It's approximations based on measured observations all the way down. Keep in mind, we cannot explain what matter and energy are. We measure and work in terms o

It's approximations based on measured observations all the way down. Keep in mind, we cannot explain what matter and energy are. We measure and work in terms of waves. What is "waving?" We literally do not know. The thing is NOT the wave. Period. But everywhere we look we detect that literally everything is vibrating/oscillating/waving. Each improved microscope/observation/meaurement reveals space and some type of vibration. However, we rely on the observed, measured properties to do things. Generate (harness) and use electricity and perform (encourage) chemical transitions and combinations, for instance. We have a significant well of practical knowledge. But the nature of existence and the grand cosmological scheme? Probably not going to crack that. It's very fun to try and you learn practical things along the way, though.