Destin (/u/mrpennywhistle) and Derek (/u/veritasium) here.

We wanted to try to solve the "toilet swirl" mystery for ourselves and decided to do it in a really unique way. We made 2 videos that sync together in a way unlike anything we've seen on the internet.

It's really cool and we want you to watch it.

Southern Hemisphere (Derek):

Northern Hemisphere (Destin):

If you can't figure out how to synchronize the videos you can use this page to view both

The videos can be synchronized by viewers on 2 separate devices, or on one computer. The editing is unlike anything we’ve seen on the internet. The two videos are made to be played in sync. Objects move from one video to another, the dialogue works between the two… even the musical instruments are split between the videos.

We're getting a lot of questions about the experiment and if it's legit. We'll answer a couple right off the bat. Feel free to ask us more!

  • We each ran three experiments.
  • In the Southern Hemisphere Derek observed clockwise rotation all 3 times.
  • In the Northern Hemisphere I observed counterclockwise rotation all three times. * Yes we leveled the pools.
  • At the equator it would go straight down.
  • We got the idea for our specific setup from an MIT demonstration performed in the 1960's.

We've also both done several other videos (Backwards Bicycle, Slinky etc.)

Here's Destin's proof.

Here's Derek's proof.

Edit Still here answering questions even though it's the next morning!!. I love it when people don't abandon their AMAs, so we aren't. Keep asking, we'll get to it even if it takes days.

Edit 2 It's kind of a personal policy of mine to try to answer every respectable question. Derek's been hard at it as well. We'll be checking in on these over the next week or so and answering the top level comments as appropriate.

Comments: 2152 • Responses: 65  • Date: 

OneAviatrix742 karma


MrPennywhistle772 karma

GASP... I can't breathe. If you say they're Red Tails I'm going to scream like a little girl. YES YES a THOUSAND TIMES YES.

wydra91229 karma

Whoa. I've watched your vids since, forever, I think I'm witnessing history right now. Lol

MrPennywhistle886 karma

We're always witnessing history.

sebastiankirk26 karma

What was OP's comment here?

MrPennywhistle88 karma

They asked me if I wanted to fly in a fighter jet. I said yes. I think it got real too quick for them.

MrPennywhistle188 karma

Seriously I'll have the flight physical you need to make this happen already in hand.

MrPennywhistle195 karma

Wy have you not responded? You can't just say "fighter jets" and not reply! I'm dying here!

meadit516 karma

Can we expect more collaborations between you two in the future? Your styles definitely complement each other's and it makes for great learning/entertainment.

(On a side note, thank you both for being awesome. Got to meet you both at an Australian meetup and it was such an amazing experience to hang out and chat with you!)

MrPennywhistle333 karma

This is the third time that I can remember that we collaborated.

I for one would love to work with Derek any time he wished, but it will probably be a while just by nature the other irons we have in the fire.

mikeh_1993343 karma

Derek: After visiting Chernobyl, what is your view on the risk/benefit ratio of nuclear power?

Destin: What aspect of space science do you feel has contributed most to society as we know it today?

MrPennywhistle276 karma

Satellite communication has changed the world. That being said, there are things going on the ISS right now that are HUGE for understanding how our bodies work. They are also pushing the envelope on life support systems. I'm eating lunch tomorrow with the guy over the urine → drinking water system on the ISS. Can you imagine what systems like that could do for placed like... oh.. I don't know... drought stricken California?

thephysicsgirl86 karma

What are you going to ask the guy with the urine to drinking water system?!

MrPennywhistle217 karma

The obvious question. "Can I drink my urine".

dfnkt68 karma

Bear Grylls would like to have a word with you.

MrPennywhistle73 karma


UseANooserChame15 karma

You should be asking if you can drink his urine. It could be a real bonding experience.

MrPennywhistle17 karma

Hahaha... man.. that's a plot twist. I might do that.

MaceWinnoob242 karma

Have you guys asked Grey and Brady about being guests on Hello Internet?

