I love amazing ideas. I recently encountered another amazing idea, one that may be an old story to some people, but it’s new to me, and I think it’s wonderful.

One of the many radioactive isotopes found naturally on Earth is an isotope of potassium called potassium 40. It decays into argon 40 with a half life of something over a billion years.

Now, potassium 40 is formed inside stars, and supernovas make lots and lots of it very quickly. Potassium 40 is very rare on Earth today, but that’s because so much of it has decayed. In the past it was much more common, which means that potassium incorporated into living things would have been much more radioactive in the past. A little radioactivity in your body isn’t such a big deal (you’ve got some now), but a lot of it could be a big problem.

One of the greatest mysteries of life on Earth is that it seems to have begun almost as soon as it could have, but remained only single-celled and simple for a very, very long time. The simplest conclusion to draw from these two facts is that the origin of life isn’t that difficult or unlikely, but the origin of complex life is much, much harder.

But what if potassium 40 has a role in this story? What if complex life couldn’t get going because every time a bunch of cells got together, the radioactivity of natural potassium was too much to handle?

If that were the case, it would put a sort of stellar stopwatch on the development of life. Life would have to wait some fairly set amount of time after the formation of a planet to get complex – that time depending on how recently the cloud from which the planet formed was seeded by a supernova.

It would also be yet another demonstration of the fact that the properties of radioactive decay are the same today as they were billions of years ago. Wonderful!

Take a look at more details here.

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