Take a Helium atom the same atom that's in Helium balloons.

But also, different isotopes of helium and hydrogen, deuterium, and helium three.

And unfortunately, the helium atoms in liquid helium are right on top of each other.

Let's say it's a helium atom.

And that's why helium's called helium.

This is a high altitude helium balloon.

Hydrogen has one proton, helium, two protons,

Deuterium and tritium goes together makes helium 5.

Helium has 2 protons. Carbon has 6 protons.

Anyway, this is a depiction of a helium atom.

A helium atom has two protons and two neutrons.

It's that shape because the helium has to expand.

And now simple atoms appear of hydrogen and helium.

And therefore, stars must begin with that much helium, and the only place that helium can come from was from primordial nucleosynthesis.

And then this whole haze around there, those are the two electrons that helium has, or that at least this helium atom has.

The universe was about 75 percent hydrogen, 25 percent helium.

But, it turns out that they can predict formation of elements all the way up to helium, in other words, just hydrogen and helium.

The first confirmation of this is through measurement of the helium abundance.

Or at least this helium atom has two protons and two neutrons.

This is the scale of the nucleus of a helium atom, right?

In the case of helium, the nucleus is even a smaller fraction.

I said, you will only make helium, but that's not quite true.

Helium 4 does not work at all because the line is essentially flat.

After about a few minutes, there was hydrogen and helium in the universe.

In the 1950s, people were trying to figure out how superfluid helium worked.

The first one was that when helium atoms touch each other, they repel.

The zero point from which it starts is 0.24 mass fraction of helium.

Helium has one more, so that will also go into the 1s orbital.

For a moment they become helium 5, because they've got five particles inside them.

Helium splits out, and a neutron comes out and lots of energy comes out.

This image of a helium atom, they say right here this is one femtometer.

Helium 3 very rare on the surface of the Earth, very common in space.

So by measuring abundance of other elements, say oxygen, and then correlating it with abundance of helium should be a line that goes through zero if there was no primordial helium created.

The only way it worked is when the helium atoms were very, very far apart.

It consisted of huge clouds of hydrogen and helium atoms, and they have no structure.

Let's take the two electrons in the Helium atom and for the language of the day,

Those two trucks you see at the very end carry 12 tanks each of compressed helium.

Here's the balloon being filled up with helium, and you can see it's a gorgeous sight.

So where you get slightly denser areas, gravity starts compacting clouds of hydrogen and helium atoms.

In the middle of stars, you're joining hydrogen together to make helium and then helium together to make carbon, to make oxygen, all the things that you're made of are made in the middle of stars.

Feynman decided, as a sort of amateur helium physicist, that he would try to figure it out.

I used to be so into fusion, specially helium 3 fusion, mining in the mood. Oh my God!

It's not just hydrogen and helium but it contains metals and roughly at about of 1 3rd solar.

This is roughly 25 by mass and this is why there's about 25 by mass of primordial helium.

However, because there was, then the intercept on the y axis gives you the primordial abundance of helium.