How long is a day.....really?
Ponder this one! On the calendar day of an equinox, from the moment that day first pops into existence somewhere on the earth, to the moment it winks out of existence, how long does it exist? How long does it exist at the solstices? Charlles
Sundial Glossary - out now
Hi Dialling Colleagues, I'm pleased to announce that the first edition of the BSS Sundial Glossary is now available. The Glossary is A4-size, has soft covers and has 42 pages (similar to a BSS Bulletin). Printed versions can be obtained from: Ms Margery Lovatt, BSS Sales Studio 5, Parndon Mill Harlow Essex CM20 2HP UK The cost is £6.50 (UK), £7.00 (EC) and £8.00 (Rest of the World), all prices including post and packing. Cheques (to BSS) and money orders in pounds sterling, please. Thanks to some tremendous work by Bob Terwilliger on the look-and-feel, and Ian Wootton's good offices, the Glossary is also viewable on-line (free!) with a link direct from the BSS front page at: www.sundialsoc.org.uk In addition to mentioning Bob and Ian, I'd like to thank everyone in the sundialling community who helped in this project. I can't mention everyone by name, but it was Margaret Stanier who got it through the publishers. The second edition is now underway, so if you have any comments or suggestions for additions or corrections, please contact me. Have fun, John -- Dr J R DavisFlowton, UK52.08N, 1.043Eemail: [EMAIL PROTECTED]
Re: How long is a day.....really?
Hi Charles, What is a day My watch says any day is 24 hours long. ( Many watches say 2 x 12 hours, but that's also 24 ) These are regular hours, all of the same length. My sundial ( for suntime ) also says any day is 24 hours long. But these are irregular hours, the length of an hour changes. ( however I won't notice it if I don't use my watch ). This is because my sundial defines a day in another way. If the sun is South or North the day starts and the day ends if the sun is at the same position again. Thus any day is 24 hours long, but measured in 2 time systems. Now I use the sundial's day and meausure it length with my watch. The result is that I get a difference, the famous EoT. And then a day is 24hours and 30 seconds around Christmas. I didn't look up for the values at the equinox or the solstices, I am too lazy for it. So I leave the exact answers to your question to you What a nice stuff, isn't it? However, it is even more complected nowadays. The timesystem of our world counts something of an atom and that's atomic time. It's very regular and very presize. Its precision is so high that from time to time we add a leap second to the atomic time to set our watches. Only with this artificial added seconds we keep the time of our watch in some relation to the sun. Some days aren't 24 hours watch time, but sometimes a day is 24 hours and 1 second watch time. Conclusions : the day in our precize world is sometimes of different length, thus irrigular. the day in sundial time always is 24 hours, thus regular. Shouldn't we go back to sundial time? We never need to add a leap second to our watch. Best wishes, Fer. Fer J. de Vries[EMAIL PROTECTED]http://www.iae.nl/users/ferdv/Eindhoven, Netherlandslat. 51:30 N long. 5:30 E - Original Message - From: Charles Gann To: Sundial List Sent: Tuesday, July 04, 2000 6:20 AM Subject: How long is a day.really? Ponder this one! On the calendar day of an equinox, from the moment that day first pops into existence somewhere on the earth, to the moment it winks out of existence, how long does it exist? How long does it exist at the solstices? Charlles
Glossary copies for NASS
Hello BSS members: I'm wondering if it might be possible to have some printed copies of The John Davis Sundial Glossary for sale at the NASS conference in August? I'm sure many of us want a hard copy. This would save a lot of trouble trying to find a US bank that makes checks out in pounds sterling. So that you have an idea of how many copies would be needed, you could get a list beforehand of those people who want a copy using the sundial list. Just a thought, John Carmichael Tucson Arizona
Re: Glossary copies for NASS
A good thought, John. I, for one, would want one. John Schilke - Original Message - From: John Carmichael <[EMAIL PROTECTED]> To: Cc: <[EMAIL PROTECTED]> Sent: Tuesday, July 04, 2000 7:57 AM Subject: Glossary copies for NASS > Hello BSS members: > > I'm wondering if it might be possible to have some printed copies of The > John Davis Sundial Glossary for sale at the NASS conference in August? I'm > sure many of us want a hard copy. This would save a lot of trouble trying to > find a US bank that makes checks out in pounds sterling. > > So that you have an idea of how many copies would be needed, you could get a > list beforehand of those people who want a copy using the sundial list. > > Just a thought, > > John Carmichael > Tucson Arizona > >
Re: How long is a day.....really?
