system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do atoms of a same radioactive element decay at different times?

For example uranium-238 has a half-life of 4.468 billion years, which means that one uranium-238 atom decays in a day and another one in one billion years.

Why do atoms of a same element have so vastly different "lifespans"?
gpt
Radiodecay is random.

Picture it like this:

The atom is rolling a random handful of dice once a second.  When all of them come up sixes, the atom blows up.

This may happen on the very first roll, or it may take all day.

Atoms with very short half lives are unstable - they’re barely held together and you only need one “six” to make them explode.

Atoms with very long half lives are extremely stable - you need a whole trash bag full of sixes all at once to blast it apart.

Uranium is very stable so it usually takes billions of years to finally get cosmically lucky and shatter the nucleus with a random quantum shudder that hits *just* right.