How do we know that 60 seconds is one minute,and there are 24 hours in a day.?
The second is currently defined as the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom. A day is defined as the rotation of the earth on its axis. By defining an hour as 60 minutes, and a minute as 60 seconds, a day can be calculated to be approx. 24 hours. The year is actually A.D. 2007 (or you can consult a Jewish calendar). Before A.D. 1, there was 1 B.C. or B.C.E. (whichever you prefer). The cavemen didn’t call it that, of course, because they didn’t know when Christ (or the Christian Era, or the Common Era, still depending on your preference) would come around. They probably kept track of time by the seasons.
Theres 365 days 5 hours 48 minutes and 46 seconds it takes the earth to do one revolution around the sun. Every 4 years a day is added to the calendar to adjust for the 5hrs 48minutes46sec. but every 128 years an adjustment is made by adding 1 day because of the 11 min.14sec offset which is about 1 day over a hundred years. This correction was made in 1582 by pope Gregory. The calendar is off only by a day, but for practical purposes its good enough. Nobody knows who made the first clock. 3500 b.c. sundials have been found in Egypt a simple stick in the ground for measuring time, then the hour glass, and the water clock all attribute to the ultimate clock we use now. Cavemen can simply look at a full moon and position of the star constellation giving the position of the earth in relation to the sun to know when the season were to change for purposes of farming and storing food. Astronomy I’m sure was the first real calendar and that theory was refined into a more accurate measure of ti