Or rather, you guys should start your own podcast so you can do a collab with them.

Wow, the possibilities of collabs are endless.

veritasium350 karma

YES - but they have a thing going which is 'two dudes talking' and adding a guest would mess up their flow.

I have joked with MinutePhysics about creating Goodbye Outernet, the companion podcast to Grey and Brady ;)

JDawg2332116 karma

How do you feel about Brady constantly messing up your name and brand?

MrPennywhistle78 karma

Asking the important questions.

MrPennywhistle126 karma

Derek has threatened to make "Goodbye Outernet" for quite some time now. A podcast though? Geeze... I don't think my life could allow participation in another big project.

roseserpentmoon13 karma

I agree!! Not just as guests but I would love all the random act of intelligence guys podcasts... Time for 'Goodbye outternet!'

MrPennywhistle41 karma

I heard that Grey started a new podcast today or something. Here it is... Cortex.

Noerdy155 karma

Do you mind if people use gifs of your videos on reddit if they provide proper credit? I have used a couple of your gifs before, and always give credit. I just want to know if you mind us doing that.

MrPennywhistle603 karma

I personally don't like it. My videos more often tend to be more focused on a single shot that took me months to capture. By taking the GIF and posting it I feel like I'm being robbed of an opportunity to teach someone science. They scroll through and say "hmm... that looks neat" and never think about it again. My goal is to engage the viewer mentally. A good example of this is my AK-47 underwater video. That video is not about an AK-47 underwater. It's about cavitation and the Rayleigh Plesset equation used to define bubble dynamics. By posting the GIF.... the viewer will never care about that. To me it's just another form of freebooting. Why not just link to the video instead. I know the standard answers "too long", "In a place where I can't have sound" "low bandwidth". I do not think these are valid reasons. I know I'm kind of on an island alone with this viewpoint.... but I'm also the only one taking my time off from work to make the video in the first place.

Noerdy140 karma

Thank you for your response. I will not use your videos in the future. As for why not the video, from my experience, reddit tends to react better to shorter "gifs" then having to sit through an 8-10 minute video. Thank you for your input, and all the work you put in your videos! <3

MrPennywhistle240 karma

If you have a specific need or idea shoot me a line. I'm by no means saying I'm an Intellectual Property hard liner.... but I've simply been taken advantage of too many times. I hope my response didn't come across as rude or anything. I just answered honestly so you would know how it makes me feel. I would be interested to know how other creators / artists feel about this.

JimmyAxel138 karma

Loved the videos! I've definitely wondered many times whether it was true. I was more intrigued by the explanation you guys gave.

My question is about the editing actually. How did you do it?! Did you use some program that edited them simultaneously or did you painstakingly have to make everything line up perfectly? (I'm thinking specifically of things like making the globe shift from one video to the other).

I'm glad you guys liked my dual-screen setup on Twitter! It's the best use for dual screens I've had so far!

Thanks for being awesome and for making learning fun and interesting!

MrPennywhistle254 karma

The most efficient editing happened when we were sitting across the table from each other. We would call out individual frames to enter on, stop talking on etc. Derek uses Final Cut Pro and I use Adobe Premiere, so we had a few issues when we exported our final videos. FCP kept removing some phantom frames and we had to manually tweak that a bit frame by frame. Gordon (/u/fatjesus) did the heavy lifting on the audio stuff. His methods were really rad. He split some songs up and put some instruments on my track and some on Dereks. Derek split up the first song and we cross faded it between videos depending on who was talking.

Man, it boggles the mind to think about all the technical things we did on this. It was certainly awesome to work with someone as technically savvy and rigorous as Derek!

fatjesus113 karma

You guys also did a lot of pre-production planning! A vertical spreadsheet-script blocked out the shots/narration which I thought was quite clever.

veritasium204 karma

the script was essential. Without it we wouldn't have gotten anywhere. But one hindrance was I did the experiment TWO YEARS AGO so we couldn't redo anything on my side. We only had clips of what I said, not what I wished I had said to fit with Destin.

