How did scientists determine that there are 365 1/4 days in a year?

Question

please be specific

Answer 1

The ancients did this. You can use Stonehenge to do it, for example.

Every day, note the direction of sunrise. It's always more or less east, but sometimes it's a little north of east, sometimes it's a little south of east. Note the days when sunrise is furthest north or furthest south. These sunrises will be 365 days apart.

To get the one-fourth, you have to observe over several years. After four years, an extra day will have slipped in to the cycle. You can get a better and better measure by observing for longer and longer.

Today, we get the length of a year by measuring the positions of stars using a technique called radio interferometry. Details here: http://ftp.nofs.navy.mil/projects/npoi/

Answer 2

You would determine our year by noting the positiion of our planet with respect to other stars. Every day the stars move with respect to the sun by 24 * 60 / 365 = 4 minutes. So you could observe the stars position overhead at exactly midnight and note when they were in that position again ( 365+ days later)

Answer 3

Actually, 365.242199 is more accurate.

It's how long the Earth takes to go once around the Sun.
The Earth going around in its orbit makes the Sun appear to move against the background of stars (actually, it's the background of quasars that are used to define a non-rotating reference system). When the Sun gets back to the same place compared to the background stars, one year has past.

Answer 4

Because that is the estimated time it takes the earth to revolve compleletly once around the sun. Also a day was determined by the earth rotating on its axis one full time around. So a year is determined by it traveling around the sun one complete time and a day is determined by it spin one full time on its axis.

Answer 5

By measuring thelength of time for the stars to return to the same positions in the sky after a year.

Answer 6

wasn't determined by scientists.... people in ancient times had this sophisticated knowledge, like the Mayans and other ancient civilizations. it has to do with the earth's path & rotation relative to the sun (astronomy+math).

Answer 7

In ancient time a year was the number of days counted from season cycles.
Today the actual time in a year year is measured relative to the precession of the poles.

Answer 8

The ancients did it by observing celestial cycles that coincided with the seasons.