Why does shaken soda explode? Does ice melt first in fresh or salt water?
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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"

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

I've created an educational product to help people learn chemistry!
You can buy it here: http://www.snatoms.com

When air is compressed very quickly, it can reach high temperatures. In this demonstration we show how cotton wool can reach the point of auto-ignition by quick compression of air in the fire syringe.

A forest is like a meadow on useless stilts.
Most amazing thing about trees: http://bit.ly/TFilQ8
Meetup in Stockholm Sunday, Apr 6 Cafe String

We often imagine that unregulated competition produces optimal outcomes, behaviours, efficiencies, but trees and baggage carousels are two examples where the stable solution is worse for everyone than another strategy. This I find surprising and interesting - that evolution doesn't come to the best solution, it comes to the most stable one.

The Forest of Friendship was a concept I first came across in Richard Dawkin's book "The Greatest Show on Earth." One point I'd like to clarify is that being taller comes with a cost - having a longer trunk requires costly expenditure of energy. However, in a forest of uniformly short trees, being a little taller conveys an advantage. That is until all the other trees catch up, at which time the extra height no longer provides a benefit. So over time as the whole forest rises up the conditions are getting worse for each tree, but they are powerless to stop the evolutionary arms race.

Huge thank you to Brady Haran for filming (and summarizing the main points at the end of the film). He is the amazing creator of:
Numberphile: http://youtube.com/numberphile
Sixty Symbols http://youtube.com/sixtysymbols
Periodic Videos http://youtube.com/periodicvideos
And many more...

The Event Horizon Telescope Collaboration observed the supermassive black hole at the center of M87, finding the dark central shadow in accordance with General Relativity, further demonstrating the power of this 100 year-old theory.

To understand more about why the shadows look the way they do, check out: https://www.youtube.com/watch?v=zUyH3XhpLTo

I will continue updating this description with more links.

Event Horizon Telescope collaboration: https://ve42.co/EHT

Animations and simulations with English text:
L. R. Weih & L. Rezzolla (Goethe University Frankfurt)
https://youtu.be/jvftAadCFRI

Video of observation of M87 courtesy of:
C. M. Fromm, Y. Mizuno & L. Rezzolla (Goethe University Frankfurt)
https://youtu.be/meOKmzhTcIY

Video of observation of SgrA* courtesy of
C. M. Fromm, Y. Mizuno & L. Rezzolla (Goethe University Frankfurt)
Z. Younsi (University College London)
https://youtu.be/VnsZj9RvhFU

Video of telescopes in the array 2017:
C. M. Fromm & L. Rezzolla (Goethe University Frankfurt)
https://youtu.be/Ame7fzBuFnk

Animations and simulations (no text):
L. R. Weih & L. Rezzolla (Goethe University Frankfurt)
https://youtu.be/XmvpKFSvB7A

Special thanks to Patreon supporters:
Donal Botkin, Michael Krugman, Ron Neal, Stan Presolski, Terrance Shepherd, Penward Rhyme

Scale animation by Maria Raykova

The atmosphere applies a pressure of about 100 000 N to every square metre on Earth's surface. We take this pressure for granted because we have the same amount of pressure pushing out. But what happens when the pressure of the atmosphere is applied to an object with no outward pressure? It implodes. In spectacular fashion.

Most people recognize that atoms are the fundamental building blocks of all matter around us. An atom itself is composed of protons, neutrons and electrons. The simplest atom is the hydrogen atom because it consists of only one proton and one electron. If a neutron is added to the nucleus, the atom is still hydrogen, just a more massive version. Atoms of the same element (i.e. those with the same number of protons) but different numbers of neutrons are called isotopes.

The US signed the metre convention and bases all customary units on SI standards. As an aside, the Utah constitution from 1895 required the metric system to be taught in schools. This requirement was repealed in 1987. ¯\_(ツ)_/¯

Huge thanks to NIST, Ben Stein and Patrick Abbott.
https://www.nist.gov/
https://www.nist.gov/pml/weights-and-measures/si-units-mass

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

Back in 1875 The US signed the Metre Convention, which basically committed the country to use the metric system. In return, French scientists sent two platinum-iridium cylinders that weigh 1kg to the US in 1889 (known by their designations K4 and K20 from a set of 40 identical objects that were produced and sent around the world). So even though everything you see and buy in the US is usually reported in pounds, all weights are traceable back to the K20 kilogram (by applying a conversion factor to get to pounds).

When I was in DC a few weeks ago, I visited the National Institute of Standards and Technology (NIST) and got up close with K20, which is still kept there and used to calibrate all mass standards in this country. I thought it was pretty cool.

Edited by Bill Connor

A planet has been predicted to orbit the sun with a period of 10,000 years, a mass 5x that of Earth on a highly elliptical and inclined orbit. What evidence supports the existence of such a strange object at the edge of our solar system?

