On Wed, 2008-05-21 at 08:48 -0400, John W Kennedy wrote: > On May 21, 2008, at 5:15 AM, Ian Lynch wrote: > > Second I believe is defined by atomic clocks these days > > The second is "the duration of 9 192 631 770 periods of the radiation > corresponding to the transition between the two hyperfine levels of > the ground state of the caesium 133 atom." > > The meter "is the length of the path travelled by light in vacuum > during a time interval of 1/299,792,458 of a second." > > The kilogram is still defined by a lump of metal in Paris;
Platinum I think. > this is > agreed to be unsatisfactory, Yes it would be difficult to see how the measurement might be checked without losing the odd atom or two :-) > and work is being done on redefining it > (for example, as the mass of x number of carbon-12 atoms), but all of > the methods proposed to date have practical problems. 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]
