LIGO gravitational wave announcement

[ben m]

How, and why, does this differ from being close enough to a BH to be spaghettified?

Sorry, the bit you quoted was not about gravity waves yet, nor about black holes; I was just trying to remind the reader that that a time-varying gravitational fields can feel like either an imperceptible frame shift (if you're in freefall) or like a real force (if there's a rigid body preventing you from freefalling).

Spaghettification is about tidal strains---if you're in a place where the gravitational field accelerating your feet is very different than the field accelerating your head. (Falling into a small black hole does this readily, falling into a big black hole less so. If you fell into the Milky Way's BH you would survive the horizon crossing!) You don't need to think about strain in order to get through my what-if-Earth-gravity-turned-on-and-off example. Gravity waves are only ever stretch-and-squish strains, not directional accelerations. (That's the difference between a quadrupole and a dipole wave.)

 

[fuelair]

Small pedantic quibble:

Evolution is observable fact -- allele frequency changes over time in many populations of organisms. Natural selection (as well as sexual selection, genetic drift, etc.) is a theory that (partially) explains this fact.

This is despite the fact that it is always (infuriatingly) called the theory of evolution. It should just be called evolution - there is nothing theoretical about it.

Part of the whole problem is that the term theory is used in different contexts for different fields. That, and laypersons (not necessarily people in this thread) confuse the terms hypothesis and theory.

Back to your regularly scheduled thread about gravity waves...

And they think a theory is a guess!!!

 

[Wunover137]

Could you imagine being the first person, probably a low-level technician, to see the traces and put "2 & 2" together? The first human to see evidence of gravity waves!

 

[Elind]

Are there any potential, practical benefits from this?

Are there any practical benefits to understanding the size and age of the universe, other than arguing with young earth creationists?

Note that your answer may say something about your state of mind.

 

[Elind]

I do have a practical question which I can't answer. If there was a star/planet relatively close to this black hole merger, aside from any EM radiation issues; would there be any noticeable effects from the gravity wave?

Reading backwards; I see that I am not the first to ask this question. I am in good company.

 

[Elind]

This is despite the fact that it is always (infuriatingly) called the theory of evolution. It should just be called evolution - there is nothing theoretical about it.

We digress, but I wish to chastise you. This is the type of comment that creationists use ad nauseam. Please look up the scientific definition of "theory".

 

[Cl1mh4224rd]

I do have a practical question which I can't answer. If there was a star/planet relatively close to this black hole merger, aside from any EM radiation issues; would there be any noticeable effects from the gravity wave?

Reading backwards; I see that I am not the first to ask this question. I am in good company.

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

 

[Elind]

From some locations in space of merging black holes, the angle of arrival of the gravitational wave at the two arms of a detector will be equal. At this angle no differential length change will occur, thus cancellation, and no output signal seen. In these directions in space (which encompass a whole plane) the observatory has zero sensitivity i.e. is blind. I see no discussion of this limiting effect.

Are you sure about that?

I do not think that the two arms are for detecting direction. They are far too small for that, which is why there is another detector many miles away which did detect the signal some 7 milliseconds after the first.

The two arms are to eliminate interference, I think.

However two detectors cannot give direction in a three dimensional universe so we still do not know where the event happened.

I read that now there are plans for others in India, maybe China and elsewhere so in the future we should be able to direct telescopes to where something happened.

 

[Elind]

Not much, apparently:

I'm talking of asking intelligent questions. Do you include yourself in the not much apparently?

Your Questions About Gravitational Waves, Answered

I suggest you read that again, aside from answering some stupid questions by a reporter I don't see the answer to my question.

 

[macdoc]

Could you imagine being the first person, probably a low-level technician, to see the traces and put "2 & 2" together? The first human to see evidence of gravity waves!

no need to imagine....read his story.

Marco Drago saw the first gravitational wave on 14 September 2015.

http://www.sciencemag.org/news/2016/02/here-s-first-person-spot-those-gravitational-waves

I'd hardly call him a low level technician tho. He certainly knew enough to go about it in the correct manner.

 

[smartcooky]

I do not think that the two arms are for detecting direction. They are far too small for that, which is why there is another detector many miles away which did detect the signal some 7 milliseconds after the first.

The two arms are to eliminate interference, I think.

Yes

However two detectors cannot give direction in a three dimensional universe so we still do not know where the event happened.

I agree. I think four would be the minimum for 100% certainty.

 

[Elind]

no need to imagine....read his story.

[qimg]http://www.sciencemag.org/sites/default/files/styles/article_main_medium/public/images/sn-Drago1.JPG.png?itok=2yhMNadZ[/qimg]


http://www.sciencemag.org/news/2016/02/here-s-first-person-spot-those-gravitational-waves

I'd hardly call him a low level technician tho. He certainly knew enough to go about it in the correct manner.

Anyone here NOT running seti@home since they had a PC?

 

[theprestige]

That's all? Just that? That's enough 'signal' to interprete this as 'huge evidence' and 'a ripple in spacetime'?

Of course.

You predicted that these mirrors would move only in a very specific circumstance. You arranged the mirrors very carefully to rule out movement from any other circumstance. You observed that the mirrors moved in exactly the circumstance that you predicted.

But somehow you have no idea why the mirrors moved.

