What is Space-time?

Nothing is not Nothing

We cannot see space-time. We can only deduce what it is and how it works through indirect means. We have not successfully done that yet. Newton had a picture that space was in Cartesian co-ordinates of 3D space with time flowing, and things happening within that framework. This is most people’s common sense picture of the world. We have very hard time, concepually, going beyond this picture.

Figure 1, Newton’s fixed space vs. Einstein’s flexible spacetime, from the film “Testing Einstein’s Universe” by Norbert Bartel.