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Astrophysicists unveil glut of gravitational-wave detections

nature.com

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Re: Astrophysicists unveil glut of gravitational-wave detections

#61

Post by dylan604 »

metalliqaz wrote: post #48
ww520 wrote: post #18

LIGO is a huge milestone. Turning it on is like the moment Galileo pointed his telescope to the moon. This is a new class of instruments observing the universe in a medium that was never utilized before. Using gravitational waves can observe things that cannot be seen before, like stars behind the dust clouds. It opens a new window to the world. We might finally be able to “see” dark matter. May be able to see the gr…

I hope to live long enough to see the evolution of interferometers that will be to LIGO as HST was to Galileo's telescope.

I thought LIGO was the HST to Galileo's telescope.

Re: Astrophysicists unveil glut of gravitational-wave detections

#63

Post by dylan604 »

techbio wrote: post #21
TheOtherHobbes wrote: post #11

Earlier quoted context omitted.

Technically we've missed at least four billion years of gravitational wave events, so a week of shutdown for an upgrade isn't going to make a huge difference to that.

I miss those days four billion years ago, before modern worries and before days.

only for Earthlings. I'm sure (hopefully) someone on a rock around a different star might have had those worries in their day too.

Re: Astrophysicists unveil glut of gravitational-wave detections

#64

Post by foo92691 »

markus_zhang wrote: post #24

Just curious, if we have gravitational waves, what are the wave lengths?

There is no upper limit to the wavelength of gravitational waves. However, the lowest frequency that we can currently detect is around 10-100 Hz. Diving the speed of light (3e8 m/s) by (10 Hz) gives 3e7 meters. 30,000 km. The upper end of our frequency range is currently around 8 kHz which corresponds to 37.5 km if I did the math right.

LISA will be sensitive to much lower frequencies (longer wavelengths). NanoGrav also searches for these lower frequency signals.

We expect most gw's to be of very low frequency. High frequency g.w.s require tremendous mass and acceleration to generate. They are only generated in the final moments of black hole collisions as far as we know.

Re: Astrophysicists unveil glut of gravitational-wave detections

#66

Post by secondaryacct »

foo92691 wrote: post #58
SavantIdiot wrote: post #52

Do gravitational wave interferometers create a single pixel of data, or do they create an "image" of gravitational distortion in a 2D region? The first few Google/Wiki hits talk about the physics of interferometry, but not the actual resulting output from real hardware. I'm assuming there is no image, otherwise there would be some associated with the articles, rather than artistic renditions?

You can think of each individual detector producing a single-channel audio signal. By combining the signals from multiple detectors it's possible to determine where the signal is coming from. But the output is neither a picture nor a single pixel: it's a brief blip of a few seconds of audio-frequency time series. A decent analogy is to think of each LIGO detector not as a camera but a microphone.

Or a 3 pixels camera whose pixel color changing is what matters :D

The only difference between a camera and a mic is the number or vibrating thing it cares about (mic only cares about the vibration of its single membrane, cameras create millions of membranes sensitive to photon vibration on a grid)

LIGO 3 interferometers care about the time-variation of the difference of distance measure in 3 groups of 2 mirrors. So it's more than a single mic, and it's a derivative of 2 distance measures, in time. It would be like a 3-pixel video, with white as a baseline for the 3 pixels, and it would varies towards green or blue depending of the negative or positive difference (random colors) between the mirror distances.

Or yeah, a 3 channel sound :S

Re: Astrophysicists unveil glut of gravitational-wave detections

#67

Post by phkahler »

foo92691 wrote: post #58
SavantIdiot wrote: post #52

Do gravitational wave interferometers create a single pixel of data, or do they create an "image" of gravitational distortion in a 2D region? The first few Google/Wiki hits talk about the physics of interferometry, but not the actual resulting output from real hardware. I'm assuming there is no image, otherwise there would be some associated with the articles, rather than artistic renditions?

You can think of each individual detector producing a single-channel audio signal. By combining the signals from multiple detectors it's possible to determine where the signal is coming from. But the output is neither a picture nor a single pixel: it's a brief blip of a few seconds of audio-frequency time series. A decent analogy is to think of each LIGO detector not as a camera but a microphone.

>> it's a brief blip of a few seconds of audio-frequency time series.

A bit more time and they should be able to point telescopes in the general direction of the event prior to a merger. Not sure what kind of directional precision can be obtained, nor if there would even be much to see.

Re: Astrophysicists unveil glut of gravitational-wave detections

#68

Post by bil7 »

markus_zhang wrote: post #51
ww520 wrote: post #37

Earlier quoted context omitted.

That depends the period of the body’s movement. The wave is generated by the body’s movement.

OK I probably got some wild thoughts. I was thinking, since light has different wave lengths and human can't see many types of light because of that, maybe dark matter is similar? Just some uneducated thoughts lol.

radios or other technology can be used to detect EM wavelengths humans can't. No tech can currently observe dark matter

Re: Astrophysicists unveil glut of gravitational-wave detections

#69

Post by foo92691 »

phkahler wrote: post #67
foo92691 wrote: post #58

Earlier quoted context omitted.

You can think of each individual detector producing a single-channel audio signal. By combining the signals from multiple detectors it's possible to determine where the signal is coming from. But the output is neither a picture nor a single pixel: it's a brief blip of a few seconds of audio-frequency time series. A decent analogy is to think of each LIGO detector not as a camera but a microphone.

>> it's a brief blip of a few seconds of audio-frequency time series. A bit more time and they should be able to point telescopes in the general direction of the event prior to a merger. Not sure what kind of directional precision can be obtained, nor if there would even be much to see.

This was in fact accomplished and is attempted for many of the detections.

Re: Astrophysicists unveil glut of gravitational-wave detections

#70

Post by btilly »

phkahler wrote: post #67
foo92691 wrote: post #58

Earlier quoted context omitted.

You can think of each individual detector producing a single-channel audio signal. By combining the signals from multiple detectors it's possible to determine where the signal is coming from. But the output is neither a picture nor a single pixel: it's a brief blip of a few seconds of audio-frequency time series. A decent analogy is to think of each LIGO detector not as a camera but a microphone.

>> it's a brief blip of a few seconds of audio-frequency time series. A bit more time and they should be able to point telescopes in the general direction of the event prior to a merger. Not sure what kind of directional precision can be obtained, nor if there would even be much to see.

I'm pretty sure that they'd have to be pointed in the right direction first.

There is very little time between the start of something detectable, and its finish. But in the case of a neutron star merger, we were able to point other telescopes and see the resulting magnetar for several hours.

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