Great question (someone's thinking!) The form used in semiconductors is actually a compound of gallium, gallium arsenide, so gallium combined with arsenic. This compound has a melting point of 1238 C, so it's completely safe even in hot computers.

http://en.wikipedia.org/wiki/Gallium_arsenide

Unfortunately the period of a pendulum's swing depends on

(a) air density
(b) distance from the center of the earth

(b) is measurable - because the earth has a bulge at the equator, so pendulums swing measurably slower there...

Then, of course, there is the problem of getting a reliable clock that does not use a pendulum - easy today, but not 200 years ago...

/Bevin

I suspect that both (a) and (b) would have effects smaller than the .005 in the 2.005, so yeah, you wouldn't use a pendulum clock to time the 100 m race at the Olympics, but for timing an egg or taking a pulse it'd work fine. Incidentally, you've probably noticed that clock pendulums tend to be very thin in the plane in which they swing, presumably as a means of reducing the influence of (a).

Actually I realized there is an age-old reliable-enough clock - the rotation of the earth! So you would adjust the length of the pendulum until it did 24*60*(60/2) swings per day, where day is measured by a star crossing a hair in a telescope....

Of course that means having someone count about 50,000 swings... unless you also invented a counting device...

/Bevin

so it is about 50/12756 = 1/240 difference in radius

so g at one place is (240/240)**2 and the other ((240-1)/240)**2 so the difference is about (2*1*240/240)**2 or (1/120)**2 or about 0.0001 << 0.005

There is another effect also - centrifugal forces - but I suspect without calculation this is even more irrelevant...

A less irrelevant topic may be the shape and density of the pendulum - you would have to agree on that also...

Yeah, the equations for the pendulum require it to have a string of zero mass and a bob that is a point mass, so the denser the better. Lead is a good start, but in a war zone maybe you could pick up some depleted uranium.

This is all very interesting but way beyond me!!

I wish I hadn't skipped out of school so much!

I'm going to assume that they don't feel this elongating in space but what about when they are back on earth. Do they feel themselves shortening? How long does it take to shorten up?

And we can't ignore the 'human sciences':

In the developing world, fertility rates vary in inverse proportion with literacy rates. For example, Afghanistan, with a female literacy rate of only eight percent has a fertility rate of 6.9 per 1,000 population. Thailand, in contrast, has a literacy rate of 88% and a fertility rate of 2.6/1,000.