Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: paul.fr on 17/05/2007 11:20:40

Title: Pendulum clocks.
Post by: paul.fr on 17/05/2007 11:20:40

how accurate can a pendulum clock be, and why?

Title: Pendulum clocks.
Post by: another_someone on 17/05/2007 16:23:07

It depends on how clever you want to make it.

Traditional pendulum clocks would suffer from mechanical friction; aerodynamic friction; changes in pendulum length due to variation in temperature; changes in gravitational fields due to alignment of the Sun and Moon, and to a lesser extent, the other planets; and vibration.

The gravitational issues will be almost impossible to remove, but most of the other sources of error can be removed, but the effort of removing them (e.g. placing the pendulum on magnetic bearings within a vacuum) would create something technically more complicated than many of the competing technologies that can provide just as accurate a clock.

Title: Pendulum clocks.
Post by: Bored chemist on 17/05/2007 20:24:58

Until quartz clocks were invented the best clocks were "Shortt" pendulum clocks. They were mounted in vacuum chambers and other such precautions were taken to avoid the influence of other thinngs. This pendulum was used to keep a check on a second pendulum that actually ran the clock. Some of them were said to be good to about 1 second a year or better.

Title: Pendulum clocks.
Post by: JimBob on 18/05/2007 02:08:16

The very first chronometers commissioned by th British Navy were a variant of pendulum clocks. The clocks before these (before ~ 1750-60) were pendulum and they continued to be the most accurate into the 20th century. (1900's - can't believe I think it necessary to explain the 20yh century.)

Title: Pendulum clocks.
Post by: lyner on 19/05/2007 23:30:22

Read the book 'Longitude'; it's brilliant.