Where does the sun go at night?
The earth is a sphere that revolves around the sun, along with the seven other planets of the solar system. One revolution of the earth around the sun takes one calendar year.

While it is going around the sun, the earth also spins on its own axis. Each ‘spin’ takes 24 hours, that is, a day and a night.
Whichever part of the earth is facing the sun has day. At the same time, the other half of the earth (the part turned away from the sun) has night. Then the earth slowly spins around and the half that was in darkness (that is, the half that was turned away from the sun) now faces the sun. So this half has day, and the other half, which turned away from the sun has night. So, in reality, the sun does not really go anywhere at night!

Try this experiment!
To understand how the earth’s rotation causes day and night, try this simple exercise.

You need:
A small rubber ball
A big torch Some felt pens
A friend

What to do:
Imagine that the rubber ball is the earth. Using the felt pens, draw the map of the world on the rubber ball. Now, imagine that the torch is the sun. Ask your friend to switch on the torch.

Place the ball (the earth) directly in the path of the torch beam (sunlight), so that India is facing the sun. Turn the ball around slowly. What do you see? When India is facing the sun, the Americas are in darkness.

As India begins to turn away from the sun, Europe and Africa come into the ‘sunlight’. Then, as the ‘earth’ continues to turn, the Americas come into the light and India becomes dark.

Keep turning the ball till India faces the sun again. This is what happens every time the earth turns around on its axis. During each rotation, India (and every other place on earth) has one day and one night.