Hubble Telescope Image

If you are reading this in a post-apocolyptic world, it is because the moment this was posted, 3:59:59, Alaska Time, there was a leap second. Air traffic controll towers and stock market computers could be influenced by the loss of this second, so lock your doors and lie low for a while.

Why do these leap seconds exist and how often do they happen?

There are multiple ways to measure time and one of them is the earth’s rotation around the sun. That varies year by year so it’s hard to measure, but overall the earth’s rotation is slowing. It’s mostly due to the the influence of the moon’s gravity creating tidal friction. This slowing of the earth’s rotation has lead to 25 leap seconds added intermittently since 1972.

So what? Without leap seconds we’d have a 25 hour day in roughly 140 million years. Eventually it is possible the earth could slow so much that the moon and the earth would be locked into each other’s gravity and a day on earth would be equal to the time it takes the moon to rotate the earth, about 47 days. Yet given the current pace of the slowdown, it’s more likely that the sun’s evolution into a red giant will cause the oceans to evaporate (2.1 billion and eventually would finish off earth (4.5 billion years).

I bring this up on a blog about immortality because it’s a reminder of the perspective people take when they know they’ll be around a while. Writing science fiction also makes you aware of those things. And if we do ever become immortal, we’d better perfect space travel.

Source:

Could the Earth’s Rotation Really Slow Down Like It Does in the New Novel The Age of Miracles?

http://www.slate.com/blogs/future_tense

/2012/06/26/age_of_miracles_by_karen_thompson_walker_could_the_earth_s_rotation_really_slow_down_.html