Time is slowing down. Seriously. The Earth’s days are getting longer.
I learned this when I looked into why post-market stock exchange trading closed five minutes early on Tuesday, June 30. The answer derives from the fact that the Earth’s rotations are getting longer, meaning a “day” is becoming longer than precisely 24 hours. I found this thoroughly interesting, so now I’m “geeking out” and exploring this here.
As a prelude, time is kept by the real geeks of the world using atomic clocks. One second is based on radiation emitted from a cesium-133 atom (one second is actually equal to 9,192,631,770 cycles of radiation of cesium-133, and kudos to the team that calculated that).
Back to time slowing down (Earth’s rotations becoming longer in duration), it’s estimated that millions of years ago, one day was 22 hours long. Admittedly, the slowing of time now is not perceptible in day to day life. Still, the Earth’s spin and position become out of synch with the atomic clock by just a tad. A “tad” in this case equates to one second every two years or so. So we insert it back and call it a “leap second.” This extra second gets added to time to resynchronize the atomic clock with the Earth’s position. That happened at 8:00 PM EST June 30th (actually, it happened at 7:59:60 . . . the extra second inserted before clocks turned to 8:00:00).
There have now been 26 leap seconds since 1972. The leap second before this one was added back in 2012.
Two more tidbits:
First, why is the Earth’s rotation slowing down? It is largely a result of the gravitational drag caused by the moon. Some scientists also think earthquakes, volcanoes, and even really bad weather storms can influence the rate of the planet’s spin.
Second, why did the stock market stop late trading five minutes early? Computers can be fussy. They don’t necessarily understand how to “add” a second (I guess this isn’t part of Microsoft’s standard update package). The financial regulators decided to play it safe. As far as I can tell, the world made it through this leap second ok (in case you were worried).
I hope you were having fun at 8:00 PM on June 30. With this leap second, you got to enjoy that moment for an extra second.