Dr Ken Libbrecht is the world expert on snowflakes, designer of custom snowflakes, snowflake consultant for the movie Frozen - his photos appear on postage stamps all over the world. This video is sponsored by Brilliant. The first 200 people to sign up via https://brilliant.org/veritasium get 20% off a yearly subscription.

Thanks to Dr Ken Libbrecht for showing us how to grow designer snowflakes. Obviously, this video would not have been possible without his help and his expertise. His website is full of information about snowflakes http://snowcrystals.com. His new book is also available to purchase from here -- https://ve42.co/SnowCrystalsBook

▀▀▀
References:
Libbrecht, K. G. (2019). A Quantitative Physical Model of the Snow Crystal Morphology Diagram. arXiv preprint arXiv:1910.09067. -- https://ve42.co/Libbrecht2019

▀▀▀
Special thanks to Patreon supporters: Luis Felipe, Anton Ragin, Paul Peijzel, S S, Benedikt Heinen, Diffbot, Micah Mangione, Juan Benet, Ruslan Khroma, Richard Sundvall, Lee Redden, Sam Lutfi, MJP, Gnare, Nick DiCandilo, Dave Kircher, Edward Larsen, Burt Humburg, Blake Byers, Dumky, Mike Tung, Evgeny Skvortsov, Meekay, Ismail Öncü Usta, Crated Comments, Anna, Mac Malkawi, Michael Schneider, Oleksii Leonov, Jim Osmun, Tyson McDowell, Ludovic Robillard, Jim buckmaster, fanime96, Ruslan Khroma, Robert Blum, Vincent, Marinus Kuivenhoven, Alfred Wallace, Arjun Chakroborty, Joar Wandborg, Clayton Greenwell, Michael Krugman, Cy 'kkm' K'Nelson, Ron Neal

Written by Derek Muller
Filmed by Derek Muller, Raquel Nuno, Trenton Oliver and Emily Zhang
Edited by Trenton Oliver
Animations by Ivy Tello and Trenton Oliver
Additional video supplied by Getty Images
Music from Epidemic Sound
Produced by Derek Muller, Petr Lebedev and Emily Zhang

The number 37 is on your mind more than you think. Head to https://brilliant.org/veritasium to start your free 30-day trial and get 20% off an annual premium subscription.

Huge thanks to Tom Magliery for sharing his 37 collection with us. Support http://thirty-seven.org by sharing your own 37 sightings to tom@thirty-seven.org!
Thanks to Dr. Todd Landman, the Academic Magician, for sharing his footage of the 37 Force. - https://www.todd-landman.com/

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

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

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

▀▀▀
References:
Simon, W. E. (1972). “Blue Seven Phenomenon” in Elementary and Jr. High Children. Psychological Reports - https://ve42.co/Simon1972
Trueman, J. (1979). Existence & Robustness of Blue Seven Phenomena. The Journal of General Psychology - https://ve42.co/Trueman1979
Saito, M. (1999). “Blue and Seven Phenomena” in Japanese Students. Perceptual & Motor Skills - https://ve42.co/Saito1999
Philbrick, J. L. (1976). Blue seven in East Africa: Preliminary report. Perceptual & Motor Skills - https://ve42.co/Philbrick1976
Hargreaves, S. (2009). The psychology of randomness. - https://ve42.co/Hargreaves2009
The 37 Force via The Magician’s Forum - https://ve42.co/37Force1
Fulves, K. (1979) Self-Working Mental Magic. Dover Publications, Inc. - https://ve42.co/Fulves1979
Random numbers via The Jargon File at catb.org - https://ve42.co/Jargon
Random Number Survey by MahoganyForest via Reddit - https://ve42.co/RedditRndm
Prime number theorem via Wikipedia - https://ve42.co/WikiPNT
Grossack, C. (2023). A truly incredible fact about the number 37. Grossack.site - https://ve42.co/Grossack2023
Least prime factor of n via oeis.org - https://ve42.co/LeastPrime
Fry, H. (2017). When should you settle down? ideas.ted.com - https://ve42.co/Fry2017
Choosing Toilets by Numberphile - https://www.youtube.com/watch?v=XIOoCKO-ybQ
Seaton, R. (2014). The Secretary Problem Explained: Dating Mathematically. rs.io - https://ve42.co/Seaton2014

