Since naturally occurring uranium (U-238) has a half life of 4.5 billion years, then it means half of the uranium on earth has decayed into lead by now. But why only half, and why that specific half? What was special about the particles that did decay? Were they different in some way?
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Imagine you have a big bag of popcorn kernels. Every minute, each kernel has a tiny chance to pop. After a certain time, let’s say an hour, you notice that about half the kernels have popped. That’s similar to the “half-life” of radioactive materials.
Now, for the uranium:
Predictable but Random: Even though the popcorn pops at a predictable rate (half in an hour), you can’t tell which specific kernels will pop first. It’s the same with radioactive atoms; we know half will decay after a certain time, but we can’t say which ones.
Nothing Special About Them: There’s nothing different about the popcorn kernels that popped first. Similarly, the uranium atoms that decayed weren’t special or different.
Always a Chance: Even after an hour, the remaining popcorn kernels can still pop. In the same way, the remaining uranium atoms will keep decaying, but it’ll take another 4.5 billion years for half of those to turn into lead.
So, it’s all about probability. Like rolling dice or flipping a coin, but on a much bigger and longer scale!
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