What is “space time” and how does it “bend”?

Question

I’ve heard the term “space time” thrown around, and that gravity “bends space-time” but how does that work?

In: 16

Answer 1

Spacetime is a 4D geometric construct on which general relativity is performed. This object bends and curves and twists in such a way that we can predict how things in the Real World behave. How it bends it dependent on the [Stress Energy Tensor](https://en.m.wikipedia.org/wiki/Stress–energy_tensor) which accounts for mass (mostly mass), pressure, velocity, etc.

Whether it actually bends depends on your model. For instance in theories of quantum gravity (note that such a theory does not *currently* exist in a complete form but it is assumed that this is the next big step in quantum physics) **gravity is not described as a bending of spacetime** however the actual effects would be the same.