On Wed, 2008-05-21 at 10:32 +0200, Daniel Carrera wrote: > Daniel Carrera wrote: > > Rod Engelsman wrote: > >> But if, as you say, a second and a metre are related that way it would > >> have to be an incredible coincidence. > > > > I've tried to double-check, but I can't find a source. I calculated the > > period of a 1-metre pendulum and I got 2.0064 seconds. So a single swing > > of the pendulum would be 1.0032 seconds. That error, while small, seems > > hard to explain by anything other than assuming that the definition of a > > second was never a metre and that this is all one big coincidence. > > Aha! I have confirmed that this is actually a coincidence. On a page > about the history of the metric system, talking about the metre, it says: > > "... there were two favoured approaches to the definition of the > standard unit of length. The suggestion of defining the metre as the > length of a pendulum with a half-period of one second suffered from the > problem of varying gravity, giving a "metre" of 99 cm in Mexico City, > but 99.5 cm in Helsinki. The other approach suggested defining the metre > as one ten-millionth of the length of the Earth's meridian along a > quadrant, that is the distance from the equator to the north pole." > > So... the metre is *not* related to the second, but they thought about > it. And we can see why it can't be related because gravity is not > constant around the Earth (btw, Canada also has low gravity, so one way > to lose weight is to move to Canada :D ).
Live on the pole. Not only will you weigh the least, but the cold will require you to burn more calories (or should I say joules?) to keep warm. Second I believe is defined by atomic clocks these days and metre on wave length of radiation, mass - can't remember. All that really matters is that there are open standards with specific precision in constancy to make measurement reliable. Derived units then depend on the number system and apart from Hex and binary in computers, decimal is the dominant global number system. Ian -- New QCA Accredited IT Qualifications www.theINGOTs.org You have received this email from the following company: The Learning Machine Limited, Reg Office, 36 Ashby Road, Tamworth, Staffordshire, B79 8AQ. Reg No: 05560797, Registered in England and Wales. --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
