Question

why is one day and one night on the earth of 24 hours

Answer 1

hey mate
This is because the earth take 24 hour to complete it's one rotation.And it take 365 days to complete it's one revolution around the sun, that's why there are 365 days in a year.

Answer 2

Because the earth rotates on its axis and completes one rotation in 24 hours.
When the earth rotates its half part gets sunlight and half part does not the part which gets light experience day and the part which doesn't get experience night.