Question

On the Earth, there are hours of sunlight and hours of darkness.
a) What do we call a time frame consisting of one such cycle.

Answer 1

Explanation:

While you don't feel it, Earth is spinning. Once every 24 hours Earth turns — or rotates on its axis — taking all of us with it. When we are on the side of Earth that is facing the Sun, we have daylight. As Earth continues its spin, we are moved to the side facing away from our Sun, and we have nighttime. If we were looking down on Earth from above the north pole, we could see that Earth rotates counterclockwise, and we would watch daylight and darkness sweeping across our globe from east to west.

Day and Night

Do other planets have day and night?

Yes! All the planets in our solar system spin on their axes (so does our Sun!) and so they have day and night cycles. There are differences, however, in the length of day and night — the cycles are made even more complex by the tilt of a planet's axis and its rate of orbit. Some planets rotate faster than Earth and some rotate slower. Mars has a day and night cycle similar to Earth. Mars rotates on its axis once every 24.6 hours. Venus turns once on its axis every 243 Earth days (which is only slightly longer than it takes for Venus to go around the Sun!). Mercury's day and night cycle is more complex. Mercury rotates one-and-a-half times during each orbit around the Sun. Because of this, Mercury's day — from sunrise to sunrise — is 176 Earth days long. The larger planets spin much faster. Jupiter rotates once every 10 hours, Saturn spins once every 11 hours, and Neptune completes a rotation in 16 hours. Pluto, at the farthest reaches of our solar system, spins on its axis once every 6.4 days.

Something to ponder: Does Pluto even have a “day” and “night” like we think of on Earth? Pluto is so distant from the center of our solar system that our Sun would look like a very bright star in its sky!