Panem finds power in the radiance of the sun, and the water which rains down upon us! District 5’s Chief Energy Researcher Derek Muller takes CapitolTV on a tour of our nation's cutting edge renewable technologies, and demonstrates one of the largest ‘Kelvin’s Thunderstorm’ experiments ever built to date… all for a brighter and more efficient Panem.

Sanctioned by the Capitol Ministry of Information, DISTRICT VOICES was made with friends from Google - http://artcopycode.com/campaign/lionsgate

For more of Panem’s finest programming, and to register for updates, visit http://CapitolTV.pn
#CapitolTV - #DistrictVoices

The Hunger Games: Mockingjay Part 1 – In theaters November 21
http://TheHungerGamesExplorer.com
#Mockingjay

The real impact of spin on a football—explained with ⁨@tombrady.

When is the acceleration (rate of speeding up or slowing down) greatest during a bungy jump?

Evidence Facebook's revenue is based on fake likes.
My first vid on the problem with Facebook: http://bit.ly/1dXudqY
I know first-hand that Facebook's advertising model is deeply flawed. When I paid to promote my page I gained 80,000 followers in developing countries who didn't care about Veritasium (but I wasn't aware of this at the time). They drove my reach and engagement numbers down, basically rendering the page useless. I am not the only one who has experienced this. Rory Cellan-Jones had the same luck with Virtual Bagel: http://www.bbc.co.uk/news/technology-18819338

The US Department of State spent $630,000 to acquire 2 million page likes and then realized only 2% were engaged. http://wapo.st/1glcyZo

I thought I would demonstrate that the same thing is still happening now by creating Virtual Cat (http://www.facebook.com/MyVirtualCat). I was surprised to discover something worse - false likes are coming from everywhere, including Canada, the US, the UK, and Australia. So even those carefully targeting their campaigns are likely being duped into spending real money on fake followers. Then when they try to reach their followers they have to pay again.

And it's possible to be a victim of fake likes without even advertising. Pages that end up on Facebook's "International Suggested Pages" are also easy targets for click-farms seeking to diversify their likes. http://tnw.co/NsflrC

Thanks to Henry, Grey, and Nessy for feedback on earlier drafts of this video.

An introduction to alpha, beta, and gamma radiation

J. Robert Oppenheimer forever changed the course of history. He may be the most important physicist to have ever lived. Part of this video is sponsored by Wren. Offset your carbon footprint on Wren: ​https://www.wren.co/start/veritasium1 For the first 100 people who sign up, I will personally pay for the first month of your subscription!

If you want to learn more about Oppenheimer, I strongly recommend the book “American Prometheus” By Kai Bird and Martin Sherwin. It was the inspiration for Christopher Nolan's 2023 film "Oppenheimer", which won multiple awards, including Oscars in 2024 for Best Picture and Best Actor (Cillian Murphy).

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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A huge thank you to Dr. Martin Rohde and Dr. Antonia Denkova from the TU Delft for proofreading the script and providing valuable feedback.

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References:

Bird, K., & Sherwin, M. J. (2021). American Prometheus: the triumph and tragedy of J. Robert Oppenheimer. Atlantic Books.

Smith, A. K., & Weiner, C. (1980). Robert Oppenheimer: letters and recollections. Bulletin of the Atomic Scientists, 36(5), 19-27. - https://ve42.co/Smith1980

Combes, J. M., Duclos, P., & Seiler, R. (1981). The born-oppenheimer approximation. Rigorous atomic and molecular physics, 185-213. - https://ve42.co/Combes1981

Rhodes, R. (2012). The making of the atomic bomb. Simon and Schuster.

Oppenheimer, J. R., & Volkoff, G. M. (1939). On massive neutron cores. Physical Review, 55(4), 374. - https://ve42.co/Oppenheimer1939b

Oppenheimer, J. R. (1927). Bemerkung zur Zerstreuung der α-Teilchen. Zeitschrift für Physik, 43(5-6), 413-415. - https://ve42.co/Oppenheimer1927

Oppenheimer, J. R. (1927). Zur quantenmechanik der richtungsentartung. Zeitschrift für Physik, 43(1-2), 27-46. - https://ve42.co/Oppenheimer1927b

Born, M., & Oppenheimer, R. (1927). Zur Quantentheorie der Molekeln Annalen der Physik, v. 84. - https://ve42.co/Born1927

Oppenheimer, J. R. (1928). Three notes on the quantum theory of aperiodic effects. Physical review, 31(1), 66.

Oppenheimer, J. R. (1928). On the quantum theory of the capture of electrons. Physical review, 31(3), 349.

Oppenheimer, J. R. (1931). Note on light quanta and the electromagnetic field. Physical Review, 38(4), 725.

Furry, W. H., & Oppenheimer, J. R. (1934). On the theory of the electron and positive. Physical Review, 45(4), 245. - https://ve42.co/Oppenheimer1934

Oppenheimer, J. R. (1935). Note on charge and field fluctuations. Physical Review, 47(2), 144. - https://ve42.co/Oppenheimer1935

Oppenheimer, J. R., & Snyder, H. (1939). On continued gravitational contraction. Physical Review, 56(5), 455. - https://ve42.co/Oppenheimer1939

Oppenheimer, J. R., & Phillips, M. (1935). Note on the transmutation function for deuterons. Physical Review, 48(6), 500. - https://ve42.co/Oppenheimer1935b

Malik, J. (1985). Yields of the Hiroshima and Nagasaki nuclear explosions (No. LA-8819). Los Alamos National Lab.(LANL), Los Alamos, NM (United States). - https://ve42.co/Malik1985

Ignition of the atmosphere with nuclear bombs -- https://ve42.co/Konopinski46

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Special thanks to our Patreon supporters:
Adam Foreman, Amadeo Bee, Anton Ragin, Balkrishna Heroor, Benedikt Heinen, Bernard McGee, Bill Linder, Blake Byers, Burt Humburg, Dave Kircher, Diffbot, Evgeny Skvortsov, Gnare, John H. Austin, Jr., john kiehl, Josh Hibschman, Juan Benet, KeyWestr, Lee Redden, Marinus Kuivenhoven, 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 & Derek Muller
Produced by Petr Lebedev, Han Evans and Derek Muller
Edited by Trenton Oliver & Katrina Jackson
Filmed by Derek Muller
Animation by Fabio Albertelli, Ivy Tello, & Mike Radjabov
Illustration by Jakub Misiek and Celia Bode
Additional video/photos supplied by Getty Images & Pond5
Music from Epidemic Sound

This is what a nuclear disaster area looks like.
Check out Audible: http://bit.ly/AudibleVe
Broadcast locations and times:

North America: PBS, July 28 & 29 @ 10pm ET / 9pm Central
Europe: ZDF/arte, July 31 @ 10pm
Australia: SBS, August 6, 13, 20 @ 8:30pm EST

Not broadcast in your country? Contact your local broadcaster and/or email www.genepoolproductions.com

Music by Kevin Macleod http://incompetech.com 'Come Play With Me' & 'Lost Frontier'

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

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

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

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

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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.
Try a free book from Audible for 30 days http://ve42.co/audible
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

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

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!