Who on Earth is exposed to the most ionizing radiation?
Check out Audible: http://bit.ly/AudibleVe
I'm filming a documentary for TV about how Uranium and radioactivity have shaped the modern world. It will be broadcast in mid-2015, details to come. The filming took me to the most radioactive places on Earth (and some places, which surprisingly aren't as radioactive as you'd think). Chernobyl and Fukushima were incredible to see as they present post-apocalyptic landscapes. I also visited nuclear power plants, research reactors, Marie Curie's institute, Einstein's apartment, nuclear medicine areas of hospitals, uranium mines, nuclear bomb sites, and interviewed numerous experts.

Notes about measuring radiation:
Sieverts are a measure of 'effective dose' - that means they measure the biological impact of the energy transferred to tissues from radiation.

Obviously I owe a debt to the fantastic chart made by xkcd, which inspired my visual approach to this video.
https://xkcd.com/radiation/

DOSES MAY VARY
The level of radiation varies widely around the world depending mainly on altitude and geology (excluding nuclear accidents).

Estimates of particular doses also vary. All numbers reported in this video should be taken as order of magnitude only.

The most contentious claim may be that smokers receive the highest dose of ionizing radiation. This is not a whole body dose, but a dose to the lungs as specified in the video. References are here:
http://en.wikipedia.org/wiki/H....ealth_effects_of_tob
http://www.rmeswi.com/36.html

Special thanks to:
Physics Girl: https://www.youtube.com/physicswoman
MinutePhysics: https://www.youtube.com/minutephysics
Natalie Tran: https://www.youtube.com/communitychannel
Bionerd23: https://www.youtube.com/bionerd23
Nigel and Helen for feedback on earlier drafts of this video.

Music is "Stale Mate"

One of the most common physics misconceptions is that an unbalanced force causes constant motion. In truth, an unbalanced force leads to changes in motion - accelerations.

In a competitive world, tiny advantages can make all the difference. Get 10% off Snatoms with code 'giveluck' in the US: https://ve42.co/USA or International: https://snatoms.com
If you would like to receive Snatoms, submit the form here: https://ve42.co/getluck

Snatoms are also available on Amazon Prime in the US but with no discount code: https://ve42.co/Asnatoms

Huge thanks to Gene and Sam from Potato Jet for filming with me: https://ve42.co/potatojet

This video was inspired by and draws examples from the book "Success and Luck: Good Fortune and the Myth of Meritocracy" by Robert H. Frank

Special thanks to Patreon supporters (and to everyone who commented on an earlier version of this video):
Marc Forand, Robert Dickerson, Christian Stauffer, LoadTooSlow, Vincent, Lyvann Ferrusca, DALE HORNE, Alfred Wallace, Kevin Beavers, Arjun Chakroborty, Joar Wandborg, Clayton Greenwell, Michael Krugman, Ron Neal, Donal Botkin

Animations by Ivy Tello

This is a video about how Japanese samurai swords, aka katanas, are made – from the gathering of the iron sand, to the smelting of the steel, to the forging of the blade. Head over to https://hensonshaving.com/veritasium and enter code 'Veritasium' for 100 free blades with the purchase of a razor. Make sure to add both the razor and the blades to your cart for the code to take effect.

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

CORRECTION: There's a typo at 18:20. The combination of Ferrite and Cementite is Pearlite, not Perlite. Thanks, @neophoys for pointing it out.

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A massive thank you to John McBride for making this entire project happen. This would not have been possible without John. Please check out his japan walking tours https://walkjapan.com/
Massive thanks to Craig Mod, Inoue-san, everyone in the Tanabe family, and Takanashi-san. Also a massive thank you to Kevin Cashen – https://cashenblades.com/

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References:
Tanii, H., Inazumi, T., & Terashima, K. (2014). Mineralogical study of iron sand with different metallurgical characteristic to smelting with use of Japanese classic iron-making furnace “Tatara”. ISIJ international, 54(5), 1044-1050.

Tate, M. (2005). History of Iron and Steel Making Technology in Japan Mainly on the smelting of iron sand by Tatara. Tetsu-to-Hagane, 91(1), 2-10.

Krauss, G. (1999). Martensite in steel: strength and structure. Materials science and engineering: A, 273, 40-57.

