It's the average length of the "apparent solar day" throughout the year, 24 hours exactly for planet Earth.
The time based on the average length of a day throughout a year is called Mean Solar Time. This time standard is used in civil timekeeping to account for variations in the length of a solar day due to the Earth's elliptical orbit and axial tilt.
We don't. The sidereal day IS used as the measure of the Earth's rotation. The mean solar day is used to regulate our daily lives because that's the average time for the Sun to complete its apparent daily journey round the sky. The difference is because the solar day takes into account the effect of the Earth's orbital motion which slightly alters the position of the Sun in the sky.
A day on Earth (referred to as a solar day) is about 24 hours long, while a day on Mars (referred to as a sol) is about 24 hours and 39 minutes long. This means that a day on Mars is slightly longer than a day on Earth.
An apparent solar day is the time it takes for the Earth to complete one full rotation based on the position of the sun in the sky. It can vary slightly each day due to the Earth's elliptical orbit and axial tilt. This is different from a mean solar day, which is a consistent 24-hour period averaged over a year.
Usually the solar day is the longest. The other two are very similar in length to each other. For example, the solar day on Earth is about 4 minutes longer than the other two "days". However, for the planet Venus the solar day is the shortest. That's because Venus has retrograde rotation.
The Earth "day" of exactly 24 hours is the "mean solar day""Mean" is basically a scientific way of saying "average". It's called a "solar day " because it's based on the position of the Sun in the sky.There are natural variations in the length of the solar day because of the Earth's elliptical orbit and axial tilt.The "mean solar day" averages out the variations that happen during the year.This makes things much more convenient for everyday life."Mean solar time" is based on the "mean solar day".The "apparent solar day" is the what we actually observe, and its length varies from day to day.A sundial measures "apparent solar time". We can convert this time to mean solar time by using something called "the equation of time".Actually, the sundial shows "local apparent solar time".That's because the time shown by a sundial depends on its exact longitude.For convenience, mean solar time has time zones (based on longitude).So, longitude also affects the relationship between these twomeasures of time.
The time based on the average length of a day throughout a year is called Mean Solar Time. This time standard is used in civil timekeeping to account for variations in the length of a solar day due to the Earth's elliptical orbit and axial tilt.
The mean solar day is 86 400 seconds (SI). The period of revolution is 365,242 199 mean solar days.
24 Hours In A Sunday (Solar day)
a solar day
Mean solar time
Because, when using "apparent solar time", the length of a "solar day" varies slightly during the year. (This is because the Earth's orbit isn't exactly circular and the Earth's axis is tilted.) "Clock time" is based on an average (or "mean") of these day lengths, called the "mean solar day". So clocks use "mean solar time". (By coincidence, on the date the question was answered (14th April) "apparent solar time" and 'clock' time are synchronised.) There's another reason for apparent solar time being different from clock time. "Clock time" uses time zones. So, over a wide area, the time on a clock equals the "mean solar time" at a particular, defining, longitude.
"Mean" simply means "average". Some days - for example, calculating from one noon to the next - are slightly longer, and some are slightly shorter, than the average. For the true solar day, "noon" would be defined as the moment when the Sun passes the Meridian (its highest point in the sky).
The average length of the day is usually just called "day".
Mean solar time
Because, when using "apparent solar time", the length of a "solar day" varies slightly during the year. (This is because the Earth's orbit isn't exactly circular and the Earth's axis is tilted.) "Clock time" is based on an average (or "mean") of these day lengths, called the "mean solar day". So clocks use "mean solar time". (By coincidence, on the date the question was answered (14th April) "apparent solar time" and 'clock' time are synchronised.) There's another reason for apparent solar time being different from clock time. "Clock time" uses time zones. So, over a wide area, the time on a clock equals the "mean solar time" at a particular, defining, longitude.
There are 86400 seconds in a solar day.