s06_jRK9...e=youtu.be

For those of us that don't understand a thing.

[Alex K]

If you ask me I can ramble on about it at will

Please, please do.

Any specific questions?

[Excited Penguin]

Please, please do.

Any specific questions?

Scratching my head.



Let me take you up on that after I've got a little more acquainted with the subject, so that I can even think of a question.

[Alex K]

Note also the 10^-21 amplitude. This means that the length of the 4km arms changed by less than 10^-17 meters. That's way smaller than a proton.

[Excited Penguin]

To what degree has the existence of black holes been proven by this discovery? I've read somewhere that because of the direct observation of gravitational waves in this instance, the existence of black holes has been further validated. Is this accurate? Don't we know for sure that black holes exist at this point?

What are the implications of this that you can think of? What does this entail for the future study of physics, do you think?

This is going to be a dumb question, but are gravitational waves related in any way to the Big Bang, and can we better grasp how the birth of our universe(or its aftermath) took place, through them?

Given this, how much more reliable does general relativity as a description of gravitation become? Is it practically infallible at this point?(I really don't know much about it, excuse my ignorance).

How do gravitational waves affect time and to how much of a degree? I've seen a lot of talk about space in this context, not so much about time. For instance, take this particular effect that those two merging black holes had on space. Was it proportional to the effect it had on time? If so, how much of an effect did it have (in layman's terms, if you could)? I'm sorry if the answer is obvious and I just missed it in everything I've read about it up to this point.

I really didn't get how this discovery was made, or rather, how the Interferometer works. I particularly didn't understand how gravitational waves are supposed to have an impact on the interference pattern. Maybe this one's too complex for me to understand right now, if so, don't even answer it   .

Is it reasonable to assume that gravitational waves will definitely continue to be observed from this point forward, given that they already were in September? If so, how come more observations weren't already made in the meanwhile? Are these occurences so rare that we can't know when the next observation will take place, regardless of how well we can measure them already?

[Alex K]

I would say that this is a very striking confirmation of the existence of black holes because the signal exactly matches the computer simulation of two black holes merging. I don't think there is anything in nature which can fake this. This also constitutes a test of the Einstein field equations in a regime where they are highly nonlinear, something not easily obtained by other means. So without having read technical literature about it yet, I'd say it is an important confirmation that the field equations are accurate even in extreme conditions, and since big bang calculations are based on them, this should provide independent confirmation that those are ok. Gravitational waves were created in the big bang and observing those would be a big deal (maybe you remember the BICEP2 fiasco a coupla years ago where they claimed it, but it was wrong...) and having confirmation that they exist might reinvigorate the searches for their traces e.g. in the cosmic microwave background.

[Alex K]

They increased the sensitivity by a factor 3-10 just last year. Not a lot at first sight, but since this means seeing farther in all three dimensions, this means a great increase in observed volume. Kip thorne said that this signal would have been just below the sensitivity before the recent detector upgrade. It is reasonable to assume that this means with current range of view those events are a relatively common occurrence. But I guess strictly speaking one needs at least two observed events to make a statistic and rule out that this one was a freaky exception. My gut feeling is that there will be another this year, possibly weaker. I think Thorne said somethingalong those lines...

[vorlon13]

Following the improvements to the array, and then seeing something just over the 5 sigma threshold is just what one would expect, if the theoretical angle is correct (machine design, relativity, analysis of signal).

If the first detected signal after the upgrade was something they would have seen with the old set up it would inspire some doubt. Am I correct they can still 'tweak' the array a little more? If so, as the volume of observable space increases we should see the noted above increase in the number of detections.

Also, they've seen something over a billion LY away at a combined mass around 60 suns. With each subsequent detection and analysis, they will be building statistics on the numbers of such objects in our neighborhood of the universe, and compare that to predictions.

In fact, we already have, to a degree, some stats, prior to the upgrade: they did NOT see, for instance, a 600 solar mass thud at 1/2 the distance during that detection time. I'm sure there are VERY few such systems within that range. As the detectors improve, and the range increases along with the observing time, they'll see more objects, smaller ones closer, and possibly some considerably larger further out.

[Jackalope]

Wife and I have been discussing this exact question over dinner just now  They probably did  fit the shape of the signal (which has features such as frequency, change in frequency, relative height of peaks) to their general relativity supercomputer simulation to fit the two masses - they hinted at that in their presentation. My guess is that from that comparison you get the radiated power, and knowing the theoretically derived power of the source and the size of the signal as measured on earth, you can derive the distance by calculating how much it has gotten weaker on the way, in this case 1.3 billion lightyears or so. From the time delay between the two detectors you get an approximate region in the sky from which it likely came (roughly the direction of one of the magellanic clouds, but of course much farther away)

I would imagine that if there had once been life in the neighborhood of the merger, there isn't any longer..