HOW TO WATCH FOX WEATHER ON TVNo surprise, timekeeping is fairly complicated. According to McCarthy, June 29 was the shortest day in recent history but only since the international adaptation of the atomic clock.
Even since his retirement in 2005, McCarthy remains a leading authority on timekeeping and continues to consult for the Observatory.
FILE - The US Naval Observatory Master Clock on Massachusetts Avenue and 34th Street in Washington, DC on Nov. 3, 2011. (Linda Davidson / The Washington Post via Getty Images)Time at the Naval Observatory is measured in two ways: by astronomical-universal means and atomic clocks.
McCarthy explains astronomical time has been calculated by observations of the stars and moon with the Earth's rotation. Currently, radio telescope observations of supermassive black holes known as quasars, the brightest objects in the universe, are the astronomical time-keeping standard."Those observations then indicate that the Earth is not always rotating at the same speed.