 Nuclear energy and nuclear technology are extremely important in today's society. Around 10% of the world's electricity is generated from nuclear power plants. And despite increases in renewable energy over the last decade, nuclear power is going to play a continued role for a long time yet. And that's because nuclear power is a form of power technology that doesn't actually produce carbon dioxide. Nuclear technology is also important in other areas. A particular example is nuclear medicine. Many of you over the course of your lifetime are likely to have a nuclear medical procedure. You may have an x-ray or a CAT scan or a technetium scan to diagnose some problem. Or it may be that you are unlucky, you get cancer and you need radiation treatment to try and kill the cancer. Another thing you may not know is that nuclear power is responsible for life on earth as we know it. The heat from the sun is generated from nuclear fusion reactions. Another thing you may not know is that all of the things that the earth is made of, all of the elements, the atoms, the molecules were all created in thermonuclear explosions in stars billions of years ago. We are actually made of the ashes of thermonuclear explosions that happened all that time ago. If you stop and think about that, it's actually pretty freaky. What I hope to do in this series of videos is tell you some of the physics of nuclear radiation. To do that, we need to go back and we need to understand first the structure of the atom and in particular the structure of the heart of the atom, the atomic nucleus. The question we are interested in is what are atoms and nuclei actually made of? It was actually back in the 5th century BC that the Greek philosophers came up with the idea of atoms. The word atomos is the Greek word for indivisible. And they theorized that if you broke matter down into smaller and smaller pieces you'd eventually reach a point where you couldn't break it down any further and they called this thing an atom. This was the state of play for nearly 2500 years until the French scientist Henry Becquerel discovered in 1896 the phenomenon of radioactivity. Becquerel made his discovery by accident. He was investigating fluorescence with photographic plates and one day he wrapped up a photographic plate in black paper and stored it in a drawer and inside the drawer he had some uranium salts. When he exposed the photographic plate he saw an image despite the fact that it had been protected by the black paper. News of Becquerel's discovery spread quickly through Europe and it was another famous French scientist Marie Curie who showed that the intensity of these uranium rays depended proportionally on the amount of uranium that was present. This observation implies that the uranium is actually emitting some type of particle and if the uranium atoms are emitting some type of particle then atoms must be made up of even smaller objects. After these initial discoveries the scientific community in Europe quickly started work on trying to identify what this radiation was. It didn't take long before they realized that there were three different types of radiation and they called them alpha, beta and gamma radiation after the three first letters in the Greek alphabet.