The morning after a pounding thunderstorm last week, I stepped out on the deck to see a birdbath that looked like this. It is located next to a railing where we scatter birdseed, and on a typical day it looks like this -
- because birds knock seeds into it while visiting the railing. I can only assume that the raindrops pounding on the birdbath set up reverberations that echoed off the walls of the bath, moving the seed toward the center. Attempts to reproduce the phenomenon de novo by shaking the bath only resulted in my splashing water on my shoes.
Addendum: Reader Andy offers this relevant video:
I should think it’s wave mechanics rather than fluid mechanics. You can see a more impressive version using sand on a flat plate here, together with some other impressive demonstrations.
ReplyDeletehttps://www.youtube.com/watch?v=Q3oItpVa9fs
It’s also very good demonstration of why electrons organise themselves in atoms the way they do.