Why does Earth have day and night? Do all planets have the same?
Earth’s spin causes night and day. It makes a complete revolution in 24 hours (a solar day). Imagine spinning a top in a darkened room. Shine a flashlight at the whirling top. A tiny bug crawling on the gyrating top experiences day and night as he passes into and out of the light — much like we do on rotating Earth. All the planets in our solar system spin and therefore have night and day but the length of day varies greatly. Venus rotates through a “day”, with respect to the Sun (not the stars), in 117 Earth solar days. A day on Mars is about the same as ours (24 hours and 40 minutes). Giant Jupiter whips through its day in only 9 hours and 57 minutes. The giant planets (Jupiter, Saturn, Uranus, and Neptune) contain most of the angular momentum of our solar system (even more than the Sun) and therefore spin faster than the inner planets. The Sun rotates slowly, only once monthly. The Sun, Moon, and the planets formed from a huge spinning gas cloud that collapsed into a gyrating disk.