Krauss, G., & Marder, A. R. (1971). The morphology of martensite in iron alloys. Metallurgical Transactions, 2, 2343-2357.

Yalçın, Ü. (1999). Early iron metallurgy in Anatolia. Anatolian Studies, 49, 177-187.

Kapp, L., Kapp, H., & Yoshihara, Y. (1987). The craft of the Japanese sword. Kodansha International.

Matsumoto, C., Das, A. K., Ohba, T., Morito, S., Hayashi, T., & Takami, G. (2013). Characteristics of Japanese sword produced from tatara steel. Journal of Alloys and Compounds, 577, S673-S677.

Inoue, T. (2010). Tatara and the Japanese sword: the science and technology. Acta Mechanica, 214(1), 17-30.


Images & Video:

Great video from NHK – https://ve42.co/NHK



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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 Petr Lebedev
Written by Petr Lebedev and Derek Muller
Edited by Trenton Oliver and Jack Saxon
Animated by Fabio Albertelli, Jakub Misiek, David Szakaly
Filmed by Petr Lebedev and Lui Kimishima
Produced by Petr Lebedev, Derek Muller, Han Evans, Giovanna Utichi, Emily Taylor
Additional research by Gregor Čavlović
Thumbnail by Peter Sheppard


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

This fungus lives on your scalp and may affect the genes you express.
Check out Head & Shoulders research on getting rid of dandruff: https://ve42.co/HS

Animation by Pindex: https://ve42.co/pindex

When I started this project, I wasn't sure what caused dandruff and I also didn't think much science would go into making a shampoo like Head & Shoulders. So what I learned really surprised me:

There are hundreds of scientists working on this shampoo. They run crazy-sounding experiments like hanging hair near Tokyo highways to understand how real-world environments deposit dirt on hair. They use sophisticated scientific techniques like electron microscopes, nuclear magnetic resonance and gene sequencing to study dandruff on the molecular level.

In fact they sequenced the entire genome of Malassezia globosa in 2002, one year after the human genome project. Their findings are published in international refereed journals. What they have found is that the Malassezia fungi create free fatty acids as byproducts of their digestion, which for some people create irritation and lead to hyper-proliferation of skin cells, flaking, histamines, inflammatory cytokines, and blood proteins reaching the surface of the skin. These findings indicate the unhealthiness of dandruff scalp and suggest a possible remedy - controlling the metabolism of the Malassezia fungi. This is achieved using different active ingredients in different products and different parts of the world, including zinc pyrithione, selenium sulfide, and piroctone olamine. With the reduction of irritants, the scalp actually expresses different genes, producing a signature more similar to a non-dandruff baseline scalp.

Music from Epidemic Sound: http://epidemicsound.com
Music also by Kevin MacLeod: http://incompetech.com

The single principle that underpins all of physics. Head to https://brilliant.org/veritasium to start your free 30-day trial and get 20% off an annual premium subscription.

A massive thank you to Prof. Steven Strogatz for his expertise and enthusiasm. As an exclusive bonus for our Patreon members, we've posted a longer interview with Prof. Strogatz over there: https://www.patreon.com/posts/....principle-of-1160428

A huge thank you to Prof. Haithem Taha, Prof. Anthony Bloch, Dr. Carl-Fredrik Nyberg Brodda, Dr. Sarah Millholland, and Dr. Andrew Mitchell for all their help with finding the story and getting it right.

A special thanks to Dr. Aurèle Adam, Ron Haaksman, Marc Serra Peralta, and everyone at the Delft Makerspace for their help with preparing and performing experiments.

00:00 One rule that replaces all of physics
00:51 The problem of fastest descent
05:09 Fermat's principle
07:17 Bernoulli's solution
10:38 Maupertuis' principle
12:28 Maupertuis attacked and ridiculed
14:01 Euler & Lagrange to the rescue
17:22 The general approach to solving these problems
19:32 Writing the principle into its modern form
23:17 Why the principle works
27:08 Another way to do mechanics
30:19 A “spooky” breakthrough

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Join us on Patreon for early access videos and exclusive bonus content https://ve42.co/PatreonDE

Patrons: Adam Foreman, Anton Ragin, Balkrishna Heroor, Bertrand Serlet, Bill Linder, Blake Byers, 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