Images & Video:
Just 37 by Tom Magliery - https://ve42.co/Just37
R4000 Processor via Molecular Expressions - https://ve42.co/micro37
The “37” Cluster by Noel Carboni - https://ve42.co/NGC2169
Charles Fleischer via Wikimedia - https://ve42.co/Fleischer

▀▀▀
Directed by Emily Zhang
Written by Emily Zhang and Derek Muller
Edited by Peter Nelson
Asst edited by Luke Molloy
Animated by Fabio Albertelli, Ivy Tello, and Leigh Williamson
Illustrated by Jakub Misiek
Filmed by Emily Zhang, Casper Mebius, Derek Muller, Michael Cimpher, and David Szasz
Additional research by Gregor Čavlović
Produced by Emily Zhang, Giovanna Utichi, Han Evans, and Emily Taylor

Thumbnail contributions by Ignat Berbeci, Ren Hurley, and Peter Sheppard
Additional video/photos supplied by Getty Images and Storyblocks
Music from Epidemic Sound

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:
https://ve42.co/PatreonDEB

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

▀▀▀
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

▀▀▀
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

▀▀▀
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

▀▀▀
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

▀▀▀
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

▀▀▀
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 do you make infinite choices? 👉 To try everything Brilliant has to offer for free for a full 30 days, visit http://brilliant.org/veritasium. You’ll also get 20% off an annual premium subscription.

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

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

▀▀▀
A huge thank you to Dr Asaf Karagila, Prof. Alex Kontorovich, Prof. Joel David Hamkins, Prof. Andrew Marks, Prof. Gabriel Goldberg and Prof. Elliot Glazer for their invaluable expertise and contributions to this video.

Head over and sign up to our Patreon for some exclusive behind the scenes footage, showing how the animations and illustrations for this video were made - https://www.patreon.com/posts/patreon-behind-126443880?utm_medium=clipboard_copy&utm_source=copyLink&utm_campaign=postshare_creator&utm_content=join_link

▀▀▀
0:00 What comes after one?
2:42 Some infinities are bigger than others
6:17 The Well Ordering Principle
10:32 Zermelo And The Axiom Of Choice
17:22 Why is the axiom of choice controversial?
23:16 The Banach–Tarski Paradox
27:53 Obviously True, Obviously False
29:58 Your Proof Your Choice

▀▀▀
References:

Up and Atom - https://www.youtube.com/watch?v=X56zst79Xjg
Minutephysics - https://www.youtube.com/watch?v=A-QoutHCu4o
PBS Infinite Series - https://www.youtube.com/watch?v=hcRZadc5KpI&t=125s
Vsauce - https://www.youtube.com/watch?v=s86-Z-CbaHA&t=474s
Ernst Zermelo via Wikipedia - https://ve42.co/zermeloBio
Axiom of choice via Wikipedia - https://ve42.co/choiceAxiom
Georg Cantor via Wikipedia - https://ve42.co/cantorMath
Gregory H. Moore (2013). Consequences of the Axiom of Choice. Dover Publications - https://ve42.co/choiceBook
Georg Cantor (1874). On a property of the class of all real algebraic numbers. Journal für die Reine und Angewandte Mathematik - https://ve42.co/MeyerCantor1874
Heinz-Dieter Ebbinghaus (Dec 2012). Zermelo and the Heidelberg Congress 1904. Historia Mathematica - https://ve42.co/SciDirect1904
Herbert B. Enderton (1977). Elements of Set Theory. - https://ve42.co/SciDirectGCH

Additional References - https://ve42.co/AoCAdRefs

Images & Video:

