One tablespoon of olive oil is dropped into a lake, and after ten minutes, a half-acre of waves are gone. How could the oil spread so far, and why does it calm the waves? Find out in this episode of What The Physics?!
Lake Vs. Olive Oil
April 14, 2016
Greg Kestin: Okay, so I just got on the lake, and there are a bunch of little tiny ripples from the wind. What I have here is it just olive oil. Let's put it in.
So it's been a couple minutes and right around the boat it seems like the oil has calmed all the waves. How could about a tablespoon of olive oil remove the waves from about half an acre of this lake. I'm Greg and What The Physics?
On the Lake something really strange must have been going on, because everything around you, like a pencil, or a rock, or this creepy primate head, is made of trillions and trillions of atoms and molecules, but they're usually all clumped together. But the oil on the lake didn't clump together, instead it spread out into a layer that was literally one molecule thick, and the crazy thing is that by looking at this you can actually figure out how big one molecule is.
But first, why did it spread so far. Well, when you put oil on water all the oil molecules flip onto their negatively charged heads because they're attracted to positively charged parts of the water molecules.
So, all the oil molecules want to touch the water, to make that happen they have to spread out to a layer that's one molecule thick. But it also calmed the waves. Benjamin Franklin, A leading author, Politician, and a founding father… of pranking people using this experiment, would carry around oil in his bamboo walking cane and would show people how he could magically calm the waves of streams.
Sailors caught on too and began leaking oil, sometimes all their cooking oils into stormy seas, which made for some smooth sailing, but left them with some pretty lackluster baked goods.
So, why does it tame the waves? Well it usually the wind builds of waves by getting traction on the surface of the water. But here the oil acts like a tangled shaggy carpet on top of the water, which doesn't bend or stretch very easily, so instead of making waves the wind it just drags the carpet across the water.
Okay now the crazy part, figuring out how big of one molecule is from looking at this. That layer was one molecule deep all the way across, right? Now imagine cutting up that layer into circles just wide enough to fit into my tablespoon. You’d have to cut that half acre into 5 million of these circles. Now imagine stacking those circles on top of each other in the tablespoon, which is about a centimeter high. So, that's 5 million layers in one cm, that means one layer or one molecule is about one 5 millionth of a centimeter.
You might think “How interesting! But totally useless to me.” Actually, if you put that one molecule thick layer of oil, or a smaller molecule like magnesium fluoride, on a pane of glass, you'll make what's called invisible glass, which has very little reflection. That's because the reflection off the glass and the reflection off the one molecule thick layer on top of the glass partially cancel each other out, which is a useful concept for making screens on things like these and these and these.
But it's not just good for practical applications, it's also good for practical joke applications.
Thank you science, Ben Franklin would be proud.
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PRODUCTION CREDITS: Host, Writer, Animator, Editor Greg Kestin Special thanks Tyler Howe Ari Daniel Lissy Herman Kurt Kolasinski David Allara Patrick Lake Ryan Mckell Lauren Aguirre Kristine Allington Anna Rotschild Allison Eck Lauren Miller Peter Behroozi Fred Behroozi Daniel Rosenberg Kesto Productions Funding provided by Foundational Questions Institute MUSIC: provided by APM C'est La Vie Magician's Waltz a Little Jynx Aquatic Flora SFX: Freesound.org IMAGES: Burnt Biscotti Anna Ginsberg Gangster Benjamin Franklin from Compton Philip Taylor FOOTAGE: Pond5 sea_waves