Climate change is slowing Earth’s rotation

This irritant was scotched in 1967 with the definition of a new second, derived from the vibrations of caesium atoms inside uber-precise atomic clocks. The two seconds are almost exactly equivalent. But not quite. The leap year 1972, for example, should have had 31,622,400 seconds. Reckoned by atomic seconds, however, Earth’s full journey around the sun took 31,622,401.14. As a result, two additional seconds were added: the very first “leap seconds”. One, on June 30th that year, made up for the lag; the second anticipated an impending additional one. It was added to the year’s very last minute.