The answer to the question - what happens to a tennis ball tied to the bottom of a slinky after the top of the slinky is let go?

For a great explanation, check out Rhett Allain's analysis here: http://www.wired.com/wiredscie....nce/2011/09/modeling

Why does time appear to speed up as we get older? Can we slow it down?
Thanks to the National Geographic Channel for sponsoring this video!
The new season of Brain Games starts Sunday, February 14th at 9/8c - http://po.st/90S7Ow

Brain Games is an Emmy-nominated TV series that explores the inner workings of the human mind through experiments and interactive games. Did you know it's estimated that you have more than a dozen senses in addition to the standard five? One of those is a sense of time or chronoception. Tune in to the new season of Brain Games to learn about all of your senses, and more, starting Sunday, February 14 at 9/8c

References:

Ageing and duration judgement:
http://bit.ly/1TRN0cr

Nerve conduction velocity slowing with age:
http://bit.ly/23Wq6oE

Experiments with rats suggest time perception is distributed across brain:
http://bit.ly/1T6IjdO

Time perception with repeated stimuli:
http://bit.ly/1TRNbo5

Energy usage in brain with age:
http://bit.ly/1nXliOU

Time perception in moments of fear / danger:
http://bit.ly/1RoK7Ps
http://1.usa.gov/1TRNa3w
http://bit.ly/1Q8tDvW

Attention’s relation to time perception and recollection of perceived time:
http://bit.ly/20odeD8
http://bit.ly/1TRNfEf

On a stream of water you can levitate light balls of all sizes and even disks and cylinders. The mechanism is not the Bernoulli effect...
Want to make this at home? https://youtu.be/BppcHF2EdAY

My friend Blake from InnoVinci emailed me with a cool idea for a video and footage of levitating balls in water streams. Initially it was tough to explain the physics of what was going on. The standard Bernoulli effect relies on the object being completely immersed in the upward-flowing fluid. But in this case the water seems to form a single stream around the object and it's deflected away and down from the stream. By Newton's third law, the force on the water by the ball is equal and opposite to the force of the water back on the ball, pushing it up into the stream. There is a stable equilibrium position because if the ball moves into the stream, it "cuts off" the water going over the ball so it drifts out. If it drifts out too far, then lots of water passes over the ball, pushing it back into the stream.

Special thanks to Patreon Supporters:
Tony Fadell, Donal Botkin, Jeff Straathof, Zach Mueller, Ron Neal, Nathan Hansen

Support Veritasium on Patreon: http://ve42.co/patreon

Filmed by Raquel Nuno
Slow motion by Hollywood Special Ops http://hollywoodspecialops.com

Music from Epidemic Sound http://epidemicsound.com "Colored Spirals 3" "Magnified X 3" "In Orbit 2" "ExperiMental 1"

SYNCHRONIZE WITH DESTIN’S VIDEO: http://bit.ly/NorthernSwirl
Both videos on one page (for desktop): http://bit.ly/ToiletSwirl
Subscribe to Smarter Every Day: http://bit.ly/SubscribeSED
Click to tweet: http://bit.ly/ToiletSwirlTWT

Some notes:
We each repeated the experiment 3 times, and got the same results every time. For those of you who might be skeptical, great! A right circular prismatic kiddie pool is only $10 and you can do the experiment for yourself at your latitude. There's really no reason you shouldn't do it for yourself.

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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 http://eisenfeuer.com/. He also made still images of the earth from the top and the bottom.

Thanks to Vanessa for filming in Sydney: http://youtube.com/braincraftvideo

MORE INFO:

There was a study performed at MIT years ago (http://web.mit.edu/hml/ncfmf/09VOR.pdf) 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:
http://www.ems.psu.edu/~fraser/Bad/Ba...

Watch the bullet block experiment first: http://bit.ly/bulletblock
Click for a free audiobook from Audible: http://bit.ly/ZJ5Q6z
An interactive vignette of the bullet block http://ivv.rit.edu/bby/

Can you figure out the spinning disk? http://bit.ly/spinningdisk

Thank you all for the awesome video responses and comments!!

