Answer:
Step-by-step explanation:
Do you mean the theory that space-time is defined by what's in it? And that mass warps space-time?
There are many instances where his observation turned out to be correct. The most popular one is the phenomena of gravitational lensing. We can see the light from stars that are actually behind the sun. The huge gravity of the sun bends space-time and this also bends light. We use gravitational lensing alllll the time when trying to see very distant stars or galaxies.