 Nuclear weapons have been in the news lately, thanks to a few interesting developments. This is probably what you think of when someone says the word nuclear. But despite that huge result, the actual process occurs on a much, much smaller scale. When atoms bond in chemical reactions, various processes occur. But no new atoms are created or destroyed. But when atomic nuclei, the core of an atom, and where atoms get the vast majority of their mass, get close enough to almost touch, very different processes and reactions occur. Two of the processes that can occur are nuclear fission and nuclear fusion. In used coverage, they're often used interchangeably, but they're fundamentally different. In fusion, two nuclei collide to form a single nucleus. The nucleus is often formed with a lot of energy, which it sheds by emitting particles. In fission, the nucleus will split into two, and sometimes more, pieces of various sizes. In the process, it will often release even more particles. In the first nuclear weapons, neutrons bombarded specific isotopes of uranium or plutonium cause fission, which released even more neutrons, which in turn caused more fission and so on and so on, producing an uncontrolled chain reaction. This process is what was used in Little Boy and Fat Man. The two fission bombs dropped on Japan at the end of World War II. The energy produced in fission in more controlled chain reactions of specific isotopes of uranium is what's used in nuclear power. Why uranium and plutonium? Well, when very heavy nuclear fission, yes, it's a verb, large amounts of energy are released. Uranium is the heaviest element that exists in large quantities on Earth in terms of atomic mass, the number of protons and neutrons at its core. And plutonium is an even heavy element that was first artificially created and isolated in 1940 and which only exists in trace quantities on Earth. Fat Man, the bomb dropped on Nagasaki, used just 6.2 kilograms of plutonium and it was only 20% efficient. But what about so-called hydrogen bombs or thermonuclear weapons? Well, while fission bombs are based on the energy released by heavy nuclei coming apart, thermonuclear bombs are based around the huge amounts of energy released when the lightest nuclei fuse into one. Fusion powers the sun and it's the same process that fuels thermonuclear weapons and it's what we aim to harness for power in the next stage of our pursuit of nuclear energy as it will be much cleaner. But it's a much more difficult reaction for us to sustain here on Earth. A thermonuclear weapon is a two or more stage process. The fission process that occurs in a standard nuclear weapon is used to push light nuclear together until fusion occurs. This is much more complex than a fission weapon. There's understandably a lot of secrecy around the technical details of this process and what technology is required to make the process small enough to fit on a missile that's capable of carrying it to a target. And that's part of the reason why there's increasing concern as North Korea apparently gets closer to doing just that.