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Key references:

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
3Blue1Brown. The Brachistochrone, with Steven Strogatz via Youtube - https://ve42.co/Brach3B1B
Vsauce. The Brachistochrone via Youtube - https://ve42.co/BrachV
PBS Space Time. Is ACTION The Most Fundamental Property in Physics? via Youtube - https://ve42.co/PBSAction

Full list of references: https://ve42.co/LeastActionRefs

Images & Video:
Voltaire. (1753). Diatribe du Docteur Akakia. - https://ve42.co/DiatribeAkakia
Philosophical Transactions cover. via Wikimedia Commons - https://ve42.co/PhilTransImage
Kids Fun Science. (Jun 28, 2017). Refraction of Light with a arrow experiment via Youtube - https://ve42.co/RefractionFunSci
Physics with Simon Poliakoff. Refraction demonstration with water and laser via Youtube - https://ve42.co/SimonPoliakoff
Mercury Transit Across Sun. via Nasa.gov - https://ve42.co/MercTransit


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Directed by Casper Mebius
Written by Casper Mebius and Derek Muller
Edited by Trenton Oliver
Animated by Fabio Albertelli, Ivy Tello, Mike Radjabov, Gregor Čavlović, Emma Wright, James Finnemore and David Szakaly
Illustrated by Jakub Misiek, Emma Wright, and Maria Gusakovich
Filmed by Derek Muller and Casper Mebius
Additional research by Gabe Strong, Gregor Čavlović, and Geeta Thakur
Produced by Casper Mebius, Derek Muller, Rob Beasley Spence, Gabe Strong, Gregor Čavlović, and Tori Brittain
Thumbnail contributions by Jakub Misiek, Ren Hurley and Peter Sheppard
Additional video/photos supplied by Getty Images, Storyblocks, and NASA SVS
Music from Epidemic Sound

Which weight hits the ground first - the free weight or the weight attached to the chain?

What happens when you decrease the pressure around a liquid? It boils. Water boils at room temperature once the pressure is low enough. What is interesting is that this decreases the temperature of the liquid. The fastest molecules escape, leaving the slower ones behind.
Using this trick with liquid nitrogen, it is possible to create solid nitrogen at a temperature of -210C. We then poured the solid and liquid nitrogen mixture onto a tray of water. The surface of the water became so cold that CO2 solidified out of the atmosphere on its surface. Then, since CO2 does not pass through the liquid phase at atmospheric pressure, it was propelled on the water surface by jets of gas as it sublimed.
Huge thanks to the Palais de la Decouverte.
Music by Kevin MacLeod of Incompetech.com (Mirage)

Starring: Christie Wykes as Chlorine, Carbon, and Sodium
Director of Photography: Sean McCallum
Gravity (John Mayer Cover) http://www.youtube.com/watch?v=u7KpH9_I2Dw
I'm Atoms (Jason Mraz Cover) http://www.youtube.com/watch?v=DBjZz0iQrzI
Electricity (Jet Cover) http://www.youtube.com/watch?v=cY-kiddvAg0
Experiments A Cappella http://www.youtube.com/watch?v=lRbI_vPyOnc

Why does shaken soda explode? Does ice melt first in fresh or salt water?
Thank you Squarespace for sponsoring this video. Go to https://squarespace.com to save 10% off your first purchase of a website or domain using code: VERITASIUM

This video features experiments that have been shown to me by science teachers over the years. Does ice melt fast in salt water or fresh water was an experiment introduced to me at the Utah Science Teachers' conference. The ring of metal over a chain demo came from a teachers event in Florida. The idea shaking a carbonated drink increases pressure came from an email.

Special thanks to Petr Lebedev for building the pressure gauge.

Links to literature are below:
Victims of the pop bottle, by Ted Willhoft. New Scientist, 21 August 1986 p.28

Carbonation speculation
The Physics Teacher 30, 173 (1992); https://doi.org/10.1119/1.2343501

Agitation solution
The Physics Teacher 30, 325 (1992); https://doi.org/10.1119/1.2343556

Filmed by Cristian Carretero, Jordan Schnabel, Jonny Hyman, and Raquel Nuno

Music from https://epidemicsound.com "Seaweed" "Quietly Tense" "Mind Shift" "Observations"

Avalanches are beautiful, majestic, and completely terrifying – this is a video all about the science of avalanches. Head to https://brilliant.org/veritasium to start your free 30-day trial, and get 20% off an annual premium subscription.

