And today, we're going to talk about this. Just kidding.

We're going to talk about this. Left.

What's left? First of all, 90% of humans, regardless of

culture or language are right-handed. And we choose a dominant hand before we've

even left our mothers. That's right.

When a baby inside its mother's womb is seen sucking its thumb, it is sucking the right

thumb 90% of the time. Animals do it too.

In fact, horses take longer strides with their right legs, which is the entire reason racetracks

are run counterclockwise. Left-handedness is so rare that across most

cultures there has been a historical stigma against being left-handed.

In fact, the word for somehow who's good at using both hands is ambidextrous and "dexter"

comes from Latin for "right." So when you call somebody ambidextrous, you're

not saying that they're good with using both hands, you're telling them that they have

two right hands. And if someone is unable to use either hand,

they're called ambisinister, because in Latin "sinister" means "left."

But why do we have to have a dominant hand in the first place?

Why can't we all just be awesome with both hands?

Well the fault lies in the brain. Now, brain wants to be efficient, so it divvies

up tasks to specific regions and it tends to avoid sending too much information between

both hemispheres, because doing so would require using the corpus callosum, which would take

more time and energy. Now, the way the brain works is kind of funny.

The left side of the brain controls the right side of the body and the right side of the

brain controls the left side of the body. So it makes sense that the hand you're best

doing precise stuff with would correlate to the hemisphere of the brain that does the

most precise processing. In 95% of right-handed people it's the left

hemisphere that deals with precise language thinking, like definitions.

But when you're left-handed, there's about a 40% chance that you're using the right hemisphere

or both. And this is where things get interesting.

Now being left-handed or ambidextrous does not mean that your brain works in one way

or the other. But it may help explain why across averages

ambidextrous people sometimes score lower on IQ tests, or why a greater proportion of

schizophrenics are left-handed or ambidextrous than the rest of the population.

Now that said, there are giant benefits to having a brain like that.

By sending information back and forth, more novel connections are made, more creative

ideas are made. Albert Einstein was left-handed.

And 5 of the last 7 US presidents have been left-handed.

There's something else left-handed people have an advantage with - keyboards.

On a QWERTY keyboard, thousands and thousands of English words can be typed using the left

hand. But on the right side of the keyboard you

can only write maybe about a 100 or so. On the left side of a keyboard the left hand

all on its own can type pretty long somewhat common words, like stewardesses, reverberated

and desegregated. But on the right-hand side the longest common

word you can type is "lollipop." Oh look, a spacebar.

When people go to space, they have left Earth. The first person to leave Earth into space

was Yuri Gagarin, a Soviet cosmonaut. But the one I'm interested in was the fourth

man into space, Gherman Titov. He may have only been the fourth person into

space, but he was the first person to have left Earth and simultaneously left wakefulness.

Titov was the first person to sleep in space. And here's what's really fun.

He was 25 years old when he did it, which means that to this day Titov is the youngest

human who has ever been to space. You know what else leaves Earth?

Helium. That's right.

Helium gas that we use in balloons is lighter than air and so molecules of helium rise all

the way to the very tip top of our atmosphere, where they get picked off by solar wind, meaning

that they leave us forever. In fact, there's a little bit of a concern

over how much helium we have left, because the only way helium comes into existence on

Earth is through radioactive decay. Alpha particles are essentially helium nuclei

and we find a lot of helium inside natural gas.

But right now we're using a lot of it and helium is quite cheap, so there's a realistic

concern that within the next 30 or 40 years we may have no helium left.

Thanks for watching.