[miramba]

Explanation needed. How can you, a primitive ape on a tiny remote planet with an average lifespan of 80 years (not meant as an insult, I am too), be sure about what happened 15, 20 or 100 BILLION years ago? I think this is what parent meant with: "people of every time thought they had (almost) complete understanding of the universe." - "Don't think it'll be different this time."

[mr_mitm]

We can literally see into the past 13 billion years ago by building space crafts that collect microwave radiation, because we aren't as primitive as you may want us to believe.

[miramba]

No, not literally…presumably. You believe that the radiation you look at is that old, because you measure certain wavelengths and study ladders, but you can‘t really prove it. Proving that something is 13 billion years old is beyond the capabilities of us apes, at least at this point.

[DrFalkyn]

We know that light has a finite speed. We've measured it.

We know that speed is independent of the relative velocities between the litter and the observer. Again, we've carried out experiments and measured that as well

[mr_mitm]

Can you really prove anything beyond your own existence? Descartes says no. Maybe all your senses are just an illusion.

[Vecr]

There's good evidence for it, inferred temperature of the early universe included. Obviously not perfect evidence, but even if you assume "tired light", it's another thing all together to come up with a new version of thermodynamics.

[miramba]

Indeed. But keyword is „inferred“, assuming that all laws worked the same at any point in a gigantic timeframe, at any point in a gigantic universe. Except singularities. And quantum mechanics as it seems? And maybe dark energy. Oh and lately, maybe gravity waves. Btw I was once in a lecture room in Berlin where they claimed that one of the thermodynamic laws where discovered…while giving a lecture. Not too long ago, perhaps 150-200 years. Doesn‘t seem so unlikely that somebody comes up with a new version at some point.