If you've seen footage from the International Space Station or any of the space shuttle missions, you know that astronauts float around as they orbit the Earth. Why is that? Is it because the gravitational force on them is zero in space? (Or nearly zero?) The truth is that the strength of the gravitational attraction is only slightly less than it is on Earth's surface. So how are they able to float? Well, they aren't floating - they're falling, along with the space station. They don't crash into the Earth because they have a huge orbital velocity. So as they accelerate towards the Earth, the Earth curves away beneath them and they never get any closer. Since the astronauts have the same acceleration as the space station, they feel weightless. It's like being in a free-falling elevator (without the disastrous landing).

Director of Photography: Stefan Smith
Camera Assistant: Raa Perajeev
Boom Operator: Maha Sivalingam

Production Coordinator: Adrian Tan
Production Assistants: James Peniata, Pratheep Ramachandran

How can you Yo-Yo without the string attached?
Check out Audible: http://bit.ly/AudibleVe
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For Beyond Slow Motion: http://bit.ly/VeBeyondSlowMo

For more on yo-yos check out: http://bit.ly/290wR3a

How to yo-yo without a string attached... So many crazy tricks and the science that makes it possible.

Edited and animated by Daniel Joseph Files

How jumping spiders reveal an entire secret world of colors. Let BetterHelp connect you to a therapist who can support you - all from the comfort of your own home. Visit https://betterhelp.com/veritasium and enjoy a special discount on your first month.

A massive thank you to everyone at Day’s Edge Productions for making this documentary happen. Check them out at https://daysedge.com/.

You can watch the full-length documentary “Spider Vision: Decoding Color” on Curiosity Stream - coming soon.

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Special thanks to our Patreon supporters! Join the community to help us keep our videos free, forever: https://ve42.co/PatreonDE

Adam Foreman, Anton Ragin, Balkrishna Heroor, Bertrand Serlet, Bill Linder, Blake Byers, Bruce, Burt Humburg, Chris Harper, Dave Kircher, David Johnston, Evgeny Skvortsov, Garrett Mueller, Gnare, gpoly, I. H., John H. Austin, Jr., john kiehl, Josh Hibschman, Juan Benet, KeyWestr, Kyi, Lee Redden, Marinus Kuivenhoven, Martin, Matthias Wrobel, Max Paladino, Meekay, meg noah, Michael Krugman, Orlando Bassotto, Paul Peijzel, Richard Sundvall, Sam Lutfi, Stephen Wilcox, Tj Steyn, Toni, TTST, Ubiquity Ventures, wolfee

If you’re looking for a molecular modeling kit, try Snatoms, a kit I invented where the atoms snap together magnetically - https://ve42.co/SnatomsV

Production by Day's Edge fully funded by National Science Foundation (Grant #IOS 1831767)

Featuring: Dr. Nathan Morehouse (University of Cincinnati); Olivia Harris (University of Cincinnati), Dr. Megan Porter (University of Hawaii); Dr. Lisa Taylor (University of Florida); Dr. Wayne Maddison (University of British Columbia); and Dr. Emma Alexander (Northwestern University)

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Directed by Neil Losin
Written by Neil Losin
Edited by Neil Losin, Andy Laub, and Alan Saunders
Animated by Root House Studio and David Hutchinson
Filmed by Neil Losin, Nate Dappen, Alex Wiles, Andy Laub, and Barend van der Watt
Produced by Day’s Edge Productions

Repurposed for YouTube by Derek Muller, Casper Mebius, Petr Lebedev, Peter Nelson, Trenton Oliver, Emily Zhang, Giovanna Utichi, Rob Beasley Spence, Emily Taylor, and Gregor Čavlović

Thumbnail contributions by Ren Hurley and Peter Sheppard

Video/photos supplied by Day’s Edge Productions and Storyblocks
Music by Adrian Younge, PBS, Epidemic Sound, and Jonny Hyman

Do odd perfect numbers exist? Head to https://brilliant.org/veritasium to start your free 30-day trial, and the first 200 people get 20% off an annual premium subscription.

Special thanks to our Patreon supporters! Join this list to help us keep our videos free, forever:
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A massive thank you to Prof. Pace Nielsen for all his time and help with this video.

A big thank you to Dr. Asaf Karagila, Pascal Ochem, Prof. Tianxin Cai, and Prof. William Dunham for their expertise and help.