A massive thank you to everyone at Whistler Blackcomb for making this shoot happen – Dane Gergovich, David Iles, Alastair Collis, Erin Taylor, and everyone else on the ski patrol team. Thank you for keeping us safe!

A massive thank you to Bruce Tremper, Niko Schirmer, and Mark Smiley for their expertise and help with this video. We are truly grateful for your time and expertise.

Check out Niko's channel here -- it's easily some of the best skiing content on YouTube. https://www.youtube.com/@Nikolai_Schirmer

If you have any intention of going into the backcountry, you have to read Bruce’s book – Staying Alive in Avalanche Terrain. It’s the Bible for this stuff, and the book that inspired us to make this video.

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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, 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

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References:
Tremper, B. (2001). Staying Alive in Avalanche Terrain. Mountaineers Books. - https://ve42.co/Tremper2001
McClung, D. & Schaerer, P. (2006). The Avalanche Handbook. Mountaineers Books. - https://ve42.co/McClung2006
Hopfinger, E. J. (1983). Snow Avalanche Motion and Related Phenomena. Annual Review of Fluid Mechanics. - https://ve42.co/Hopfinger1983
Schweizer, J. et al. (2003). Snow avalanche formation. Reviews of Geophysics. - https://ve42.co/Schweizer2003
Schweizer, J. et al. (2008). Review of spatial variability of snowpack properties and its importance for avalanche formation. Cold Regions Science and Technology. - https://ve42.co/Schweizer2008
Jamieson, B. (2006). Formation of refrozen snowpack layers and their role in slab avalanche release. Reviews of Geophysics. - https://ve42.co/Jamieson2006
Schweizer, J. et al. (2016). Avalance release 101. International Snow Science Workshop Proceeding. - https://ve42.co/Schweizer2016
Schweizer, J. (2008). Snow avalanche formation and dynamics. Cold Regions Science and Technology. - https://ve42.co/Schweizer2008-2

Images & Video:
Skiing and snowboarding footage by Niko Schirmer - https://ve42.co/NikoYT
World's Biggest Avalanche (c)Thom Goddard/All Star Films Ltd 2015. Thank you to the Thom Goddard Channel for use - https://ve42.co/ThomGoddard
Newspaper clippings via Newspapers.com – https://ve42.co/Newspapers
Video of a snow slab avalanche via Trottet, B. et al. (2022). Transition from sub-Rayleigh anticrack to supershear crack propagation in snow avalanches. Nature Physics. - https://ve42.co/Trottet2022
Remote Triggered Avalanche via Henry’s Avalanche Talk - Remote Triggering of an Avalanche
WW1 images via Brugnara, Y. et al. (2016). December 1916: Deadly Wartime Weather. Geographica Bernensia - https://ve42.co/Brugnara2016
Major Avalanches via Geomorphological Hazards - https://ve42.co/MajorAvi
White Friday avalanche illustration via Avalanches WIllow - https://ve42.co/WhiteFriday
White Friday aftermath via Lost In History - https://ve42.co/AviGraves
Field mass on Marmolada via Austrian National Library - https://ve42.co/AviMass
Yungay disaster via NOAA - https://ve42.co/Yungay
Yungay aftermath via AMC Museum - https://ve42.co/YungayAMC
Bruce Tremper Image via utavy - https://ve42.co/BruceTPic
Snowpack via SnowStudies.org - https://ve42.co/SnowStudies
Snowpack via Avalanche.org - https://ve42.co/SnowPackAvi
Snow crystals via Reiweger, I. (2011). Failure of weak snow layers. ETH. - https://ve42.co/Reiweger2011

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Directed by Petr Lebedev
Written by Petr Lebedev and Derek Muller
Edited by Peter Nelson (Additional editing by James Horsley)
Animated by Jakub Misiek, Fabio Albertelli, Alex Zepherin, and Alex Drakoulis
Additional Research by Gregor Čavloviċ
Filmed by Petr Lebedev and Ryan Regehr
FPV Drone by Mitch Winton
Produced by Petr Lebedev, Derek Muller, Han Evans, Giovanna Utichi, Rob Beasley Spence, Emily Taylor and Gregor Čavloviċ

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

The Salton Sea is the largest body of water in California, home to the second most diverse group of birds in America and it exists by accident.
Another great video on the Salton Sea: https://youtu.be/otIU6Py4K_A
I used archive from this video.

