10,000-year clock
The November Discover Magazine carries an article about a super-clock being designed to remain accurate for 10,000 years (and if it doesn't make it the whole way, one of those engineers should get canned!). So I'm reading along, because I can't resist stories like that, and I get to this:

Everything about this clock is deeply unusual. For example, while nearly every mechanical clock made in the last millennium consists of a series of propelled gears, this one uses a stack of mechanical binary computers capable of singling out one moment in 3.65 million days. Like other clocks, this one can track seconds, hours, days, and years. Unlike any other clock, this one is being constructed to keep track of leap centuries, the orbits of the six innermost planets in our solar system, even the ultraslow wobbles of Earth's axis.

And I'm screaming the question that no doubt you are also: What the *?!% is a "leap century"?! I guess I should remember, since we just lived through one a few years back:

Because the old Julian calendar was 3/4 of a day too long per century, the new Gregorian calendar skipped the leap year in three out of four century years and created what could be called "leap centuries." By the new calendar, 1600 was a leap year, but 1700, 1800, and 1900 were not. [ed.: so, 2000 was a leap year also...and I didn't even know century years usually were not...too bad we couldn't skip the Presidential election.]....In the Julian calendar there was a leap year every four years and thus a year was 365.25 days long. But we use the Gregorian calendar which drops a leap year every 100 years ( — .01) and adds it back in every 400 years ( + .0025). Years now average to 365.2425 days.

And the Wikipedia entry on this topic offers other "long-term" calendar considerations.

The accumulated difference between the Gregorian calendar and the vernal equinoctial year amounts to 1 day in about 8,000 years. This suggests that the calendar needs to be improved by another refinement to the leap year rule: perhaps by avoiding leap years in years divisible by 8,000.

However, there is little point in planning a calendar so far ahead because over a timescale of tens of thousands of years the number of days in a year will change for a number of reasons, most notably:

1. Precession of the equinoxes moves the position of the vernal equinox with respect to perihelion and so changes the length of the vernal equinoctial year.
2. Tidal acceleration from the sun and moon slows the revolution of the earth, making the day longer.

In particular, the second component of change depends on such things as post-glacial rebound and sea level rise due to climate change. We can't predict these changes accurately enough to be able to make a calendar that will be accurate to a day in tens of thousands of years.

So, Bush is not only screwing up the environment with refusal to address climate change problems, he's messing up our clocks...the next time you're late to something, think about blaming W.