Planetary Science

What event causes day and night?

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February 21, 2014 3:23PM

the planet spinning on it's axis
The sun and the gravity pull from the sun cuases the earth to spin at a pole though so as the earth spins around the sun it also spins on its axis to cause day and night
the earth rotates on its axis as it moves around the sun. The side facing the sun is lit up by the sun (day). The side facing away from the sun is not being lit up by the sun (night).
It is called "a day", which may be confusing because of the two different meanings

  • time between sunrise and sunset,
  • the 24-hour cycle

It may also be called a "circadian cycle".

The cycle is caused by the rotation of the Earth on its axis.

The Earth is a ball floating in space and orbiting the Sun our local star. This star gives off allot of light and the side (hemisphere) of the Earth facing the star is illuminated by it. This hemisphere is said to be in day light. The other hemisphere (facing away from the Sun) is in shadow and this hemisphere is said to be in darkness.

However, the ball that is the Earth is rotating on its own axis and this means that if you are standing on the day-lit side of the Earth, you are carried round to the dark side and then back into the day lit side. This rotation therefore causes the cycle of day and night.

In broad terms, the entire day-night cycle is referred to as a day. One day contains a daytime segment and a night time segment almost everywhere.

However, because the axis of rotation of the Earth is tipped over some 23.5 degrees relative to the plane in which it goes round the Sun, the Arctic and Antarctic regions are illuminated for 6 months at a time and are then in darkness for 6 months. Here a day lasts 1/2 a year.

Words related to the 24 hour period are: diurnal and circadian. The day as we experience it is directly related to what is called the synodic rotation of the earth-- its rotation relative to the position of the sun in the sky. This idea sounds simple, but it is a tricky concept to grasp fully.
Earth's rotation causes day and night.
The rotation of the Earth causes the Sun to pass out of view, then back into it, at regualr intervals.
We get day and night because the Earth is rotating on it's axis and because it won't stop rotating we will keep getting day,night, day, night,etc.