Music by Kevin MacLeod, www.incompetech.com ‘Mirage’, ‘Hyperfun’, ‘Marty Gots a Plan’, ‘Past the Edge’

Tiny particles from distant galaxies have caused plane accidents, election interference and game glitches. This video is sponsored by Brilliant. The first 200 people to sign up via https://brilliant.org/veritasium get 20% off a yearly subscription.

This video was inspired by the RadioLab Podcast "Bit Flip" https://ve42.co/BF -- they're brilliant science storytellers.

A Huge thanks to Dr Leif Scheick, Calla Cofield and the JPL Media Relations Team.

Thanks to Col Chris Hadfield. Check out his book: https://chrishadfield.ca/books/

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References:
J. F. Ziegler, "Terrestrial cosmic rays," in IBM Journal of Research and Development, vol. 40, no. 1, pp. 19-39, Jan. 1996, doi: 10.1147/rd.401.0019. -- https://ve42.co/Ziegler1996

D. Binder, E. C. Smith and A. B. Holman, "Satellite Anomalies from Galactic Cosmic Rays," in IEEE Transactions on Nuclear Science, vol. 22, no. 6, pp. 2675-2680, Dec. 1975, doi: 10.1109/TNS.1975.4328188 https://ve42.co/Binder1975

Ziegler, J. F., & Lanford, W. A. (1979). Effect of cosmic rays on computer memories. Science, 206(4420), 776-788 https://ve42.co/Ziegler1979

Drury, L. O. C. (2012). Origin of cosmic rays. Astroparticle Physics, 39, 52-60. https://ve42.co/Drury2012

Hess, V. (2018). On the observations of the penetrating radiation during seven balloon flights. arXiv preprint arXiv:1808.02927. --https://ve42.co/Hess2018

Carlson, P., & De Angelis, A. (2011). Nationalism and internationalism in science: the case of the discovery of cosmic rays. The European Physical Journal H, 35(4), 309-329. -- https://ve42.co/Carlson2011

Höeffgen, S. K., Metzger, S., & Steffens, M. (2020). Investigating the effects of cosmic rays on space electronics. Frontiers in Physics, 8, 318. -- https://ve42.co/Hoeffgen2020

Edmonds, L. D., Barnes, C. E., & Scheick, L. Z. (2000). An introduction to space radiation effects on microelectronics. Jet Propulsion Laboratory, National Aeronautics and Space Administration. -- https://ve42.co/Edmonds2000

NASA Mars 2020 website covering the specifications of the Perseverance Rover https://ve42.co/RoverBrains

Australian Government Australian Transport Safety Bureau report on QF72 -- https://ve42.co/ASTBQantas

Australian Government Australian Transport Safety Bureau summary on QF72 --https://ve42.co/ASTBQantas2

Great Blog post about QF72 -- https://ve42.co/DempseyQantas

Michael Barr's report on the Toyota acceleration issue --https://ve42.co/Barr2015

NASA's Report on Toyota -- https://ve42.co/NASAToyota

T. C. May and M. H. Woods, "A New Physical Mechanism for Soft Errors in Dynamic Memories," 16th International Reliability Physics Symposium, 1978, pp. 33-40, doi: 10.1109/IRPS.1978.362815. --https://ve42.co/May1978

P. M. O'Neill and G. D. Badhwar, "Single event upsets for Space Shuttle flights of new general purpose computer memory devices," in IEEE Transactions on Nuclear Science, vol. 41, no. 5, pp. 1755-1764, Oct. 1994, doi: 10.1109/23.317386. -- https://ve42.co/ONeill1994

Wikipedia about radiation hardening -- https://ve42.co/RadHardening

Toward Monitoring Fault-Tolerant Embedded
Systems (Extended Abstract) -- https://ve42.co/Goodloe2009

