I watched the Chernobyl miniseries recently and read up about some of the specifics a bit. A lot of it is still beyond my comprehension, but I ran into the picture below (i hope you can see it):
It says (among other things) that sleeping next to someone increases your absorbed dose of radiation, and also that eating a banana increases your absorbed dose. From what I understand so far, many things (I assume mostly organic things) are a bit radioactive. Is this true and if so, why?
In: Physics
In this context, radioactivity refers basically to the debris being released when an atom breaks apart. You are correct: basically, an atom of every kind of chemical element *will* break apart eventually, and when it does, it will release radiation. The closer you are to literally anything — including another person — the more times you’ll be hit by that radiation. In the case of bananas, they will contain very trace amounts of atoms more prone to breaking down, like potassium-40.
**However** the amount of radiation released by these background naturally occurring objects is pretty much always miniscule compared to what could be released in something like the Chernobyl accident. This is where the “half-life” concept that gets referenced frequently in Chernobyl comes in. We can roughly gauge how dangerous something could be by how long its half-life is, meaning, how long it will take for this natural breakdown process – called decay — to destroy half of a sample of something. The half-life of the potassium-40 that’s giving you that radiation dose from a banana is about a billion years. At that point, the amount of radiation being emitted from a banana is so miniscule that it’s never going to hurt you in the course of a human lifetime, even if you could somehow carry it around in your pocket for your whole life.
In contrast some chemicals produced and released in the course of something like the Chernobyl accident are very radioactive and have short half-lives. For instance, iodine-131 has a half-life of only a week, which means that if you had a banana-sized sample of *that* in your pocket, it would be releasing quite a lot of radiation.
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