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.

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.

Some months a go I filmed a slinky falling in slow motion. Now I have interviewed the public about what they expect to happen for ABC TV's Catalyst program and this is the result.

An introduction to alpha, beta, and gamma radiation

Aerogel has extraordinary properties but it can be tough to work with. This video looks at modifying aerogels to take advantage of their unique characteristics.
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Huge thanks to Dr. Stephen Steiner and the crew at Aerogel Technologies. To find out more or buy your own aerogel sample, check out: http://www.aerogeltechnologies.com/

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

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

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 This makes silica aerogel incredibly light (it was once the lightest solid but has now been superseded by graphene aerogel), transparent and adsorbent.

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

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

Filmed by Paul Gramaglia

Thumbnail by Ignat Berbeci

Animations by Catherine Chooljian

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

This is an educational, scientific video.

The crazy story of the arbitrary temperature scale used in a tiny minority of countries.
Check out Audible: http://bit.ly/AudibleVe
Snatoms are available again! http://www.snatoms.com
Support Veritasium on Patreon: http://bit.ly/VePatreon

Celsius didn't invent Celsius: http://bit.ly/VeCelsius

Video animated by Marcello Ascani: http://bit.ly/VeMarcello

Thanks to Patreon supporters:
Nathan Hansen, Bryan Baker, Donal Botkin, Tony Fadell, Saeed Alghamdi

Music by Kevin MacLeod: http://incompetech.com "Modern Piano Zeta - Improbable" "Ice Demon" "Divertimento K131" "Sneaky Adventure" "Sheep May Safely Graze" "Professor and the Plant"

References:
A History of the Thermometer and its uses in Meteorology by W. E. Knowles Middleton

Absolute Zero and the Conquest of Cold by Tom Shachtman

The Science of Measurement, A Historical Survey by Herbert Arthur Klein

Lehrbuch der Chemie by Jöns Jakob Berzelius

Script:
As an Australian-Canadian the Fahrenheit temperature scale always seemsed a bit arbitrary. I mean why does water freeze at 32 degrees? And what exactly does zero represent?

According to many sources the Fahrenheit scale was defined by setting zero degrees equal to the temperature of an ice, salt, and water mixture and 100 degrees being roughly equal to human body temperature. But that isn’t true.

The real story is much more interesting, and scientific...

August 14th 1701 was almost certainly the worst day in the life of fifteen year-old Daniel Gabriel Fahrenheit. On that day both of his parents died suddenly from mushroom poisoning. He was sent from Poland, where he lived, to Amsterdam to become an apprentice bookkeeper.

But Fahrenheit couldn’t stand his apprenticeship and ran away so many times his employers put out a warrant for his arrest. Traveling from city to city around Europe, he became fascinated with scientific instruments and in particular thermometers.

In 1708, possibly seeking help with the warrant, Fahrenheit met with the mayor of Copenhagen, who happened to be the famous astronomer Ole Romer.

Romer is known for observing the eclipses of Jupiter’s moons and realizing that variations in the timing of those eclipses was caused by the time it took light to reach Earth. In other words, he found a way to accurately measure the finite speed of light.

But more pertinent to this story, in 1702 Romer was housebound after breaking his leg. To pass the time he devised a new temperature scale with the freezing point of water at 7.5 degrees and body temperature at 22.5 degrees.

This might seem odd until you consider that Romer wanted the boiling point of water to be 60 degrees (as an astronomer, he had experience dividing things by 60). If you take this scale, divide it in half, in half again, and in half once more, you find the freezing point of water 1/8th up the scale, and human body temperature 3/8th up the scale.

So at their meeting in 1708, Fahrenheit learned of Romer’s temperature scale and adopted it as his own, adjusting it slightly because he found it “inconvenient and inelegant on account of the fractional numbers”. So he scaled them up to 8 and 24.

That is the original Fahrenheit scale. He produced thermometers for some time using this scale.