Article about speed run -- https://ve42.co/BurttSpeedrun

Article about speed run -- https://ve42.co/BountySpeedrun

Article about redundant systems in spaceflight -- https://ve42.co/NASAComputers

Article about the PowerPC750 -- https://ve42.co/Wener-FlignerNASA

Fuglesang C, Narici L, Picozza P, Sannita WG. Phosphenes in low earth orbit: survey responses from 59 astronauts. Aviat Space Environ Med. 2006 Apr;77(4):449-52. PMID: 16676658. -- https://ve42.co/Fuglesang2006

Good article about Cosmic Rays causing flashes -- https://ve42.co/AtkinsonEye

Good article about radiation resistance -- https://ve42.co/RoverResistance

Special thanks to Patreon supporters: Paul Peijzel, 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, 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 and Petr Lebedev
Animation by Ivy Tello, Mike Radjabov, Fabio Albertelli, Jakub Misiek and Charlie Davies
SFX by Shaun Clifford
Filmed by Derek Muller, Raquel Nuno, and Emily Zhang
Edited by Derek Muller and Petr Lebedev
SFX by Shaun Clifford
Additional video supplied by Getty Images
Rover Footage From NASA/JPL-Caltech
QF72 footage from the Smithsonian channel https://youtu.be/H3q5S9PCoJA
SM64 footage from https://ve42.co/pannenkoek2012
Music from Epidemic Sound
Produced by Derek Muller, Petr Lebedev and Emily Zhang

Discover the explosive story of Alfred Nobel. Sponsored by Opera - Upgrade your browsing experience with Opera today. Download it right here: https://opr.as/Opera-browser-veritasium

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

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

CORRECTIONS:
30:36 The molecular chain we showed here when talking about cellulose was actually starch, the glycosidic bonds should be bent (beta) not straight (alpha) bonds - Thank you to someriversong1793 for spotting this
37:38 The animation shows the casing flying away with the bullet, this is incorrect, only the bullet accelerates down the barrel like that - Thank you to kettusnuhveli for pointing this out

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A huge thank you to Jesse Taylor for making the demonstrations possible and sharing his experience with us!

And a big thanks to Dr. Katharine Tibbets, Dr. Julien Glorian & Sabrina DePiero for their expertise and participation in this video.

Also thanks to Steven Johnson, author of The Infernal Machine (as featured on 99% Invisible) and to Jonah Sachs and professor Terry Reynolds for their help on the project

▀▀▀
0:00 The Nobel Armament Factory
4:18 Gunpowder vs Nitroglycerine
10:58 How safe is nitroglycerin?
14:50 Blast Caps
19:09 Why does nitroglycerin explode on impact?
22:19 The invention of dynamite
26:56 Dynamite vs TNT
27:53 Explosive Cotton - Gelignite
32:43 The Merchant of Death
35:42 Smokeless Guns
38:04 The Birth of Terror
42:08 Why did Nobel start the prize?
43:11 What happened to Nobel?

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References: https://ve42.co/NobelRefs

Images & Video: https://ve42.co/NobelImRefs

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Special thanks to our Patreon supporters:


Adam Foreman, Albert Wenger, Alex Porter, Alexander Tamas, Anton Ragin, Anupam Banerjee, armedtoe, Balkrishna Heroor, Bertrand Serlet, Blake Byers, Bruce, Dave Kircher, David Johnston, David Tseng, Evgeny Skvortsov, Garrett Mueller, Gnare, gpoly, Ibby Hadeed, Jeromy Johnson, Jon Jamison, Juan Benet, KeyWestr, Kyi, Lee Redden, Marinus Kuivenhoven, Matthias Wrobel, Meekay, meg noah, Michael Bush, Michael Krugman, Orlando Bassotto, Paul Peijzel, Richard Sundvall, Robert Oliveira, Sam Lutfi, Tj Steyn, Ubiquity Ventures, wolfee

