Does it have a sense to ask what is Spacetime made of? Because we know: Spacetime can be bent, which results in gravity and gravitational lensing effects etc. If it was made of "nothing" it could'be bent, right? Spacetime "flows" into a black hole and at the event horizon the speed of its flow is faster than c. Again, to speak about flow of "nothing" wouldn't make sense. So Spacetime is clearly "something" it has an objective and observable existence and it's probably meaningful to ask what it is made of. Do we have any clue or this question doesn't make sense?