Expert: Jayendra Upadhye - 5/9/2004

Question
I've heard that the earth's rotational period was much shorter when it was young. Has anyone estimated just how short it might have been shortly after its formation?

Answer
Hi,
Reg, frankly I dont have the facts. You could get them on the web.
However there is something interesting connected with your question you would like to know.
It is about how simple "mundane" mechanical laws actually affect the working of the cosmos on larger scales.
The earth was indeed spinning faster in earlier epochs, and the moon was also much closer then. The law of conservation of angular momentum dictated that the higher angular momentum of the earth be transferred to the moon if gravity was to serve as the "coupling bond".
Consequently, the moon has been working away ceaselessly using the ocean tides as a brake, and slowing the earth down by a known rate. (it is available on the web and so i dont remember it!). The reward for this is that the moon itself speeds up in its orbit and moves away from the earth as a result at about 4 cms per year! this is called the "current recession rate of the moon". you will find a lot of info on this on the web too. (also search for 'tidal intearctions' on google).
Jayen