Final answer:
The Earth rotates on its axis every 24 hours, and time zones are based on this rotation with each zone covering 15 degrees of longitude to correspond with the Earth's 360-degree turn. A sidereal day is around 4 minutes shorter than a solar day, but we use the 24-hour solar day for practical timekeeping.
Step-by-step explanation:
The Earth rotates on its axis once every 24 hours, which is a period commonly referred to as a day. During this rotation, half of the Earth is exposed to the sun while the other half experiences night. This rotation results in the familiar cycle of day and night. As the Earth rotates, it does so at a rate of 15 degrees per hour, completing a full 360 degrees in 24 hours.
Time zones were created to reflect this rotation, with the world divided into 24 time zones, each covering 15 degrees of longitude. This ensures that the sun is approximately overhead at noon in each time zone. However, due to the Earth's elliptical orbit around the sun and the tilt of its axis, there is a small variation in solar time known as the equation of time. The sidereal day, which is the true rotation period of the Earth with respect to the stars, is about 4 minutes shorter than the solar day of 24 hours. Nevertheless, for practical purposes, we use the 24-hour solar day to define time zones and keep time.