A thought experiment is a way of challenging what you think you know and understand by eliminating all of the extraneous stuff. For instance, we already talked about astronauts floating in empty space. But i cannot do that experiment in reality. I can have astronauts floating near the earth, but they're going to see the earth. That confuses this argument i'm trying to make. Here's a beautiful thought experiment that m is due to einstein, that he called the happiest thought of his life. He imagined gravity as your falling freely in the space time around. To him, gravity was no weight at all. Was no aid at all. It's weight, not headless into how heavy is