Foundations of a general theory of sets by Georg Cantor via ViaLibri - https://ve42.co/grundlagen
Alfred Tarski by George Bergman via Wikimedia Commons - https://ve42.co/tarski
Alfred Tarski Offprint Group by Alfred Tarski via Bonhams - https://ve42.co/tarskipaper
La mission strasbourgeoise de Maurice Fréchet by Laurent Mazliak via Images des mathematiques - https://ve42.co/frechet
Kurt Gödel by Alfred Eisenstaedt via New Yorker - https://ve42.co/godel
Leopold Kronecker by Granger via Fine Art America - https://ve42.co/kronecker
Lashi Bandara (2006). Zermelo-Frankel Set Theory and Well Orderings. ResearchGate - https://ve42.co/zermelofrankel
Heidelberg, Germany 1936 by Wagner & Debes via Ward Maps - https://ve42.co/heidelberg
Pythagoras by J. Augustus Knapp via the marginalian - https://ve42.co/pythag
Paul Cohen by C. J. Mozzochi via C. J. Mozzochi - https://ve42.co/paulcohen
Instituto de Matemática Pura e Aplicada. Lecture 01: Introduction: a non-measurable set via Youtube - https://www.youtube.com/watch?v=llnNaRzuvd4&t=834s
Simons Foundation. Fields Medal: James Maynard. Youtube https://www.youtube.com/watch?v=un-z8kgOrV0&t=8s

▀▀▀
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


▀▀▀
Directed by Kaela Albert
Written by Kaela Albert and Emily Zhang
Edited by Jack Saxon and Luke Molloy
Assistant Edited by James Stuart
Animated by Fabio Albertelli, Andrew Neet, Alex Zepharin, Mike Radjabov, Emma Wright and Ivy Tello
Illustrations by Jakub Misiek, Maria Gusakovich, Cainejan Esperanza, Tommy A. Steven and Emma Wright
Additional research by Emilia Gyles, Gabe Bean, Geeta Thakur and Vincent Cheng
Produced by Kaela Albert, Casper Mebius, Derek Muller, Emily Zhang, Zoe Heron, Rob Beasley Spence, and Tori Brittain
Additional Editing by Luke Molloy and James Stuart

Thumbnail contributions by Ben Powell, Peter Sheppard and Ren Hurley

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

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/

The title and thumbnail play a huge role in a video's success or failure.
Check out http://kiwico.com/Veritasium50 for 50% off your first month of any subscription!

▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀
Special thanks to Patreon supporters: Alvaro Naranjo, Burt Humburg, Blake Byers, Dumky, Mike Tung, Evgeny Skvortsov, Meekay, Ismail Öncü Usta, Paul Peijzel, Crated Comments, Anna, Mac Malkawi, Michael Schneider, Oleksii Leonov, Jim Osmun, Tyson McDowell, Ludovic Robillard, Jim buckmaster, fanime96, Juan Benet, Ruslan Khroma, Robert Blum, Richard Sundvall, Lee Redden, Vincent, Marinus Kuivenhoven, Alfred Wallace, Arjun Chakroborty, Joar Wandborg, Clayton Greenwell, Pindex, Michael Krugman, Cy 'kkm' K'Nelson, Sam Lutfi, Ron Neal

▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀
Written by Derek Muller
Animation by Ivy Tello
Filmed by Derek Muller and Emily Zhang
Additional video supplied by Getty Images
Produced by Derek Muller, Emily Zhang and Petr Lebedev

How Thermite turned the clickety-clack of railroads into seamless, silent tracks. Get an exclusive 15% discount on Saily data plans! Use code veritasium at checkout. Download Saily app or go to https://saily.com/veritasium
A massive thank you to everyone at Goldschmidt for making this possible. With special thanks to Dr. Axel Hoeschen, Christof Gassmann and Claudia Koch.

If you want to learn all the details about why we don’t need expansion joints anymore, check out Grady’s excellent video here: youtu.be/zqmOSMAtadc

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

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

▀▀▀
00:00 The problem with continuous welded rail
03:33 How to weld two rails together
10:16 Why is rapidly cooled steel brittle?
11:40 Thermite reaction and a see-through mould
16:30 Clean up
19:11 Metallurgy
22:15 How strong is the weld?
24:26 Why don’t the rails buckle?

