Do two people on the planet have the exact same number of body hairs? How about more than two? There's a simple yet powerful mathematical principle that can help you find out the answer. Kelsey Houston-Edwards breaks down the Pigeonhole...

In which John Green teaches you about the Mexican-American War in the late 1840s, and the expansion of the United States into the western end of North America. In this episode of Crash Course, US territory finally reaches from the...

Picture this: you're working a shift in a hotel lobby when someone approaches the front desk. They found a lost wallet around the corner, but they're in a rush and don't have time to follow up. Looking at the wallet you see it contains a...

Hank addresses a highly requested topic - liquid fluoride thorium reactors - and tells us how LFTR might be the future of energy in ... China?

In the year leading up to this talk, the web tool Twitter exploded in size (up 10x during 2008 alone). Co-founder Evan Williams reveals that many of the ideas driving that growth came from unexpected uses invented by the users themselves.

Sherwin Nuland, a surgeon and a writer, meditates on the idea of hope -- the desire to become our better selves and make a better world. It's a thoughtful 12 minutes that will help you focus on the road ahead.

Josh Silver delivers his brilliantly simple solution for correcting vision at the lowest cost possible -- adjustable, liquid-filled lenses. At TEDGlobal 2009, he demos his affordable eyeglasses and reveals his global plan to distribute...

Lesley Hazleton sat down one day to read the Koran. And what she found -- as a non-Muslim, a self-identified "tourist" in the Islamic holy book -- wasn't what she expected. With serious scholarship and warm humor, Hazleton shares the...

The Great North American Locust Plague

Gayla Benefield was just doing her job -- until she uncovered an awful secret about her hometown that meant its mortality rate was 80 times higher than anywhere else in the US. But when she tried to tell people about it, she learned an...

You'd think that two planets with similar stats, orbits, and parent stars would grow up to be pretty similar, but these twins have atmospheres that beg to differ.

Plenty of other planets in the Solar System have rings. So why not Earth?

If you weighed 99 lbs, and ate 1 lbs of nachos, would that make you 1% nacho? Hank attempts to answer this question with a series of deeper questions on this episode of SciShow quick questions.

Null results often get a bad rap, sometimes characterized as a study "finding nothing," but there's a lot we can learn from studies whose results fail to support their hypotheses.

Throughout history and around the world, most people dislike hyenas. But why?

Last year LIGO announced the detection of gravitational waves from the merger of two black holes. The science world went a little crazy. Only a few weeks ago a new rumour emerged: that LIGO had, for the first time, spotted gravitational...

If most people got on a skateboard, they would roll forward slowly for a few feet, then fall down and break their wrists. But there are a proud few who can do some pretty amazing tricks on a board, and they use physics to pull them off....

Evolution vs Natural Selection

Flinching in response to an unexpected loud noise might not be pleasant, but it's also not a problem for most people. For one family, however, getting startled would cause their bodies to go stiff and fall.

How do we consume data? At TED@SXSWi, technologist JP Rangaswami muses on our relationship to information, and offers a surprising and sharp insight: we treat it like food.

In a fun, exciting talk, teenager Henry Lin looks at something unexpected in the sky: distant galaxy clusters. By studying the properties of the universe's largest pieces, says the Intel Science Fair award winner, we can learn quite a...

There’s lots of debate as to which original starter Pokémon is the best fighter among squirtle, bulbasaur, charmander, and pikachu, but only one is the most biologically plausible.

Hank talks about how your toilet is actually one of the cleanest places in your house, despite its function. Research has shown that cutting boards, dish towels and sponges have FAR more fecal bacteria on them than your toilet seat,...

It's getting really cold where Jessi and Squeaks live, and that has her thinking about a super cool animal that's always ready for super cold weather: Reindeer!