Spectroscopy of star light has given us repeatable data on star composition.
By noticing that some stars that have the same composition but with a shifted spectrum, a Mr Hubble came to the conclusion that... The universe is moving apart.
Repeatable.
The theory of the big bang predicts a background radiation that permeates the cosmos. That was observed and can be observed at any time.
I often wonder how flat earthers explain the earth's magnetic field, the origin of lava, and daytime in Europe, while it's night time in China.
By noticing that some stars that have the same composition but with a shifted spectrum, a Mr Hubble came to the conclusion that... The universe is moving apart.
Repeatable.
The theory of the big bang predicts a background radiation that permeates the cosmos. That was observed and can be observed at any time.
I often wonder how flat earthers explain the earth's magnetic field, the origin of lava, and daytime in Europe, while it's night time in China.