▀▀▀
References:
Practical Engineering. Why Railroads Don't Need Expansion Joints youtu.be/zqmOSMAtadc
Stress–strain curve In Wikipedia - https://ve42.co/stressstrain
The Efficient Engineer. Understanding Metals via Youtube https://youtu.be/PaGJwOPg2kU
moodlemech. Properties and Grain Structure via Youtube - youtu.be/uG35D_euM-0

Images & Video:
bhadeshi123. Martensitic transformation via Youtube youtu.be/OQ5lVjYssko
Stratford Works In Wikipedia - https://ve42.co/stratford
Electric Tram 1881 In Wikipedia - https://ve42.co/tram
Water Quenched Steel In Wikipedia - https://ve42.co/quench
Synagoge 1922 In Wikipedia - https://ve42.co/synagoge

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

Alexander Tamas, Autodidactic Studios, Farbod Mansorian, Gnare, Juan Benet, Lee Redden, Meekay, Orlando Bassotto, Paul Peijzel, Richard Sundvall, Sam Lutfi, Ubiquity Ventures, Adam Foreman, Albert Wenger, Anton Ragin, Bertrand Serlet, Blake Byers, Bruce, Dave Kircher, David Johnston, Evgeny Skvortsov, Garrett Mueller, gpoly, Greg Scopel, I. H., KeyWestr, Kyi, Marinus Kuivenhoven, Matthias Wrobel, meg noah, Michael Krugman, Spilmann Reed, Tj Steyn, TTST, wolfee.

▀▀▀
Directed by Derek Muller and Casper Mebius
Written by Derek Muller and Casper Mebius
Edited by Trenton Oliver
Animated by Mike Radjabov, Rokas Vikšraitis and Fabio Albertelli
Filmed by Derek Muller, David Bochmann, Casper Mebius, Luise Dietert, Henning Fischer and Harald Schweiger
Additional research by Geeta Thakur
Produced by Derek Muller, Casper Mebius, Gregor Čavlović, Geeta Thakur, Rob Beasley Spence, Emily Lazard and Tori Brittain
Thumbnail contributions by Peter Sheppard and Ren Hurley
Additional video/photos supplied by Getty Images and Story Blocks
Music from Epidemic Sound

Negative Pressure Exists! http://bit.ly/TFilQ8
Vsauce's Space Straw: http://bit.ly/XubIm3
Smarter Every Day's Prince Rupert's Drop: http://bit.ly/10VQBGW
ViHart's Optimal Potatoes: http://bit.ly/14egJoe

Thanks to Questacon for filming! Check out their slow-mo playlist: http://bit.ly/ZoWFGR
Science Alert brings science to your news feed: http://on.fb.me/14ehuxA

Music by Kevin Mcleod (http://incompetech.com): Pale Rider & The Cannery

*Watch with headphones on!
Is 45 minutes really the longest anyone can stay in a perfectly silent, pitch-black room?
Support Veritasium on Patreon http://bit.ly/VePatreon
Check out Audible: http://bit.ly/AudibleVe
Want to watch the whole hour of silence? http://youtu.be/jr1UMFC9DV0

Many stories have circulated claiming the longest anyone has stayed in an ultra-quiet anechoic chamber is 45 minutes, the reason being any longer would drive you insane. To me this sounded like unsubstantiated rubbish, like the claim the Great Wall is the only manmade structure visible from space. So I put my own psyche on the line, subjecting myself to over an hour of the most intense quiet on Earth. No, this was not THE quietest room on Earth (-9dB) but it is one of the quietest, and the truth is once you put a person inside, they are by far the loudest thing in there so the sound rating of the room is irrelevant.

I was not surprised to find that I could stay in there for as long as I liked and feel perfectly fine. What was surprising is that my heartbeat was audible. You can hear it on the sound recording. Now I wasn't consciously aware of the sound of my heart while in the room, but I was more aware of the feeling of it beating.

Huge thank you to everyone at BYU: Duane Merrell, Spencer Perry, Cameron Vongsawad, Jazz Myers, Ann Clawson, and Robert Willes.

Audio illusions show us that hearing is about more than just sensing frequency. Which ones trick you every time? Head to https://brilliant.org/veritasium to start your free 30-day trial and get 20% off an annual premium subscription.

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

▀▀▀

A big thank you to Titus Grenyer over at Pep Organ for showing us around the Sydney Town Hall Organ, to Dr. Diana Deutsch for providing her illusions and insight into the field, to Casey Connor for advice on building sound illusions, and to Dr. Michael Bach for providing the motion-bounce illusion.