To try GIMPS out yourself: https://ve42.co/GIMPS

These sources were particularly helpful:
Perfect numbers via MacTutor - https://ve42.co/MTPerfect
Cai, T. (2022). Perfect numbers and fibonacci sequences. World Scientific. - https://ve42.co/Cai2022
Dunham, W. (2022). Euler: The master of us all (Vol. 22). American Mathematical Society. - https://ve42.co/Dunham2022

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References:
https://www.youtube.com/watch?v=T0xKHwQH-4I&pp=ygUPcGVyZmVjdCBudW1iZXJz
https://www.youtube.com/watch?v=q8n15q1v4Xo&pp=ygUPcGVyZmVjdCBudW1iZXJz
Dickson, L. E. (1919). History of the Theory of Numbers.. (Vol. 1). Carnegie Institution of Washington.
Knill, O. (2007). The oldest open problem in mathematics. NEU Math Circle, December2. - https://ve42.co/Knill2007
Perfect number via Wikipedia - https://ve42.co/WikiPerfect
Introduction to Arithmetic via HalthiTrust - https://ve42.co/IntroArithmetic
Nicomachus of Gerasa via MacTutor - https://ve42.co/MTNicomachus
Sonja, B. (1988). The First Perfect Numbers and Three Types of Amicable Numbers in a Manuscript on Elementary Number Theory by Ibn Fellûs. Erdem, c. IV, 11. - https://ve42.co/Sonja1988
Ibn Fallus via Wikipedia - https://ve42.co/WikiFallus
Mersenne prime via Wikipedia - https://ve42.co/WikiMP
List of Known Mersenne Prime Numbers - https://ve42.co/ListOfMP
Marin Mersenne via MacTutor - https://ve42.co/MTMersenne
Leonhard Euler via Wikipedia - https://ve42.co/WikiEuler
Frank Nelson Cole via Wikipedia - https://ve42.co/WikiFNCole
GIMPS History via Mersenne.org - https://ve42.co/GIMPSHistory
EFF Cooperative Computing Awards via EFF - https://ve42.co/EFFAwards
Jonathan Pace via Primewiki - https://ve42.co/PWikiPace
Book with just one number sells out in Japan via BastillePost - https://ve42.co/PrimeBook
Predicted distribution of Mersenne primes via John D. Cook - https://ve42.co/JDCookMP
Euler’s Odd Perfect Numbers Theorem via Cantor's Paradise - https://ve42.co/EulerOPN
A Perfect (Math) Mystery via Medium - https://ve42.co/Machado2024
Brent, R. P., Cohen, G. L., & te Riele, H. J. (1991). Improved techniques for lower bounds for odd perfect numbers. Mathematics of Computation, 57(196), 857-868. - https://ve42.co/Brent1991
Ochem, P., & Rao, M. (2012). Odd perfect numbers are greater than 10¹⁵⁰⁰. Mathematics of Computation, 81(279), 1869-1877. - https://ve42.co/Ochem2012
Mathematicians Open a New Front on an Ancient Number Problem via Quantamagazine - https://ve42.co/QuantaSpoofs
Descartes number via Wikipedia - https://ve42.co/WikiDescartesNumber
Andersen, N., Durham, S., Griffin, M. J., Hales, J., Jenkins, P., Keck, R., ... & Wu, D. (2022). Odd, spoof perfect factorizations. Journal of Number Theory, 234, 31-47. - https://ve42.co/Andersen2022
Pomerance’s Heuristic that Odd Perfect Numbers are Unlikely via OddPerfect.org - https://ve42.co/Heuristic

Images & Video:
Clip of Piergiorgio Odifreddi - https://www.youtube.com/watch?v=y0paHEA8-gA
Euclid’s Elements 1 via Claymath - https://ve42.co/CM1
Euclid’s Elements 2 via Claymath - https://ve42.co/CM2
Euclid’s Elements 3 via Claymath - https://ve42.co/CM3
Diophanti - https://ve42.co/Diophanti
Gauss book - https://ve42.co/GaussDis
Euler’s Archive 1 - https://ve42.co/Euler1
Euler’s Archive 2 - https://ve42.co/Euler2

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Special thanks to our Patreon supporters:
Anton Ragin, Balkrishna Heroor, Bertrand Serlet, Bill Linder, Blake Byers, Burt Humburg, Chris Harper, Dave Kircher, David Johnston, Diffbot, Evgeny Skvortsov, Garrett Mueller, Gnare, I.H., John H. Austin, Jr., john kiehl, Josh Hibschman, Juan Benet, KeyWestr, Lee Redden, Marinus Kuivenhoven, Matthias Wrobel, Max Paladino, Meekay, meg noah, Michael Krugman, Orlando Bassotto, Paul Peijzel, Richard Sundvall, Sam Lutfi, Stephen Wilcox, Tj Steyn, TTST, Ubiquity Ventures, wolfee

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Directed by Casper Mebius
Written by Casper Mebius and Derek Muller
Edited by Peter Nelson
Illustrated by Jakub Misiek
Animated by Fabio Albertelli, Ivy Tello, David Szakaly, Alondra Vitae, Alex Drakoulis, and Leigh Williamson
Filmed by Derek Muller, Raquel Nuno, and Peter Nelson
Additional research by Aaron Santos, Camilla Machado, and Gregor Čavlović
Produced by Casper Mebius, Gregor Čavlović, Han Evans, and Derek Muller

Thumbnail by Ren Hurley
Additional video/photos supplied by Getty Images and Pond5
Music from Epidemic Sound

