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[BrightestSupernova]

Interactive Gravitational Waves Simulation

Just found this video on YouTube. I wish I can play with them now.

Edited February 12, 2016 by BrightestSupernova

[p1t1o]

Found this, might include some enlightening titbits:

http://physics.stackexchange.com/questions/235356/how-is-it-that-distortions-in-space-can-be-measured-as-distances

 

Turns out, the extremely simplified visualisation we all instinctively build are not an exact representation of what is going on.

 

I think.

 

When I read words like "manifold" and "metric" in a physics context I know Im almost at the point where I'll just assume its all kosher and walk to the coffee machine.

 

 

**edit**

Also this:

http://physics.stackexchange.com/questions/153657/can-ligo-measure-anything

Including this text:

".. the interference pattern doesn't come about because of the difference between the length of the arm and the wavelength of the light. Instead it's caused by the different arrival time of the light wave's "crests and troughs" from one arm with the arrival time of the light that traveled in the other arm. "

 

 

Basically its boiling down to: "Because....jesus...because...because FU**ING SCIENCE THATS WHY!" <trashes room with red lightsabre>

Edited February 12, 2016 by p1t1o
more info

[micr0wave]

38 minutes ago, Rakaydos said:

Except you have photons coming if "from outside" continuously. Really, the detector is measuing hw much TIME it takes light to travel through distorted space, since light always travels the same speed. So an arm that is distored longer, the next photon has to travel longer, and when it bounces back it's slightly out of phase.

 

37 minutes ago, sevenperforce said:

Well, the interferometer does function based on the interference between the wavelengths of the two beams, IIRC, but it's the phase shift (due to the change in the total length of the beam) that is being measured; the wavelength change is not really detectable.

Here, I'll try to do a visual depiction.

Suppose you have two lasers that cross perpendicularly. Where they meet, they form an interference pattern:

Now, suppose that a gravitational wave comes along from the left of your screen and changes the length of the horizontal laser:

The interference pattern is now "bent" and points in a slightly different direction because the horizontal laser's phase meets the vertical laser's phase at a different point than it did before.

Make sense?

the methods of measuring i think i understood, but i really fail to understand that ... assuming i'm a photon (let me be the horizontal one) , i'll need a fixed time (1year) to travel a fixed distance (1 ly), the spacetime i'm in get squeezed but for me the distance and speed will still be the same, i'll reach the 1ly distance after a year. So will the vertical ones. Do i (the photon) have a slightly different colour when i exit the distortion ? Or do i actually really need more time to cross that 1ly than 1year ?

The 'photons from outside' would explain it, but i don't get it totally, wouldn't that somehow say that c is different for the photons outside than the ones inside ?

Sorry for spam, but i really want to understand it better

 

 

-------

edit: the gravitational lenses might lead me to the path of wisdom but i think i'll have to digest it a bit longer

Edited February 12, 2016 by micr0wave

[SuperFastJellyfish]

I can't help but picture it like changing the resolution of your monitor from 640x480 to 1920x1200 and back.  All the distances in the game you are playing are still the same inside the game, but if you look from the outside in like we do while we are playing the game then we can measure a change.  The avatar in the game itself will notice no difference.  Somehow the avatar(LIGO) is measuring a change.  Obviously, this is a flawed way to look at it, but I keep coming back to it when thinking about this.

[sevenperforce]

It's complicated and simple at the same time -- once you get it, it makes a fair bit of sense, but until you do, it's really unpleasant.

Let's say that you and your evil clone twin from an alternate universe are hanging out together in the park one day, and you decide to have a foot race.

Because the two of you are identical in every respect (except, you know, him being evil), you both have identical reaction times and both start parallel to each other at exactly the same time. Your strides, breathing, speed, and everything are all exactly the same.

An observer watching the pair of you from the sidelines would see that your feet kept hitting the ground at the exact same time, the exact same distance with each stride.

Suddenly, suppose that you encounter a small dip in your side of the track. Traveling down into the dip and back up makes your side of the track just a couple of centimeters longer than his. You cross the dip and you're still traveling at the same speed, but the observer can now see that you're slightly out of step with your evil twin and just slightly behind him.

That's what has happened here. The two laser beams have identical wavelengths (comparable to your stride length) and speed. However, the gravitational ripple extends the path length of one laser beam slightly. This causes the peak of that laser beam's wavelength to reach the interferometer a split second later than the peak of the identical laser beam coming from the perpendicular direction, instead of in perfect alignment.

[micr0wave]

But wouldn't it be the same distances for me and my twin, since in my spacetime i wouldn't notice the dip, for me it'll still be a straight line.

Is it a little bit like watching the whole race from a different frame of reference than for me and my twin ?

Our both racetracks are drawn on two pieces of rubber (spacetime) which has marks every cm, we both need the same time to travel from mark to mark, now my spacetime gets a bit squeezed and stretched but i still travel the whole distance in the same time as my twin so we should arrive at the same time unless i watch the whole scenery from 'outside'.

 

When you take a rubberband and stretch it quickly, it'll make a sound. Is it a bit like that what pushes one of us out of sync and can be detected ?

Or is it more the difference between the 2 frames of reference watched from a third one ?

( i probably really don't get it right anyway :/ thanks for the effort though)

[SuperFastJellyfish]

44 minutes ago, sevenperforce said:

It's complicated and simple at the same time -- once you get it, it makes a fair bit of sense, but until you do, it's really unpleasant.

Let's say that you and your evil clone twin from an alternate universe are hanging out together in the park one day, and you decide to have a foot race.

Because the two of you are identical in every respect (except, you know, him being evil), you both have identical reaction times and both start parallel to each other at exactly the same time. Your strides, breathing, speed, and everything are all exactly the same.