Pep organ: https://ve42.co/peporgan
Casey Connor’s Psychoacoustics: https://ve42.co/CaseyConnor

▀▀▀

References: https://ve42.co/AudioIllusionsRefs

Images & Video:

Aircraft Detection before radar, 1917-1940 - https://ve42.co/DetectionBeforeRadar
Women’s Auxiliary Air Force operator Denise Miley - https://ve42.co/ChainHomeRadar
Daventry Experiment Van, operated by “Jock” Herd - https://ve42.co/ChainHome
Perfect fifth - https://ve42.co/PerfectFifth
Denge acoustic mirrors - The original uploader was Jksolomon at English Wikipedia. - https://ve42.co/DengeSoundMirror
Denge sound mirrors | Sound Mirrors https://ve42.co/SoundMirrorsDenge
Mayer telescope in 1880, US patent number 224199. NAE Website - Acoustic Source Localization Techniques and Their Applications https://ve42.co/AcousticSoundL....ocalizationTechnique
Professor Mayer’s Topophone - https://ve42.co/Topophone
AR_Speaker_v12 - Download Free 3D model by steveMarketscale [6ca6a0a] - Sketchfab https://ve42.co/ARSpeaker
Ear Phenotypes https://ve42.co/Earhenotypes

▀▀▀
Special thanks to our Patreon supporters:

Adam Foreman, Anton Ragin, Balkrishna Heroor, Bertrand Serlet, Bill Linder, Blake Byers, Bruce, Burt Humburg, 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, Matthias Wrobel, Meekay, meg noah, Michael Krugman, Orlando Bassotto, Paul Peijzel, Richard Sundvall, TTST, Tj Steyn, Ubiquity Ventures, wolfee

▀▀▀
Directed by Sulli Yost and Derek Muller
Hosted by Derek Muller
Written by Sulli Yost and Derek Muller
Edited by Jack Saxon and Peter Nelson
Animated by Fabio Albertelli, David Szakaly, and Ivy Tello
Illustrations by Jakub Misiek
Filmed by Derek Muller
Produced by Sulli Yost, Derek Muller, Rob Beasley Spence, Emily Lazard, Tori Brittain, Emily Zhang, Petr Lebedev, Gregor Čavlović, and Gabe Strong

Thumbnail contributions by Peter Sheppard and Ren Hurley

Additional video/photos supplied by Getty Images, Storyblocks, and Envato

Music from GarageBand, Virtual Piano, and Epidemic Sound

Space junk is a real problem. NASA now tracks around 20,000 pieces of debris orbiting Earth, most of them larger than 10cm across. Since the average speed of a collision between orbiting objects is 10 km/s these pieces of trash can cause a lot of damage despite their small size.

Scientists in Switzerland have a plan to clean up space junk - it involves creating a 'Janitor Satellite' that will seek out pieces of space junk to drag back into the atmosphere causing them to burn up.

This video was created for the Aussie science show Catalyst on the ABC: http://www.abc.net.au/catalyst

Vitamins are 13 molecules essential for life that our bodies can't make themselves.
Watch Vitamania here: https://ve42.co/vita

Now available worldwide, except France and Germany where it will be broadcast on ARTE soon. Subscribe on the Vitamania website for updates.

Use #vitamania to join the conversation on Twitter and Facebook.

Vitamania is a Genepool Productions feature documentary for SBS Australia, CuriosityStream, and ARTE France. Principal production investment from Screen Australia, in association with Film Victoria.

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

Grant Thompson - the King of Random - teaches me how to start a fire with a Sandwich bag. And we tried to melt glass in my backyard: https://goo.gl/zb0uE0
Check out his channel: http://ve42.co/KoR

The intensity of sunlight on Earth is about 1300 Watts per square meter. When you focus the sun's rays using a magnifying glass (or in this case sphere of water) you can increase the intensity roughly ten thousand fold. This increases the temperature of wood to its autoignition point starting the reaction with oxygen in the atmosphere. By protecting the hot embers and adding more energy and fuel, you can get these hot coals to start a roaring fire.

