On Tue, 2 Jan 2007, Rob Seaman wrote: > Daniel R. Tobias replies to Poul-Henning Kamp: > > >> Has anybody calculated how much energy is required to change > >> the Earths rotation fast enough to make this rule relevant ? > > > > Superman could do it. Or perhaps he could nudge the Earth's rotation > > just enough to make the length of a mean solar day exactly equal > > 86,400 SI seconds. > > Only briefly. Consider the LOD plots from http://www.ucolick.org/ > ~sla/leapsecs/dutc.html. The Earth wobbles like a top, varying its > speed even if tidal slowing is ignored. > > Actually, rather than being merely a troublemaker, the Moon serves to > stabilize the Earth's orientation. The "Rare Earth Hypothesis" makes > a strong case that a large Moon and other unlikely processes such as > continental drift are required for multicellular life to evolve, in > addition to the more familiar issues of a high system "metal" content > and a stable planetary orbit at a distance permitting liquid water. > Without the Moon, the Earth could nod through large angles, lying on > its side or perhaps even rotating retrograde every few million > years. Try making sense of timekeeping under such circumstances. > > Rob Seaman > NOAO
Hang on a minute, statistically planets in the Solar System do not have a large moon and yet are "upright"; for example Mars comes very close to the conditions required to generate a leapseconds email exploder. Pete.
