LIGO gravitational wave announcement

[Mikemcc]

You don't address my point regarding differences in lensing due to wavelength. However while I am no expert, I read enough to feel pretty sure that "media" in interstellar (or inter galaxy) has no significant effect on the speed of photons other than possibly changing their polarization or frequency/wavelength.

That's because I'm unsure of the answer concerning the effects of the wavelength and gravitational lensing and didn't want to give a potentially wrong one.

Whilst the effects on the speed of light are very small in interstellar space the distances involved are huge, so even small effects are detectable. There are time differences between X-ray and visible light propagation times (used to watch for GMBs and novas). The Gravitational Waves are different in that they aren't slowed in the way that light is.

 

[JeanTate]

Not much, apparently:

Now assume that we are 2 m (~6.5 ft) tall and floating outside the black holes at a distance equal to the Earth’s distance to the Sun. I estimate that you would feel alternately squished and stretched by about 165 nm (your height changes by more than this through the course of the day due to your vertebrae compressing while you are upright). This is more than survivable.

Your Questions About Gravitational Waves, Answered

Thanks!

Now what would be really, really terrific is at least an overview of how she arrived at her estimate, like a BOTE calculation ...

Here's my BOTE (Back Of The Envelope) calc:

Strain observed by LIGO: 10^-21
Length of a LIGO arm: 4 km
Amplitude of GW observed: 4x10^-18 m
Distance to GW150914: 410 Mpc
Distance ratio, 410 Mpc/1 au: 8.5x10^13
Strain at 1 au from BBH merger: 8.5x10^-8
Amplitude of GW at 1 au, for a 2m object (e.g. a tall human): 1.7x10^-7 m

Which is 170 nm, in agreement with Dr. Amber Stuver. Yay!

Like many people, I had assumed that what was observed follows an inverse square relationship ... that's true for the energy of the GW, but what was observed was the amplitude, which goes as inverse distance!

"like many people"? One was Scott Aaronson, in his blog post The universe has a high (but not infinite) Sleep Number The blog post ends with this:

As if I needed to say it, this post is an invitation for experts to correct whatever I got wrong. Public humiliation, I’ve found, is a very fast and effective way to learn an unfamiliar field.

The blog post, and the comments, are a delight to read.

 

[jonesdave116]

For anybody interested, there is an absolutely hilarious thread on this by the geniuses at Dunderdolts: http://www.thunderbolts.info/forum/phpBB3/viewtopic.php?f=3&t=16172
Well worth a read if you are running out of things to find funny.

 

[Elind]

For anybody interested, there is an absolutely hilarious thread on this by the geniuses at Dunderdolts: http://www.thunderbolts.info/forum/phpBB3/viewtopic.php?f=3&t=16172
Well worth a read if you are running out of things to find funny.

Weird. What is this obsession with electricity that they apply to anything?

 

[smartcooky]

For anybody interested, there is an absolutely hilarious thread on this by the geniuses at Dunderdolts: http://www.thunderbolts.info/forum/phpBB3/viewtopic.php?f=3&t=16172
Well worth a read if you are running out of things to find funny.

Weird. What is this obsession with electricity that they apply to anything?

Reading the stupidity of electric universe nitwits as they discuss/dismiss GWs is somewhat reminiscent of a cartoon I once saw many years ago, in which a couple of Daleks (original ones) are at the foot of a flight of stairs, and one is saying to the other.....

"Well, this stuffs our plans to conquer the universe!!"

 

[rjh01]

Not read the entire thread recently and only read a little of it just now. I do not think though, how they knew the size of the black holes. It has just occurred to me how they might have done it. The waves they detected are the sum of two sine waves. The amplitude of each wave is related to the size of one of the black holes. So that gives them the relative sizes of the black holes. They then work out the absolute size of the black holes by noting at how fast they were orbiting each other when they merged. Once they know the absolute size of the black holes it is easy to work out the distance from earth they are.

How close am I to the facts? If I am wrong wheat is the correct answer?

 

[MikeG]

........If I am wrong wheat is the correct answer?

