A key plot point in the 1978 Superman film found Supes flying around the Earth so fast it reversed the spin of the planet. But how fast would he actually have to fly to make that happen?
A team of physics students from the University of Leicester did the math, and it turns out the Man of Steel would have to fly at 660 million miles per hour. He’d also need to do it for a lot longer than the 50 approximate seconds shown on screen in the film. As IGN notes, that would equate to an angular velocity of 46.296 radians per second. Put another way: He’d have to hit 98 percent the speed of light.
Of course, it’s not quite that simple. Mass would also play a role, so Superman would have to increase his mass 13.7 million times over ... which isn’t exactly one of his listed superpowers. Flying at the speed of light would help build a larger relativistic mass, which would help. But, yeah, it’s still not quite as effortless as this cinema classic made things seem.
There’s also the fact that Superman’s actions would almost certainly cause any near-Earth objects to shoot toward the planet. So he’d need to punch some asteroids to make sure he didn’t inadvertently take out a city.