Päikesepäevarustuse

Päikesepäevarustuse, also known as the solar day, refers to the time it takes for the Sun to appear in the same position in the sky on two consecutive days. This is the basis for our common understanding of a day. While a sidereal day, which is the time it takes for the Earth to complete one rotation relative to distant stars, is approximately 23 hours and 56 minutes, the solar day is slightly longer, averaging around 24 hours. This difference is due to Earth's orbit around the Sun. As the Earth rotates, it also moves along its orbital path. Consequently, the Earth has to rotate a little more than 360 degrees to bring the Sun back to the same apparent position in the sky.

The length of a solar day is not perfectly constant throughout the year. This variation is caused by two main factors: the eccentricity of Earth's orbit (its orbit is not a perfect circle) and the axial tilt of Earth's rotation. These factors lead to the equation of time, which describes the difference between apparent solar time and mean solar time. Apparent solar time is based on the actual position of the Sun in the sky, while mean solar time is based on a hypothetical average Sun that moves at a constant rate. The difference between these two can be up to about 16 minutes. However, for practical purposes and everyday life, the average solar day of 24 hours is used as the standard.