On Mon, Jan 18, 2010 at 8:22 PM, Captain Joy <[email protected]> wrote:
> The retention of water by dams and >> reservoirs at higher latitudes away from the equator has already had a >> measurable impact on the spin of the earth for decades >> > > "measurable impact"? Source, please. > - He's not making this up. The three Gorges dam (the huge new one in China) is responsible for increasing the day by about 0.06 microseconds, and shifting the poles (the axis of rotation, really) a centimeter or two. It's okay, though. The increase in day length was more than made up for by the 2004 earthquake that caused the big tsunami. That shortened the day by 2.68 microseconds. (NASA published a paper about this; it was widely reported at the time. I may have the numbers slight wrong, but I've got their magnitudes right.) Yes, these are measurable effects: instruments are very good. Do they matter? Not a whole lot... (Related: one of the things that complicates models of sea level change from climate change is that as ice melts, the shape of the geoid changes, and changes the location of mean sea level. The east coast of the US is likely to see much larger rises than "average" numbers reported because of this, for instance.) -- David Scheidt [email protected] _______________________________________________ GurpsNet-L mailing list <[email protected]> http://mail.sjgames.com/mailman/listinfo/gurpsnet-l