Does light take all possible paths at the same time? 🌏 Get exclusive NordVPN deal here ➵ https://NordVPN.com/veritasium It’s risk free with Nord’s 30 day money-back guarantee!✌

A massive thank you to Dr. Andrew Mitchell for all his help and expertise. If you want to delve further into this topic then we highly recommend his lecture on Classical physics derived from quantum mechanics: https://www.youtube.com/watch?v=2iuLwWDYC4U&t=1s

We’re incredibly grateful to Prof. David Kaiser, Prof. Steven Strogatz, Prof. Geraint F. Lewis, Elba Alonso-Monsalve, Prof. Christopher S. Baird, Prof. Anthony Bloch, and Prof. Stephen Bartlett for their invaluable contributions to this video.

A special thanks to Mahesh Shenoy from FloatHeadPhysics for his help with this video. Check out his excellent intuitive video on the UV Catastrophe here (Sep 2024): https://www.youtube.com/watch?v=ALEDjjAVZSY

Sign up to the Veritasium newsletter for weekly science updates - https://ve42.co/Newsletter

▀▀▀
0:00 What path does light travel?
2:40 Black Body Radiation
6:47 How did Planck solve the ultraviolet catastrophe?
9:42 The Quantum of Action
13:25 De Broglie’s Hypothesis
15:16 The Double Slit Experiment
20:00 How Feynman Did Quantum Mechanics
25:01 Proof That Light Takes Every Path
31:16 The Theory of Everything

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Sign up to our Patreon to watch the Q&A for free: https://www.patreon.com/c/veritasium

Try Snatoms! A molecular modelling kit I invented where the atoms snap together.
https://ve42.co/SnatomsV

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References:
Armin Hermann (Nov 1974). The Genesis of Quantum Theory (1899-1913). - https://ve42.co/genquanttheor
Richard P. Feynman (1985). QED The Strange Theory of Light and Matter. - https://ve42.co/qed
A fantastic book on the history of the Principle of Least Action: Rojo, A. and Bloch, A. The
Principle of Least Action: History and Physics. - https://ve42.co/Bloch2018
Coopersmith, J. (2017). The lazy universe: an introduction to the principle of least action. Oxford University Press. - https://ve42.co/LazyU
PBS Space Time. (Nov 2021) - https://www.youtube.com/watch?v=Q_CQDSlmboA
Sabine Hossenfelder. (May 2022) - https://www.youtube.com/watch?v=A0da8TEeaeE
Max Planck (1901). On the Law of Distribution of Energy in the Normal Spectrum. Annalen der Physik - https://ve42.co/lawdistenergy
Paul Ehrenfest (1911). Welche Züge der Lichtquantenhypothese spielen in der Theorie der Wärmestrahlung eine wesentliche Rolle?. Wiley Online Library - https://ve42.co/quantthermrad
Nils-Erik Bomark and Reidun Renstrøm (Aug 2023). The Ultraviolet myth. Proceedings of Science - https://ve42.co/uvmyth
Planck's law. In Wikipedia - https://ve42.co/planckslaw
PBS Space Time. (Jul 2017). - https://www.youtube.com/watch?v=vSFRN-ymfgE&t=10s
Einstein and The Photoelectric Effect. (Jan 2005) via APS News - https://ve42.co/einsteinphotoelec
Louis de Broglie (1924). On the Theory of Quanta. - https://ve42.co/theoryquanta
Larry Sorensen (2012). Path Integrals 1. University of Washington - https://ve42.co/pathintegrals
Feynman’s Method of “A Particle Exploring All Possible Paths”. (Mar 2018) via Pure Dhamma - https://ve42.co/allposspaths

Additional References - https://ve42.co/AdditionalReferences-PoLA2

Images & Video:
Nobistor Altona 1880 via NDR - https://ve42.co/streetlight
Edison incandescent lights by William J. Hammer via Wikimedia Commons - https://ve42.co/edinclights
The full expanded form of the Standard Model Lagrangian by Chen Ning Yang et al. via Wikipedia - https://ve42.co/stmodellang
Muon Ray. (2011). https://www.youtube.com/watch?v=-QUj2ZRUa7c
Muon Ray. (2011). https://www.youtube.com/watch?v=1C7abO7LtV0
Bohrs Atomic Model via EEEGUIDE.COM - https://ve42.co/bohrmodel

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Special thanks to our Patreon supporters:
Adam Foreman, Albert Wenger, Alex Porter, Alexander Tamas, Anton Ragin, Autodidactic Studios, Balkrishna Heroor, Bertrand Serlet, Blake Byers, Bruce, Dave Kircher, David Johnston, David Tseng, Evgeny Skvortsov, Garrett Mueller, Gnare, gpoly, Greg Scopel, Juan Benet, Keith England, KeyWestr, Kyi, Lee Redden, Marinus Kuivenhoven, Matthias Wrobel, Meekay, meg noah, Michael Krugman, Orlando Bassotto, Paul Peijzel, qiaohui wei, Richard Sundvall, Sam Lutfi, Tj Steyn, TTST, Ubiquity Ventures, wolfee

