Eli5: Why does splitting an atom cause such a giant explosion?

458 views

Where does all the energy come from?

In: 10

7 Answers

Anonymous 0 Comments

E=mc^2. Fission converts a bit of mass to energy. Though the mass is small, the c^2 factor is huuuuuge. Also, in a fission bomb, you are splitting many many atoms.

Anonymous 0 Comments

Splitting a *lot* of atoms releases a lot of energy.

Just like burning one molecule of gasoline does nothing, splitting one atom of uranium does nothing.

Burning a gallon of gasoline releases a lot of energy. Splitting thirty pounds of uranium will destroy a town.

The energy comes from forces within the nucleus. One force holds it together, while another tried to push it apart. By splitting it, we allow that repulsive force to violently fling the nucleus apart, and release a ton of energy.

Anonymous 0 Comments

Splitting *an* atom does not release all that much energy. It’s just enough to produce a visible flash (which is already a huge amount of energy for an atom).

But there are a *lot* of atoms in even a small piece of material, and a nuclear bomb causes a significant percentage of *all* of those atoms to split within a fraction of a second.

Anonymous 0 Comments

When atoms were born they were all the same, hydrogen atoms, one proton, one electron… that’s it.

But they had gravity and they grouped together forming stars. A star is when all this atoms group in a gigantic ball, but the ball gets too big, the pressure inside compress the hydrogen and they fuse together. This makes a lot of energy. This energy heats all the star and a billion year fusion reaction starts. Inside, it’s a gigantic mess. Atoms love to get bigger, but not too big. They keep fusing one into another forming bigger and bigger boring atoms like iron. But some atoms by chance are fused with other ones too much and that makes big angry atoms like uranium, a very big atom with too many protons and neutrons inside. Protons and neutrons don’t like to be pressed together in so little space and they want to separate, but they don’t have enough force, just a little too weak to divide.

Then the star explodes and shoots all this atoms around the space.

Some days later, actually not days, billions of billions of day, this atoms are again together because of gravity, and form a planet. A planet with water. And this planet makes animals and some are intelligent and at a certain point a scientist figures out that atoms love to get big but not too big. And had the idea to take the very big atoms and give them a chance to separate into smaller ones.

When they separate they release part of the gigantic energy that was shot into them when they were made.

Idk why atoms would love to be iron (they like to fuse together to make it or split to make it) most will never be iron, but they want to. But anyway it’s a fact, I just don’t know why.

Anonymous 0 Comments

It turns out that an atoms don’t split quite evenly. In a nuclear reactor, a uranium atom decays into a thorium atom and a helium atom (roughly speaking). Uranium has mass 235.0439299, thorium has mass 231.03630, and the helium atom has mass 4.001506466. If you add all those up, though, you’ll notice that about 0.0061 mass is missing. What happened to it?

Atoms have very specific mass amounts, so we can’t just tack the extra onto one of the two new atoms. Instead, the leftover mass gets directly converted to energy according to the famous e=mc^(2) equation. Since the c^(2) factor is massive (roundabouts 18 zeros if you’re using meters per second), even the tiny amount of mass converted adds up *extremely* quickly. It adds up even faster when you consider that you aren’t just doing this to one atom, you’re doing it to a whole bomb or reactor core’s worth at a time and atoms are REALLY tiny (add another 20+ zeros)

Disclaimer: I got the exact numbers from a quick google search, so they might not be entirely accurate, but the process is.

Anonymous 0 Comments

The nucleus is made out of particles called protons. These little things have something called charge which lets them push and pull on other things with charge, similar to magnets. Now the push protons put on each other gets stupidly big when they get really close in the nucleus. It takes an equally stupid amount of energy to keep them together. It’s not very much on our scale but for their size, it enormous.

Imagine holding the north pole of two magnets close together. The closer they get the stronger you have to work to keep them together. Now try to hold 92 of them together. This would be an analogy for a single uranium atom.

When this atom “splits” its like you’re letting go of the magnets. All that energy you were using gets released. If you do this with 1 kilogram of uranium metal, it does this a quadrillion more times. That’s a lot of energy getting released. If it’s done fast, that’s a nuclear bomb. If you can let it leak out, that’s nuclear power.

Anonymous 0 Comments

There’s a lot going on inside an atom, lots of stuff moving around. Normally it’s fine and doesn’t bother anything else, as all the energy is contained inside it. But you poke it the right way and it causes that energy to release.

Imagine you’ve got a powerful box fan. While it’s spinning you can move it around and set it on stuff in your house without destroying anything because it’s contained, just like an atom. It’s stable.

But if you poke it with a steel rod — an action that doesn’t take much energy for you to do — a fan blade is going to shear off and maybe go flying through its enclosure and hitting something with much more force than your little poke. You made it explode!

Keep in mind this is only a loose analogy — you’re not actually just shearing off the orbiting electrons or something. Since this is ELI5 I’m not going to go into specifically what’s happening, but the key point is that splitting an atom isn’t like splitting a log. You’re destabilizing a very energetic system.

If you want to know more, pbs spacetime at least one great video on it:

and if the idea that mass is just confined energy is a bit confusing for you, here’s a second video that includes the most intuitive example I’ve seen: a system of massless components that overall actually has mass: https://youtu.be/gSKzgpt4HBU

(edit: I know the potential energy bound up inside atoms isn’t best described as “stuff moving around” but I’m trying to avoid having to explain that so I’ve stuck to this loose analogy)