An observer watching the pair of you from the sidelines would see that your feet kept hitting the ground at the exact same time, the exact same distance with each stride.

Suddenly, suppose that you encounter a small dip in your side of the track. Traveling down into the dip and back up makes your side of the track just a couple of centimeters longer than his. You cross the dip and you're still traveling at the same speed, but the observer can now see that you're slightly out of step with your evil twin and just slightly behind him.

That's what has happened here. The two laser beams have identical wavelengths (comparable to your stride length) and speed. However, the gravitational ripple extends the path length of one laser beam slightly. This causes the peak of that laser beam's wavelength to reach the interferometer a split second later than the peak of the identical laser beam coming from the perpendicular direction, instead of in perfect alignment.

 

I thought that example turned on a light bulb for me, but that's just how an interferometer works.  In our frame of reference, I don't see how we could measure a change in the fabric of space.  I guess, I don't understand what a gravitational wave actually affects.  If it affects matter and light differently then it all makes sense, and the laser beam would be phase shifted.  My understanding is that spatial dilation affects matter and light the same though.

Edited February 12, 2016 by SuperFastJellyfish

[sevenperforce]

6 minutes ago, micr0wave said:

But wouldn't it be the same distances for me and my twin, since in my spacetime i wouldn't notice the dip, for me it'll still be a straight line.

Our both racetracks are drawn on two pieces of rubber (spacetime) which has marks every cm, we both need the same time to travel from mark to mark, now my spacetime gets a bit squeezed and stretched but i still travel the whole distance in the same time as my twin so we should arrive at the same time unless i watch the whole scenery from 'outside'.

You won't notice the dip, and if you time yourself your stopwatch will read just the same as his does, but you'll realize when you get to the end that he beat you.

[fredinno]

5 hours ago, Darnok said:

Wow Tesla was right Aether exists

http://imgur.com/gallery/0VhrXPV

https://en.wikipedia.org/wiki/Michelson%E2%80%93Morley_experiment

 

Gravitational waves are NOT aether.

Edited February 12, 2016 by fredinno

[PB666]

5 hours ago, p1t1o said:

4 hours ago, sevenperforce said:

Well, the interferometer does function based on the interference between the wavelengths of the two beams, IIRC, but it's the phase shift (due to the change in the total length of the beam) that is being measured; the wavelength change is not really detectable.

Here, I'll try to do a visual depiction.

Suppose you have two lasers that cross perpendicularly. Where they meet, they form an interference pattern:

Now, suppose that a gravitational wave comes along from the left of your screen and changes the length of the horizontal laser:

The interference pattern is now "bent" and points in a slightly different direction because the horizontal laser's phase meets the vertical laser's phase at a different point than it did before.

Make sense?

No offence PB666 but that was about as clear as mud! Axis theta? Defy Newtonian Physics?

Theta is the angle of destrotion along the distorted axis.

**edit**

Is it the *frequency* that is changing rather than the *path-length*?

Because that would tally with what I know about gravitational red/blueshift and does not require a measured *distance*.

According to Manly's video its the phase interferencance for waves passing at 90' Angle as a intensity osscilation, They put a upper limit on the size of the graviton of 10-15.

[HebaruSan]

6 hours ago, p1t1o said:

As for Hubble, as far as I understood, they could only extrapolate the direction that the signal came from to within quite a large "banana shaped" portion of the sky.

Related to that, how are they able to determine the masses and distance based on the "chirp"? Are there absorption spectra for gravitational waves?

When do they expect the next one?

[PB666]

1 hour ago, HebaruSan said:

Related to that, how are they able to determine the masses and distance based on the "chirp"? Are there absorption spectra for gravitational waves?

When do they expect the next one?

Sets the upper limit of graviton based on I, i believe. Masses and distance are based Hubble distance of the surrouding stars. Masses based on intensity of gravitational lensing . . . . . .

 

6 hours ago, sevenperforce said:

Well, the interferometer does function based on the interference between the wavelengths of the two beams, IIRC, but it's the phase shift (due to the change in the total length of the beam) that is being measured; the wavelength change is not really detectable.

Here, I'll try to do a visual depiction.

Suppose you have two lasers that cross perpendicularly. Where they meet, they form an interference pattern:

Now, suppose that a gravitational wave comes along from the left of your screen and changes the length of the horizontal laser:

The interference pattern is now "bent" and points in a slightly different direction because the horizontal laser's phase meets the vertical laser's phase at a different point than it did before.

Make sense?

This is not apparently what they did, they used wave annihilation from interference and measured basically tiny amplitude shifts, see the Manley video.

[AngelLestat]

Kip thorne, the physicist behind the movie "interstellar", must be jumping in one leg, he is the father of Ligo.
He was the first to come out with the idea and one of the scientist who most work on this since 1970 formulating the physics and predicting the type of signals that would be seen in the detector.

 

[Spaceception]

Hey guys:

 

[PB666]

Yep more.

http://phys.org/news/2016-06-gravitational-pair-colliding-black-holes.html

http://www.bbc.com/news/science-environment-36540254

 

Edited June 15, 2016 by PB666

[Streetwind]

Darn, LIGO is on a roll.

It's good news for the scientific community, proving that the first detection wasn't a fluke and you can reliably produce results with the right tools. Another step forward for gravitational wave based astronomy.

[RainDreamer]

How rare are the black hole colliding events that let us detect the waves? We get 2 in spans of months. And how do we filter out the waves from multiple sources?

[PB666]

13 minutes ago, RainDreamer said:

How rare are the black hole colliding events that let us detect the waves? We get 2 in spans of months. And how do we filter out the waves from multiple sources?

The visible universe is pretty big, and the last set closer but represent two smaller system holes, so bunches of these, not like gbh which require galaxies to merge.