Simulation: http://bit.ly/19SCVnl
Web comic: http://bit.ly/17o8HrR
Wired Blog: http://bit.ly/17o9Dwu
Science Blogs: http://bit.ly/17o9au3
Scientific American: http://bit.ly/19SDoWC
Le's Blog: http://bit.ly/18q1m8a

Video responses from which I borrowed:
http://www.youtube.com/watch?v=hup-l4_Qt_U
http://www.youtube.com/watch?v=uwZ1Mhy0BS0
http://www.youtube.com/watch?v=SgylTbknFdM

Thanks to everyone at RIT and Dickinson College who helped with the making of this video:
Rochester Institute of Technology
Robert Teese, Katelyn Wilkerson, Andrew Gillie, Andrew Stidwill

Dickinson College
This experiment was the brainchild of David Jackson based on a demo at Princeton.
Priscilla Laws, Catrina Hamilton-Drager, Maxine Willis

High-speed camera support:
Charles Zwemer and Bria Antoine

Music: Temper Trap "Love Lost (Instrumental)" and Lights & Motion "Epilogue" licensed from CueSongs.com

Mounting evidence suggests a lot of published research is false.
Check out Audible: http://bit.ly/AudibleVe
Support Veritasium on Patreon: http://bit.ly/VePatreon

Patreon supporters:
Bryan Baker, Donal Botkin, Tony Fadell, Jason Buster, Saeed Alghamdi

More information on this topic: http://wke.lt/w/s/z0wmO

The Preregistration Challenge: https://cos.io/prereg/

Resources used in the making of this video:

Why Most Published Research Findings Are False:
http://journals.plos.org/plosm....edicine/article?id=1

Trouble at the Lab:
http://www.economist.com/news/....briefing/21588057-sc

Science isn't broken:
http://fivethirtyeight.com/fea....tures/science-isnt-b

Visual effects by Gustavo Rosa

What happens when single photons of light pass through a double slit and are detected by a photomultiplier tube? In 1801 Thomas Young seemed to settle a long-running debate about the nature of light with his double slit experiment. He demonstrated that light passing through two slits creates patterns like water waves, with the implication that it must be a wave phenomenon.

However, experimental results in the early 1900s found that light energy is not smoothly distributed as in a classical wave, rather it comes in discrete packets, called quanta and later photons. These are indivisible particles of light. So what would happen if individual photons passed through a double slit? Would they make a pattern like waves or like particles?

The solution to 4 rotation-related riddles, including the mystery cylinder, bike pedal pulling puzzle, track problem, and train part going backwards. Thank you to everyone who responded, liked, shared, or made a video response.
Please fill out this short survey for research: http://ve42.co/Rresearch

Special thanks to:
Mathematician George Hart: http://georgehart.com/
For allowing me to use excerpts from his pedal pulling puzzle solution: http://ve42.co/ppp

Petr Lebedev for combing through thousands of comments and providing the stats I gave in this video.

Video responses I used in this video (or watched):
everWonder? https://www.youtube.com/watch?v=5Ub2Cuclh1M
A Random Nerdy Channel https://www.youtube.com/watch?v=I9RB9TrZGps
The Physics DoJo https://www.youtube.com/watch?v=Pns0LCGLu9k
Oblivious Jim https://www.youtube.com/watch?v=12WZIMEPi1A
Armchair Explorers https://www.youtube.com/watch?v=S1yX_LTqtms
MrEngineeringGuy https://www.youtube.com/watch?v=DRF82Rx9_YI
Professor Cubers https://www.youtube.com/watch?v=qOd5orH-jfM
Scoop Science https://www.youtube.com/watch?v=uzLO6GqmfhI

A few notes on the puzzle:
1. A half-full container of honey does pretty well in reproducing the behaviour of the mystery cylinder. I wonder if the motion is a little smoother or more periodic with the ping-pong balls because they move as organized objects - also the delays between motion seemed to be longer with them than without ping pong balls.

2. For the average speed track problem, every time I said velocity I meant speed. Sorry to the pedants out there who are perhaps looking for some trick answer due to displacement being zero when you run around a track.

3. Although a lot of people identified it was something about a train's wheels that move backwards, fewer identified that specifically it was the part of the flange below the rail. Some simply said the bottom half of the wheel.

4. The bicycle question is perhaps the most complex of these riddles. If you tried it with a bike you likely found that it went backwards. But what happens if you sit on the bike and only push backwards on the bottom pedal. The answer might surprise you so give it a shot!

Bayes' theorem explained with examples and implications for life.
Check out Audible: http://ve42.co/audible
Support Veritasium on Patreon: http://ve42.co/patreon

I didn't say it explicitly in the video, but in my view the Bayesian trap is interpreting events that happen repeatedly as events that happen inevitably. They may be inevitable OR they may simply be the outcome of a series of steps, which likely depend on our behaviour. Yet our expectation of a certain outcome often leads us to behave just as we always have which only ensures that outcome. To escape the Bayesian trap, we must be willing to experiment.

