system
Given the following post, respond as if you're commenting on Reddit:
human
If all of the atoms of heavier elements were formed in supernovae, why are they found all clumped together on earth?

One might expect a fairly uniform distribution of molecules under the conditions of a supernova, so then how do all the gold atoms find each other so as to form the veins that we ultimately find in mines?  Why are there separate "copper mines" and "gold mines" and not just "mines"?
gpt
Earth was once a larger planet (Theia)  that formed from the dust cloud surrounding the new Sun. Some of this dust was heavy elements from nearby supernovae. The heavy elements sank to the middle of Theia, and lighter silicates floated to the top. Earth would be very metal-poor at the surface ... except a body the size of Mars collided with Theia, blasting off a lot of the surface material and mixing heavier metals back into the crust. The impactor and freed silicates coalesced into the moon, what was left of Theia became Earth.