January 2019 Newsletter: Let’s Get Weird Volume 5

Once again, it’s time to enter the weird world of acoustics; this time we’re going everywhere but our planet as we travel into the cosmos.  Most people assume sound in space is impossible because there is no medium for it to travel through.  But once you get weird, anything is possible…

Einstein Got it Right (Again)

The theory of general relativity is centered around how bodies of great mass are connected to gravity.  The formulae derived by Einstein propose that gravity is a force created as a consequence of how planets manipulate and bend space and time.  Moreover, he suggests that gravitational orbits are not constant, i.e., the Earth will eventually crash into the Sun.  As planets, stars, and black holes slowly spin down to their inevitable collision, their gravitational energy is lost, but where does it go?  Einstein theorized that this lost energy travels through space as gravitational waves. These waves utilize compression and rarefaction of space-time as their propagation medium and can therefore journey through the vacuum of space as opposed to traditional sound waves, which rely on particles of matter.  Because these waves move at frequencies within the audible spectrum, we would be able to hear them if we were able to catch them.  All efforts to prove Einstein right and snag a gravitation wave failed until 2015, when finally, the first gravitational wave was detected from a very short (200 millisecond), very big (29 solar masses) signal. The source: two black holes dancing around each other 1.3 billion light years away.  You can listen to the signal here.

Starting Things Off with a Hum

The first and arguably most famous sound in history originated 13 billion years ago; there’s even a popular TV show named after it.  Of course, we are talking about The Big Bang Theory, an explosion of condensed matter that must have created an indescribable instantaneous bang, right? Well, not so much. Physicist John Cramer of the University of Washington has determined that the Big Bang was more like the Big Hum.  The hum sustained for the first 760,000 years of the universe because matter was still close enough together that sound could travel through it.  But as the universe expanded, the frequency of the hum became lower and lower until it disappeared.  You can listen to the Big Hum here, but be aware that Dr. Cramer had to increase the frequency of the sound by a factor of 100 septillion so that it would land in the audible range.

Smurfs are From Venus

We’ve learned that sound as we know it needs an atmosphere to exist, but other planets, like Venus, have atmospheres, too.  A Venusian local would apparently sound like a “bass Smurf” according to Dr. Tim Leighton of the University of Southampton because vocal chords would vibrate more slowly and sound would travel more quickly in the thicker atmosphere.  We have, unfortunately, never captured sound from another world; in 2005, the Huygens probe to Titan came close when it carried a microphone, but it was stunted by limited bandwidth.  Luckily NASA has plans to mic up the 2020 Mars rover; I wonder what Matt Damon would actually sound like on Mars…hopefully not a Smurf with a Boston accent.

This does it for another edition of Let’s Get Weird. We hope you are off to a great start for the new year! Whether you are traveling to Venus, riding a shooting star, or floating out in space, remember that you can’t escape the weird world of acoustics.

February 2019 Newsletter: Listening to Light?
December 2018 Newsletter: Long Distance Communication? Use Your Head!