Here is my 100% guaranteed proof for entropy:
There is no such thing as a true "black box", it doesn't exist. You can try as hard as you want, every single object or container will have a radiation signature, if only a small one.
This means that any closed system will always be emitting radiation.
Which means that radiation must always be spreading out through the universe, getting ever more diffuse. Since energy is conserved, and this is always happening no matter what, it means that entropy always increases