Special thanks to Patreon supporters:
Tony Fadell, Jeff Straathof, Donal Botkin, Zach Mueller, Ron Neal, Nathan Hansen, Saeed Alghamdi

Useful references:
The Signal and the Noise, Nate Silver
The Theory That Would Not Die: How Bayes’ Rule Cracked the Enigma Code, Hunted Down Russian Submarines, and Emerged Triumphant from Two Centuries of Controversy, by Sharon Bertsch McGrayne

Bayes' theorem or rule (there are many different versions of the same concept) has fascinated me for a long time due to its uses both in mathematics and statistics, and to solve real world problems. Bayesian inference has been used to crack the Enigma Code and to filter spam email. Bayes has also been used to locate the wreckage from plane crashes deep beneath the sea.

Music from http://epidemicsound.com "Flourishing Views 3"

Scientists are being inspired by nature to design the next generation of security devices. Arrays of nanoscale holes create beautiful reflected colours that are almost impossible to forge. This video was supported by TechNyou - check out their series on logical fallacies: http://bit.ly/WBsD31

Soon these nanoscale security devices could replace holograms. They are many times more reflective than holograms, and although the structures are smaller scale, they are lower aspect ratio and therefore easy to manufacture in bulk.

The electron wiggle simulation is from PhET, the best physics simulations ever: http://phet.colorado.edu

Special thanks to Thomas from Copenhagen who showed me around the city including the science museum where he assisted with the soap bubble demonstration.

Clint Landrock is the Chief Technology Officer for Nanotech Securities: http://www.nanosecurity.ca

Music is "Firefly in a Fairytale" by Gareth Coker

SEE THE SETUP FIRST: http://bit.ly/bulletblock
Click here for the explanation: http://bit.ly/1dHPk2K
Spinning Tube: http://bit.ly/Va43Z6
Spinning Disk: http://bit.ly/14MSKsT
Chain Drop: http://bit.ly/1713VQO
Spool: http://bit.ly/14wkxfn

Special Thanks to:
Henry (MinutePhysics): http://www.youtube.com/minutephysics
Destin (Smarter Every Day): http://www.youtube.com/smartereveryday
Greg and Mitch (ASAP Science): http://youtube.com/asapscience
Elise Andrew (I F***ing Love Science): http://youtube.com/iflscience

Thanks to everyone at RIT and Dickinson College who helped with the making of this video:
Rochester Institute of Technology
Robert Teese, Katelyn Wilkerson, Andrew Gillie, Andrew Stidwill

Dickinson College
This experiment was the brainchild of David Jackson based on a demo at Princeton.
Priscilla Laws, Catrina Hamilton-Drager, Maxine Willis

High-speed camera support:
Charles Zwemer and Bria Antoine

Music Licensed from CueSongs.com: The Temper Trap "Love Lost"
Lights Motion "Epilogue"

In a zero-g plane I experimented with flames and slinkies with surprising results.
Check out e-penser's video: http://ve42.co/EPzeroG
Check out Physicsgirl's video: http://ve42.co/PGzeroG

Thanks to Novespace: http://ve42.co/novespace

Special thanks to Patreon Supporters:
Tony Fadell, Donal Botkin, Nick Luchsinger, Jeff Straathof, Zach Mueller, Ron Neal, Nathan Hansen

The zero-g plane allows for a lot of experiments to be conducted without the expense of getting equipment into orbit. Apparently 80% of microgravity research can be performed in a zero-gravity plane, which is much cheaper than going to space. The flame from the lighter seemed much lazier in zero-g because without weight there is no buoyant force and therefore no convection. This makes the process of combustion more challenging because it's difficult for oxygen to reach the fuel.

Music from the Epidemic Sound: http://ve42.co/epidemic
"Serene Story 2" "In Orbit 2"

A rare look inside the Svalbard Global Seed Vault which is closed ~350 days a year
Check out Audible: http://bit.ly/AudibleVe
More info on the seed vault: http://wke.lt/w/s/EKFlK
My trip to Norway was funded by Screen Australia, Film Victoria and Genepool Productions as part of a new project. More information soon.

Special thanks to Bente Naeverdal and the Crop Trust: https://www.croptrust.org

Do negative air ions improve mood, anxiety, depression, alertness?
Part of this video was sponsored by LastPass, click here to find out more: http://bit.ly/2RZZTZk

Special thanks to Prof. Jack Beauchamp and Dr. Nathan Dalleska from Caltech for all their help running these experiments and discussing the research. For more, check out the links below:
http://www.cce.caltech.edu/peo....ple/jesse-l-jack-bea
http://beckmaninstitute.caltech.edu/eac.shtml

If you want to dig into the research on negative ions yourself, I suggest starting with the review studies:

