Can you prove to me that Gravity isn't just density?

it's still not a rind

re your first question the answer I've heard is that nothing has no mass so its density is 0.

re your second no idea what they explain, all I've haerd is "ITS DENSITY THE MASS PER UNIT VOLUME IS THE REASON" but that makes no sense

can you prove that a rind is not just a thick apple skin?

proof?

Yes. If it was an apple skin it would be on an apple and not an orange

...

sounds tautological