On 09/10/2015 06:54, Quadibloc wrote:
On Thursday, October 8, 2015 at 11:03:07 PM UTC-6, Paul Schlyter wrote:

Any clocks contain s two parts:

1. Something that oscillates. E.g. the Sun in our sky, a spring, a
pendulum, a quartz crystal, an atom.

Not all water clocks and candle clocks oscillate (neither are they
particularly accurate). Flow of water from a specially shaped calibrated
vessel or burning of an Advent candle for instance.

2. Something that counts the oscillations. E.g. people counting
sunrises, sunsets or transits, mechanical gears, electronic counters.

The stability of the clocks depends on the stability of the
oscillatior. The rotating Earth is no longer our best available
oscillator.

Note that atomic clocks aren't really clocks in most cases; instead, they're
frequency sources - used to calibrate associated quartz crystal clocks that
tell time, if that functionality is desired (i.e. for broadcasting the WWV time
signal).

Depends what you mean by atomic clock. The ones sold to consumers are
merely picking up broadcast time signals that are derived from the
ensemble of atomic clocks used to maintain true clock time.

You can buy Rubidium or Caesium frequency standards and true atomic
clocks new for a price or secondhand on eBay. A UK electronic magazine
had a build your own atomic clock project fairly recently.

They are not all that expensive although you have to figure out how to
drive them.

http://www.ebay.co.uk/sch/i.html?_nk...uency+standard

These days a GPS with the ability to output the time is also a possible
solution (and it can correct for light travel time whereas a simple
domestic "Atomic" clock receiver lags true atomic time by distance/c).

--
Regards,
Martin Brown