MTBGuru is a new site that enables bikers, hikers and runners to upload GPS info, along with photos and comments, from their routes that get mashed up with Google Maps to create an ever-expanding trail resource. Mostly Bay Area now but that is changing.
posted by fenriq
on Nov 29, 2006 -
Does relativity have any practical significance? In fact, relativity had to be taken into account by the designers of the Global Positioning System. The GPS satellites are affected both by special relativity (since the satellites are moving, clocks aboard them appear to run slower as seen from the ground), and by general relativity (since the satellites are farther away from the mass of the earth, clocks appear to run faster as seen from the ground). The net effect of both is that clocks aboard GPS satellites would gain 38 microseconds per day relative to the ground, if relativistic effects were not corrected for--a figure which can be confirmed by using Google calculator.
posted by DevilsAdvocate
on Nov 30, 2004 -