Listen to Gravity

June 16, 2008 — Leave a comment

I found out today that I have annoyed some of my gravity-wave-studying contemporaries with My Beef with Gravity Waves. It got me thinking about gravity waves again and about black holes. I found a website, black-holes.org which has some interesting stuff. One highlight I thought I’d share are the sounds of black holes and other gravitational events.

Gravity waves, like any wave, can be interpreted as sounds and when they are, you get some interesting combinations of clicks and tones. Here are a few of the most interesting ones. Apparently they were all created by Teviet Creighton.

To begin we have the sound of a nice, steady object: a pulsar. These rapidly spinning, neutron stars produce gravity waves with a nice, regular tone. One day, I hope someone creates a gravity-wave telescope/instrument combination using pulsars as the keys.

[audio:periodic.mp3]

Two black holes that meet will merge and coalesce into a single, larger black hole. Here’s the sound of just such an event, where each black hole is about ten times as massive as the Sun.

[audio:inspiral.mp3]

An extreme mass-ratio binary is a system where two objects orbit each other, but one is far bigger than the other. This type of system is very well understood and takes a long time to evolve and infall. This next sound is that of an extreme mass-ratio black hole binary as it collapses…

[audio:extremebh.mp3]

and here is the same kind of event, but with more lead in time. This lets you hear the gradual change of the pitch and the ‘knocking’, as the black holes are drawn slowly closer together.

[audio:extremebh2.mp3]

The brightest events in the universe are supernovae: the death of giant stars. This cosmic flash is very different when observed through the microphone of gravity waves. Here is a supernova, blipping out of existence:

[audio:supernova.mp3]

Another familar idea seen through an unfamiliar, gravitational lens is that ‘sound’ of the early universe. The Big Bang left a kind of echo, which was also represented by a gravtational background noise. If you had been detecting gravity waves during the early life of the universe it would have sounded like white noise.

[audio:earlyuniverse.mp3]

Finally, what is actually heard by a gravitational wave detector? They are not yet powerful enough to actually have made any detections because of noise. Like trying to see faint stars with all the street lights on, gravity wave detection suffers the problem of the Earth and its associated tremors. Earthquakes, lorries, even people create quakes and shakes which are confusing to gravity wave detectors. The microphone on a gravity wave detector would actually not hear the crisp tones so far discussed, but would actually hear this:

[audio:microphone.mp3]

There’s more to be found on the black holes website, and there will be more here on Orbiting Frog on the matter of gravity waves as soon as I collect my thoughts and actually get some work done!

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