Measurement of length of year?

Question

In the 4th century AD in the Roman world, the length of the year was thought to be 365 days, 5 hours, 55 minutes, and 25.4 seconds (in modern units). The modern estimate for the vernal equinox year back then is 365d 5h 48m, 45.9s. How did the ancient philosopher / scientists figure the year with an error of less than 9 minutes?

Or in other words, how did they measure durations of over 365 days, to an accuracy of better than 9 minutes?

( = 8765+ hours)

Answer 1

It is actually fairly simple to measure the exact length of a year. Simply watch as a bright star passes the meridian (passes from the Eastern sky to the Western sky). You can do this by setting up two stationary points of reference and just watching until the star disappears behind one. You only need to measure the time from the last sunset to that meridian crossing so clocks more accurate than a few seconds a day are not necessary.

The star Sirius (the brightest star in the sky) was used for this purpose and it is why our year starts on January 1st.

What caused all kinds of problems was that this meridian crossing drifted over time due to procession and the fact that our year is not exactly divisible by our days. Over hundreds of years the calendar drifts to where unless you have leap years and add an extra day in every 4 years winter will eventually fall in June.

Answer 2

Hi. They would watch a star passing the meridian. The hard part of the question is how did they measure time to that accuracy.

Answer 3

Its all in the stars. Even the ancients could measure pretty accurately the position of stars. When you see the same thing in the same place at the same timeof day, its been a year.

Answer 4

Or whole calender is messed up thanx to a whole bunch of stupid people whose things we cannot change because we have used them for so long. I don't trust them.