But then, at some later time Fahrenheit multiplied all numbers on his scale by four, setting freezing point to the now familiar 32 and body temperature to 96. It’s unclear exactly why he did this. He may just have wanted finer precision in his measurements but I think there was a better reason.

You see, Fahrenheit was an excellent instrument maker. His thermometers agreed with each other precisely, at a time when that was unheard of. He pioneered the use of mercury as a measuring liquid, which has the benefit of a much higher boiling point than the alcohol used in most other thermometers at the time. For these accomplishments, he was inducted into the British Royal Society.

And we know he read the works of Newton, Boyle, and Hooke, in which he would have come across the idea that a one degree increase in temperature should correspond to a specific fractional increase in the volume of the measuring liquid.

And today a one degree Fahrenheit increase in temperature increases the volume of mercury by exactly one part in 10,000. Is this just a coincidence? We’ll probably never know for sure because as an instrument maker Fahrenheit was secretive about his methods. But I think the data strongly suggests this was the case.

So what exactly did zero represent on the scales of Fahrenheit and Romer? By many accounts it’s the temperature of a salt, ice and water mixture. But there are different descriptions of these mixtures and none of them actually produces the temperature they’re supposed to. More likely I think they picked the coldest temperature in winter, set that as zero and later used ice and brine to calibrate new thermometers. Now his scale is only used regularly in the Cayman Islands, Bahamas, Belize, oh and the United States of America.

An experiment on how turbulent convection in Earth's core makes a magnetic field
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Huge thanks to Prof. Dan Lathrop and team: http://ve42.co/Lathrop

Companion video to explain Earth's magnetic fields in more detail:
https://youtu.be/lWHxmJf6U3M

Australians! I'm on my way. I'll be doing live shows in Perth, Sydney and Melbourne. Details and tickets here: http://ve42.co/tour

Find out more about the film Vitamania: http://ve42.co/VITA

Special thanks to Brady Haran and Periodic Videos for sodium vs water footage. Original clip is here:
https://www.youtube.com/watch?v=mzEOL-N2cbw

Special thanks to Patreon supporters:
Donal Botkin, Michael Krugman, Jeff Straathof, Zach Mueller, Ron Neal, Nathan Hansen, Yildiz Kabaran, Terrance Snow, Stan Presolski

I learned a lot in making this video and the one on my second channel with Prof. Jon Arnou. I changed a lot of my preconceptions, specifically I thought:

1. That the Earth's magnetic field was a passive thing - it shouldn't need a continuous input of energy to maintain itself (that seemed reasonable to me because the magnetic field has been around for a long time and it seems mostly stable). But as it turns out, the Earth is a giant electromagnet, and so of course those currents dissipate their energy as they encounter resistance in the liquid metal through which they flow. So the energy to continuously create these currents comes from the kinetic energy of the liquid metal flows in the Earth's outer core.

2. If it's convection, I'm thinking hot things rising, cooler things falling. But apparently the main effect driving convection is the compositional differences at the boundary with the Earth's inner core. This is because of the differential freezing at the boundary. Things like iron freeze into the inner core, while elements like sulfur do not. Hence the pockets of lighter material which then rise outwards.

3. I didn't get why the fluid motion was necessary for the generation of the magnetic field. I mean if it's a conducting liquid, it can conduct currents whether it moves or not. But the key is that the liquid metal can 'trap' magnetic fields. I imagine this like how iron channels magnetic fields. Then once these fields are channeled, they can be pulled and stretched, making more magnetic field.

4. Fluids operate very differently in rotating frames of reference. This is something I didn't intuitively grasp. But, as fluids move from the inner core outwards, those particles are moving much more slowly in the direction of rotation than the matter that has been there for a long time, which means the convection currents get deflected and form helices.

Music by Kevin MacLeod http://incompetech.com Brandenburg Concerto No4

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'

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

Inspired by this article by Prof. Emily Oster: http://bit.ly/Cellcancer
Check out Audible: http://bit.ly/AudibleVe
Featuring Physics Girl: http://bit.ly/PhysGirl

Special thanks to Chris Gale and Physics Girl for filming this video.

