The Earth takes a little under 24 hours to rotates on its axis. But what if that leisurely paced pick up—and up and up and up?
In this week's What If, Randall Munroe decided to answer that exact question. If the Earth rotated so fast that a day lasted a single second, things would go very wrong, very quickly—not least because the equator would be travelling at about 10 percent of the speed of light. Munroe explains what damage that would cause:
Centrifugal force would become much stronger than gravity, and the material that makes up the Earth would be flung outward... The Earth's crust and mantle would break apart into building-sized chunks. By the time a second had passed, the atmosphere would have spread out too thin to breathe—although even at the relatively stationary poles, you probably wouldn't survive long enough to asphyxiate. In the first few seconds, the expansion would shatter the crust into spinning fragments and kill just about everyone on the planet.
It does, however, get worse—at least for the rest of the Solar System—because Munroe goes on to explain how "[t]he debris from the Earth would slice outward like an expanding buzzsaw. " Eek. Go read his full explanation over on What If. [What If]