Hm. If I had to give an answer, I’d say it’s the stuff that’s conserved because the laws of physics don’t change over time. But that’s pretty theoretical—maybe an extensional definition would be better.
Hm. If I had to give an answer, I’d say it’s the stuff that’s conserved because the laws of physics don’t change over time. But that’s pretty theoretical—maybe an extensional definition would be better.