system
Given the following post, respond as if you're commenting on Reddit:
human
How do we know that the laws of physics are constant?
gpt
Almost every physical law has breakdown points. Two common ones are inside black holes and during/before the big bang. 

A lot of things we know because we can look out in the universe and we can apply our earth-laws to anything we want out there and we can still accurately predict what's happening.

A law is just a relationship that can be used to make predictions. As long as we keep testing predictions and we're spot on - then the law is constant.