Are you a truly nerdy, geeky person who cares about such technological or physics details? If so, consider the many wrinkles in how time seems to flow, all introduced by the very technology designed to measure it: Wrinkle one: Satellites travel at 8,700 miles per hour, slowing their clocks. Wrinkle two: They’re distant from Earth in a reduced gravitational field, which accelerates their time relative to Earth’s surface. Wrinkle three: GPS users on the Earth’s surface are located at various distances from Earth’s center (at Denver’s high altitude versus low-altitude Miami, say), producing a
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