wikipedia.org photo
We just passed in 2014 and started in 2015. In this year, the Earth has 365 recorded the same day by the year 2014. However, true in 2015 and every year on earth has a 'bonus' of more than 365 days, which is 5 hours and 48 minutes 45.1814 seconds or nearly one per four days. How can?
Benchmark the number of days in a year on earth guided by our position in the solar system. Given all the planets, including the earth revolves around the sun (evolved), then one round of each planet signifies a year on that planet.
It makes Jupiter are located farther from the sun than Earth has a longer track revolution so that the number of days in a year in Jupiter can reach 12 years on earth.
So, how on earth can have a revolution like the current trajectory?
It all began when the universe was first formed billions of years ago, when the particles that exist in the universe to merge and collide, so was born the stars, one of which is the sun.
After that, the energy and the force of gravity which issued the sun helps the rest of the other space dust around it turned into planets and other celestial bodies. Circular motion of the sun that generates the planets or the new satellite spin and form a solar system.
Then, each planet was finally has its own gravitational force that make it together and form a revolution trajectory or orbit that does not intersect with other planets.
On earth the case is somewhat different, the formation of the current path can not be separated from the role of a dwarf planet named 'Theia'. According to the study, Theia known to hit the earth about 4.4 billion years ago. As a result, not only the earth's orbit has changed, lacing Theia make the earth at the speed (rotation and revolution) that is maintained until now.
Finally, with speed lacing Theia's results, one rotation of the earth around the sun 365.25 days commencing be the same as 2015's.
The rest of one per four-day or 5 hours 48 minutes 45.1814 seconds that is collected in the fourth year, known as leap year, where one year is equal to 366 days. This new leap year we will feel in 2016 later.
So, when we ask why 2015 has only 365.25 days, the answer is not because provision is made by humans, but the mechanism of the universe.
(From various sources)