▀▀▀
Directed by Casper Mebius
Written by Casper Mebius and Derek Muller
Edited by Trenton Oliver and Peter Nelson
Animated by Fabio Albertelli, Mike Radjabov, Ivy Tello, Andrew Neet and Emma Wright
Illustrations by Jakub Misiek, Tommy A. Steven and Cainejan Esperanza
Filmed by Derek Muller and Casper Mebius
Produced by Casper Mebius, Derek Muller, Rob Beasley Spence, Gabe Strong, Geeta Thakur, Emilia Gyles, Zoe Heron, Emily Zhang and Tori Brittain

Thumbnail contributions by Ignat Berbeci, Ben Powell, Jakub Misiek, Ren Hurley, and Peter Sheppard

Additional video/photos supplied by Getty Images and Storyblocks
Music from Epidemic Sound

How the Black-Scholes/Merton equation made trillions of dollars. Go to https://www.eightsleep.com/veritasium and use the code Veritasium for $200 off your Pod Cover.

Special thanks to our Patreon supporters! Join this list to help us keep our videos free, forever:
https://ve42.co/PatreonDEB

If you’re looking for a molecular modeling kit, try Snatoms, a kit I invented where the atoms snap together magnetically - https://ve42.co/SnatomsV

▀▀▀

A huge thank you to Prof. Andrew Lo (MIT) for speaking with us and helping with the script.

We would also like to thank the following:
Prof. Amanda Turner (University of Leeds)
Owen Maher (Electrify Video Partners)

▀▀▀
References:

The Man Who Solved the Market: How Jim Simons launched the quant revolution, Gregory Zuckerman. Penguin Publishing Group. - https://ve42.co/GZuckerman

The Physics of Finance: Predicting the Unpredictable: Can Science Beat the Market? James Owen Weatherall. Short Books. - https://ve42.co/FinancePhysics

The Statistical Mechanics of Financial Markets, J.Voigt. Springer. - https://ve42.co/Springer

Black, F., & Scholes, M. (1973). The pricing of options and corporate liabilities. Journal of political economy, 81(3), 637-654. - https://ve42.co/BlackScholes

Cornell, B. (2020). Medallion fund: The ultimate counterexample?. The Journal of Portfolio Management, 46(4), 156-159. - https://ve42.co/Medallion

Images & Video:
Ed Thorp on The Tim Ferris Show - https://www.youtube.com/watch?v=CNvz91Jyzbg
Jim Simons on TED - https://www.youtube.com/watch?v=U5kIdtMJGc8
Jim Simons on Numberphile - https://www.youtube.com/watch?v=QNznD9hMEh0

▀▀▀
Special thanks to our Patreon supporters:
Adam Foreman, Anton Ragin, Balkrishna Heroor, Bill Linder, Blake Byers, Burt Humburg, Chris Harper, Dave Kircher, David Johnston, Diffbot, Evgeny Skvortsov, Garrett Mueller, Gnare, I.H., John H. Austin, Jr. ,john kiehl, Josh Hibschman, Juan Benet, KeyWestr, Lee Redden, Marinus Kuivenhoven, Max Paladino, Meekay, meg noah, Michael Krugman, Orlando Bassotto, Paul Peijzel, Richard Sundvall, Sam Lutfi, Stephen Wilcox, Tj Steyn, TTST, Ubiquity Ventures


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Directed by Will Wood and Derek Muller
Written by Will Wood, Emily Zhang, Petr Lebedev and Derek Muller
Camera operation by Raquel Nuno
Additional research by Gregor Čavlović
Edited by Jack Saxon and Trenton Oliver
Animated by Fabio Albertelli, Jakub Misiek, Ivy Tello, David Szakaly and Will Wood
Produced by Will Wood, Han Evans and Derek Muller

Thumbnail by Ren Hurley
Additional video/photos supplied by Getty Images and Pond5
Music from Epidemic Sound

Why we can't seem to agree on what's true when it's easier than ever to check.
Videos like this are usually on 2Veritasium: http://bit.ly/2Veritasium
Support Veritasium on Patreon: http://bit.ly/VePatreon

This video was filmed at a meetup in Stockholm, Sweden on Dec. 9, 2016. Huge thanks to everyone who attended - I had a great time. Sorry to those of you I missed, especially Lund and Gothenburg.

