The original question title was too long, so i changed it. My question is: Does the detection of gravitational waves prove the existence of space time? The question may sound odd. I had an argument with one of my friends, who says space time is only a mathematical concept, space does not exist, there is only matter. He quotes [Mentors' note: link to crackpot site removed] this site, this is the page of some dissident Hungarian scientist, Janos Rohan. He says that gravitation is a pushing force, not pulling, and writes crazy stuff about gravitons mostly, saying Einstein and Hawking (and everyone else in the world) is wrong, there is no singularity, space cannot bend, etc.. I am in no way a physics expert ( nor is he), but i am a huge fan of physics, and space. As far as i know the recent discovery LIGO made proves the theory of realtivity , so i think it proves the esxistence of space time too. Does it? Can you give me any explanation with which i can prove the existence of space time (or simply space) to my friend? Thank you for your help, and sorry for my english, i hope everything i said makes sense and understandable.