Earth, Jupiter, and Uranus all revolve around the sun. Earth takes 1 yr, Jupiter 12 yr, Saturn 30 yr, and Uranus 84 yr to make a complete revolution. One night, you look at those three distant planets and wonder how many years it will take before they have the same position again.

Question

a) How often will Jupiter and Saturn appear in the same position in the night sky as seen from Earth tonight?
b) How often will Jupiter, Saturn, and Uranus appear in the same direction in the night sky as seen from Earth?

Answer 1

660 years

Answer 2

660 years