What does GMT stand for?
In 1972, the world's scientists stopped using GMT, and change to a new system called UTC = Coordinated Universal Time (the order of the letters comes from the French). Every UTC second is exactly as long as an atomic second, and the days are generally a millisecond or so longer than 24 hours. After a few years, the difference adds up to close to a second, and the time lords put in a "leap second" into UTC.
We don't measure time by using the Sun at Greenwich any more. Instead, we use radio-telescopes around the world, to measure the Earth's rotation in relationship ...more