CodexArcanum , 6 months ago

We kind of don’t?

One of the basic axioms (that is, assumptions) of cosmology and physics is that the rules are the same everywhere. We see a big ball of burning gas in the center of our system. We have observations of other bright lights that appear to also be balls of hot gas. Our continued observations fit with predictions we can make, predictions based on our observations and codification of the rules of physics and chemistry and so on. We assume that all these big balls of gas operate on the same principles.

There’s also a general assumption that the rules don’t change over time. That axiom doesn’t fit with what we can observe about the earliest universe, so there are many theories on why physics seemed to work differently in the very first moments of the universe. Likewise, other observations that don’t quite fit those assumptions have led to ideas like dark energy and various theories of quantum gravity.

If those assumptions were extremely wrong, say the universe outside our solar bubble actually obeys totally different laws, and our observations have been misinterpreted, then we’d have no way to know. We need some observation that contradicts our previous observations in order to formulate new theories on why. It’s similar to a simulation argument: maybe god aliens or time beings or super AI or Satan have engineered a fake universe to trick us, but without some true observation that grounds our theories in the repeatable, it’s pointless to speculate because almost anything could be true. We have to build theories on what is repeatedly observed.