Question

Would the rotation of a Jupiter sized Earth be any different, both spinning and orbiting around the sun? Would we have longer or shorter days?

Answer 1

If Earth was the size of Jupiter the year would be the same length and the day would probably be shorter.

Explanation:

The orbital period `T` in years of all bodies in the solar system is directly related to the semi-major axis distance `a` is AU by Kepler's third law `T^2=a^3`. So, as long as Earth is the same distance from the sun, the year will always be the same.

Jupiter is the fastest rotating planet with a day on just 10 hours. Earth used to rotate faster but its rotation is constantly being slowed by the Moon's gravity. If the Earth was the size of Jupiter the slowing effect of the Moon would be much smaller.

If the Earth was the size of Jupiter it would have a significant effect on the other planets. Venus and Mars have orbits quite close to that of Earth, so could either become moons or even get ejected from the solar system.