In <[EMAIL PROTECTED]> [EMAIL PROTECTED] (joost witteveen) writes: > > Now, we know the length of a year/day better, and > only 1 in for of those turn-of-century years are leap years. Maybe that > will change again. And about the seconds: we (currently, prossibly always) > simply cannot calulate the length of a day accurately enough to know > well in advance when to insert them. But I'd say the two animals are > at least related, if not mother and daughter.
It is my understanding that: Leap days are used to keep the calendar in sync with the season. That is, you don't want winter to be in August (in the northern hemisphere.) Leap seconds are used to keep the time of day in sync with the sun rise. That is, you don't want the sun to be rising at midnight (out side the article circles.) The length of the year is almost constant over time periods of thousands of years. It does vary due to gravitational interactions with other planets, but it only makes a "significant" difference (10%?) when dealing with time periods of around 100,000 years. These gravitational interactions are predictable, so if you really wanted to, you can calculate the exact length of the year 1million years ago. (It is my understanding that there are people who do this.) The length of the day is not quite as constant. It depends on how quickly the earth rotates which depends on things like how much snow has fallen on mountain peaks and how much water is in man made reservoirs. I kid you not, these things are significant enough to change things on the order of a second or two per year. Neither the weather nor people's water usage/reservoir building is very predictable. This makes predicting leap seconds futile. -wayne -- Wayne Schlitt can not assert the truth of all statements in this article and still be consistent. -- TO UNSUBSCRIBE FROM THIS MAILING LIST: e-mail the word "unsubscribe" to [EMAIL PROTECTED] . Trouble? e-mail to [EMAIL PROTECTED] .
