Q&A: Galaxies, Galaxy Clusters, AGN, and Quasars
What is the uncertainty in the frequency of this sound discovered
in Perseus? By specifying the note (to the 1/2 step) you are implying a
precision of about 6%. Do we know the distance to the Perseus cluster and
the speed of sound in the intergalactic gas well enough to support this
small an error?
The scientists give a period for the sound waves, which can be converted
to a frequency. The nearest note that this corresponds to is a B-flat
57 octaves below the B-flat above middle-C. The scientists do not quote
errors for their period estimate, but there are a number of sources of
uncertainty, and we would estimate that the total error is in fact larger
than 6%. However, even if the scientists had done an error analysis, an
error discussion isn't appropriate for a press release, so a degree of
mathematical naivete is acceptable.
The interesting point about the "note"
is not whether it is a B-flat or a C, or an A, but that it is so many
octaves below middle-C. These are extraordinarily large sound waves.