MindOfMetalAndWheels221 karma

I keep thinking I can't get more impressed by this project but then I am.

MrPennywhistle160 karma

Yeah that was pretty interesting actually. "Destin, wish me luck" was said by Derek 2 years ago. So future Destin is wishing past Derek luck. I was actually Skyping with Derek when he did one of those first pool drainings. It was really awesome.

caud3x34 karma

Grey showing up to a Veritasium+SED AMA IS THE THE BEST OR WHAT

MrPennywhistle38 karma

The only thing that could make this better is if /u/jeffdujon showed up.

JimmyAxel13 karma

Followup for /u/fatjesus. Did you add the audio after the final videos were exported? I'm trying to understand how you were able to crossfade between the two videos unless you had a way of controlling the audio of both simultaneously. This is so cool!

fatjesus31 karma

Not this time due to time restrictions. I received stems for one track and split them into rhythmic and non-rhythmic sections (one video would get rhythmic and another would get non-rhythmic, so they'd complement each other) and composed and separated another looping track specifically to be lenient with sync.

Audio for Smarter Every Day is pretty fast and loose, and a perfect audio edit/mix actually doesn't suit the run & gun aesthetic of the channel so I usually provide Destin with the necessary audio and let him cut it in. Then rag on him when he forgets to fade his regions.

MrPennywhistle34 karma

or when I double a track to make it louder....

regnar_exa13 karma


MrPennywhistle19 karma

Gordon tries his best to keep me straight with respect to sound.

kuhnie90 karma

Dirk from Veritaslium, how would you describe your friendship with Brady Haran?

veritasium163 karma


MrPennywhistle48 karma

LOL. Now I have to call Beyonce from Numberfest and let him know about this. Heck, we'll just summon him. Hey /u/jeffdujon!

weramonymous53 karma

How's the battle against freebooting going? Anything an average redditor can do to help?

fatjesus78 karma

I don't think we've had any maaajor freebooting incidents since the slow-motion tattoo thing (though I'm sure smaller ones are happening all the time). I've been doing my part by not participating in giving views, which is more passive than Destin's suggestion but calling out every radio station page can be exhausting.

I've been using a chrome extension called Facebook Purity (it's AWESOME) which allows me to automatically remove all kinds of things I don't want to see from facebook, so I simply do not see any of the videos that are being freebooted and therefore cannot contribute to views. I have more or less culled my FB to nothing but original content and updates from friends.

MrPennywhistle78 karma

That's Gordon by the way. He does the music for Smarter Every Day.

carcerus49 karma

@mrpennywhistle: How do you keep your life so well balanced? You have a family to take care of and you make amazing videos and collaborations like this one and go on tours and do all sorts of amazing stuff. @Derk from veritablium (sry could not resist) How do you keep yourself informed of the various topics and newcomings? What journals do you read, what sites do you visit?

@Both of you: Thanks for the very interesting videos you keep making. You are amazing!

MrPennywhistle108 karma

My wife. She is an amazing person who encourages me to do everything I can to change the world. The only way I can explain our marriage is that the whole is greater than the sum of the parts.


Destin: I've seen that your bicycle video got used in a show called "galileo" (here in Germany). Did they ask you for permission first?

MrPennywhistle77 karma

Kristina Stojic from ProSiebenSat.1 TV Deutschland GmbH asked for permission. I said no because they've stolen my stuff in the past. I'm quite staggered that they would run it anyways after such clear communication. It would be great if you could somehow capture this freebooting for me via video screen capture.


I've checked their online library but it seemed they cut it out there. When it airs on the TV again, I will capture it for sure :) Keep your video going, they are great!

MrPennywhistle31 karma

I would greatly appreciate this. Freebooting is something I deal with often. Looks like this was beyond an active decision to freeboot. Can you tell me when the next airing date is?

edwino34542 karma

First, you guys are awesome and so was the video! Question time, what were your major obstacles to overcome other than the distance between you two?

