burn out in just a few millennia? So how is it still here after 4.5 billion years? Physics.

The sun is like a big nuclear submarine… in the sky. That's right - it's fueled by

nuclear reactions that fuse hydrogen atoms together into helium and other heavier elements,

releasing huge amounts of energy in the process. In this way the sun is slowly converting its

mass into energy – in the form of sunlight! And it has more than enough fuel to last billions

of years.

But nuclear fusion's no walk in the park - on earth we need to heat hydrogen up 100x hotter

than the sun to get a fusion reaction. So how does the sun do it? Quantum tunneling.

There's a small chance (which I'll explain later) that hydrogen atoms, even if they aren't

quite hot enough for fusion, will fuse together anyway. And the sun is SO big and has so much

hydrogen that these small chances happen all the time, and that's what keeps the sun energized!

So when the sun shines tomorrow, give thanks to quantum mechanics.