Wednesday, February 29, 2012

Leap Years, Leap Seconds

Leap years are curious occasions. They occur every four years. Well, almost.

There are some four year stretches when a leap year is not observed. A century is not a leap year unless it is divisible by 400. That's why the year 2000 was a leap year and why 2100 is not.

This little factoid got me reading further and that's when I found the "leap second:" an adjustment to time made to coordinate atomic time with the earth's rotation. Atomic time is based on periods/oscillations of the Cesium-133 atom at the ground state (if you want to know more about that, it's easy to look up). The earth is very gradually slowing down (to find out why, that can also be looked up). To keep the clock and the earth in sync, there's the leap second.

Let's say you what to capitalize on a topic of current interest and reinforce information fluency with students. You could have them search for NEXT LEAP SECOND. These happen more often than leap years. And there's another one coming up later this year.

But if you look at the returns from this search in Google, you may see two conflicting reports:

About Leap Seconds › Time Zones
Next leap second on 2012-06-30 23:59:60 UTC. The last leap second was inserted like this, in the UTC time scale, and corresponding times elsewhere in the ...

When will the next leap second occur? - Yahoo! Answers › ... › Science & MathematicsAstronomy & Space
3 answers - Feb 2, 2010
Top answer: None are currently in the works. Since leap seconds depend on factors that can only be observed, not predicted, leap seconds themselves cannot be ...

Obviously, these answers don't agree. If searchers don't pay attention to the date information, they could be misled.  It's a good opportunity to point out the importance of paying attention to the published date of information.

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