Iron-56, the most common isotope of iron, is what all material in the universe “wants” to be. That is, the nuclei of matter is all gradually exhausting its energy, and iron-56 is the form of matter with the lowest energy per nucleon. Eventually, stars will turn into iron—huge balls of iron. Everything will be iron. The good news is that this won’t happen for 10^1500 years, a period of time so long that we can’t really grasp it. That’s a quingentillion years away. For comparison, there are probably no more than 10^81 atoms in the entire universe, so 10^1500 is just a mind-bogglingly long amount of time. The universe right now is just over 10^10 years old, so you can see that it’s really just a mewling infant at this point. →