Music by:
Amarante Music "One Last Time": http://bit.ly/VeAmarante
Kevin McLeod, Incompetech.com "Harlequin"

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.

JJ Thomson proposed the first model of the atom with subatomic structure. He had performed a series of experiments and was credited with the discovery of the first sub-atomic particle, the electron. He therefore proposed a new model of the atom called the plum pudding model. In this model, the plums represent negatively charged electrons which can be plucked out of the atom, leaving behind some positively charged pudding. In this film, cherry tart is used as a delicious substitute for plum pudding.

Countries are powered by a diverse range of energy sources, but in Australia electricity generation mainly has one source: fossil fuels. Coal, natural gas, and oil account for over 90% of the country's electricity. Hydro provides 7% with only 0.3% provided by wind and solar. Should Australia consider nuclear power? It is a complicated issue leaving many uncertain about its place in Australia's energy future.

Sound waves in a tube of gas create flames of different heights that dance to the music. A metal tube with holes in it is filled with gas. The gas is lit to create a row of tiny flames. A speaker at one end plays sound into the tube, which creates a standing wave of sound: areas where air molecules are vibrating rapidly separated by areas where the air is fairly still. This produces the different heights of flames and allows the wavelength of the sound wave to be estimated.

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.

What was the procedure to launch a nuclear missile?
Uranium premieres: July 28 & 29 on PBS at 10pm ET/ 9pm Central
France and Germany: July 31 at 10pm on ZDF/arte
Norway: August 5 & 6 at 21:30 on NRK2
Australia: August 9, 16, 23 at 8:30pm on SBS
Sweden: TBD
Middle East: TBD

For more information on other screenings go to
https://www.facebook.com/uraniumtwistingthedragon
www.genepoolproductions.com

A big thank you to The Titan Missile Museum, Yvonne and Chuck.
http://www.titanmissilemuseum.org/

Space footage courtesy of NASA

People have a lot of different ideas about what gravity is: a downward force that stops you from flying off into space, an attraction smaller objects experience towards larger objects, or a mutual attraction between all masses. It is the last of these ideas that best reflects a scientific conception of gravity.

I have the photic sneeze reflex so I sneeze when I look at bright light.
Check out 23andMe: http://ve42.co/23andme
*So technically the single nucleotide swap (C instead of T) is not actually in a gene per se but in an intergenic region on chromosome 2. It's also not clear exactly how this affects physiology or causes the sun sneeze but there is correlative evidence that every copy of this single nucleotide polymorphism (SNP) is associated with a 1.3x increase in likelihood of having the photic sneeze reflex.

I have wanted to make a video about sun-sneezing for a long time. It is something I've experienced my whole life. When I go from a dark room indoors into full sunlight I invariably sneeze. I thought everyone did it. So my original question was why do people sneeze when they see bright light? That led me to consider what possible evolutionary advantages there could be to sneezing in sunlight. The obvious advantage to me is that sunlight kills pathogens of which there may be many in your snot or mucus. So sneezing in sunshine is a much better idea than sneezing inside a dark, damp cave where you may be living.

For more info, check out:
Web-Based, Participant-Driven Studies Yield Novel Genetic Associations for Common Traits
http://journals.plos.org/plosg....enetics/article?id=1

Filmed by Raquel Nuno

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

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

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

Edited and animated by Daniel Joseph Files

Everything is not as it first appears. This simple plastic ball looks purple until you swing it in a circle and reveal its true nature. Inside are three light emitting diodes (LEDs), which are red, green and blue. They turn on and off in sequence very quickly. When still, the ball appears purple because your eyes and brain don't 'refresh' quickly enough to perceive the changing colours. However, when swung in a circle, the ball changes colours at different locations so the colours don't merge with each other and the ball's true nature is revealed. Now let's not think too carefully about how this illusion is conveyed through video (because the camera doesn't refresh quickly enough to perceive the colours changing either - so you have no hope of seeing it on YouTube even frame by frame).