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

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"

This is what a nuclear disaster area looks like.
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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'

*Watch with headphones on!
Is 45 minutes really the longest anyone can stay in a perfectly silent, pitch-black room?
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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.

Inspired by this article by Prof. Emily Oster: http://bit.ly/Cellcancer
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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"

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.

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?
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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

In April 2012, I was part of a team of scientists, teachers and students who travelled to Alaska to observe the Northern Lights or Aurora Borealis. Our mission was a unique one - to launch weather balloons up to 100,000 feet loaded with experiments, tracking devices and HD cameras. This is the result of our trip, produced for Catalyst on ABC1 http://www.abc.net.au/catalyst/

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).

Subscribe to Veritasium - it's FREE! http://bit.ly/YSWpWm
Check out other unanswered science questions: http://youtu.be/UFydagCS9fg

The universe is huge. That means two things: 1. there is probably life elsewhere, 2. It is likely too far away to have reached us.

Fast, Furious & Funny - http://www.youtube.com/fastfuriousand... (http://www.youtube.com/watch?v=YWxub2...)

The Brain Scoop - http://www.youtube.com/thebrainscoop (http://youtu.be/mNuu0y6ZmAs)

ASAPScience - http://www.youtube.com/AsapSCIENCE (http://www.youtube.com/watch?v=wgxJhp...)

The Royal Institute of Great Britain - http://www.youtube.com/TheRoyalInstit... (http://www.youtube.com/watch?v=gm02Oi...)

PBS Idea Channel - http://www.youtube.com/pbsideachannel (http://www.youtube.com/watch?v=TbNymw...)

The Spangler Effect - http://www.youtube.com/TheSpanglerEffect (http://www.youtube.com/watch?v=4fQ4uB...)

Minute Physics - http://www.youtube.com/minutephysics (http://www.youtube.com/watch?v=2yHDeK...)

Head Squeeze - http://www.youtube.com/HeadsqueezeTV (http://www.youtube.com/watch?v=UPBJX1...)

Vsauce - http://www.youtube.com/Vsauce (http://www.youtube.com/watch?v=L45Q1_...)

Space is big. You just won't believe how vastly, hugely, mind- bogglingly big it is. I mean, you may think it's a long way down the road to the chemist's, but that's just peanuts to space. ~Douglas Adams

Thanks to Dr. Simon O'Toole for talking exoplanets with me! We also discussed the Drake equation but there wasn't really room for it.

Camera by Charles Clement

Music by Kevin McLeod (incompetech.com) Mirage, Scissors

The aurora borealis or northern lights is one of the most spectacular natural displays on the planet. Theories about its origins have been debated for centuries and common misconceptions persist that the aurora is the sun's rays scattered off ice crystals in the high atmosphere. In truth, the light is created more than 100km above Earth's surface as high speed electrons and protons ejected from the sun in a solar flare or coronal mass ejection collide with air molecules in the upper atmosphere. The charged particles from the sun excite air molecules which then de-excite by emitting light. The display is most common around the north and south poles because the Earth's magnetic field deflects the solar wind from the equator to the poles. Here the magnetic field dips towards the Earth's surface, channeling the charged particles into the atmosphere.

Music is by Kevin MacLeod http://incompetech.com, the song is called Mirage

How to light a candle without touching a flame to the wick. A common misconception is that a candle burns by burning the wick. What is actually burning is wax vapour which is drawn up through the wick. When you blow a candle out, wax vapour continues to rise off the candle so you can light this vapour which burns back down to the wick, relighting the candle.

How should we depict an atom? Like a solar system with electrons orbiting the nucleus on hula hoop orbits? That idea is so last century! Bosi takes us into the quantum world, where an electron's position and velocity aren't well defined - all we can calculate are the probabilities e.g. of finding an electron at different points in space. When we do that, we find electrons do not neccessarily occupy circles or spheres in space. Rather their probability densities make all sorts of interesting shapes from the dumbell to the peanut with the donut around it.

Pioneering NASA mathematician Katherine Johnson has died at the age of 101. Johnson was part of a group of African-American women who worked on critical mathematical calculations in the early days of human spaceflight, as chronicled in the best-selling book and hit movie “Hidden Figures.”

"She was an American hero and her pioneering legacy will never be forgotten,” said NASA Administrator Jim Bridenstine.

Launching Americans from U.S. soil, sending a new rover to Mars and continuing to prepare for human missions to the Moon are just a few of the things NASA has planned for 2020.

This video is available for download from NASA's Image and Video Library: https://images.nasa.gov/detail....s-NHQ_2019_1231_2020