Does Water Swirl the Other Way in the Southern Hemisphere?

The definitive answer about the direction water swirls in two hemispheres
Sync the videos yourself:

For the record Destin and I repeated the experiment 3-4 times each in each hemisphere and got the same results every time.

The idea that water going down a drain or flushed down a toilet swirls in opposite directions in the Northern and Southern Hemispheres has a long history. But few have ever done the experiment. Destin from Smarter Every Day and I performed identical experiments in the Northern and Southern hemispheres. What we found is the direction of water swirl in a toilet, sink, or bathtub is determined by other sources of angular momentum. However if the body of water is big enough, e.g. a kiddy pool, and left still for long enough (at least 24 hours), then the Coriolis effect is observable with water swirling counterclockwise in the Northern hemisphere and clockwise in the Southern hemisphere.

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Gordon McGladdery did all of the sound design for the video. We used two songs from other artists (licensed of course). Derek split the first one up so it fades from video to video, and Gordon split the instruments up on the second one. There are violins on one video and percussion on the other for example. It's really neat.

The neat earth animation at the beginning and the synchronizing timer was made by He also made still images of the earth from the top and the bottom.

Thanks to Vanessa for filming in Sydney:


There was a study performed at MIT years ago ( that explained the physics involved. We repeated some of these demonstrations, but on opposite sides of the globe…and in a way that can be easily understood.
This site is a great resource on the Coriolis effect and ways people have gotten it wrong:

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Author Andrew VanCamp ( ago)
but what about near the equator? hmmmmmmmm? you ever think about that?

Author MomoPiano ( ago)

Author Dzon Vejn ( ago)

Author Kevin Klatman ( ago)
My dairy queen ice creem swirled the same way in US and australia though.

Author Findivist ( ago)
not bad, but it would be good to repeat same experiment a few times to see if there is any consistency.

Author W2S 2 ( ago)
I ' m just asking : What causes the water going down a drain to swirl clockwise in the northern hemisphere and counter clockwise in the southern hemisphere ? Plz answer

Author Colin McPhail ( ago)
I love how they had to make this huge experiment to prove that the Coriolis Effect was real, when all they had to do was talk to a commercial jet pilot or look at a hurricane.

Author Intelligent Gaming Agar ( ago)
Legends have it that if you are exactly on the equator, water will come out of the drain instead of water going in the drain.

Author Derrick CFT ( ago)
I just want to say that I really like your videos. Keep em coming and thank you

Author BoxySama ( ago)
this animation help me understand the Coriolis effect 100%

Author Kargadan ( ago)
I am not buying this. It cannot be the effect of earth's rotation. specially on such a tiny diameter pool!! it is more than negligible. to prove such a thing you would need a very big pool (like the one shown on the cartoon). there must be other factors at play here that we either don't know of, or that we are not considering(gravity curving space/time or etc..). imagine an ant being on top of a globe, from the ant's perspective the globe would look flat cause it is so tiny that the curviture is minuscule/negligible. there is not way that earth's rotation has such an effect on such a small scale. if you had a pool the size of what you showed on the cartoon it would make a lot more sense.

Author pratik : } ( ago)
hey bro,i liked your most of the videos. keep it up:)

Author MomoPiano ( ago)
Wow do you know our language?? This is so fantastic!

Author Manish Jones ( ago)
The things we do for science ! Derek ,for Science...

Author Nick Robinson ( ago)
What happens when the center of the pool is on the equator?

Author Stephan K. ( ago)
was that a 5σ experiment?

Author TiggrrZ ( ago)
I always laugh at this, water doesn't really swirl at all in the UK.

Author HeLaXeRN HeLVeT ( ago)
counter clock wise bottom of the sphere and clockwise on the top,tornadoes goes the opposed way of the sphere because air its less dence than water?

Author Vgamer 3802 ( ago)
then what happens in the equator?

Author Berfras ( ago)
I believe that the experiment has some small flaws that make the results inconclusive. For example, it looks like adding the dye during the experiment created noticeable water waves. However, it's a nice video. :)

Author 444mrjimmy ( ago)
thank you so much for uploading this Derek, I did manage to get the videos to sink on the very first try but haven't been able to do it sins

Author Aryaman Mishra ( ago)
what if they were perfectly on equater

Author Mark TNS ( ago)
what happens when you put the pool right on a pole?

Author Benther ( ago)
Yeah Dustin.. we knew the Coriolis effect is real....

Author Martin Ducharme ( ago)
That a really cool experiment, I hope you'll do more cooperative videos like that.

Author Niklas Kaplan ( ago)
What happens if it's on the equator? :P

Author Ibrar Khan ( ago)
dear sir have you an email ,i want to contact with you

Author Edward Ramirez ( ago)
Insufficient sample size! Awesome none the less!

Author stereosphere ( ago)
I think water swirls the same direction in both hemispheres. The problem is that the Australians are standing on their heads looking at the bottom of the swirl.

Author Jen L ( ago)
this is ... A M A Z I N G

Author David Niedbala ( ago)
What happens if a hurricane crosses the equator? will it come to a halt and start spinning the other way?

