What is the orbital period of each of the planets? How is the orbital period found?
Mercury 88.8 days Venus 224.7 days.Earth 365.24 days.Mars 687.0 days.Jupiter 4332 days.Saturn 10760 days Uranus 30700 days
Neptune 60200 days.
Observing their position on a star map and wait till they return to that position again. and counting days elapsed..