During World War II , American pilots were given hollow metal spheres to be used when their planes went down over water. The spheres, being rather heavy for their small size, didn’t exactly act as great flotation devices. So why were these pilots given chunks of metal? Well, they were told that if they dropped the sphere into the ocean, their current position could be worked out by allies in the region, and they would be rescued. However, as foreign intelligence was soon to find out, the spheres were just that – hollow metal spheres – no electronics, no radio equipment, no imbued magical properties. So was the military just playing with it’s pilots, or was there actually something to these spheres?
Well, some of the details are still kinda top secret, but with a little physics and an active imagination, it’s possible to work out how they were used. Arrgh! Scary! I just said the P word. Don’t worry, I’ll try to summarize things without delving to deep into the physics.
Simple Facts: The Ocean
The deeper you go, the colder it gets
The deeper you go, the higher the pressure
Simple Facts: Soundwaves
Sound travels in waves
These waves bend towards where the sound travels _slower_
Sound travels faster in warm temperatures than cold temperatures
Sound travels faster in high pressure than low pressure
Combining the facts:
Keep your eye on the sphere:
So, the spheres that the pilots were dropping into the ocean were of a specific thickness that would be crushed by the ocean pressure at about 1km deep. This would cause a “ping” that could be detected by underwater microphones thousands of miles away. By triangulating the sound (kinda like how GPS works) the Navy was able to work out where the sphere was dropped and go rescue the pilot!
Implications – LOFAR:
I don’t believe it – I am about to recommend a Tom Clancy novel, The Hunt for Red October. Tom goes into details as to how the US Navy took this technology and used it to detect submarines that entered the sound channel. I’d totally recommend buying it here for those of you who have enjoyed reading this posting.
Implications – Nature:
It turns out that nature beat us to the punch. Whales have been using the sound channel for years to communicate with each other over long distance via Whale Song!
Maurice Ewing was the scientist given credit for this awesome invention