Air ions and mood outcomes: a review and meta-analysis.
Perez V, Alexander DD, Bailey WH.
BMC Psychiatry. 2013 Jan 15;13:29.
https://www.ncbi.nlm.nih.gov/pubmed/23320516

Air ions and respiratory function outcomes: a comprehensive review
Dominik D Alexander, William H Bailey, Vanessa Perez, Meghan E Mitchell, and Steave Su
J Negat Results Biomed. 2013; 12: 14.
https://www.ncbi.nlm.nih.gov/p....mc/articles/PMC38485

Exposure of laboratory animals to small air ions: a systematic review of biological and behavioral studies.
Bailey WH, Williams AL, Leonhard MJ.
Biomed Eng Online. 2018 Jun 5; 17(1):72.
https://www.ncbi.nlm.nih.gov/pubmed/29866122

Thumbnail photography by Raquel Nuno

VFX by Alan Chamberlain

Sound recording by Whitney Clavin

Motion Graphics by Charlie Kilman

Music from Epidemic Sound: http://epidemicsound.com "Capture a Picture 1" and "Seaweed"

When a tube spins with an X and an O labelled at either end, why do we see only one letter during the rotation?

This is how a slinky falls in slow motion - it appears to defy gravity but the centre of mass is accelerating at 9.8m/s^2 meaning the top is accelerating faster than that and the bottom is not falling at all until the entire slinky collapses.

Read a pre-print of the physics paper here: http://arxiv.org/abs/1208.4629
Music by Kevin McLeod http://incompetech.com
Songs: Industrial Music Box, Heavy Interlude, Pale Rider, Decisions.

Slow motion photography courtesy of Questacon http://questacon.edu.au

The original goal of Veritasium was to show the beauty of science and I think the first minute and a half of this is the closest I've come. This is the last in a series of six videos about slinkies.

Explanation of gyro precession: http://bit.ly/U4e8HQ
More: http://bit.ly/GyroMORE
Less Than: http://bit.ly/GyroLESS
Equal To: http://bit.ly/GyroEQUAL

Huge thanks to A/Prof Emeritus Rod Cross, Helen Georgiou for filming, Alex Yeung, and Chris Stewart, the University of Sydney Mechanical Engineering shop, Duncan and co. Ralph and the School of Physics.

In this video I attempt to lift a 19kg (42 lbs) wheel over my head one-handed while it's spinning at a few thousand RPM. This replicates an earlier experiment by Professor Eric Laithwaite. He claimed the wheel was 'light as a feather' and could not be explained by Newton's Laws. I wanted to find out for myself what I really felt like.

Music By Kevin MacLeod www.Incompetech.com "Tempting Secrets"

Celsius never devised nor used the scale that now bears his name.

Veritasium is now on Patreon: http://patreon.com/veritasium

Special thanks to Michael Stevens of Vsauce! http://youtube.com/vsauce1

More info about Celsius and temperature scales: http://wke.lt/w/s/2I6Nu

References for this video:

A History of the Thermometer and its uses in Meteorology by W. E. Knowles Middleton

Absolute Zero and the Conquest of Cold by Tom Shachtman

The Science of Measurement, A Historical Survey by Herbert Arthur Klein

Lehrbuch der Chemie by Jöns Jakob Berzelius

Special Thanks to the Uppsala University Museum
I filmed this in Uppsala in the summer of 2012! So I've been thinking about this idea for a very long time. I'm glad to finally have it out there in the world.

Uranium is a unique element, used in research, medicine, space travel, and of course weapons.
Not broadcast in your country? Contact your local broadcaster and/or email www.genepoolproductions.com

Documentary Dates:
US: PBS, July 28 & 29 @ 10pm ET / 9pm Central
France & Germany: ZDF/arte July 31 @ 10pm
Australia: SBS, August 6, 13, 20 @ 8:30pm EST

If you're wondering where the title comes from...
“A number of ingenious experiments were devised to test the speed of the fission reaction, and the limit was pushed. But even so, I thought it would be very nice to go one step nearer to a real atomic explosion. Dick Feynman, who was present, started to chuckle and to say that this is just like tickling the tail of a sleeping dragon.”
Professor Otto R Frisch, January 1969 Physicist, the Manhattan Project.

The sun has been producing light for about five billion years but where does all its energy come from? The most common idea is that the sun is burning gas - like a giant fireball in the sky. If this were true, the sun would have gone out long ago. So how is the sun actually fuelling itself? It is converting its own mass into energy. By combining protons (the nucleus of hydrogen) into helium, it squeezes some mass into energy - 4.3 billion kg per second. It is Einstein's famous E=mc^2 which gives us the quantitative relationship between mass and energy, where c is the speed of light.