Tom, Phil and other Fellow Dialists Thanks for warm acceptance of my recent post on a really hot issue of time. And short continuation.
1. Most important Internet servers are synchronized by radio signals and/or electric time signals (telegraphy since its beginnings had been used for time signals) and maybe other independent means. Other millions of computers use the mentioned Internet protocols. A series of packets is sent to the time server which sends the packets back with the server's time stamp in each. The originating computer measures by its own clock the time period between sending the packet and receiving the response (with the time stamp in it). Approximately we may assume that the packet needs same time period each way. So knowing how long the packet traveled, our time of sending it, and the time stamp it brought from the time server, we may calculate the correction for our computer clock provided that the times spent by packets in each direction were same. Of course a series of packets is sent and usual statistical tricks are used to get the most probable results. Gordon Uber's site http://www.ubr.com/clocks/ has links to various synchronization programs, both freeware and shareware, which you may use for your personal computer. Other famous time signals were time balls dropped at precisely defined times and visible for many miles. Those established for sailors dropped the ball at 1 PM. Traditionally on sail ships, whether in harbour or offshore, noon was busy time for navigators so 1 PM was more convenient for checking chronometers. There are still few tiem balls operated around the world as a tourist attraction. Long ago I read a book about the Greenwhich Time Lady in XIX century in London. She inherited a pretty good chronometer. Every day she visited the Greenwhich Observatory where the correction to her chronometer was precisely determined and the certificate issued. Then she took the chronometer and visited London clock masters and laboratories delivering time (what else) to them. 2. TAI is maintained collectively on many atomic clocks around the world. Their readings are averaged and arbitrated as the basis of TAI. There is no escape, our ever rushing world needs more and more accurate clocks. Atomic clocks do detect General Relativity effects due to gravitation. The stronger the gravity the slower the time flows. Even 15 km or so above the Earth surface is enough the the clock carried by an air-plane for few hours to show the difference between its counterpart on the ground. Experiments were carried out many times. Special Relativity effects of same magnitude would require too high speeds to perfom similar experiments. Moreover during accelerating the clock to high speed, General Relativity effects would enter anyway. One of the principles is that basically there is no difference between gravity and acceleration, one may be replaced with the other and physical phenomena (human beings included) would not care nor notice. Those are not the only experiments confirming Relativity which is still the current working model in physics (until a more suitable one appears) whether we like it or not. Gentlemen, those are facts so being gentlemen we have to accept them gently. 3. 11 days issue If I remeber well it was 11 days in 1582. Nearly 200 years later the discrepancy grew, morevover 1600 was a leap year in Catholic countries. The Orthodox Church is still using the Julian Calendar so their Christmas falls well into our January. Russia used Julian Calendar till 1918 and thanks to this the October Revolution happened in November. It would be relatively easy to view diplomatic documents from the beginning of the century to see how they dealt with the date problem. Julius Ceasar did his best to establish good solar calendar which was and still is of essence for agricultural communities and smooth running of big empires. I think it was also he who moved the beginning of the year from March (spring equinox) to January. Mid winter is slack time in farming and business with ancient means of travel so it was convenient to close accounts in December. When Julian Calendar visibly ran out of step with seasons the Pope reformed it, not only for religious reasons but for economical as well. 4. There is lots of literature on time and calendars in every library. I assure you that you will find it fascinating. Slawek Slawek Grzechnik 32 57.4'N 117 08.8'W http://home.san.rr.com/slawek
