Previous: The Most Venomous Animals in the World
Next: How To Make Antivenom



View count:929,897
Last sync:2022-10-31 14:30
Does your toilet water drain differently than in the other hemisphere? Is it because of the Coriolis effect? Hank has some things to clarify about these questions, and more in this edition of I Don't Think It Means What You Think It Means.

Like SciShow? Want to help support us, and also get things to put on your walls, cover your torso and hold your liquids? Check out our awesome products over at DFTBA Records:

Check out SciShow's podcast SciShow Tangents at
Looking for SciShow elsewhere on the internet?

Hank Green: Hey, Australian people! Have you ever been in the northern hemisphere? Have you ever noticed whether your toilet drains differently than it does here? No? You heard maybe it has something to do with the Coriolis effect? Welcome to another edition of I Don't Think It Means What You Think It Means. [intro music] You probably don't spend a lot of time thinking about how water drains from your toilet, but somehow the idea that water drains differently in northern and southern hemispheres has made its way into our collective consciousness. Furthermore, the reason for this phenomenon has been pinned to the Coriolis effect, which refers to the way the Earth's constant eastward rotation influences how we view the trajectory of certain moving objects. Because the diameter of the Earth at the equator, at 40,076 kilometers, is so much greater than it is at the poles, at 0 kilometers, the land at the equator is moving lots faster than the land everywhere else -- about 1,638 kilometers per hour at the equator compared to about half that at 60 degrees north latitude and pretty much stationary at the poles. And yes, the Coriolis effect, named for 19th century mathematician Gustave Coriolis does indeed influence objects traveling across the face of the Earth due to this constant eastward rotation. If you tried to throw a baseball from the equator up to your friend standing at the north pole, your ball would appear to veer to the right, because it would maintain the greater momentum of the place it started from. On the other hand, if you were throwing the ball to the south pole from the equator, the ball would appear to veer to the left for the same reason. So although the Coriolis effect is totally a thing, the application of this principle to draining water in Earth's two hemispheres is just... bunk. Our planet spinning around once every 24 hours isn't a big enough deal to affect a toilet that takes five seconds to flush. Basically, the direction water drains is dictated by the shape of the basin it's in -- the sink or toilet bowl or whatever. The Coriolis effect does however influence bigger, slower moving fluids (global air and ocean currents, for instance) which can end up giving hurricanes their spin. If the Earth didn't rotate on its axis, among the very many and unpleasant things that would be different, one of them would be that winds wouldn't blow either west or east. They'd flow from the poles, which are naturally high pressure areas, to the equator, where there's low pressure, and back again. But the Coriolis effect deflects these winds to the right in the northern hemisphere, to the left in the southern hemisphere, which creates weather systems that rotate clockwise in the northern hemisphere and counterclockwise in the south. Coriolis effect working at that scale does affect entire climate patterns, but it can't make itself felt on whatever you left in your toilet. Sorry. So, the Coriolis effect: weather, not toilets. Got it? Good. Thank you for watching this episode of I Don't Think It Means What You Think It Means. If you have any questions, comments, or suggestions for us, you can find us on Facebook, Twitter, or of course in the comments below, and if you wanna continue getting smarter with us here at SciShow you can go to and subscribe. [outro]