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

Right: https://www.youtube.com/watch?v=AS9OXzSRBMQ
Left: http://www.youtube.com/watch?v=FWQ-HJ4oGKQ
It Depends: https://www.youtube.com/watch?v=R3GHiMOHEy8
What happens when nylon rope is wound around a spool and pulled horizontally to the right? Will the spool go to the right, to the left, or does it depend on how the rope is pulled?

This was a pretty extraordinary experience - thanks to NASA for inviting me! The Atlas V 541 rocket took off carrying the Perseverance rover and Ingenuity the Mars helicopter at 7:50 am July 30, 2020. They should arrive in about seven months on February 18, 2021

Thumbnail by Fictionalhead https://www.youtube.com/fictionalhead

Or almost any garage - it's particularly good with fixed code gates and garages. Samy proposes other weaknesses with rolling codes.
This video was sponsored by LastPass: http://bit.ly/2oscAe9

I don't condone malicious hacking of gates, garages or other property. The point of this video was to discuss how it could be done using fairly basic technology like this toy that was originally intended as an instant messaging device. I learned a lot in making this video about how codes are sent and received, how they are encrypted or not encrypted. I found out how hard it is to execute in practice something which in principle doesn't seem that difficult.

Special thanks to Samy! His original videos on using the IM ME to open radio frequency garages and gates can be found here: https://www.youtube.com/user/s4myk
He's got a really cool channel so be sure to subscribe if you're interested in this stuff.

Music from http://epidemicsound.com "Critical thinking 2" "I think I was there" "Magnified X 3"

And music by Kevin MacLeod http://incompetech.com "Marty Gots a Plan"

Innovative research conducted in Lausanne, Switzerland has shown that a combination of neurotransmitters and electrical stimulation can restore movement to the lower limbs of previously paralysed rats. But in order for this motion to be made voluntarily the rats must be motivated to walk. This motivation comes in the form of cheering, visual cues, and of course, chocolate.

Why Trees Are Amazing: http://bit.ly/TFilQ8
Space Junk: http://bit.ly/XlLdjG
Why Astronauts Are Weightless: http://bit.ly/SuF2p1
Higgs Boson Update: http://bit.ly/Vw1Sgu

A nuclear war doesn’t take weeks or days, it unfolds in minutes. In this scenario, 86 missiles are on the way and only you, the president, can authorize a counterattack. What would you do?

#kurzgesagt
#inanutshell #kurzgesagt_inanutshell #learnwithshorts #science #nuclearwar #nuclearthreat

Sources & further reading:
https://sites.google.com/view/kgs-tiktok-sources

Follow us for more sciencey content! 🦆

OUR CHANNELS
▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀
German: https://kgs.link/youtubeDE
Spanish: https://kgs.link/youtubeES
French: https://kgs.link/youtubeFR
Portuguese: https://kgs.link/youtubePT
Arabic: https://kgs.link/youtubeAR
Hindi: https://kgs.link/youtubeHI
Japanese: https://kgs.link/youtubeJA
Korean: https://kgs.link/youtubeKO


HOW CAN YOU SUPPORT US?
▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀
This is how we make our living and it would be a pleasure if you support us!

Get Products designed with ❤ https://shop.kgs.link/shorts
Become a Part of kurzgesagt by joining the Patreon Bird Army 🐧 https://kgs.link/patreon


DISCUSSIONS & SOCIAL MEDIA
▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀
Instagram: https://kgs.link/instagram
TikTok: https://kgs.link/tiktok
Reddit: https://kgs.link/reddit
Discord: https://kgs.link/discord
Twitter: https://kgs.link/twitter
Bluesky: https://kgs.link/bluesky
Facebook: https://kgs.link/facebook
Newsletter: https://kgs.link/newsletter


OUR VOICE
▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀
The Kurzgesagt voice is from
Steve Taylor: https://kgs.link/youtube-voice


OUR MUSIC ♬♪
▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀
700+ minutes of Kurzgesagt Soundtracks by Epic Mountain:

Spotify: https://kgs.link/music-spotify
Soundcloud: https://kgs.link/music-soundcloud
Bandcamp: https://kgs.link/music-bandcamp
Youtube: https://kgs.link/music-youtube
Facebook: https://kgs.link/music-facebook