system
Given the following post, respond as if you're commenting on Reddit:
human
How come supernovae produce heavy elements, but the big bang didn't?

It makes some intuitive sense to me that lighter elements (helium through iron, I believe) are synthesized in stars, but the heavier elements require a more energetic environment, namely a supernova.  Why is it that the most energetic event ever only produced hydrogen and deuterium?
gpt
Because it wasn't an explosion. It wasn't a force pressing atoms already in existence into each other causing them to fuse to higher mass nuclei. The early big bang is too hot to even form protons and neutrons, let alone nuclei to speak of. Then, as it cools, it can form the early protons and neutrons, but they are too "hot" to bind, then it cools a bit more and if they bind at all in this phase, they bind mostly into helium and a little lithium, and maybe a scant amount of beryllium if memory serves. But then it cools too much for them to keep binding into larger structures. That ends up requiring gravity and time, to pull them together into stars and for stars to put on a gravitational force to push them together again.