Thanks to Patreon supporters (but this is a non-paid post):
Meshal Alshammari, Nathan Hansen, Bryan Baker, Donal Botkin, Tony Fadell, Saeed Alghamdi, Ron Neal

A story is worth a thousand data points.
My second channel: http://bit.ly/2veritasium
More info on this topic: http://wke.lt/w/s/TzNC0

My hypothesis is that the algorithm, rather than viewer preference, drives views on the site. As the algorithm shifts, various YouTubers experience burnout (as what used to work no longer works) and right now click-through rate is the key metric. So clickable titles and thumbnails are the only way to get a lot of impressions and hence views - they are the only way to go viral. This leads me to wonder which audiences will become most prevalent on the site and if there will even be a place for educational content. In the long-term, hopefully YouTube is able to measure satisfaction through surveys and other metrics to ensure an optimal experience for everyone on the site.

Flipchart artwork by Maria Raykova
Filmed by Raquel Nuno
Thumbnail by Ignat Berbeci

Microwave grape plasma: http://www.youtube.com/watch?v=RwTjsRt0Fzo
Northern Lights: http://www.youtube.com/watch?v=knwiWm4DpvQ
Nanodiamonds in candle flames: http://www.youtube.com/watch?v=KzOkuGQC3Rw
Relight Candle Trick: http://www.youtube.com/watch?v=1tXPVTIisl0

Is a flame really a plasma? Well it depends on your definition of plasma, but there are certainly ions in a flame, formed as molecules collide with each other at high speed, sometimes knocking electrons off of their atoms.

Special thanks to the Palais de la Decouverte for helping me perform this experiment. Using tens of thousands of volts on two metal plates, we created a strong electric field around the plasma. This pulled positive ions in one direction and negative ions in the other direction elongating the flame horizontally and causing it to flicker like a "papillon" (butterfly). Then we showed that much longer sparks can be made through the flame than through air since the ions increase the conductivity.

A song about Gravity set to the tune of John Mayer's Gravity.

Gravity is working with me
And Gravity, keeps me on the ground

All mass attracts all other mass
a force proportional to mass one and two
and inversely to the distance between them squared

Oh, gravity is working with me
and gravity, makes apples fall to ground

Oh twice the mass has twice the pull
but the force on each is still equal
It keeps the moon and the satellites
going round

Oh twice the mass has twice the pull
but the force on each is still equal
It keeps the moon and the satellites
going round

Oh gravity, the force that makes weight on me
Woah, gravity, now general relativity (how can that be?)

The force between us all is
The force between us all is
The force between us all is
Gravity between us all is
Gravity between us all is
Gravity between gravity between us all is

What is the specious present? And how do our brains perceive time?
Get a 30-day free trial on Audible: http://bit.ly/AudibleVe
More info about this topic: http://wke.lt/w/s/z8TeR

Acrylic Ball: http://bit.ly/BBBacrylic
Ping-Pong Ball: http://bit.ly/BBBpingpong
Balanced: http://bit.ly/BBBbalanced

This problem has made the rounds on the internet but I felt it deserved a treatment like this.

Special thanks to Gary and the Department of Earth, Planetary and Space Sciences at UCLA, to the students for participating, to Ivy for helping me coordinate everything and to Raquel for filming.

Music by Kevin MacLeod, http://incompetech.com "Monkeys, Spinning Monkeys"

How Schlieren imaging works in color, black and white and slow-mo.
Get a free audiobook with a 30 day free trial at http://www.audible.com/veritasium

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

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

Filming by Raquel Nuno
Sound Effects by A Shell in the Pit

Many technologies have promised to revolutionize education, but so far none has. With that in mind, what could revolutionize education?
These ideas have been percolating since I wrote my PhD in physics education: https://ve42.co/phd
I have also discussed this topic with CGP Grey, whose view of the future of education differs significantly from mine: https://www.youtube.com/watch?v=7vsCAM17O-M

I think it is instructive that each new technology has appeared to be so transformative. You can imagine, for example, that motion pictures must have seemed like a revolutionary learning technology. After all they did revolutionize entertainment, yet failed to make significant inroads into the classroom. TV and video seem like a cheaper, scaled back film, but they too failed to live up to expectations. Now there is a glut of information and video on the internet so should we expect it to revolutionize education?

My view is that it won't, for two reasons: 1. Technology is not inherently superior, animations over static graphics, videoed presentations over live lectures etc. and 2. Learning is inherently a social activity, motivated and encouraged by interactions with others.

Filmed and edited by Pierce Cook

Supported by Screen Australia's Skip Ahead program.

