Question

If the earth contracts suddenly, how will the length of day be affected

Answer 1

It depends on whether or not Earth’s mass shrinks with its radius. Let’s assume that the mass stays the same, so that the Earth just compresses as its radius shrinks. We’ll also make the simplifying assumption that Earth is a sphere of uniform density.

So planet Earth would rotate about four times in 24 hours, reducing our day length to six hours.