I don't know, but I'm pretty sure it isn't this

 

[DuvalHMFIC]

For anybody interested, there is an absolutely hilarious thread on this by the geniuses at Dunderdolts: http://www.thunderbolts.info/forum/phpBB3/viewtopic.php?f=3&t=16172
Well worth a read if you are running out of things to find funny.

I, uh, I guess I need to get out more. I didn't even know that there are people who are certain that gravity waves travel way faster than c. When did this happen and where did these people come from? More importantly-what the hell are they basing this on?

 

[Cl1mh4224rd]

More importantly-what the hell are they basing this on?

Observations of their local brown hole would be my guess...

 

[JeanTate]

<snip>

More importantly-what the hell are they basing this on?

Good luck with getting a clear answer to that!

One source is a guy, now dead, who proposed a wide range of crackpot ideas; another is their personal intuition, in which 'common sense' plays a central role.

An example: the gravitational pull of the Sun, on the Earth, seems, to us here on the Earth, to 'point' directly at the Sun. In Newtonian gravity, this is easy to understand, because gravity 'propagates' instantaneously. In GR, you'd expect the 'pointing' to lag somewhat, due to the delay in gravity propagating at c. But it doesn't!

There's no contradiction; if you work through the (tough!) GR math, you'll find that gravity 'points' in the exact direction determined by experiment/observation. However, EU fanatics don't 'do math', they rely upon personal intuition ... therefore, to them, gravity travels at a speed far exceeding c ...

 

[macdoc]

Excellent article on the history and uncertainty of GW.

Even Einstein Didn't Think Gravitational Waves Existed

Wired Science
For 20 years Albert Einstein equivocated about gravitational waves, unsure whether these undulations in the fabric of space and time were predicted or ruled out by his revolutionary 1915 theory of general relativity.

http://www.wired.com/2016/02/even-einstein-didnt-think-gravitational-waves-existed/

Note Feynman's sticky bead argument ....that's a visual.....and had an important role to play in the search for GW

snip

“Well, since we know that the particles move, all we have to do is imagine a stick, and on the stick we can put some beads. As the wave passes by, the beads will move back and forth, but the stick will stay rigid because the electromagnetic forces in the stick will try to keep the atoms and electrons in the same positions as they were previously. So the beads will drag against the stick, and the friction will produce energy. And the energy must have come from the gravitational wave. So I conclude that the wave has energy.” So this famous “sticky bead” thought experiment convinced a lot of people that there wasn’t any reason for the skepticism that Rosen had advanced. And then people like Joe Weber started trying to detect gravitational waves shortly after.

Einstein showed in 1918 that dumbbell-like systems that rotate about two axes at once, such as binary stars, radiate gravitational waves

wow - effective graphic showing theory prediction versus actual detection

The gravitational-wave “chirp” observed by Advanced LIGO’s Hanford (top left) and Livingston (top right) detectors, compared to theoretical predictions (bottom row) of the chirp from two black holes of 29 and 36 solar masses, respectively, merging 1.3 billion light-years away. B. P. ABBOTT ET AL., OBSERVATION OF GRAVITATIONAL WAVES FROM A BINARY BLACK HOLE MERGER, PHYS. REV. LETT. 116, 061102

story conclusion .....this should be in everyone's lexicon of "How science works"...

There’s this hope that LIGO will “open up a new window on the universe” by detecting gravitational waves from previously unknown astrophysical objects. Considering the effort that went into recognizing the signal from a black-hole merger, how will we be able to see the unexpected?

Yes, the real excitement would be to find something we didn’t expect. One possibility is that the unexpected might help us out by being a very large signal. Our hopes for that have been dampened somewhat, because the original LIGO was online for quite a while and if the signal were very large it might have seen it. It does look like the unexpected is not going to be easy, so how do we dig the signal out of the noise?

One answer is that there are certain kinds of techniques that people have been looking at where you don’t commit yourself to knowing precisely what the signal looks like, but you just look for certain kinds of regularities—for instance, maybe this unexpected signal is at least a periodic signal. And LIGO is certainly doing that. They even have an “Einstein@Home” project, where they’ll send a piece of LIGO data to your home computer if you sign up for this, and your computer will help look for simple things like that. Another approach is to use machine learning to try to teach machines to look for signals. You start with what you know, but there is some hope that over time these techniques might grow and develop to where they become sufficiently flexible to catch things that aren’t what you expect.

