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The Sound of a Black Hole

Posted by michael on from the subwoofer dept.

Snags writes "Astronomers have used the Chandra X-ray Observatory to observe the deepest, lowest-frequency sound waves ever observed. By my calculations, the 'B-Flat 57 octaves below middle-C' has a period of 9.8 million years. Despite arguments that explosions in space movies should be silent, it is legitimate to call these sound waves because at that frequency, particles of space dust can 'see' each other through gravity. These notes are 'over a million billion times deeper than the limits of human hearing', so to call it infra-sound would be a bit of an understatement."

2 of 78 comments (clear)

  1. It is not sound by node+3 · · Score: 0, Troll

    Sound is the word defining that which the ears hear. Is it possible to listen, directly, to that shock wave even if one were standing (floating) in the midst of it? If not, it ain't sound.

    1. Re:It is not sound by node+3 · · Score: 0, Troll

      Definition (b) is an imprecise usage of the word. The word "sound" came about to describe the phenomena of hearing. There is no sound without hearing.

      Once we learned that sound is transmitted by vibration, we used the word sound to label those vibrations in general. Such usage leads to ambiguity and is primarily useful for describing a general phenomena. If one makes a point to call vibrations in general a sound, and the sound is unhearable, the person is being imprecise.

      It's like calling Bach a classical composer. As a general term, it's correct, but if you make a point that Bach is indeed classical as a precise category, it would be wrong. He was a baroque composer.

      If the poster has simply said that the sound of a black hole was measured, that's a generality, and correct. But instead chose to make a specific point that the vibration was indeed sound, and not just a low, unhearable, vibration.

      Who am I to say the dictionary is wrong? Consider this, according to definition (b), if I shake you, your body's motion is sound, even if it doesn't make a sound. Even a photon is sound, since it is a vibrating particle, transmitting its vibration through space-time.