[time-nuts] Setting clocks 100 years ago

Bill Hawkins bill at iaxs.net
Fri Nov 5 03:49:56 UTC 2010


Antonio,

The earliest purpose for mechanical clocks was religious, so they
appeared in church towers in the 1600's. They were set by sundials.
The 1800's brought the telegraph and precision telescopes. Once it
was possible to transmit time signals at near the speed of light,
and to determine star crossings with millisecond precision, time
could be synchronized among those clocks the could be set electrically.

See "Einstein's Clocks, Poincare's Maps: Empires of Time" by Peter
Louis Galison for a fascinating history of this era. Accurate maps
could not be made without an accurate sense of time, provided by
telegraph cables from a central clock in Paris.

The accuracy of pendulum clocks increased dramatically once true time
could be known, leading to the Riefler and Shortt free pendulum clocks,
where the free pendulum swung in a vacuum. These mechanical marvels
gave way to the crystal oscillator in the 1930's.

Church clocks were fine with local sundial time until the railroads
discovered the need to accurately schedule trains on the same track
to avoid collisions, say in the 1850's. Central time standards were
necessary to enforce a common sense of time over a wide geographic
area, like the United States at the time. Paris had a pneumatic
system for setting tower clocks across the city using pipes under
the streets that carried pressure pulses from a central clock in 1880.

Synchronization was done with star-crossing observatories and telegraph
signals driven by precision clocks that could keep steady time between
one night's star crossing and the next. One of these was Goodsell
Observatory at Carleton College, in Northfield, Minnesota, USA. See
http://www.carleton.edu/departments/PHAS/astro/pages/history2.html

"From the 1870s until the Second World War the Carleton observatory was
among the best and most prominent in the United States. It set time for
all the major railroads from Chicago to Seattle."

I visited the observatory a few years ago with a group of time enthusiasts.
The remains of the telegraph board that distributed time far and wide were
still there, but our guides couldn't tell us anything about them. Several
accurate pendulum clocks were set around the concrete base of the telescope
on the floor below it, but they were not in good repair. There was a Riefler
clock in the basement that was missing the lower vacuum chamber because
someone drilling holes for a computer network had drilled through a wall
without looking to see what was on the other side. Corrosion has had its
way with the mechanism since then.

The observatory building had been turned into classrooms and a faculty
lounge in the room with the star crossing detector. No one seemed to know
what they were treading on, or what prevented them from having more room.
No one knew the purpose or value of the spare parts stores. I can't bear to
go back there.

In short, church bells stopped being the time standard about 300 years ago.
Heck, 100 years is only 30 years after I was born. I used to think my
grandfather, born in 1880, had seen a lot of change. Now I've seen a lot
of change, and lately none of it seems to be for the better.

Bill Hawkins

I hope someone appreciates the last two hour's work . . .


-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of iovane at inwind.it
Sent: Thursday, November 04, 2010 4:47 PM
To: time-nuts at febo.com
Subject: [time-nuts] Setting clocks 100 years ago

This evening I happened to hear the nearby church's bell tolling 10 pm, and 
thought 
that 100+ years ago this could have been the "official" time of the town, 
which 
maybe was used by people to set their own clocks (if any). But then I 
wondered, 
who told the priest what time was it? To what extent the clocks of two towns

were expected to be close to one another? Does anybody know?

Antonio I8IOV

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