Last week we talked about fusion, where atoms come together to form heavier elements. This week, everything comes apart as we talk about nuclear fission. How it occurs naturally in the Universe, and how it has been harnessed by science to produce power, and devastating weapons.

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. We’ll also look into the controversy of cold fusion.

Now we’re going to answer a question that a 4-year old might ask – what is temperature? Why are things hot and why are they cold? How hot or cold can they get? And how is this all important for astronomy?