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Writer, Director & Producer: Henry van Dyck
Presenters: Derek Muller & Henry van Dyck
Editor: Trenton Oliver
Camera Operators: Wesley Wright, Prescott McCarthy, Joel Schöppe & Henry van Dyck
Animators: Andrew Neet, Fabio Albertelli, Emma Wright, Rokas Viksraitis, Saif Javed & Ivy Tello
Illustrators: Jakub Misiek, Maria Gusakovich, Nataly Zhuk, Isaac McRee, Grace Nemanic, Sofia Constantini & Veronika Pasynkova
Additional Editors: James Stuart, Peter Nelson & Spencer Wright
Researchers: Aakash Singh Bagga & Gabe Strong
Thumbnail Designers: Abdallah Rabah, Ren Hurley, Ben Powell & Henry van Dyck
Production Team: Josh Pitt, Nicola Griffiths, Rob Beasley Spence, Matthew Cavanagh, Anna Milkovic & Zoe Heron
Executive Producers: Casper Mebius & Derek Muller

Additional video/photos supplied by Getty Images, The David Rumsey Historical Map Collection, Pond5 & StoryBlocks
Music from Epidemic Sound

When we touch something that is hot or cold, what are we actually sensing? Is it the temperature of the object, or the rate at which heat flows between the object and our hand?

In 2018 the kg will be defined by Planck's constant, not a hunk of metal.
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Special thanks to the staff at NIST who made this possible: Darine Haddad, Jon Pratt, Stephan Schlamminger, and Ben Stein.

Additional footage and animations by Sean Kelley, Jennifer Lauren Lee, and Frank Seifert.

I have been obsessed with measurement for a long time and I'm not sure quite how it happened. The world's roundest object played a role in this. I guess I'm just fascinated by how difficult it is to pin down a quantity like a kilogram. A physical object seemed like a good idea until the mass of the international prototype kilogram wasn't as constant as expected. These methods of the Kibble balance and silicon sphere have shown better precision than 20 parts per billion, making them superior to the old method. The agreement between Avogadro approaches

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

Interferometer video by TSG Physics: https://www.youtube.com/watch?v=j-u3IEgcTiQ

Music from http://epidemicsound.com "ExperiMental1" by Gunnar Johnsén

Studio filming by Raquel Nuno

I saw my first wild koalas while driving on the great ocean road. Generally their days are not very exciting. They spend most of their time sleeping and the rest of the time eating eucalyptus leaves. The eucalyptus leaves are tough to digest which explains their consumate napping. Plus they require bacteria in their gut to help them break down their food. This bacteria must be passed down from mother to child through the mother's poo. It's a tough start to life for koalas!

The surprising science of escalators. Sponsored by Brilliant - check out https://brilliant.org/veritasium to start learning for free.
Plus, our viewers get 20% off an annual Premium subscription for unlimited daily access to all Brilliant courses.

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


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A massive thank you to Emily Zhang for suggesting this idea and helping shape it.

A huge thanks to the team at OTIS, especially Ed Jacovino, Gregory Sefcik and Dirk Winkelhake, for their time and expertise.

Thank you also to Professor Gero Gschwendtner, Professor Michael Fu, and Dr. Peter Kauffmann for all their help on the project.


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0:00 When escalators go wrong
2:43 The first escalator
5:01 How does an escalator work?
8:35 Why do escalators have grooves?
10:05 Why do escalators have brushes?
10:21 The hand rail moves faster than the steps
12:05 You generate electricity on escalators
14:09 How does an escalator break?
18:47 How safe are escalators really?


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References: https://ve42.co/EscalatorRefs
Images & Video: https://ve42.co/EscalatorImgRefs


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Special thanks to our Patreon supporters:
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Writers - Darius Garewal, Casper Mebius, Emily Zhang & Derek Muller
Presenters - Derek Muller & Latif Nasser
Producer & Director - Darius Garewal
Editor - Spencer Wright
Camera Operators - Derek Muller, Darius Garewal & Gregory Sefcik
Animators - Mike Radjabov, Fabio Albertelli, Saif Javed, Andrew Neet & Rokas Viksraitis
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Researchers - HyoJeong Choi, Callum Cuttle & Gabe Strong
Thumbnail Designers - Ren Hurley, Ben Powell & Abdallah Rabah
Production Team - Nicola Griffiths, Josh Pitt, Rob Beasley Spence & Casper Mebius
Executive Producers - Casper Mebius & Derek Muller

Additional video/photos supplied by Getty Images, Pond5 & StoryBlocks
Music from Epidemic Sound

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/

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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

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

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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

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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

How an unlikely physics paradox controls these counterintuitive structures.