LIGO gravitational wave announcement

[alfaniner]

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

If they think they can, what am I missing?

If it were coming from A, it would have hit #2 first.

 

[3point14]

GR cannot explain the observed motions of galaxies or the way the universe seems to expand. If Einstein’s model of gravity is correct, around 96 percent of the cosmos is missing. To make up the difference, cosmologists have posited two mysterious, invisible, and as yet unidentified ingredients: dark matter and dark energy. Fudgefactors in order to keep your falsified theory of gravity. A theory of gravity, falsified by the evidence. Falsified by the motion of stars and galaxies.

Which specialty was your post graduate physics degree in?

 

[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 ...

 

[MaartenVergu]

The main question is: how can you exclude the possibility of something you don't know anything about?

There is the implicit presupposition among the researchers that they know everything about the possible variables which can influence the detector. Maybe there are unknown phenomena yet to discover.

It is not true that you can think that you have excluded every possible factor by excluding everything we know. What about the variables we don't know yet?

How do you exclude something you don't know anything about (yet)?

 

[3point14]

The main question is: how can you exclude the possibility of something you don't know anything about?

There is also an implicit presupposition among the researcher that they know everything about the possible factors which can influence the detector. Maybe there are some unknown phenomena.

It is not true that you can think that you have excluded every possible factor by excluding everything we know. What about the variables we don't know?

How do you exclude something you don't know anything about (yet)?

One is only allowed to posit a theory when one has utterly complete information?

 

[JeanTate]

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

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.

I had a go at reformatting your post, to make it clearer (I hope!); if I got it wrong, please fix it.

As to the content ...

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

That may be so ... but it doesn't make his ideas any less, um, inconsistent with the relevant observational and experimental results. Not to mention that, as far as I know, none of his work has been published in any relevant peer-reviewed journal (please give references to show otherwise, if you know of them).

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.

It would seem that Max Wallis is quite unfamiliar with "the models", and with what sorts of signals would be expected from "merging two megamasses" which are not BHs. He would benefit from a more detailed, and careful, reading of the relevant literature.

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.

Perhaps Max can give us a bit more, re the estimated maximum mass of a NS, beyond his bald assertion?

Einstein himself did not believe in Black Holes

Really? But even if he did not so "believe", why is that important? Thousands of physicists have worked with GR, and the "black holes" conclusion is robust.

this discovery of gravitational waves implies asymmetric rebalancing of large condensed masses – his quadrapole formula – and opens up a way to investigate their structure

Perhaps it does ... it'd be nice to have something more than Max Wallis' bald assertion. Like a reference.

 

[JeanTate]

The main question is: how can you exclude the possibility of something you don't know anything about?

You can't. I can't. And no one else can either.

Personally, I'm quite taken by the idea of invisible pink fairies cavorting with invisible greblu lxxuaffs.

There is the implicit presupposition among the researchers that they know everything about the possible variables which can influence the detector.

No, there isn't. You should try reading some of the published papers.

Maybe there are unknown phenomena yet to discover.

Maybe there are; maybe there aren't.

So?

It is not true that you can think that you have excluded every possible factor by excluding everything we know. What about the variables we don't know yet?

What about them?

How do you exclude something you don't know anything about (yet)?

I dunno.

How do you?

But this is the Science, Mathematics, Medicine, and Technology section of ISF, not the philosophy one. So how is any of what you've written relevant to the science we're discussing in this thread?

 

[JeanTate]

These may be the diagrams you saw:

https://books.google.co.uk/books?id...nsitivity of ligo gravitational waves&f=false

Thanks.

Yes, something like that.

I found something more like what I remember, on p10 (slide 10) of this presentation (link is to a PDF version).

Wish I could find a simple figure, in the form of a JPEG (or similar) file ...

 

[DuvalHMFIC]

The main question is: how can you exclude the possibility of something you don't know anything about?

There is the implicit presupposition among the researchers that they know everything about the possible variables which can influence the detector. Maybe there are unknown phenomena yet to discover.

It is not true that you can think that you have excluded every possible factor by excluding everything we know. What about the variables we don't know yet?

How do you exclude something you don't know anything about (yet)?

Let's say you make a hypothesis that you are going to find this thing called water on another planet. You have theories about what water is, and what parameters you are going to use to look for it. Now, when you come to the planet and find methane, do you call it water? Or do you say "in our search for water, we found something else instead."

When I'm looking for my keys, I either find my keys, or I find something else. I don't find fake keys. When I find something else, it may or may not be of interest to me.

Einstein laid out what gravity waves should be like. THAT is what we went searching for. If we found something else, it wouldn't match the descriptions laid out by Einstein's maths. Do you see the problem with your reasoning?

You are trying to attribute names to things which do not need them. A gravity wave is a placeholder name for something described by General Relativity. We found what GR predicted. Whether it's called "Gravity Waves" or "Leftover Nutella" doesn't really matter. What DOES matter is that we found something that matches the predictions of the equations-which is exactly what we've been trying to do. Your "something else" would still be that which matched Einstein's equations, and therefore, we found what we were looking for.

