The exact time lenth of one day?

[Aki]

I think I heard somewhere that one day is actually 23 hours and 56 minutes, is that true?

[pgrmdave]

yes, sort of. 23 hours and 56 minutes is the true amount of time it takes the earth to rotate once around it's axis. It is called a sidereal day, and is measured by the motion of the stars. One solar day is a little longer, as the earth has also moved along it's orbit, making the time between when the sun transits the meridian to it's next transit closer to 24 hours, most of the time. It varies with the seasons but it is, on average, four minutes longer than sidereal time.

 

Here is a website that explains it a little better:

http://www.encyclopedia.com/html/section/time1_PhysicalTimeandItsMeasurement.asp

[Turtle]

And further the turtle said, the Earth day is lengthening as Earth steadily slows down on its axis. A day in the day of a day. :hihi:

[Aki]

If one day is 23 hr and 56 min, then how do we end up with a year being 365.25 days? Where does that 0.25 come from?

[pgrmdave]

the .25 comes from the fact that the earth's rotation and revolution are not perfectly synchronized. A year is the amount of time that it takes for the earth to complete one revolution around the sun, and is independent of it's rotation on it's axis.

[maddog]

If one day is 23 hr and 56 min, then how do we end up with a year being 365.25 days? Where does that 0.25 come from?

 

The time is the year is measured against solor days (close to 24 hrs).

 

It was the Babalonians who invented the notion time increments of Hours, Minutes and

Seconds and their interrelationship (3600, 60, 1) as well as diving a day into 24 hrs.

However, there is some indication that the Summerian civilization before had also used

these or similar increments. All were base on astronomy.

 

Maddog

[Queso]

this fact alone proves astrology is completely bs.

if the time is just rounded off at the end of the year, that would mean that the month system isn't constant, just something aproximate, lined up with the seasons.

[maddog]

this fact alone proves astrology is completely bs.

if the time is just rounded off at the end of the year, that would mean that the month system isn't constant, just something aproximate, lined up with the seasons.

 

It may very well (Astrology) be BS, for casting Horoscopes about ones fate. It may hold

some merrit about predicting personality traits (though I think it has nothing to do with the

stars). Note: Astrology as well as Astronomy use Sidereal Time as the measure of time.

Since Astronomy did originate from Astology. People were interested in looking at the

sky to better predict their futures. Many cultures had many Gods they paid homage to

all to better predict their futures. As constellation and later stars got names, little by

little the whole process got more scientific. Though it was during the middle ages when

the Arab culture who had also invented the represention of zero we use today and also

named a lot of the stars we have today, that a separate field known as Astronomy began

for its own sake. So at the very least some good has come out of Astrology. For laughs,

I even check my horoscope now and then... :) :)

 

Maddog