nanog mailing list archives
Re: F-ckin Leap Seconds, how do they work?
From: valdis.kletnieks () vt edu
Date: Tue, 03 Jul 2012 16:54:24 -0400
On Tue, 03 Jul 2012 21:49:40, Peter Lothberg said:
Leapseconds can be both positive and negative, but up to now, the earth has only slowed down, so we have added seconds.
That's what many people believe, but it's not exactly right. Leap seconds are added for the exact same reason leap days are - the earth's rotation isn't a clean multiple of the year. We know we need to stick in an entire leap day every 4 years or so, then add the 400 hack to get it closer. At that point, it's *really* close, to the point where just shimming in a second every once in a while is enough to get it back in sync. The earth's slowdown (or speedup) is measured by *how often* we need to add leap seconds. If we needed to add one every 3 years, but the frequency rises to once every 2.5 years, *that* indicates slowing. In other words, the slowdown or speedup is the first derivative of the rate that UT and TAI diverge - if the earth rotated at constant speed, the derivative would be zero, and we'd insert leap seconds on a nice predictable schedule.
Attachment:
_bin
Description:
Current thread:
- Re: Fwd: Re: F-ckin Leap Seconds, how do they work?, (continued)
- Re: Fwd: Re: F-ckin Leap Seconds, how do they work? valdis . kletnieks (Jul 03)
- Re: Fwd: Re: F-ckin Leap Seconds, how do they work? Chris Adams (Jul 03)
- Re: F-ckin Leap Seconds, how do they work? Jay Ashworth (Jul 03)
- Re: F-ckin Leap Seconds, how do they work? Peter Lothberg (Jul 03)
- Re: F-ckin Leap Seconds, how do they work? Peter Lothberg (Jul 03)
- Re: F-ckin Leap Seconds, how do they work? Tony Finch (Jul 03)
- Re: F-ckin Leap Seconds, how do they work? Eugen Leitl (Jul 03)
- Re: F-ckin Leap Seconds, how do they work? Leo Bicknell (Jul 03)
- Re: F-ckin Leap Seconds, how do they work? Jay Ashworth (Jul 03)
- Re: F-ckin Leap Seconds, how do they work? Peter Lothberg (Jul 05)
- Re: F-ckin Leap Seconds, how do they work? valdis . kletnieks (Jul 03)
- Re: F-ckin Leap Seconds, how do they work? Peter Lothberg (Jul 03)
- Re: F-ckin Leap Seconds, how do they work? Steven Bellovin (Jul 03)
- Re: F-ckin Leap Seconds, how do they work? Peter Lothberg (Jul 05)
- Re: F-ckin Leap Seconds, how do they work? Steven Bellovin (Jul 05)
- Re: F-ckin Leap Seconds, how do they work? Tony Finch (Jul 03)
- Re: F-ckin Leap Seconds, how do they work? Owen DeLong (Jul 03)
- Re: F-ckin Leap Seconds, how do they work? Brett Frankenberger (Jul 04)
- Re: F-ckin Leap Seconds, how do they work? valdis . kletnieks (Jul 04)
- Re: F-ckin Leap Seconds, how do they work? Brett Frankenberger (Jul 04)
- Re: F-ckin Leap Seconds, how do they work? valdis . kletnieks (Jul 04)