system
Given the following post, respond as if you're commenting on Reddit:
human
How do we know the laws of physics don't change over time?

So much of what we know about the universe is based on our understanding of the laws of physics as we know them today. For example, the age of the universe and the rate of expansion are measured using this current understanding and application of the known laws since we cannot actually go back in time to do the measuring. Is it possible that throughout time, especially during periods of chaos like moments after the big bang, the equations and limits we know to be true and verifiable today could potentially be invalid? If so, what are some of the major implications, and how could we go about mitigating them?
gpt
As far back as we are able to acquire data, the same laws of physics appear to hold.

When we look at distant galaxies and stars, we are looking at objects from long ago.  And we measure their spectra, for example, which tell us that the atoms and molecules a long time ago behave the same way as those on Earth do today.  These spectra depend on the mass and charge of the electron, the nuclear physics that allows atomic nuclei to form, the nature of the electric force, and so on.

We can also look at the abundance of nuclei today, and we see the universe is about 3/4 hydrogen and 1/4 helium, and a tiny bit everything else.  Then you take the laws we know, and you see nuclei would form in the first minutes after the Big Bang (5 to 20 minutes), and you calculate the amounts that would form, and you find that the nuclei formed would be 3/4 hydrogen and 1/4 helium.

Looking at things like supernovas or the cosmic microwave background radiation give us additional insights into the past.

Thus, there is concrete evidence that the laws of physics we see today here on Earth have applied throughout the history of the universe, as far back as we have been able to check.