The planet must not be so inclined that its poles are close to the orbital plane, or the day on most of the planet will be the same as the planet’s year. The North and South Poles of the planet Uranus point alternately toward the Sun. Since it takes Uranus 84 years to revolve around the Sun, one cycle of light and darkness there is also 84 years long. On the other hand, some orbital inclination is needed to produce seasons. The Earth’s spin axis is inclined 23 degrees from vertical relative to the Earth’s orbital plane. This makes noontime sunlight shine from high in the sky on a summer day. It shines from low near the horizon in winter. The variation in temperature this produces during the year corresponds to important cycles of renovation among plants and animals.