In Brian Greene's documentary The Fabric of the Cosmos, the thesis of the documentary is that empty space has physical properties even if there are no atoms or molecules in it. As I recall, most of the documentary shows the story of how NASA had a goal of sending a gyroscope up into space to see if gravity moved the gyroscope which would prove that empty space has physical properties. Most of the documentary is about the obstacles that NASA faced to send this gyroscope into space and to monitor the gyroscope. To make a long story short, NASA eventually got the money and sent the gyroscope into space, and gravity caused the gyroscope to turn slightly just as people who said that empty space has physical properties predicted. I don't really see what the point of it was, and why NASA spent so much taxpayer dollars on something that I thought was already proven. As I recollect, the NASA experiment with the gyroscope happened in 2004. Einstein published his Theory of Relativity in 1915. Didn't Einstein's Theory of General Relativity that gravity is just curves on the fabric of spacetime already prove that empty space had physical properties? I mean, hadn't Einstein's Theory of General Relativity been proven by countless falsifiable experiments long before NASA launched the gyroscope in 2004?