LIGO gravitational wave detector breaks 'quantum limit' to find deep universe black hole collisions

[Admin]

The sensitivity of LIGO has squeezed the quantum limit, meaning it can now detect merging black holes and neutron stars on smaller scales and at greater distances than ever before.

LIGO gravitational wave detector breaks 'quantum limit' to find deep universe black hole collisions : Read more

 

[Classical Motion]

"The gravitational wave is a perturbation to spacetime," Jia explained. "When it propagates through the LIGO detector, it will change the length difference of the two 4-kilometer arms of LIGO as if it’s stretching one arm while shortening the other arm."

"To be clear, the actual arms of LIGO aren't changing length. The lasers within them are — and this length change also forces the beams to increase in amplitude during the part when they reunite. So, in other words, the length difference resulting from the passage of gravitational waves leads to an amplitude change. And that causes the lasers' power to change as well."

Which is it?

What is the principle of detection?

 

[Torbjorn Larsson]

The sensitivity of LIGO has squeezed the quantum limit, meaning it can now detect merging black holes and neutron stars on smaller scales and at greater distances than ever before.

LIGO gravitational wave detector breaks 'quantum limit' to find deep universe black hole collisions : Read more

Elegant! I knew they were working on improvements but I had no idea that they were going to take the squeezing further.

 

[Torbjorn Larsson]

"The gravitational wave is a perturbation to spacetime," Jia explained. "When it propagates through the LIGO detector, it will change the length difference of the two 4-kilometer arms of LIGO as if it’s stretching one arm while shortening the other arm."

"To be clear, the actual arms of LIGO aren't changing length. The lasers within them are — and this length change also forces the beams to increase in amplitude during the part when they reunite. So, in other words, the length difference resulting from the passage of gravitational waves leads to an amplitude change. And that causes the lasers' power to change as well."

Which is it?

What is the principle of detection?

It seems poorly written. I think the article wants to point out that the arm lengths are not always changed in totality as the gravitational wave pass (depending on the sizes) and definitely not after wave passed. But in all cases that the photon travel distances will change.

The amplitude description may refer to the interference detection.

Here is LIGO's own description:

Gravitational waves cause space itself to stretch in one direction and simultaneously compress in a perpendicular direction. In LIGO, this causes one arm of the interferometer to get longer while the other gets shorter, then vice versa, back and forth as long as the wave is passing. The technical term for this motion is "Differential Arm" motion, or differential displacement, since the arms are simultaneously changing lengths in opposing ways.

As described above, as the lengths of the arms change, so too does the distance traveled by each laser beam. A beam in a shorter arm will return to the beam splitter before a beam in a longer arm--as the wave passes, each arm oscillates between being the shorter arm and the longer arm. When they arrive back at the beamsplitter (where they re-merge), the light waves no longer meet up nicely; they are out of phase. Instead, they shift in and out of alignment for as long as the wave is passing. In simple terms, this shifting alignment results in a flicker of light emerging from the interferometer.

https://www.ligo.caltech.edu/page/what-is-interferometer

 

[Classical Motion]

Thanks, that's what I had read.

How's come the LIGO light is not effected by the compression and expansion of space.........but the redshift of stars is? With current theory, can we trust this dynamic?

I believe the whole setup is poorly designed, for they are using a flux, full of phase and noise. Why not use radio....and use sequentially spaced photons? Remove that flux. These longer photons are much quieter and the duration is long enough to measure much more exact phase differences.

What are the frequencies of the g waves that have been detected? They are low frequency if I recall.

And I wonder if there is any temperature flutter from it. Does it need to be constantly corrected and tuned?