[TILWISHBW] Leap Seconds
(Just to load up the site a bit and get it going, I'm going to contribute with a little more frequency then when I level off and find a sustainable pace.)
You've probably heard of Leap Years, a convention based on the fact that our Earth doesn't behave nicely with respect to nice round numbers (it takes a little under 365 and 1/4 days to get back to where we started going around the sun), or our strange way of doing it (add an extra day to February every 4 years, except every 100 years where we skip over the leap year and don't add the extra day, or every 400 years where we skip over skipping over the leap year and add the friggin day back as in the first place), but our time system is a bit more screwy than that.
We actually have an extra second that we end up adding about every 18 months to the last second of the month, GMT (although it only tends to happen at the end of June or the end of December), or right before 8 PM Eastern time. The jist of it is that because of the moon's orbit around the earth, and some action relating to tidal acceleration and a gradual loss of spin motion (angular momentum), the earth is very minutely slowing down its spin. As a result, each day is just the slightest bit longer than the last, until about every 18 months when the amount adds up to a whole second longer (cumulatively), and we do a leap-second to resync our totally accurate atomic clocks from their perfect measurement of the defined "second" to rematch the reality of what exact time it is in the time of day with regard to the Sun.
(Check the Wikipedia entry on this for where I got most of the hard information from. I saw some discussion about how to account for leap-seconds in the linux kernel mailing list a long long time ago too...)
-G
You've probably heard of Leap Years, a convention based on the fact that our Earth doesn't behave nicely with respect to nice round numbers (it takes a little under 365 and 1/4 days to get back to where we started going around the sun), or our strange way of doing it (add an extra day to February every 4 years, except every 100 years where we skip over the leap year and don't add the extra day, or every 400 years where we skip over skipping over the leap year and add the friggin day back as in the first place), but our time system is a bit more screwy than that.
We actually have an extra second that we end up adding about every 18 months to the last second of the month, GMT (although it only tends to happen at the end of June or the end of December), or right before 8 PM Eastern time. The jist of it is that because of the moon's orbit around the earth, and some action relating to tidal acceleration and a gradual loss of spin motion (angular momentum), the earth is very minutely slowing down its spin. As a result, each day is just the slightest bit longer than the last, until about every 18 months when the amount adds up to a whole second longer (cumulatively), and we do a leap-second to resync our totally accurate atomic clocks from their perfect measurement of the defined "second" to rematch the reality of what exact time it is in the time of day with regard to the Sun.
(Check the Wikipedia entry on this for where I got most of the hard information from. I saw some discussion about how to account for leap-seconds in the linux kernel mailing list a long long time ago too...)
-G
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