what i am mainly asking by this question is that were the laws of physics same when the universe has less entropy in the very beginning to right now when its has a lot more entropy
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According to Grand Unified Theory, in the very early universe, when everything was extremely hot, the forces (other than gravity) were all one force and weren’t distinguishable from each other. Then as things cooled down, the forces started to separate into the strong, weak, and electromagnetic forces we’re aware of today. This happened very very quickly, though, so it was only true for a ridiculously small percentage of the lifetime of the universe. I can’t really think of an ELI5 way to explain why that was the case though lol. At a high level, it’s due to certain symmetries getting spontaneously broken, but that’s already very not ELI5.
As for whether the laws of physics will stay the same when the heat death of the universe occurs, to my knowledge the answer to that based on our current theories is yes, though on cosmological scales it’s really difficult to say that our theories will hold up when we’ve only been able to observe the universe for such a brief blip of its existence.
This seems to be the case.
Light takes time to cross the vast distances of space so when you look at a galaxy 12 billion light years away you’re also seeing it as it was twelve billion years ago.
This is annoying because you can’t see what’s happening there *now*, but it also gives us an invaluable ability to see back in time to a much younger universe.
When we analyze the chemical and stellar spectrums of these ancient galaxies we do see that they’re no different than our own. The physical rules that drive their chemical and nuclear reactions is the same as our own, across the vast distance and time.
Now what *will* happen is impossible to know, but what *has* happened suggests that the laws of physics remain constant for the observable universe across time and distance.
“The laws of physics” is a bit of a vague term. There are well-established theories in physics that describe systems going through substantial changes in entropy. There are also some models that describe a system that is in a fixed-entropy state and would need to be modified to describe something else. There is no single universal theory of physics, and if there were, then surely it would have to cover everything.
There were certainly processes that went on in the early universe that don’t happen any more, and processes that happen now and didn’t in the early universe. e.g. today we get stellar nucleosynthesis, but in the early universe we got Big Bang nucleosynthesis. I suppose it’s a matter of debate whether you consider those to be different “laws” or just different things happening within the same “laws”.
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