This variation in orbital speed means that the Sun's apparent motion across the sky is not perfectly uniform throughout the year. The rotation defines the physical spin, while the orbit dictates the changing orientation of that spin relative to the Sun.
How Earth's Rotation Speed Affects the Length of a Day
These two movements occur at slightly different rates and in relation to different reference points, creating the variations we observe. According to Kepler's laws, a planet moves faster in its orbit when it is closer to the Sun (perihelion) and slower when it is farther away (aphelion).
Solar Day The sidereal day is the time it takes for Earth to complete one full 360-degree rotation relative to the distant stars. 0916 Distant Stars Solar Day (Average) 86,400 Mean Sun Solar Day (Maximum Variation) 86,400 ± 20 Apparent Sun.
How Earth's Rotation Speed Affects the Length of a Day
Consequently, the length of a solar day can vary by up to 20 seconds depending on the time of year. A solar day, the standard 24-hour day, averages 24 hours or 86,400 seconds.
More About What is the length of a day
Looking at What is the length of a day from another angle can help expand the discussion and give readers a second clear paragraph under the same section.
More perspective on What is the length of a day can make the topic easier to follow by connecting earlier points with a few simple takeaways.