Author Chris Reich ( ago)
Wow, I didn't expect to ignite controversy. Really, my whole point is to encourage people to think scientifically and question results. That doesn't mean we never accept proof, but we should think deeper than we normally do. Science isn't a debate of opinions, it's a quest for fact. When an experiment is conducted, we want to look for flaws that could be tainting the results.
I love physics and encourage people to think about these things. When an experiment is conducted, we should look for potential flaws. As we know, in the case of the directional flow of drains, starting conditions can make the swirl go in either direction in either hemisphere. Knowing that, we should be especially diligent about starting conditions. Real scientific discussion is valuable and can be a lot of fun if we skip the vitriol and enjoy the topic.

Author Só mais um aglomerado de células pensante ( ago)
what happens in the equator? does It moves in anticlock direction or in the clock direction?

Author Yangven ( ago)
But... what if its on the equator?

Author ThatGuyMike ( ago)
People claim to see this a lot, but most plugs these days have designs that affect the waters directional vortex.

And the video is anyone going as hell. They were not meant to be put together like this.
1 muted and 1 with audio maybe, but it gets annoying to hear the same thing twice.

Author Super-patfan39 ( ago)
Wow.......... cool

Author Aaron Osher ( ago)
By far my favorite collaboration on YouTube ever.

Author Lizard Mods ( ago)
I've already seen both videos but I never realized how much work you guys put into it crazy!!!

Author Shakeel Alam ( ago)
i think this all due to "Coriolis effect". not only the ocean water but also the air current swirl through the same phenomenon. is this so?

Author Adnan IB ( ago)
Why re upload old video?

Author kevin ( ago)
science channels on youtube are by far my favorite

Author andrei oprea ( ago)
this is not a ultrawide video.. them black bars on a 21:9 monitor thow

Author Tristen Hernandez ( ago)
Any idea where i can get a list of book siggestions from Veritasium?

Author Skope Theo ( ago)
But what if you try this experiment in the equator?Will the water not rotate at all?

Author fudgesauce ( ago)
I remember watching this video two years ago. I didn't believe the conclusion then, and I don't believe it now. You took one data point, essentially. Coriolis effects manifest on the very large scale, not over the span of a meter or two.

Author Sy Fontenot ( ago)
Will a cyclone never form at the equator because of this? What if a tornado from the north enters the south? Will it die or will such a thing never happen?

Author Billy Overton ( ago)
please spam flat earthers with this, I want their explanation.

Author Jone Robbins ( ago)
I thought that is why vehicles manufactured in Southern hemisphere bolts and screws go the opposite way.

Author Wood By Wright ( ago)
still one of my all time favorite colabs!

Author Tom Tom ( ago)
That was very lazy... nice to rewatch it though... and I am still annoyed at the definitive conclusion based on one experiment.

Author Eclipse007 ( ago)
If they have just said that the "experiment" was just a demonstration of the real experiment done years back, then the people saying that this is not scientific would have been silent since... but this is the Internet, i dunno what you guys want.

P.S. famlit

Author Granolees ( ago)
Yeah but the earth is flat sooo....this is fake

Author J Z Drake ( ago)
Quick answer to the title: only because of construction.

Author Mint Slice ( ago)

Author Sergey K ( ago)
Probability of the same result accruing by random chance is 1:4. You could repeat the experiment on a non spinning planet and 25% of the time you would get this results.
So is it a "proof"?
PS great explanation and well done for trying.

Author CNCmachiningisfun ( ago)
And with that, the flat earth 'theory' goes down the drain :) .

Author No Gandalf ( ago)
Aside from all the other variables others have mentioned a sample of one experiment provides evidence but not confidence (let alone "proof"). If this arrangement does indeed demonstrate measurable Coriolis effect I'd be interested to know how small the pond must become before the effect vanishes into noise.

Author Dark Horse ( ago)
Actually you can see it in a sink now, bathtub and toilet. 🙄 The only questionable test conclusion would be the toilet which a person would have to take into consideration did the manufacturer adjust how the water entering the toilet would actually flow or enter during the moment of flushing. For instance whether slots were cut a certain shape in the toilet bowl which would account for the rotational and directional created spin of the water. The calculation for water pressure also comes into play during such a test as the force then forces the water to flush the toilet.

Author VVindowZ ( ago)
sorry for the CAPSLOCK :D


Author Monkeysrock ( ago)
That was really well done.

Author Sly Rocko ( ago)
What if you drain it exactly at the equator or at least as close as possible?

Author Nancy Lee Fransen ( ago)
I have been wanting to see these vids this way since I first watched consecutively. THANK YOU!!!

Author Sean Haggard ( ago)
so...why does water swirl at all? I don't mean to explain the Coriolis effect, I mean why does water draining form a a vortex.

Author Something Wrong ( ago)
so, how it works on the equator ?

Author justsomeguy ( ago)
Sci show my ass!

Author GlowBox ( ago)
I love this

Author Nourredine Kebaili ( ago)
One experiment can not make a rule, you have to do it many times and make some statistical conclusions. You have to be able to predict the direction at least in the equator!

