My mom wanted to understand what fusion was all about in layman's terms. Why not try to think of ways to save the world on Yom Kippur. Fusion is one of the better answers that I have heard. I probably failed but tried to explain it and may have gotten the science wrong since I was doing it from memory so correct me where I am wrong. She was interested in the project called ITER Tokemac.

This is what I sent her.

I'm not sure which part of the chemistry is confusing to you but the basics are this.

Atoms are these stable states of matter, which is probably just bundled-up energy. The stable states are finite, not continuous. So think of them like a staircase with big steps. You can be on stair one or two but not in between because you would fall to the stair below.

So we have a periodic table of atoms. In there we get Hydrogen, Oxygen, Carbon, .... Etc. Each of these atoms has different properties based on things like mass, electrons, protons, neutrons, etc. such that we have the world we live in where Carbon is useful because it can make 4 bonds (a stable state is when you have 8 bound electrons and carbon atoms have 4). All of this is very nice but just something to understand as a backdrop of the stuff we are dealing with.

These atoms have to come from somewhere. The atoms can be created by combining atoms or splitting them up. So atoms are created by taking the stuff (protons, neutrons, electrons, energy) that makes up two hydrogen atoms and make a helium atom (fusion) or by splitting a big heavy atom like Uranium (fission).

But a helium atom isn't exactly two hydrogen atoms combined into one ball of stuff. The system together has a different overall stability and mass that are connected. Stability is like when you are on a stair at the top vs. the bottom. There is a difference at the top - you can fall down the stairs. At the bottom you already fell down and it will take work to get back up to the top. In general things in the universe become more stable and are always falling down the stairs. This trend should be obvious when you mix food coloring with water. It is a lot easier to turn the water green then to suck the food coloring back out into a spoon leaving the water clear again. The same thing is at work. The state that is more stable sticks around after the system is bounced about through states that aren't so likely.

Before we look at nuclear energy you can quickly understand chemical energy. The difference is that chemical energy, burning oil, is not about combining or splitting atoms, but instead about combining or splitting molecules. When you take a molecule like a hydrocarbon and burn it you are rearranging the bonds between atoms. If you have an one bond swapped for another bond then there has been a real change in the sytem because one is stronger or weaker, more stable or less stable, than the other. To break a bond then make a new one therefore either generates a net surplus of energy or requires energy. You can imagine in this case someone breaking down the materials from one bridge to build another one and when they take down the first bridge they use all of the materials from the first one to build the second one. So if it takes more energy to build the second bridge then you need more materials. If it takes less materials then you have extra materials. So when you make and break chemical bonds energy is released or consumed. It takes the sun's solar energy to make the bonds that ultimately created the hydrocarbons that we burn into CO2, etc. and it releases energy when we burn them. The problem is that we only have so much hydrocarbon fuel stored-up from old organic matter.

So the fun part with nuclear energy is that when you combine or split atoms you get a similar effect. But the size of the effect is actually much larger, not smaller because the combination of atoms to form a stable state can either reduce or increase their mass. If you reduce the mass to reach the stable state then you release the lost mass as energy (since mass and energy are basically the same stuff). This energy is released as heat(atoms moving faster) and radiation(energy particles that travel at the speed of light),. The heat is very useful because it can be transferred into systems we can use to generate electricity. The radiation can be an annoying side effect.

Getting atoms to fuse or split isn't as easy as making molecules burn because the amount of energy that needs to be put into the system is much higher before the reaction occurs. In general the image for activation energy needs to be considered to understand this. Basically if you were to look at an activation energy chart for any chemical reaction it looks like a hill with a trough on either side at different heights. So if I am looking relative to sea level and I am currently at 100 ft. and the hill is at 500 ft. but the sea is on the other side of the hill. I can't get to the sea to go swimming without first climbing the hill. If I am riding a bicycle with no brakes it will take me work to get to the top. If I don't put enough work in to get to the top of the hill, since I have no brakes, I will slide back down to where I came from. If I do get to the top of the hill and it is a very slippery hill once I am the slightest bit over the edge my bike and I will fly down to the sea. In this case since the sea is lower (and the next stable state) it took energy to get "activated" so that I could go down to the sea. The truth was that if I had an energy recovery mechanism on my bicycle since the sea is lower than the place I started I would have more energy at the bottom than I had at the top. Since I don't the energy was distributed out somehow, probably as kinetic energy when I crashed into the water at the bottom.

So the idea of an activation energy is very much at play with atoms fusing. They will be very unlikely to fuse without getting enough energy into them to do so even though once they fuse they will release a lot of energy. It's a high stakes game. Luckily for us atoms did fuse because we are made of some pretty complex ones like carbon, oxygen, nitrogen, and sulfur and use even bigger ones like magnesium all the time to work our organic chemistry magic. The way that carbon is created through fusion naturally is in a star like the sun where immense amounts of gravitational pressure cause molecules to get very close together start to heat-up and fuse. So the sun is a big reactor converting hydrogen to helium, releasing energy then converting the helium to bigger molecules up the periodic table. The spectrum of what colors a sun is depends on the fusion reactions currently at work when you see the light from it. Light is that radiation(energy particles that travel at the speed of light). Think red dwarfs, etc. So you can get a good idea of what is going on in the sun by looking at the spectrum from it since the light wavelengths coming out from each fusion reaction has a signature based on the energy that is standardly released from rolling down the mountain for hydrogen combining to form helium.

So we would like to get into this fusion game ourselves but we don't have the benefit of creating a big ball of gaseous radioactive crap in the middle of our planet like the sun does. The activation energy requirements for fusion of hydrogen are quite high by our living standards. The atoms start to fuse and release energy at a few hundred million degrees Celsius. Everything in the sun is a gas which is what happens when you heat mass up. Think tanks of liquid nitrogen. At room temperature the nitrogen just converts to a gas. At a few hundred million degrees celsius a lot of things we like to see as solids switch to liquids, think ice to water. This presents a problem if the metal we are using for our fusion reactor melts and the fusion crap goes flying all over the place at 100 million degrees celsius. Getting hit with stuff this hot could cause a slight burn with uncomfortable itching and rashes for a few days. So the idea of a tokemac was created to keep that hot stuff away from the container. The basics are to make a field that contains the hot stuff as a gas in a torus, think donut, such that the hottest stuff doesn't need to reach the outside of the container. This hottest stuff is heated and condensed by some tricks in the donut using magnetic fields because hydrogen at our temperatures is a molecule, H2, and not an atom H. with an extra electron. Hydrogen is most stable with two electrons close to it which is why it releases energy when it binds to other H. atoms to form H2. But when you heat it up and get the H2s into H.s you have charged particles with a negative charge. Things with a charge move away from things with a certain magnetic field. So if the torus has a strong field everywhere on the inside surface those H. ions will concentrate in the center (not the O) but an imaginary line within the donut circle and not bump into the walls to melt them.

You can then get to fusion and collect the extra energy using the resulting inflow of energy from the fusion to keep the reaction going and since it doesn't take much conversions of hydrogen atoms to helium to generate a ton of energy we would have abundant energy and finally put an end to this silly conflict over oil in the Middle East. Instead we can just fight about religion which is much more fun because nobody can prove anything but everyone thinks they are right. Because of this the fight over religion is a more stable system than fighting over oil.