Music By Kevin MacLeod, www.incompetech.com "The Builder" and by Amarante Music: http://www.amarantemusic.com

Spinning objects have strange instabilities known as The Dzhanibekov Effect or Tennis Racket Theorem - this video offers an intuitive explanation.
Part of this video was sponsored by LastPass, click here to find out more: https://ve42.co/LP

References:
Prof. Terry Tao's Math Overflow Explanation: https://ve42.co/Tao

The Twisting Tennis Racket
Ashbaugh, M.S., Chicone, C.C. & Cushman, R.H. J Dyn Diff Equat (1991) 3: 67. https://doi.org/10.1007/BF01049489

Janibekov’s effect and the laws of mechanics
Petrov, A.G. & Volodin, S.E. Dokl. Phys. (2013) 58: 349. https://doi.org/10.1134/S1028335813080041

Tumbling Asteroids
Prave et al. https://doi.org/10.1016/j.icarus.2004.07.021

The Exact Computation of the Free Rigid Body Motion and Its Use in Splitting Methods
SIAM J. Sci. Comput., 30(4), 2084–2112
E. Celledoni, F. Fassò, N. Säfström, and A. Zanna
https://doi.org/10.1137/070704393

Animations by Ivy Tello and Isaac Frame

Special thanks to people who discussed this video with me:
Astronaut Don Pettit
Henry Reich of MinutePhysics
Grant Sanderson of 3blue1brown
Vert Dider (Russian YouTube channel)

Below is a further discussion by Henry Reich that I think helps summarize why axes 1 and 3 are generally stable while axis 2 is not:

In general, you might imagine that because the object can rotate in a bunch of different directions, the components of energy and momentum could be free to change while keeping the total momentum constant.

However, in the case of axis 1, the kinetic energy is the highest possible for a given angular momentum, and in the case of axis 3, the kinetic energy is the lowest possible for a given angular momentum (which can be easily shown from conservation of energy and momentum equations, and is also fairly intuitive from the fact that kinetic energy is proportional to velocity squared, while momentum is proportional to velocity - so in the case of axis 1, the smaller masses will have to be spinning faster for a given momentum, and will thus have more energy, and vice versa for axis 3 where all the masses are spinning: the energy will be lowest). In fact, this is a strict inequality - if the energy is highest possible, there are no other possible combinations of momenta other than L2=L3=0, and vice versa for if the energy is the lowest possible.

Because of this, in the case of axis 1 the energy is so high that there simply aren't any other possible combinations of angular momentum components L1, L2 and L3 - the object would have to lose energy in order to spin differently. And in the case of axis 3, the energy is so low that there likewise is no way for the object to be rotating other than purely around axis 3 - it would have to gain energy. However, there's no such constraint for axis 2, since the energy is somewhere in between the min and max possible. This, together with the centrifugal effects, means that the components of momentum DO change.

Can we really touch things? Well if by touch we mean exchange a force-carrying particle with, then yes. The photon is the force-carrier of the electromagnetic interaction. But if the photon is also a particle of light then why aren't magnets glowing? Because the photons are virtual particles, which means they can't be directly detected (without changing the outcome we are trying to measure.
Supported by Audible: http://bit.ly/ZJ5Q6z
Who would win in a chin-up competition between me and MinutePhysics? What is going to be the most exciting area of scientific discovery in the next few decades? Where can you get a Veritasium t-shirt? http://dft.ba/-vetshirt
Huge thanks to Brady, CGP Grey, and Henry for their cameos.

Thank you to PhET for the Bohr model simulation: http://phet.colorado.edu/

Aerogel has extraordinary properties but it can be tough to work with. This video looks at modifying aerogels to take advantage of their unique characteristics.
Subscribe to Veritasium: https://ve42.co/sub

Huge thanks to Dr. Stephen Steiner and the crew at Aerogel Technologies. To find out more or buy your own aerogel sample, check out: http://www.aerogeltechnologies.com/

Thanks to Dr. Steven Jones and Dr. Mihail Petkov at NASA's Jet Propulsion Laboratory

And thanks to FLIR for loaning us the awesome high definition thermal camera. The footage is amazing! https://www.flir.com

Aerogel’s extraordinary properties are due in large part to its structure. Aerogel is a solid but on the nanoscale it has a mesh or sponge-like structure. The struts of this structure are nanoscale, as are the pores at around 20nm across. This makes silica aerogel incredibly light (it was once the lightest solid but has now been superseded by graphene aerogel), transparent and adsorbent.

An ice-cube sized piece of aerogel has an internal surface area roughly equal to half a football field. Aerogel is used in high end museum cases to regulate humidity. Plus it helps maintain the vacuum on the Mars Insight seismometers - it adsorbs moisture and other outgassed volatiles that come from the spacecraft itself. Proposed uses include as a physical insecticide by ‘drying out insects’ reducing the need for chemical and toxic pesticides.

Special thanks to all my Patreon supporters especially those who contributed feedback to an earlier draft of this video:
a human, Albert Jachowicz-Brzeziński, Alfred Wallace, Arjun Chakroborty, Brent Stewart, Chris Vargas, Chuck Lauer Vose, Clip Tree, Coale Shifflett, Colin Bellmore, DALE HORNE, Eric Velazquez, Fedor Indutny, Fran Rodriguez, James Wong, Jasper Xin, Joar Wandborg, Johnny, Jorge Angel Sandoval, June Kang, Kevin Beavers, Kishore Tipirneni, Levan Ferr, Listen Money Matters, Manuel Zürcher, Mark Bevilacqua, Mathias Göransson, Michael Bradley Wirz, Michael Krugman, Mohammed Al Sahaf, Nicholas Hastings, OddJosh, Patrick Čalija, Peter Tajti, Philipp Volgger, Roberto Rezende, Robin DeBank, Ron Neal, Stan Presolski, Swante Scholz, Tiago Bruno, Tige Thorman, Warrior8252

Filmed by Paul Gramaglia

Thumbnail by Ignat Berbeci

Animations by Catherine Chooljian

Music from https://epidemicsound.com “Tonic Zone” “Betelgeuse” “Insidious Mice” “Seaweed” “It’s not that serious” “Platin00m - Sum It”

This is an educational, scientific video.

