Top Vídeos

Water on the Moon?

Veritasium
14 vistas · 7 años hace

NEW CHANNEL! http://youtube.com/sciencium

For a long time we thought the Moon was completely dry, but it turns out there are actually three sources of lunar water.
Thanks to Google Making and Science for supporting the new channel! http://youtube.com/makingscience

Thanks to Patreon supporters:
Nathan Hansen, Donal Botkin, Tony Fadell, Zach Mueller, Ron Neal

Support Veritasium on Patreon: http://bit.ly/VePatreon

References:
Great history of water on the moon: https://arxiv.org/pdf/1205.5597.pdf

Filmed by Raquel Nuno

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

Gravitational Wave Discovery! Evidence of Cosmic Inflation

Veritasium
14 vistas · 7 años hace

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).

Making Liquid Nitrogen From Scratch!

Veritasium
14 vistas · 7 años hace

I used a nitrogen membrane and Stirling cryocooler to liquefy nitrogen out of the air. For this video I partnered with Starbucks to celebrate their Nitro Cold Brew. Order one here: https://starbucks.app.link/derekmuller

Making liquid nitrogen is hard - in fact up until 150 years ago scientists doubted whether it was even possible to liquefy nitrogen. In 1823, At the royal institution in London, Michael Faraday first produced liquid chlorine, kind of accidentally by putting it under high pressure. He similarly liquefied ammonia.

Borrowing a mixture from Thilorier in France, a combination of dry ice, snow and ether, he reached a temperature of -110C. By 1845 he used this mixture plus a hand pump to pressurize gases to liquefy all the known gases except six, which included oxygen and nitrogen. These became known as the “permanent” gases.

A French Physicist Aimé compressed oxygen and nitrogen in tanks and then lowered them into the ocean over 1.6km deep, where the pressure got up to 200 atmospheres. Still the gases didn’t liquefy.

Only at the end of 1877 were the first droplets of liquid oxygen and liquid nitrogen produced, by Cailletet in France. He first tried oxygen by compressing it up to 300 atmospheres, cooled to -30C, but that wasn't even enough to liquefy oxygen. But when he suddenly released the pressure, the expanding gas cooled, he estimated to -200C and he saw a mist and then droplets slide down the walls of his vessel.

It's amazing how far we've come in that now I can purchase a helium-based cryocooler. It compresses and expands the gas to absorb heat from the tip of the cold finger and eject it into the surroundings at ambient temperature.

Free Higgs!

Veritasium
14 vistas · 7 años hace

To celebrate the announcement of the discovery of a particle consistent with the Higgs Boson at the LHC, I took to the streets with Vi Hart to give out free Higgs. Now giving out a subatomic particle, especially the Higgs, would have been incredibly difficult so instead we gave out hand-drawn cards of the Standard Model, our current best theory of all matter particles in the universe and their iteractions (now with Higgs!). We also offered a hug with an integer spin, usually 1 or 2 (and in rare cases 0). This is a way of showing others that you care about the Higgs Boson.

Why Do Venomous Animals Live In Warm Climates?

Veritasium
14 vistas · 7 años hace

As a Canadian-Australian, I have always wondered why it is that Australia has so many venomous animals that can kill you while Canada has virtually none.
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But it's not just Australia - it seems like all beautiful, warm places are cursed with venomous native species. So I set out to find the truth: why have all these venomous species evolved in the world's best holiday destinations?

I asked chemists, visited the zoo, interviewed entomologists and snake experts. The answer I found was complicated:
1. The majority of venomous species are ectotherms, cold-blooded creatures whose internal temperatures are governed by their surroundings.
2. This means they have limited periods of activity - mainly while it's warm out, and can only exert short bursts of energy, so they are generally "sit and wait" predators. This may explain why they, more than mammals or birds, evolved venom.
3. It also explains why there are more of these species in warm climates. There are more of all species in warm climates, but this trend is especially pronounced for ectotherms.
4. So there are a greater number of venomous species in warm places, simply because there are more species in warm places. Cold climates still have venomous creatures, like the rattlesnakes of Canada and European vipers.
5. But history also has a role to play. In Australia, there were no snakes until 20 million years ago when a venomous sea snake from Asia encountered the land, sending venomous species to all corners of the continent. Later non-venomous arrivals have done well in the tropics but not as well in Australia's colder climates, so venomous types still dominate there. Hawaii has no venomous land snakes and nor does Jamaica.
6. The recent ice age also would have driven ectotherms from the northern parts of the Northern Hemisphere. This is why there are no snakes in Ireland, for example.

Special thanks to Prof. Rick Shine, Prof. Dieter Hochuli, Prof. Roger Lowe, Prof. Martyn Poliakoff and Taronga Zoo, especially Joe Haddock and Dean Purcell.

Cinematography by Charles Clement