28. The planet’s rotation is gradually slowing.
One day today is about 1.78 milliseconds longer than one day a century ago. This figure is because the Earth’s spin is slowing down at rates so slight that they are undetectable unless you travel back thousands of years. So that’s precisely what scientists did. They looked at ancient records of eclipses and found that one eclipse, measured by Babylonian astronomers in 780 BCE, should have happened one-quarter of the Earth away. Comparing these findings to other records, they discovered that the planet’s rotation has slowed down enough to have lost about six hours in the past 2740 years.
“But, why – now?” you may be asking. Well, let’s look into that. It’s mainly because of the tidal forces between the moon and the Earth. Approximately every century, the day gets about 1.4 milliseconds longer. That may not seem like much, but when you add up all the centuries the Earth has been through, you can see where we’ve gotten to such a big difference. In fact, June 30, 2012, got one extra second in the day as a “leap second” to provide a standard time across the world – basically to keep UTC timing (Coordinated Universal Time). It sounds fancier than it was; it just meant clocks and timekeeping apps switched off for one second.