Every few years without any regular schedule or planning,

officials at the International Earth Rotation and Reference System Service

will add an extra second to the year.

The reason why this is done makes some sense,

but adding an extra second to a year can cause

a host of problems and many are wondering if it's a practice that should be continued.

Learn more about leap seconds, why they exist, when they happen and if they should continue to exist on this

episode of Everything one second.

One second, which may or may not be tacked on to a year.

One second over the course of a year may not seem like much,

and in a human frame of reference it really isn't a big deal.

If it weren't for the fact that occasional leap seconds were publicly announced, nobody would ever

even know that they occurred. Before I get into why leap seconds exist, it's important to know just what a second is and

how it's defined, because it's the key to understanding everything I'll be discussing.

I've done several episodes on the subject of time. I've talked about why the calendar is the way it is, how the months were named and the order they're in, and why there are seven days in a week.

However, the fundamental unit of time is not a year, month, week, or day.

It's the second.

Defining a unit of time is much more tricky than defining a physical unit.

When the meter and kilogram were defined, they were defined based on an actual physical object which sat in the vault in Paris.

There was a literal piece of metal, and that piece of metal was by definition one meter, and the was true with a metallic weight which was the definition of a kilogram

You can't really do that with a second a second is a unit of time so short that the ancient really didn't have any use for it.

There was no way to track time with such precision, and there were no uses for a unit of time so small.

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