Day lengthened. The process of watching and individual scientists, and a specially created organization – the International Earth Rotation Service iers (Paris). Fixing and reacting to it from time to time disposed to extend day – more often for a second. Since 1972, these additives and the corresponding "translation arrow" was over 20. Which tends to work, though not soon, but it comes up that extra second will not be saved, and will have to redo the dial. Why the Earth is gradually stop? Some suggest that the blame for the moon – inhibits its gravity. Others blame everything on the atmosphere, the third – ocean currents.
Someone is a giant planet rotor motor and assures that it is affected by cosmic radiation. Someone accuses people – say, building a reservoir and thus create on the surface of "goods" that prevent rotation. English astronomer Richard Stephenson of the University of Durham was able to determine the length of the day as much in 2700 bc – they were really short. Compared with the current – just a fraction of a second. But over the past century, as they say, ran up: time of sunrise shifted about 7 hours. For as many would have had to move the arrow, if iers began to work back then.
It is learned that about 530 million years ago Earth rotated quickly that it was in days of 21 hours, a year – 420 days. A billion years days ago gave way to generally at breakneck speed – lasted only 15 hours. Sediments showed: in the history of the planet was at least two periods when it dramatically increases their speed. And gradually lengthened day suddenly shortened hours for two or three. This has happened 400 and 200 million years ago.