How a single phone call from a student helped uncover a flaw that nearly toppled Citicorp. Get an exclusive 15% discount on Saily data plans! Use code veritasium at checkout. Download Saily app or go to https://saily.com/veritasium

If you’re looking for a molecular modeling kit, try Snatoms, a kit I invented where the atoms snap together magnetically - https://ve42.co/SnatomsV

Correction: From construction images of Citicorp, sharp-eyed viewers might see that the mid-V columns are still there. Those columns help prevent buckling of the diagonal and the weight of people on the floor above, but do not take the majority of the gravity load. So we left them out of our diagram to clearly explain the load paths. See page 70 of this source for more details - https://drive.google.com/file/....d/1ODFo66-_V7Y9vKANb

Sign up to the Veritasium newsletter for weekly science updates - https://ve42.co/Newsletter

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0:00 Why is the citicorp building on stilts?
4:44 How wind load works
7:49 Tuned Mass Dampers
11:17 The Anonymous Student
14:00 Quartering Winds
18:38 What were the odds of collapse?
20:31 How was the citicorp building fixed?
25:40 Hurricane Ella
27:00 TMDs Take Over The World
28:36 Conspiracies and Cover Ups

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A big thank you for the incredible people without whom we couldn't have done this! 🖤

To Michael Greenburg, author of The Great Miscalculation, for his insights that really brought the story and its context to life. He gave us a pre-copy of his upcoming book, and it is fantastic: https://ve42.co/Miscalc
To Eric Hines for all his help with the technical details, fact-checking, and making sure we got the engineering right.
To Michael J. Vardaro for helping us uncover the details of the story and the resources he provided.
To Brock Hedegaard for helping us dive deep into the Citicorp structural analysis. Learn the fundamentals of structural analysis on his brilliant channel, @StructuresProfH, and see here for his analysis of the citicorp center; https://www.youtube.com/watch?v=lE_DspFE2ZM
To Michele Barbato from UC Davis for his inputs on the load calculations.
https://faculty.engineering.ucdavis.edu/barbato/
Matt from @mvvvc for talking us through his wind load analysis.
To Prof. Chris Letchford who helped us understand the impact of wind on Citicorp's structure.
To DongHun Yeo from NIST for discussing his research about wind effects on buildings similar to citicorp: https://ve42.co/WindLoad
Finally, to Team Columbia —who built the epic TMD and ran wind tunnel experiments that made this story come alive.
This includes the folks at the Mechanical Engineering Teaching Laboratory
(Follow all the cool stuff they’re doing: @mechcu, @columbiaengineering or visit https://teachinglab.me/)
Amanda Lombardo, Manager of Instructional Laboratories
Daniela Durón García, Assistant Manager of Instructional Laboratories
Jorge Casas, Machinist
And the amazing seniors from the Columbia Space Initiative:
(Support their awesome work here: columbiaspace.org/support-us/, Follow them: @columbiaspaceinitiative)
Michael Sheehan
Claudio Solano
Jessica Bolar
Kathryn Lampo

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References:
Michael M. Greenburg. The Great Miscalculation via. nyupress.org - https://ve42.co/Miscalc
Joe Morgenstern. The Fifty-Nine-Story Crisis via. The New Yorker - https://ve42.co/59Crisis
National Academy of Engineering. William LeMessurier-The Fifty-Nine-Story Crisis: A Lesson in Professional Behavior - https://www.youtube.com/watch?v=um-7IlAdAtg
Diane Lee Hartley. Implications of a Major Urban Office Complex: The Scientific, Social and Symbolic Meanings of Citicorp Center via. princeton.edu - https://ve42.co/CitiSymbol
Addition References here: https://ve42.co/citiref

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Special thanks to our Patreon supporters:
Adam Foreman, Albert Wenger, Alex Porter, Alexander Tamas, Anton Ragin, Autodidactic Studios, Balkrishna Heroor, Bertrand Serlet, Blake Byers, Bruce, Dave Kircher, David Johnston, David Tseng, Evgeny Skvortsov, Garrett Mueller, Gnare, gpoly, Greg Scopel, HydrochloRick, Jon Jamison, Juan Benet, Keith England, KeyWestr, Kyi, Lee Redden, Marinus Kuivenhoven, Matthias Wrobel, Meekay, meg noah, Michael Krugman, Orlando Bassotto, Paul Peijzel, Richard Sundvall, Sam Lutfi, Tj Steyn, TTST, Ubiquity Ventures, wolfee

