Skip to content

Leap Second Time Comes Again

2015-06-30

Add a second at midnight, because the Earth is slowing down.

Leap seconds are added at the end of the day on June 30 or December 31, depending on necessity.  The reason the occasional leap second is needed is that the earth’s rotation is slowing down.  In 1820, the length of the day was defined as 86400 seconds.  Since then, the earth’s rotation has slowed by two milliseconds a day, so, for example, the last leap second was added in 2012.  Those two milliseconds a day do add up; five hundred days and you’ve lost a whole second.

So, as expected, the earth’s rotation is slowing down, and has slowed down, since the earth was created, some four or four and a half billion years ago.  To be precise, the United States Geologic Survey says that the Earth and the solar system were created 4.54 billion years ago.

Here is an official-looking website that tells what will happen at midnight tonight.

Advertisements
No comments yet

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: