LETTERS TO THE EDITORS
Ears in Space
To the Editors:
I'm quite taken with Craig Hogan's use of sound as a metaphor for
gravitational waves ("The Sounds of Spacetime,"
November-December). In fact, maybe it is more than mere metaphor.
Human hearing is incredibly sensitive: we can perceive vibrations
with atomic-scale amplitudes. So if we were close enough to, say, a
black hole merger, we could literally hear it. A quick
back-of-envelope calculation suggests that an astronaut within 10
astronomical units of a binary stellar-mass black hole could
directly hear the gravitational waves—the waves would stretch
the bones of the inner ear by a perceptible amount.
Glen Ridge, NJ
Dr. Hogan responds:
Like the LISA detector, human hearing can detect subatomic motions
over a factor of almost 1,000 in frequency. The final merger of two
black holes of, say, 10 times the mass of the sun, emits waves in
the easily audible kilohertz range, so a brave astronaut would hear
their brief chirp with no extra apparatus. Human hearing also uses
extraordinary tricks of signal processing that might help pick out
recognizable sound sources from the cacophonous LISA data stream. I
for one can hardly wait to listen with my own ears to the sound of
real LISA data—sped up by a factor of 200,000 or so to be audible.