MrPennywhistle81 karma

Schedule. My schedule is quite difficult with the family and being an Engineer. Derek went to the ends of the earth to make this happen (in an airplane).

veritasium69 karma

Making two videos that you could play at the same time with different editing software that did its best to thwart syncing at every turn!

MrPennywhistle96 karma

Shakes fist at Final Cut Pro

SlightlyMoreThan41 karma

Do you guys know of any other 'scientific' differences between the northern and southern hemispheres you could test? (If so, any chance of more collaborations?)

MrPennywhistle51 karma

Oooh, good question. I don't know of any. I bet Derek does.

xluto33 karma

Wow, the first AMA that I've ever been on time for!

Destin, when did you start getting so interested in science? I remember from one of your videos that your father works at NASA. What were some ways that he influenced you to go into your field?

Derek, same question, but I don't have any clue of how you got interested in your field. By the way, the jellyfish stinging video was cool.

MrPennywhistle64 karma

I've always been a tinker thinker. It was my Grandfather who worked for NASA. He never even mentioned the word "Engineer" to me. It was actually my neighbor who taught me what an Engineer was. My Dad was a skilled tradesman in the auto industry and he would often take me with him at night when he did stuff like program coordinate measurement machines etc. We had awesome conversations and used to play a game called "Do you know". It was basically a curiosity game where we'd ask each other questions. He was really good about asking interesting questions and he still is. The Backwards Balloon video was his idea.

GlassOrange32 karma

How negligible were the drops of food coloring to the water movement?

MrPennywhistle43 karma

Super negligible. Just to be sure that the order in which we inserted them didn't influence the swirl... we alternated the ways that the inserted them. For example, I dropped them in the clockwise direction, then in the counterclockwise direction. I was a bit concerned that they might cause some sort of ripples and affect the rotation, similar to how a phased array radar can be steered. (I hope that makes sense). The coolest thing about the water drops falling in is that they created little vorices. I'll see if I can upload a video real quick to show you. Derek, can you handle questions when I'm away?

MrPennywhistle45 karma

Alright here's a video showing you what I'm talking about. There were about 5-7 drops put in a line in each Cardinal direction, but as you can see the drops separated when they hit the water.

GlassOrange11 karma

Alternating how you inserted them sounds smart just to make sure, despite being so negligible in effect...

*googling "phased array radar" * ...processing... ...processing...

MrPennywhistle56 karma

Imagine a bunch of fat kids on the side of a pool in a line. If they all jump in at once one wave moves across the pool like a wall. If they jump in the pool in order from one side to the other, the wave moves across the pool on a diagonal. The angle of the wave is determined by the delay in their jumps. You now understand how a phased array radar steers.

Amster230 karma

What are your favorite videos from each other channel?

(Destin's favorite Veritasium video, and Derek's favorite SmarterEveryDay video)

MrPennywhistle54 karma

Derek made a video a while back called "Forest of Friends, Baggage Carousel of Jerks". I loved that video and think about it every time I'm at the airport.

melonologist23 karma

Loved the video. What part did you find the most fascinating in all of this?

MrPennywhistle41 karma

The first time I opened the valve and dropped the die in and it started draining counter clockwise I almost lost my mind. Seriously... it was like one of those moment when you say to yourself.. "We've prepared for this for SO LONG".... but there was still a bit of doubt that it would actually happen. That was very very exciting.

MindOfMetalAndWheels61 karma

What was the plan if it didn't work?

MrPennywhistle46 karma

There was no plan B Grey. It's like being a high flyer without a trapeze net. We just trusted the physics, and the physics didn't let us down. Admittedly, Derek took FAR more risks than I did. He was the man who really made this happen. He deserves the credit here. Which is why everyone reading this should go subscribe to him.

veritasium44 karma

Um... kill the video?

We found this paper from the 1960s that said it would work with about a 6 foot pool so I was pretty confident. Then I did the experiment two years ago and it worked so Destin had it easy ;)

MrPennywhistle55 karma

This is Grey we're talking to man. Make it sound scary.