Huge thanks to:
Prof. Konstantin Batygin, Caltech
Prof. David Jewitt, UCLA

I had heard about Planet 9 for a long time but I wondered what sort of evidence could support the bold claim: a planet at the very limits of our ability to detect one, so far out that its period is over 60 times that of Neptune. The planet 9 hypothesis helps explain clustering of orbits of distant Kuiper belt objects. It also explains how some of these objects have highly inclined orbits - up to 90 degrees relative to the plane of the solar system. Some are orbiting in reverse. Plus their orbits are removed from the orbit of Neptune, the logical option for a body that could have ejected them out so far. The fact that the perihelion is so far out suggests another source of gravity was essential for their peculiar orbits.

Special Thanks to Patreon Supporters:
Alfred Wallace, Arjun Chakroborty, Bryan Baker, Chris Vargas, Chuck Lauer Vose, DALE HORNE, Donal Botkin, Eric Velazquez, halyoav, James Knight, Jasper Xin, Joar Wandborg, Kevin Beavers, kkm, Leah Howard, Lyvann Ferrusca, Michael Krugman, Mohammed Al Sahaf, Noel Braganza, Pindex, Ron Neal, Sam Lutfi, Stan Presolski, Tige Thorman

Music from http://epidemicsound.com "Observations - From Now On" "Magnified XY"

The kilogram, mole, kelvin, and ampere will be redefined by physical constants. For a limited time, get 3 months of Audible for just $6.95 a month: http://audible.com/VERITASIUM or text VERITASIUM to 500500

Will this be the last video I make about SI units? Quite possibly. There's something about being so precise and defining the systems within which science works. When we can more accurately and routinely measure a kilogram, a mole, a kelvin and an ampere, then we can make better observations, we can better detect anomalies and improve our theories. That is why this is so important to me.

Special thanks to Patreon supporters:
Donal Botkin, Michael Krugman, Ron Neal, Nathan Hansen, James M Nicholson, Terrance Shepherd, Stan Presolski

Special thanks to NIST: http://nist.gov

Additional graphics by Ignat Berbeci

Music from http://epidemicsound.com "Experimental1"

*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.

Baby photos of our universe show huge early growth spurt!
Check out Audible: http://bit.ly/AudibleVe
Regression to the Mean: http://bit.ly/1lgZQAQ

Some clarifications:
- The lengthening of wavelengths is not strictly due to stretching by the expanding universe but by the way the photons were emitted and absorbed in different frames of reference.
- The effects of gravitational waves have been observed in the decaying orbital periods of some binary star systems, however detectors built to measure gravitational waves stretching and squeezing matter on Earth have not as yet detected them.
- In the video I sometimes use the term Big Bang to refer to the beginning of time as we know it. The Big Bang actually refers to the whole process from the formation of our universe, through inflation, to the expanding mass of plasma in the early universe (not just the first instant).
- Quantum gravity is by no means established by this observation but it is suggestive that General Relativity and Quantum Mechanics are working together here.

Thank you to Professor Geraint Lewis and Henry Reich for comments on earlier drafts of this video (even if I haven't accepted all of your corrections).

Well an atom's made of protons, neutrons, and electrons
the first two in the nucleus, the third around it
it's mostly empty space, but it feels solid in any case

The elements are all the different types of atoms
they differ by the number of protons in the middle.
Hydrogen has only one, but Uranium has a ton

It's just chemistry that you and me are made of these atoms

Well atoms bond together to form molecules
Most of what's surrounding me and you
Water, sugar, things yet undreamed of of of of

Look around you, see the combinations in a eucalypt tree
Mendeleev's periodicity
gives us sand and water and the air above ove ove ove ove

It's just chemistry that you and me are made of these atoms:
Hydrogen, Oxygen, Carbon, Nitrogen, make up the world's life forms

Do do do you, do do do do
but do you wonder how
matter forms something strange
when there's a chemical change?

Where did these atoms come from? They were fused in stars
Light elements combine releasing light from afar
Fusion in the sun, creates Helium

I guess what I be saying is you gotta use your reason
To open up your mind and see the cause of the seasons
-How do we know what's true? The scientific method shows you

It's just chemistry that you and me are made of these atoms

Atoms bond together to form molecules
Most of what's surrounding me and you
Water, sugar, sand and you'll find things undreamed of

So Argon, Neon, Xenon
There's no need to overstate
'Cause we are of course
This, of this, of this, we're made: atoms

There are a few persistent misconceptions about what causes the seasons. Most believe it is the distance between the Earth and sun which varies to give us seasonal temperature variations. However it is actually the directness of the sun's rays leading to more intense sunshine in summer and less in winter.

In 2020, NASA will send a new rover to the Martian surface with one of its objectives to search for evidence of ancient life on the planet. I made this clip as a correspondent for Bill Nye Saves the World on Netflix.

Touring the Jet Propulsion Lab (JPL) in Pasadena was an awesome experience. I didn't think we were going to get into the control room but we got lucky. Some of the greatest moments in the history of space exploration have taken place there. They have a giant vacuum chamber where they can take the rover down to the atmospheric pressure on Mars (roughly .01x Earth's atmosphere) and test all of the devices to make sure there are no electrical discharges due to the reduced pressure. I also enjoyed seeing how the rocks will be cored and stored in tubes and deposited on the Martian surface awaiting pickup by the following mission.

