Still no leap seconds

[pne]

Just got a copy of Bulletin C telling me there will be no leap second at the end of June 2004.

That makes over five years now without a leap second (the bulletin said that the difference between TAI and UTC has been constant at UTC-TAI = -32s since 1999-01-01T00:00:00), which surprises me a bit; I thought that leap seconds were introduced, on average, every two or three years.

I suppose the earth has been spinning a bit more regularly since then, or something.

Comments

[nik-w.livejournal.com]

Perhaps they're saving up for a leap minute?

[lovewithnoface.livejournal.com]

leap seconds?

leap seconds

[pne.livejournal.com]

Short answer: the earth doesn't spin at a constant speed, due to several things (such as friction caused by tides), so a day isn't exactly 84600 seconds long. However, the second is defined as being exactly a certain length.

Consider a clock that runs slow; every now and then you'd want to set it to the correct time again in comparison with an accurate clock. In this case, it's the other way around: the accurate clock is adjusted since we can't really adjust the earth :)

So every now and then, a leap second is inserted or (theoretically; this hasn't been necessary yet) deleted in order to make time based on atomic clocks never be more than one second apart from the time based on the earth's rotation.

Long, technical answer: See (http://maia.usno.navy.mil/leapsec.html) various (http://tycho.usno.navy.mil/leapsec.html) places (http://maia.usno.navy.mil/eo/leapsec.html) on (http://www.boulder.nist.gov/timefreq/general/leaps.htm) the (http://en.wikipedia.org/wiki/Leap_second) web (http://www.google.com/search?q=leap+seconds). (Try the one under "the" first.)

Hmm

[whimemsz.livejournal.com]

Might it have something to do with this (http://www.usatoday.com/news/science/2004-01-01-earth-spin_x.htm)?

Re: Hmm

[pne.livejournal.com]

That does look very relevant in this context. Thanks for the link!

And I'm glad to see I'm not the only one who's wondering about the "missing" leap secons; scientists are, too!

Re: leap seconds

[lovewithnoface.livejournal.com]

Thats ok, I think that the short answer will suffice.