Fursber22 karma

Great job guys! I love both your channels, and you two are really inspirations to the next generation of scientists.

Do either of you have even more hidden talents that we don't know about? I would probably cry if I saw one of you playing the cello or something.

MrPennywhistle62 karma

I like woodworking and fabricating things in my garage. I'm no Ron Swanson, but I enjoy building practical things with my hands.

whendoesOpTicplay22 karma

Any future collabs with the Slo Mo Guys?

MrPennywhistle27 karma

We've talked about it!

DrMody20 karma

Huge fan! I'll be honest, it's on my bucket list to meet you some day. Question: if you could eat lunch with any three people dead or alive, who would you eat with, what would you eat, and what would you talk about?

MrPennywhistle45 karma

Where do you live?

pranitkothari20 karma

How you research your topic? Please give detailed step by step approach.

MrPennywhistle62 karma

  1. It usually comes to me in a flash. A question that I don't know the answer to.
  2. I ask everyone in the immediate vicinity the question.
  3. I Google it.
  4. I find the world expert.
  5. I pick up the phone and call the world expert.
  6. I pick the brain of the world expert in a hand wavy kind of way.
  7. I try to collocate myself with the world expert.
  8. I film stuff, and ask my serious questions when the camera is running.
  9. In short... I learn on camera but often have a good idea of what's going on first. It's more fun if I have an a ha moment with the viewer instead of by myself off camera.
  10. I save all the footage and usually make the video a year later.

zwolfp16 karma

I have read other similar studies with different results. Is it possible there was just a 50% chance of it going either way and you just got lucky?

MrPennywhistle28 karma

I would like to see those studies.

roadkillturtle15 karma

Hi Derek. I have to say, I think my favorite of your videos was of the archer who stress-tests his arrows for maximum accuracy. How do you meet people like him?

MrPennywhistle29 karma

That was a guy in one of my videos (Destin). He lives in my home town. Byron Ferguson. I'm convinced he's a wizard, so i was tickled pink to find that he had a little science lab of sorts setup in his shop. Here's the video in question.

jackalus_22212 karma

How did you guys edit the videos to sync up perfectly?

veritasium37 karma

With GREAT difficulty. Destin edits on Premiere. I edit on FCP X. We did some of the preliminary edits sitting side by side in Destin's house. Saying 'what frame should I put this?' '1:02:25' and on we went like that. The worst thing was our editing software didn't play well together. My file's frame numbers didn't export correctly so Destin had to do final tweaks to match my export. It took many, many days, long Skype conversations, and unplanned sleep deprivation experiments.

mingz9 karma

why not, just 1 of you do all the editing?

MrPennywhistle17 karma

This was a very big project with lots and lots of footage. We're both capable with video editing software so it made sense to play to our strengths and be as efficient as possible.

catcatdogcat10 karma

Do you think this effect applies to very slow moving processes? For example, the paths of magma intrusions which are emplaced over millions of years?

MrPennywhistle9 karma

I have no idea. Derek?

pete1010118 karma

I know collaborations are fun, but with the distance between all the YouTubers you're associated with (Dirk, Michael, Henry, Brady, etc.), how often would you like to see collaborative videos like these? (Both dual-styled and just good ol' one videos)

edit: Can't forget about CGPGrey, either!

Also would like to thank you for your awesome work, all of you!

MrPennywhistle17 karma

I love collaboration videos. It's like you get to be excited about your project with one of your friends! Adventures are always more fun with others.

MadnessBunny7 karma

Ok, first I am huge fan of both of you! I really love your videos and it really makes me love science more and more, so keep up the amazing job!

Now my question, what would you say to convince someone to pursue a career in the science field?

Thanks for doing this, and again amazing videos!

MrPennywhistle26 karma

My goal wouldn't be to convince them with words.... buy them a microscope or a programmable lego set. In a world of talkers be a thinker and a doer. Show things by DOING.

AirplaneBottleOfBour4 karma

Why don't we see the same effect in static water (when the pool isn't draining)? What about a draining pool makes the effect more pronounced and visible?

