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Astronomy Cast, episode 205 from Monday, November 1, 2010. Nuclear Fusion.

Welcome to Astronomy Cast, our weekly facts-based journey through the cosmos, where we help you understand not only what we know, but how we know what we know.

My name is Fraser Cain, I'm the publisher of University, and with me is Dr. Pamela Gay, a professor at Southern Illinois University, Epsville.

Hi Pamela, how are you doing?

I'm doing well, how are you doing Fraser?

Good, good, we got the big Halloween chocolate bomb around here, so our kids are in these kind of sugar comas walking around.

I love that point in the evening when you have sugar-high children and foot sore parents who just want it to be done.

Yeah, I didn't think my daughter could do this, but she sprinted to every house, it was unbelievable.

Hey, so when the universe formed after the big bang all we had was hydrogen, but through the process of fusion these hydrogen atoms were crushed into heavier and heavier elements.

Fusion gives us warmth and light from the sun, destruction with fusion bombs, and might be a source of inexpensive energy.

And then there's that whole controversy of cold fusion.

Right Pamela, well let's go right back to the beginning then and get right to the heart of it.

So when we say nuclear fusion, what are we talking about?

We're talking about anytime you take two atoms and you smoosh them together and get one atom unusually by products and hopefully energy, but not always.

Now when you say smoosh, that's obviously a technical term, but what's actually going on?

I literally, I don't know how else you describe it, then smooshing scientifically you say you take two particles and you collide them together at high enough velocities to overcome the repulsive forces in the centers of the nuclei.

So you could fire two atoms at each other and if they hit perfectly they would fuse.

If they had sufficient energy to overcome the desire to repulse each other.

Right, right. So there's some speed, some amount of energy that you would impart to these atoms, they would smash into each other and they would fuse.

But then when we think about say the inside of a star, we talk about tremendous gravitational energy smooshing.

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