 

[thedopefishlives]

Okay, I think I see what Maarten is getting at. He's thinking there may be some unknown phenomena out there that looks exactly like gravitational waves on the detectors, but isn't gravitational waves at all. So, to address this critique, there is this: We don't know for sure if there's some other explanation. We do have a theory that expected a thing like gravitational waves, and this observation fits that expectation, so we're putting it in that category for now. If the models get revised later on and the expectations get changed, then we can go back and revisit this observation and say, well, where does it fit in the new model? But since we have no need to extend the model right now - there's nothing "out there" that we're expecting to observe - we can call it a confirmation of the existing model.

 

[Elind]

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

[qimg]https://dl.dropboxusercontent.com/u/98915197/JREF/triangulation3D.png[/qimg]

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?

I think that the result depends on the orientation of the plane of the three detectors to the source of the signal. If the source is perpendicular to the plane, or close to it, then there can be two results, but if not then three detectors are enough. A fourth is needed for solving for any signal, as long as the 4th is not also in the same 2d plane.

 

[slyjoe]

The 3 detector problem shown above is not accurate. The arms of the 3 detectors are not coplanar. That's why you don't need 4.

 

[smartcooky]

If it were coming from A, it would have hit #2 first.

No, that just my poor drawing skills.

As I explained in the text of the post, the distance from point A to 1, 2 and 3 consecutively is the same distance as from S to point 1, 2 and 3 connections, or put more succinctly

Distance from A to 1 = Distance from S to 1
Distance from A to 2 = Distance from S to 2
Distance from A to 3 = Distance from S to 3
(I have amended the diagram in post #159 to reflect this)

The 3 detector problem shown above is not accurate. The arms of the 3 detectors are not coplanar. That's why you don't need 4.

At first I was going to say no, because any three points in 3D space are always coplanar, i.e. changing the position of any corner if a triangle in three 3D space moves the plane of the whole triangle.

Are you saying that the arms of the detectors would not be parallel to the plane of the triangle, and that this is why they only need three detectors, If so, then my understanding of how LIGO works is lacking. AIUI, the arms are part of ONE detector, they are not two detectors as such, and the detection is made in only one place... the photo-detector behind the beam-splitter.

 

[Elind]

The 3 detector problem shown above is not accurate. The arms of the 3 detectors are not coplanar. That's why you don't need 4.

Any three points are always coplanar.

 

[rwguinn]

Any three points are always coplanar.

arm!=point...

 

[JeanTate]

<snip>

Are you saying that the arms of the detectors would not be parallel to the plane of the triangle, and that this is why they only need three detectors, If so, then my understanding of how LIGO works is lacking. AIUI, the arms are part of ONE detector, they are not two detectors as such, and the detection is made in only one place... the photo-detector behind the beam-splitter.

As GWR is quadrupole, unlike light, the relative strengths of the received signals - at each observatory (i.e. Hanford or Livingston) - carries useful information, which helps somewhat in determining direction; the directional sensitivity of each observatory is ~the same, but they have different orientations (wrt the celestial sphere). I think.

This is covered in great detail in one of the ~dozen 'supplementary' GW150914 LIGO publications (but I don't know, offhand, which one ).

 

[smartcooky]

As GWR is quadrupole, unlike light, the relative strengths of the received signals - at each observatory (i.e. Hanford or Livingston) - carries useful information, which helps somewhat in determining direction; the directional sensitivity of each observatory is ~the same, but they have different orientations (wrt the celestial sphere). I think.

Of course, the two detectors are 3000 km apart so they are significantly around the curvature of the earth from each other, and therefore, the arms not parallel to each other.

 

[Cl1mh4224rd]

Any three points are always coplanar.

What slyjoe is trying to point out is that the GW detectors are not single points. They each have two perpendicular arms which will be at different orientations with respect to the other detectors. This can provide an additional ability to locate the source.

I'm pretty sure this is how they were able to determine the source of this GW came from a certain patch of the sky, with only two detectors, rather than somewhere in a 360º ring.

 

[ben m]

What slyjoe is trying to point out is that the GW detectors are not single points. They each have two perpendicular arms which will be at different orientations with respect to the other detectors. This can provide an additional ability to locate the source.

I'm pretty sure this is how they were able to determine the source of this GW came from a certain patch of the sky, with only two detectors, rather than somewhere in a 360º ring.

That's exactly right. In fact, you can see both effects in that image: first the time-of-flight alone (which is measured very accurately) constrains the source to a narrow 360º ring. On top of that, they have the difference in intensities at the two sites, which (less accurately) tells you at what angle the wave passed through each detector, and that rules out a subset of the TOF-compatible ring.

 

[alfaniner]

No, that just my poor drawing skills.

As I explained in the text of the post, the distance from point A to 1, 2 and 3 consecutively is the same distance as from S to point 1, 2 and 3 connections, or put more succinctly

Distance from A to 1 = Distance from S to 1
Distance from A to 2 = Distance from S to 2
Distance from A to 3 = Distance from S to 3
(I have amended the diagram in post #159 to reflect this)

I see -- I was thinking two-dimensionally. To clarify, S and A could be above and below the viewing plane, respectively, and thus the same distance from 1. Think of 1-2-3 as an equilateral triangle in 3D space, sort of lying on its back, and A and S are somewhere "behind" it at the same distance.