Big bang is also just an reverse-extrapolation from the fact that the universe is expanding. The universe expanding is also just another guess based on the fac

Big bang is also just an reverse-extrapolation from the fact that the universe is expanding. The universe expanding is also just another guess based on the fact that the light is red. We also have all these weird guesses with dark matter and energy. It all sounds flimsy... But to be fair this is probably the most difficult subject to tackle. We are not due for a physic reckoning yet. We will need to probably wait for another 100 year (like a reckoning when we are convinced that Newtonian is inaccurate). I think the reckoning will come when our technology is advanced enough to perform physic experiments on other planets, and we will see that some of our theories (especially around gravity) are wrong. Right now we just assume gravity on Jupiter, for example, work in the same way like gravity on earth. Another aspect is that our technology may be good enough to measure smaller particles or detect a very weak gravity force in particles.