Where Does The Sun Get Its Energy?

It's another beautiful day in Sydney. I'm out enjoying the sun and looking to find out if anyone knows why the sun shines? So the sun gives us a lot of... ?

• Heat?
• Sunshine?
• Provides energy? (yes)
• Heat energy.

Where does the sun get that energy from?

• I have no idea.
• Some kind of chemical reaction...

Mmmmmmmm...

• Yeah, gas explosions.

Does it burn gas?

• It burns gases?
• It's burning air.
• Fire.

The fire that's on the sun. But is the sun really a giant ball of fire? I mean, wouldn't it go out after five billion years? This is one of the things that you just assume you know, but you don't actually know.

So in this bucket I have the components of the sun. Well, I have protons and neutrons. There's some electrons, but I didn't bring them. Most of the sun is actually protons.

• OK.

So what do the protons do in the sun?

• They dance together.

Yeah. Okay, okay. Like this. When they come close, you know what they do?

• They just...

• Collide.

Actually, they bounce off each other.

• I'm coming in...

• UOOOOOOH.

Why do the protons bounce off each other?

• Something about the electrons...

• Positive and negative electrons?

'Cause they don't like each other.

• They don't like each other.

That's because a proton needs a neutron, right? You know why they... they repel like that?

• Magnetic force?

The repelling magnetic type thing?

• Magnetic field, uh?

• Electric field. Positives and negatives.

Positive and negative. It's to do with the positive negative, right? We got protons. Protons are?

• Positive

• They're positively charged.

• Yeah, so the positives repel each other, okay?

This is why it's so important that the sun's hot. 'Cause if the sun is hot enough, it gets these things moving so fast that sometimes they can't avoid a collision.

• Ok.

And when they get too close, they actually go

• Pshh Pshh Pshh Pshh

• Smash the protons.

• Positive?

• Yeah, yeah, yeah, yeah.

• No, no, no, sma... ahhh, and now they're stuck together and you saw what happened when they smashed together.

What happened?

• They leaked.

• They leaked.

Pshh Is that energy?

• Yeah.

• Sick!

Well, the water poured out, but I guess energy would have poured out then.

• The energy came out.

• The energy came out! What was the energy before it was energy?

• Kinetic energy?

• Stored energy.

So what's happening there?

• It's releasing some mass... like lighting?

• Yeah, yeah. And that mass is, uh?

• It's converted as energy, yeah.

It was the mass of the proton.

• (Ahhh!)

When the protons smashed together, they got lighter!

• Yeah, yeah, yeah.

And they lost that mass, and the mass was converted to energy.

• Yeah, yeah.

You know the famous equation about that?

• (E = mc^2)

• Yeah! E = mc^2?

????? (French) have your the famous equation

• which? process proton makes energy?

Well.. Ha ha ha ha.

• E = mc^2 squared? Yes?

So what's E?

• The sun, I don't know, ha ha ha.

• E, E is energy, um, m is mass. C is..

• Cassidy Kelvin?

I don't remember what C means...

So C is...

• The speed of light.

• Speed of light?

No, right? Really?

• Yeah.

• Oh, I thought it was something different.

• Isn't that weird? The speed of light.

(Right, Ahh) (Wow, no wonder we jumped science).

It seems most people have a tough time remembering that C is for the speed of light. Maybe that's because C is a bit of a strange letter to represent a speed. In fact, in Einstein's original paper, he used the letter V for velocity of light, but nowadays everyone uses the letter C for constant.

It's a constant of the universe: the speed of light. Though some people claim the letter C stands for celeritas, the Latin word for swiftness.

What is that equation telling us about energy and mass?

• Energy equals constant mass?

The mass and the energy... combine together, create the energy.

Ha ha ha ha, it's basically saying like this mass that comes out

• yeah

gets converted to a lot of energy.

And the speed of light is a huge number.

• Yeah.

If you think about that, a tiny bit of mass is a huge amount of energy. So every second the sun is actually losing 4.3 billion kilograms.

• Every second?

• That amount of mass is being converted into

• energy.

In the sun, hydrogen fuses together to form helium. But that's a little confusing, because how out of only protons do we create a helium nucleus which has two protons and two neutrons?

Well, the thing is when the first two smash together, one of the protons actually emits a positron and a neutrino and quickly becomes a neutron.

Next thing that happens is another proton smashes in Pshh and again we get more energy released.

Now if two particles like this collide Pshh, they emit two protons and what we're left with is a helium 4 nucleus.

There you have hydrogen fused into helium and a lot of mass lost, a lot of energy.

Hehehe. If you wanna know more about fusion in the sun, check out this video by MinutePhysics. It explains how the protons can fuse even though they're not really going fast enough to overcome their repulsion (...for fusion will fuse together anyway).

(And the sun is so big it has so much hydrogen that these small chances happen all the time.)