What if gravity suddenly stopped working? Or what if e gradually came to equal mc3 rather than mc2? Could the fundamentals of physics really change? Or Is this just the stuff of science fiction?

Throughout human history, every time we think we know what the universe is, it turns out that there is not just one of those things, but a lot of them. First we thought the universe was Earth, a sun and a moon, and a sky with a lot of mysterious points of lights. Then there turned out to be a number of planets with their own moons. Then a lot of suns, with their own planets: a lot of solar systems.