 

[smartcooky]

Anyone here NOT running seti@home since they had a PC?

Well, I run einstein@home on my PC. You can probably imagine, they are all over this!

 

[Cl1mh4224rd]

I suggest you read that again, aside from answering some stupid questions by a reporter I don't see the answer to my question.

The answer I quoted in my previous post was in response to the following question:

How far away do you have to be from this kind of black hole merger to live to tell the tale?

While not identical to...

If there was a star/planet relatively close to this black hole merger, aside from any EM radiation issues; would there be any noticeable effects from the gravity wave?

...the answer I quoted does appear to address your question. Here it is again:

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).

Did you have something else in mind when you said "relatively close"? Did you have something else in mind when you said "noticeable effects"? Or did you actually mean gravity waves rather than gravitational waves? If so, that would make your question off-topic (not to mention nonsensical).

If you were looking for a simple yes/no answer, that would obviously depend on the sensitivity of the detector. Is 165 nm something a person would notice? No. Other, more sensitive detectors? Quite possibly.

Please clarify.

 

[Cl1mh4224rd]

I agree. I think four would be the minimum for 100% certainty.

A minimum of three is what I've been reading.

http://math.ucr.edu/home/baez/physics/Relativity/GR/grav_radiation.html - "In order to determine the source of the signal, a third detector, far from either of the first two, would be necessary. Timing differences in the arrival of the signal to the three detectors would allow triangulation of the angular position in the sky of the signal."

http://arxiv.org/pdf/1202.4031.pdf - "Although a reasonable detection of a signal can be made with two detectors alone, useful triangulation can only be done with three or more detector sites in the network."

http://www.icra.it/MG/mg12/talks/gw4_zanolin.pdf - "GW detectors are capable to find source location with a few degrees resolution
• at least three detectors are required"

 

[malbec]

Taken from Paul LaViolette's site , I refer you to a part of his initial response . There are many who consider that this is the guy who has taken Relativity into Sub Quantum Kinetics and overcome the several weaknesses of Einstein's relativity theories
QUOTE
This gravity wave was seen on September 14, 2015 in LIGO’s raw signal data as a 35 Hertz oscillation which sped up to 250 Hertz. The scientific community in their highly elated state leapt onto the bandwagon to proclaim that they had just observed the fusion of two black holes, having masses of 36 and 29 solar masses respectively.

But how much of what they say is really true? As Max Wallis has pointed out to the physicsworld.com editor:

“Interpretation of G-wave signatures is not unique. The merging Black Holes idea is problematic, if only because point BHs don’t get ‘close’ spatially. The models assume the merging objects are of the size of the Schwartzschild radius. The same type of signals would come from merging two megamasses. The two cannot be neutron stars, assert the modellists, but they retain the outdated claim that neutron stars cannot exceed twice the sun’s mass. Einstein himself did not believe in Black Holes; physicists should at least accord him respect in allowing that this discovery of gravitational waves implies asymmetric rebalancing of large condensed masses – his quadrapole formula – and opens up a way to investigate their structure, instead of the unphysical assumption of structureless point singularities.”

 

[MikeG]

Malbec, it is difficult to see which words in your post are quotes, and which originate with you. Could you edit, please, or post again making this more clear. if there are quotes in there, could you link to the original, please.

 

[smartcooky]

A minimum of three is what I've been reading.

http://math.ucr.edu/home/baez/physics/Relativity/GR/grav_radiation.html - "In order to determine the source of the signal, a third detector, far from either of the first two, would be necessary. Timing differences in the arrival of the signal to the three detectors would allow triangulation of the angular position in the sky of the signal."

http://arxiv.org/pdf/1202.4031.pdf - "Although a reasonable detection of a signal can be made with two detectors alone, useful triangulation can only be done with three or more detector sites in the network."

http://www.icra.it/MG/mg12/talks/gw4_zanolin.pdf - "GW detectors are capable to find source location with a few degrees resolution
• at least three detectors are required"

I agree that is what they say, but I can't see how... and this is my point

Imagine 1, 2 and 3 are three GW detectors on the surface of the earth and "S" is the source of a gravitational wave

#1 detects it
#2 detect is 2ms later
#3 detects it 5ms later

This is a straight-forward problem in 3D trig. If I can define a point in 3D space that is X, Y and Z distances from the three corners of a triangle, there is always going to be another point in 3D space, on the other side (through the plane) of the triangle that can be at those same three distances... the source of the GW could be at an alternate location "A".

How can they determine which it is without a 4th detector?

If they think they can, what am I missing?

 

[thedopefishlives]

Are you sure about that?

I do not think that the two arms are for detecting direction. They are far too small for that, which is why there is another detector many miles away which did detect the signal some 7 milliseconds after the first.

The two arms are to eliminate interference, I think.

However two detectors cannot give direction in a three dimensional universe so we still do not know where the event happened.

I read that now there are plans for others in India, maybe China and elsewhere so in the future we should be able to direct telescopes to where something happened.

The two arms, offset by 90 degrees, are to get the differential signal - the gravitational wave will move one mirror in a different direction than the other, causing the light pattern to interfere and generating a signal. I suspect that they can estimate some kind of entry cone or plane based on the specific way the mirrors moved, and by combining these estimates across three observatories, they can pinpoint a location in space.