Length of day
The length of the day is how long a day is. On Earth, it is 24 hours long. There are other planets with different types of day.
Length of the day on other planets
This uses Earth time.
Mercury - about 59 days
Venus - 243 days
Earth - 1 day
Mars - about 1 day, 0. 6 hours
Jupiter - 9 hours
Saturn - about 10 hours
Uranus - about 13 hours
Neptune - about 15 hours
Increasing day length on Earth
The Earth is constantly losing angular velocity and rotational energy through a process called tidal acceleration, which leads to a slow lengthening of the day. Tidal acceleration is an effect of the tidal forces between an orbiting natural satellite (e. g. the Moon), and the primary planet that it orbits (e. g. Earth).
A century ago, the average day was about 1. 7 milliseconds shorter than today. In the late Neoproterozoic about 620 million years ago a day had only about 21. 9+-0. 4 hours.
Related pages
Sidereal day
Rotation period
References
Days
Earth sciences