Images courtesy of NASA.

Filmed by Raquel Nuno from 3:30 onwards.

Music: http://epidemicsound.com "Serene Story 2"

Is it possible to reconstruct sound from high-speed video images?
Part of this video was sponsored by LastPass: http://bit.ly/2SmRQkk
Special thanks to Dr. Abe Davis for revisiting his research with me: http://abedavis.com

This video was based on research by Dr. Abe Davis and colleagues. I found out about this work years ago and was fascinated by the way he was able to capture vibration information in image-only video. I always imagined the motions of objects would be visible as when recording a tuning fork in slow motion - so deriving sound from high speed images seemed a feasible task. But the reality is much more difficult.

Sound vibrations only cause objects to wiggle by about a micrometer. This is much smaller than a pixel, so the algorithm must understand the characteristics of the image. A move in one direction should cause some pixels to lighten slightly, while others darken - and this behavior is correlated along the edges of the image. So noise can be reduced because it's random over the image and there are enough places to sample that you can get it to cancel out.

Something I'm wondering now is - would it be possible to capture sound in a single image? I'm thinking it would have to be an image of a large object or space because the wavelengths of typical sounds are quite long. Maybe a high frequency sound could be imaged in a suitable medium...

Animations by Alan Chamberlain

Music from http://epidemicsound.com "Seaweed"

Apollo astronauts trained in nuclear bomb craters at the Nevada National Security Site. But why?Thanks Audible! Start listening with a 30-day trial and your first audiobook plus two Audible Originals free when you go to http://audible.com/veritasium or text veritasium to 500500

I found this story fascinating because in a way a nuclear bomb crater is more like a meteorite impact site than an impact site itself. Consider: Barringer Crater was claimed to be a meteorite impact site but geologists dismissed it as a volcanic formation. It was only after studying nuclear bomb craters and the minerals found there that geologists concluded the energy and pressures that created Barringer Crater were too high to be from volcanic activity and therefore must have formed from a meteorite impact.

Special Thanks to:
Nevada National Security Site
The National Atomic Testing Museum
Jonny Hyman and Verse: https://youtu.be/7bUUGzi-AAY
Active Galactic for footage of craters in Arizona: https://youtu.be/yhoooBpndog

Special thanks to Patreon supporters:
a human, Alfred Wallace, Arjun Chakroborty, Brent Stewart, Bryan Baker, Chris Vargas, Chuck Lauer Vose, Clip Tree, Coale Shifflett, Colin Bellmore, DALE HORNE, Daniel Milum, Donal Botkin, Eric Velazquez, Illya Nayshevsky, James Knight, James Wong, Jasper Xin, Joar Wandborg, Johnny, June Kang, Kevin Beavers, kkm, Leah Howard, Listen Money Matters, Lyvann Ferrusca, Manuel Zürcher, Mathias Göransson, Michael Bradley Wirz, Michael Krugman, Mohammed Al Sahaf, OddJosh, Philipp Volgger, Pindex, Roberto Rezende, Robin DeBank, Ron Neal, Sam Lutfi, Stan Presolski, Tige Thorman, Warrior8252

Filmed by Raquel Nuno
Story and Editing by Derek Muller and Jonny Hyman
Music and Animation by Jonny Hyman
Produced by Casey Rentz

The story of three impressive high school science projects. Can you guess which student won $250,000 in the #RegeneronSTS? Applications open June 1: http://bit.ly/2HkLXT1 This video was sponsored by Regeneron. The Science Talent Search was founded and produced by the Society for Science and the Public.

Huge thanks to the students: Ronak Roy, Ana Humphrey, and Anjali Chadha. It was great getting to meet all of you and learn about your original scientific research.

Special thanks to Assistant Professor Konstantin Batygin for discussing Ana's research and Planet 9 with me. More is coming on the Planet 9 front.

Ronak came up with a new design for the phoropter, the device used to determine eye-glass prescriptions. It's basically been unchanged for 200 years. Using a liquid lens, he miniaturized the device and wrote an algorithm to determine your prescription.

Ana used math and physics to search for hidden exoplanets. There are a number of reasons why the transit method and Kepler telescope may have missed them: they're too small, too inclined, or take too long to orbit and so were not seen. By considering which planetary systems have additional space for more planets, Ana came up with 560 locations where we may look again for planets in future.

Anjali developed an internet enabled device for measuring arsenic concentrations in drinking water. The device performs several chemical reactions to release the arsenic into a measurable state. It then reacts the arsenic with a test strip to produce a color output. This color is sampled by a camera and processed to determine the concentration of arsenic in the water sample. This has significant potential applications around the world helping reduce exposure to arsenic and potentially other contaminants.

Filming by Raquel Nuno

Everyone is familiar with liquid water, ice and water vapour, but what are the differences between these three states of matter? Solids, liquids and vapours of the same substance differ in the motion of the molecules and the distance between them.

Animations courtesy of VisChem (Trade Mark), Copyright 1995, Roy Tasker. Thanks for all your help!