Author Saeed Zafar ( ago)
Well that is about Pole and Hemisphere, What about Equator itself?

Author Slick1G3 ( ago)
all rivers on one side of the earth flow north to south ..the opposite flows south to north

Author Philip Freeman ( ago)
I do wish you had repeated the experiment a few times. It makes sense that this effect could be real under such controlled conditions, but there is also a 1/4 chance of getting this result due to random chance. A couple of repeats would have made for a much stronger result. As it is we don't really know if this effect is truly observable.

Author Tim Barton ( ago)
toilets are bad examples.

Author Crystal Smith ( ago)
Also, the pump generators need to be the exact same pump as the magnetics within the generator will determine which way the blade spins in the generator. If the same and the flow still is opposite then I believe it has more to do with the magnetism involved with the Hall currents and the "Magnetosphere'' , electrical currents in the air, than the water, which gives the motors it's magnetics. Not sure on that one exactly. There are more things to consider in this than just filling up pools and pumping out the water with pumps. But that was enough for you to make a You Tube vid and get clicks and 'prove' something that doesn't seem to be very scientific proof. Hats off to you for having the gumption to make vids for You Tube. Good luck!

Author Crystal Smith ( ago)
It appears to me that the spinning earth models you show are having the Earth spin clockwise in one and counter clockwise on the other. As if it would appear to spin in the opposite direction from the vantage point of the which 'pole' one is observing. That WOULD NOT be the case. Also, which way the water flows would also be proportionate to which way the HOSE is falling, I.e., more left or more right of the suction end of the hose in the pool, and also any bumps or hills on the ground. This is not any solid proof that "holds water". ;) the 'experiment' needs more controls on it as in a lab, to be "scientifically" sound. And you called this 'science' or just a layman's experiment? The toilet one was more right since flooring is USUALLY, leveled out on building and laying the floor. This in my haughty opinion, not so humble, as most commenters never are as I see, is a FAIL of PROOF of anything. But... Low analyzers will buy it in a heart beat!

Author Wi1dcard86 ( ago)
There's a place in Ecuador called the "la mitad del mundo" Which translates to "the middle of the world". It's a park that is placed at exactly 0 degrees latitude which is marked by a line splitting the park into the north side and the south side. For scientific purposes I went in and flushed the toilets on both sides...despite what this video said about interfering angular momentums from toilets, I guess I got lucky and saw swirls going counterclockwise and clockwise from the north and south respectively. Can confirm legitness.

Author Darrell and Sondra Holden ( ago)
Hmmm, let's see, you might want to also talk to professionals who have worked with water systems in both hemispheres - there is no doubt - it DOES swirl in opposite directions. We know, we've lived in both hemispheres!

Author Kevin De Le Ree ( ago)
So if the earth didn't spin at all, would we have tornado's?

Author Randall Kelley ( ago)
OMG, like no way dudes. You just burst my bubble, dang...just to complicated...

Author Andrew Miller ( ago)
wait what dose water do exactley at the equator?

Author Obertone3 ( ago)
The Sci show does not do it`s own science. Circumcise that

Author ShadowCatGambit ( ago)
Does the gravitational pull from the moon effect the swirl in any way, and what would happen if these experiments were done directly on the north pole, south pole, and equator?

Author Brian ( ago)
would have been cool if you'd thought to synchronize the experiments in real time as you were doing them. not for any reason. just for fun

Author Mac ( ago)
I live in huntsville

Author tupakveli ( ago)
cool, so the right hand rule is useful for something other than annoying the f**k out of me in class :D

Author Marlon James Dimailig ( ago)
The snyncronizing part was satisfying

Author FMJPatriot ( ago)
"Anti-clockwise"? 🤔

Author Randi Rain ( ago)
Scientific America disagrees with you...

Author Brian Kelly ( ago)
Wait a minute - the Aussie said it's a 5 foot wide pool and the guy from Alabama said one and a half meters... I need a drink.

Author DBXD ( ago)
very cool!

Author sweggy mcsweg ( ago)
What would happen if you repeated this experiment at the equator?!?!

Author JOHN KRANE ( ago)
So much for flat earth

Author Christian Battestin ( ago)
Simpsons did it!

Author Philippe Marseille ( ago)
These are the videos that got me to become a subscriber to both you channels. Keep up the great work guys, you both are, really, both, part of the best channels on Youtube!

Author Nicholas Fanelli Hugueney ( ago)
Awesome work, guys!!
I love both of your channels.

Author blue frost ( ago)

Author Ovie Imoni ( ago)
Nonsense. It's turtles, all the way down. :)

Author Christian Burwell ( ago)

Author General-Idea ( ago)
Would It be possible to possibly do a short video one of your channels regarding Maglev trains? I know the science behind them isn't particularly advanced, but finding a good quality video about them seems to be non-existent.
Keep up the great Videos on all the channels!

Author Alexander Ehn ( ago)
Great that you did this version!

Author Pope ( ago)
It literally depends on the toilet. I live in the northern hemisphere and I've had toilets that go either way.

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