MrPennywhistle7 karma

We don't? I'm not so sure about that. Have you heard of a Foucalt Pendulum?

GreenGinkgo4 karma

Can you describe the biggest challenge(s) you faced during the production of this sydeo?

veritasium8 karma

ALL OF THE THINGS. Mainly distance, time, planning - that's why I flew to Alabama, because we had talked about doing this video for so long and hardly made progress on it. Face to face is still so important when it comes to getting things done.

MrPennywhistle7 karma

100x this. Had Derek not called me and said "I will be in Alabama in 2 weeks" I wouldn't have built the platform. We didn't really have the time to do this. We just didn't sleep. It was rather insane.

josephwdye4 karma

What journal do you plan to publish to?

MrPennywhistle8 karma

Interesting question. I find that because a lot of the stuff I do is on YouTube, it's often discredited by the academic community as entertainment. More often than not, someone publishes on the subject about 6-8 months after the video is released. Sometimes they'll call me and ask me questions, and if I express interest in being a coauthor or something like that they express insincere interest just long enough to get me off the phone. If I had to guess, I'd say it's about time for another paper on curling stone physics or bird flight dynamics.

BemusedRat4 karma

Did you try sitting in the pool to see if the effect was strong enough to twirl you around?

Did you consider using heavier liquids to see how that would affect the results?

MrPennywhistle5 karma

Sitting in the pool would induce vorticity in the fluid and ruin the experiment. We're talkling about a SERIOUSLY small effect.

meadit3 karma

What's the most fun experience either of you have had while making a video?

MrPennywhistle6 karma

I really enjoyed this one. It was the first time I had ever been diving with a full face mask and microphone. When I started talking at 1:56 those were some of the first words I ever said underwater. I didn't know how to regulate my breathing or when to take breaths etc. I just looked at the camera and tried to talk like I knew what I was doing. That was fun.

meadit3 karma

What do both of you look forward to in the future?

MrPennywhistle9 karma

I'm about to spend several days with my family. I'm really excited about that. I'm also about to start taking flying lessons from an experienced military test pilot!!

EStew423 karma

Hey guys! I really just wanted to say that I really enjoy your videos, but I guess I'll ask some questions, too...

For both of you: What is your daily life like? What is your favorite video so far? And what topic do you most look forward to making a video about in the future?

MrPennywhistle4 karma

There's a specific video I'm looking forward to at NASA that involves the brain. Daily life is pretty hectic here. My favorited video... hmm... I like "why you didn't die at birth", "Operation Rocket", Prince Rupert's drop, and the Backwards bike. Hard to pick a favorite.

AutoModerator1 karma

Users, please be wary of proof. You are welcome to ask for more proof if you find it insufficient.

OP, if you need any help, please message the mods here.

Thank you!

I am a bot, and this action was performed automatically. Please contact the moderators of this subreddit if you have any questions or concerns.


/u/MrPennywhistle has shown many times who he is, this should be fine.

MrPennywhistle27 karma

Thank you ANUS_CAPTAIN. Lulz.

Boonmonster1 karma

What are your recommended books from various disciplines of science that you found are enlightening?

MrPennywhistle3 karma

We're both sponsored by Audible on occasion. I actually use the service to listen to awesome books. The latest one I listened to was "Endurance"... the story of Shackleton's journey to cross Antarctica. I find that I really enjoy listening to fiction or adventure stories when I drive. I personally leave the heavy stuff to textbooks and journal articles.

Stowcenter931 karma

My question is for both of you.

You both seem to have good friendships and working relationships with a lot of educational YouTube channels. I love seeing you guys collaborate like Destin on SloMoGuys or Derek on VSauce.

But I wanted to know what are some of your favorite, for lack of a better word, "Non-Educational" YouTube channels and have you ever thought of doing a crossover with them?

MrPennywhistle2 karma

There was a channel that a friend of mine made a while back called "Joe and Buzz". This is my favorite video of theirs. Fantastic writing.