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Written and Directed by Sulli Yost
Edited by Trenton Oliver
Additional Editing by Axel Oliver, James Horsley and Peter Nelson
3D Modeling by Maydelis Anaya Romero
Animation by Mike Radjabov, Andrew Neet, Fabio Albertelli, Jakub Misiek, and Emma Wright
Illustration by Jakub Misiek, Maria Gusakovich and Cainejan Esperanza
Filmed by Sulli Yost, Henry van Dyck, Andrew Abballe, Derek Muller
Produced by Sulli Yost, Derek Muller, Casper Mebius, Zoe Heron, Rob Beasley Spence and Tori Brittain
Additional research by Geeta Thakur
Thumbnail contributions by Ren Hurley and Ben Powell
Additional video/photos supplied by Getty Images, Pond5, Axiom Images and Storyblocks
Music from Epidemic Sound

An engineer came up with a plan to drop tungsten telephone poles from space - the idea has been seriously considered on multiple occasions, so we tested it. Head to https://brilliant.org/Veritasium to start your free trial. The first 200 will get 20% off Brilliant's annual premium subscription.

Special thanks to our Patreon supporters! Join the community to help us keep our videos free, forever:
https://ve42.co/PatreonDEB

Massive thanks to Archisand for building such a beautiful sandcastle. https://www.youtube.com/@GregLeBon

Huge thanks to John and Angie Miller for helping us with securing the shooting location and going above and beyond to make this shoot happen – http://highdesertlocations.com/

Thanks to Inland Empire Film Services and the San Bernardino County Film Office for portions of the video shot in the County of San Bernardino.

Massive thanks to Dr David Wright for the interview and providing invaluable guidance during the research for this video.

Here’s a great video about space-based missile defense – https://www.ucsusa.org/resourc....es/space-based-missi

Massive thanks to Adam Savage for being part of this video.

Additional photos from NASA and ESA.

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References:
USAF. (2003). The US Air Force transformation flight plan.

Preston, R., Johnson, D. J., Edwards, S. J., Miller, M. D., & Shipbaugh, C. (2002). Space weapons earth wars. Rand Corporation.

Wright, D., Grego, L., & Gronlund, L. (2005). The physics of space security. A Reference Manual, Cambridge.

DeBlois, B. M., Garwin, R. L., Kemp, R. S., & Marwell, J. C. (2004). Space weapons: crossing the US Rubicon. International Security, 50-84.

Baucom, D. R. (2017). The Rise and Fall of Brilliant Pebbles 1. In United States Military History 1865 to the Present Day (pp. 329-376). Routledge.

Hitchens, T., & Samson, V. (2004). Space-based interceptors: still not a good idea. Georgetown journal of international affairs, 21-29.

National Research Council. (2012). Making sense of ballistic missile defense: An assessment of concepts and systems for US boost-phase missile defense in comparison to other alternatives. National Academies Press.

Borger, J. (2005). Bush likely to back weapons in space. The Guardian, 19.

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Special thanks to: Bernard McGee, James Sanger, Elliot Miller, Brian Busbee, Jerome Barakos M.D., Amadeo Bee, TTST, Balkrishna Heroor, Chris LaClair, John H. Austin Jr., OnlineBookClub.org, Eric Sexton, John Kiehl, Diffbot, Gnare, Dave Kircher, Burt Humburg, Blake Byers, Evgeny Skvortsov, Meekay, Bill Linder, Paul Peijzel, Josh Hibschman, Mac Malkawi, Mike Schneider, John Bauer, Jim Buckmaster, Juan Benet, Sunil Nagaraj, Richard Sundvall, Lee Redden, Stephen Wilcox, Marinus Kuivenhoven, Michael Krugman, Cy 'kkm' K'Nelson, Sam Lutfi

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Written by Petr Lebedev, Derek Muller, and Emily Zhang
Filmed by Trenton Oliver, Derek Muller, Petr Lebedev, Emily Zhang, Raquel Nuno, and Eddie Lopez
Animation by Mike Radjabov, Fabio Albertelli, and Jonny Hyman
Edited by Trenton Oliver
Slow Motion Camera: Shawn Sanders and Anthony Corrales
Sandcastle Timelapse by Greg LeBon and Archisand
Phantom rental from Panny Hire LA
Helicopter Pilots: Rick Shuster and Cliff Fleming
Helicopter Safety Officer: Ryan Hosking
FPV Drone Pilots: Sammie Saing and Josh Ewalt
Production Assistants: Roman Bacvic and Eddie Lopez
Intern: Katie Barnshaw
Additional video/photos supplied by Pond5 and Getty Images
Music from Epidemic Sound
Thumbnail by Ignat Berbeci
Produced by Derek Muller, Petr Lebedev, and Emily Zhang