What do you take away from this story?

I am struck by the collective nature of the endeavor. It had to be a collaborative effort; each step was sufficiently difficult that it had to link to the next step. And collective efforts come with vitriol and disputes. People shouted at each other. But the finer qualities of human nature won out. People got over their anger. Einstein got over his anger. People admitted they were wrong. And eventually, as a community, we got there.

 

[smartcooky]

An example: the gravitational pull of the Sun, on the Earth, seems, to us here on the Earth, to 'point' directly at the Sun. In Newtonian gravity, this is easy to understand, because gravity 'propagates' instantaneously. In GR, you'd expect the 'pointing' to lag somewhat, due to the delay in gravity propagating at c. But it doesn't!

There's no contradiction; if you work through the (tough!) GR math, you'll find that gravity 'points' in the exact direction determined by experiment/observation. However, EU fanatics don't 'do math', they rely upon personal intuition ... therefore, to them, gravity travels at a speed far exceeding c ...

I don't think you even need the math actually, I think all you have to do is look at what the two theories propose

If gravity were a force as Newton suggested, but travelling at c then the lag of one object orbiting the other would exist.... the forces would not "point" directly at each other

However, gravity is not a force, its a three dimensional distortion of the fabric of spacetime. That distortion "exists where it exists" regardless of the relative speeds of the two objects.

NOTE: Regardless of what someone else has said here, its not difficult to visualize the distortion in 3D; I have no trouble doing it.

 

[carlosy]

What happened in the nearby vicinity when those two BH coalesced?

Talking about distances like our solar system. How big was the gravitational wave impact to nearby objects?

 

[Wolrab]

What happened in the nearby vicinity when those two BH coalesced?

Talking about distances like our solar system. How big was the gravitational wave impact to nearby objects?

"Cowabunga!" said the Silver Surfer.

 

[macdoc]

about right....most everything in a solar system radius would be included in the sudden conversion of 3 solar masses to energy....the most giantest flashbulb evah.

 

[Elind]

about right....most everything in a solar system radius would be included in the sudden conversion of 3 solar masses to energy....the most giantest flashbulb evah.

Hold on a minute there. The wave may contain 3 solar masses of energy, directed in all three dimensions equally, and there is no suggestion that any time it encounters an object with mass it transfers all that energy to the mass it encounters. If it did it would never survive a billion or more light years of space travel. In any case it is not an interactive energy wave, it is a modification of space time. I question if it actually deposited any energy to the detectors at all. Many things are detectable without drawing energy from them.

 

[macdoc]

The wave may contain 3 solar masses of energy,

This is incorrect...

What do thing the big flash was? .....the gravitational wave was a RESULT of the ginormous conversion of mass to energy....we didn't see the flash...anything within a solar system distance was blasted to whatever raw bits apply by that 50 x output of all the stars in the universe flash.

The gravitational wave occurred because of the abrupt change in mass that occurred as a result of the conversion of mass to energy.
That change in mass generated the gravitational wave,.

 

[carlosy]

So, how close would a human had to be to notice the gravitational wave itself (not the energy blast / em-waves) on his own body? Would that even be possible?

 

[Craig B]

So, how close would a human had to be to notice the gravitational wave itself (not the energy blast / em-waves) on his own body? Would that even be possible?

I already asked that, more or less, at #108.

I was wondering what would have happened if we had been much closer to the event, so that let's say the arms of the LIGO momentarily changed length by a hundred metres. Would that have caused utter disruption of all material structures, including the planet, or would it just have rippled past leaving things as unaffected as is a cork floating on a pond agitated by a breeze?​

The responses I received haven't really enlightened me, I must admit.

 

[macdoc]

I think there is a conceptal issue here....you don't "notice" curved space you notice the change in gravity that causes the change to the curve in space which a gravitational wave engenders.

Collapsing orbiting black holes managed to dispose of 3 solar masses in a very short time with an incredible amount of accompanying sturm und drang as Einsteins equation of mass and energy was demonstrated.....the result of that was a sudden change in gravity.....if you were outside the blast and radiation zone ....I doubt very much you would "notice" a gravitational wave of exceedingly short duration moving at the speed of light.