How many hours are there in a day to the 8th decimal point?

Question

It isn't 24 exactly....it is supposed to be close to 24. Thanks for all the help

Answer 1

This question cannot be answered to the degree of accuracy that you desire, and I'll tell you why:

It will help if I start with UT. This stands for 'universal time' and is more or less equivalent to what is colloquially referred to as GMT. These days, really precise measurements of UT are kept with atomic clocks, which can keep really, really accurate time. Atomic clocks are currently set to allow 86400 seconds per day. 24 hours EXACTLY.

Now, there's another version of UT called UT1. UT1 refers to the time as measured by the EARTH, instead of an atomic clock. It didn't take too much use of atomic clocks to discover that these two measures of time do differ. But the interesting thing about the difference is that it's not just in one direction or another... the Earth is constantly both speeding up and slowing down in its rotation!

The reasons for this a manifold. Rotation is affected by the moon, magma flows, the weather, and even human activity to some extent. But because it is useful to keep UT and UT1 near each other, adjustments have to constantly be made.

You can see the variances if you look at a version of the corrections called DUT1. UT is usually only adjusted in full second increments, but DUT1 is listed in tenths of seconds. Here's a list of some of the most recent ones:

2006-09-28 +0.1 s
2006-04-27 +0.2 s
2006-01-01 +0.3 s
2005-03-17 -0.6 s
2004-04-29 -0.5 s
2003-04-03 -0.4 s
2002-10-24 -0.3 s
2002-02-14 -0.2 s
2001-10-04 -0.1 s
2001-03-01 +0.0 s
2000-10-19 +0.1 s

As you can see, in the past six years the Earth has both sped up and slowed down in its rotation.

Another interesting wrinkle shows up in the adjustments that are made to UT. Even though the DUT1 reports show both increases and decreases, since UT is only changed to correspond to UT1 when there's a full second of difference, changes only normally have to be made every few years. But as it turns out, if one waits long enough for an accumulation in this way, one only ever has to change UT in ONE DIRECTION. Thus, although the Earth speeds up and slows down all the time, overall it is always slowing down.

And this is what we expect. Measurements from the geologic record suggest that the day was hours shorter if you go millions of years back, and it likely will be hours longer millions of years from now. Since June 30th 1972, there have been 23 leap seconds.

A little calculation translates that into 0.67 seconds per year, or 0.0018533441 seconds per day. So ON AVERAGE every day is that much longer than the one before (to eight decimal places). But as you can see, the specifics actually vary quite widely.

Answer 2

by definition : 24.0000 0000 ....
the day (sunrise until next sunrise) is divided into 24 parts, one such part is called an hour

u have been thinking toooo much.

Answer 3

If you're talking about mean solar hours & mean solar days, it's exactly 24.00000000

If you're talking mean solar hours and sidereal days, it's 23.93489708

Answer 4

not 24? or 23.59 somewhat