I thought the ball dropped at noon. Perhaps you were there in the summer, and they had advanced 1 hour for summertime (daylight savings).
Rob K -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of WB6BNQ Sent: 05 November 2010 12:11 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Setting clocks 100 years ago OK Bob, I'LL bite ! Why is it 1:00 pm for the ball ? Bill....WB6BNQ Bob Marinelli wrote: > Hi Murray, > > Actually, the ball at Greenwich drops at 1:00 pm every day. For > everyone who can get to London, the observatory is well worth at least > a half day visit, they have several working Harrison clocks and yes > you can set your wristwatch at 1:00 when the ball drops :) there is > also a wonderful transit. > > Cheers, > > Bob > > On Nov 4, 2010, at 4:30 PM, Murray Greenman wrote: > > > Navigators used chronometers to determine their longitude. If they > > were stopped in one place long enough, they could work out longitude > > by a complicated process of star and lunar observations; however, > > when they left an established port, they usually took with them a > > time standard based on local measurements of the sun and the known > > location of the port. > > > > These measurements used a device called a 'Transit', which was a > > simple telescope mounted so that it pivoted in elevation, but was > > fixed N-S in azimuth. Midday was marked by the time at which the sun > > transited the telescope. It thus had higher resolution than a > > sundial. Getting N-S axis correct involved determining by iteration > > and surveying the axis that gave maximum elevation at time of > > transit. > > > > Once the transit was observed, a large ball on top of the building > > was dropped, indicating midday, and in some locations a cannon was > > also fired. Ships in port could observe the ball drop and hear the > > cannon. To this day the ball drops at midday at Greenwich. > > > > > > 73, > > Murray ZL1BPU > > > > > > _______________________________________________ > > time-nuts mailing list -- [email protected] To unsubscribe, go to > > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > and follow the instructions there. > > _______________________________________________ > time-nuts mailing list -- [email protected] To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