> Shouldn't we go back to sundial time? We never need to add a leap second to our watch. That leap second is only necessary to synchronize our watches with the sundials isn't it? - Thibaud Taudin-Chabot 52°18'19.85" North 04°51'09.45" East home email: [EMAIL PROTECTED] (attachments max. 500kB; for larger attachments contact me first)
Printing the BSS Sundial Glossary
I successfully printed the Sundial Glossary from the BSS website using Netscape 4.73 and a laser printer; the total was 44 pages. I have DSL and the download was quick. This printed copy, of course, is not bound and cannot access the many handy links embedded in the web version of the Glossary. However, this process did solve my personal difficulty of paying in UK Pounds. I, for one, would be pleased to purchase a bound copy at the NASS meeting in San Francisco if I could pay in US Dollars. John's suggestion is an excellent one. I am hopeful that PayPal (http://www.paypal.com), the popular US Internet credit transfer facility, will soon offer, as promised, international credit card funds transfer between individuals as they currently provide in the US. This will certainly alleviate the international small-funds transfer costs under which we currently suffer. The PayPal service is currently free to both parties; even a modest fee for international transfers would be welcome. -- Best wishes, Larry McDavid W6FUB Anaheim, CA (20 miles southeast of Los Angeles, near Disneyland)
Re: How long is a day.....really?
On Tue, 4 Jul 2000, T.& M. Taudin-Chabot wrote: >> Shouldn't we go back >> to sundial time? We never need to add a leap second to our >> watch. > > > That leap second is only necessary to synchronize our watches with the > sundials isn't it? Yes, which is to say, it synchronizes our watches to the inconstant rate of the Earth! Dave
Re: Sundial Glossary - out now
John, the Glossary is beautiful! And kudos to Bob Terwilliger, for a fine job implementing it as a set of Web pages. I agree, having copies available through NASS would be a good idea, and should serve to expand the BSS's sales, through distribution. How do you feel about making the Web page set available for local installation on members' PCs? It's quite modest in size, for any recent application, and would be directly accessible to any browser, without going on line... Dave Bell
Re: How long is a day.....really?
Thibaud, Yes, that's right. If we don't add leap seconds to our watch, the watch is no longer related to the sun but only to the atoms. We want to keep the relation to the sun and that's why we have to correct our watch from time to time. Fer. Fer J. de Vries[EMAIL PROTECTED]http://www.iae.nl/users/ferdv/Eindhoven, Netherlandslat. 51:30 N long. 5:30 E - Original Message - From: T.& M. Taudin-Chabot To: sundial@rrz.uni-koeln.de Sent: Tuesday, July 04, 2000 8:37 PM Subject: Re: How long is a day.really? > Shouldn't we go back to sundial time? We never need to add a leap second to our watch.That leap second is only necessary to synchronize our watches with the sundials isn't it?-Thibaud Taudin-Chabot52°18'19.85" North 04°51'09.45" Easthome email: [EMAIL PROTECTED](attachments max. 500kB; for larger attachments contact me first)
Re: How long is a day.....really?
> Charles Gann wrote: > > Ponder this one! > > On the calendar day of an equinox, from the moment that day first pops > into existence somewhere on the earth, to the moment it winks out of > existence, how long does it exist? > > How long does it exist at the solstices? In addition to the answer of Fer de Vries and others, I would say that it is also a matter of definition. If the day is defined as the interval between two moments of crossing of the meridian, I have nothing to add to Fer's answer. Things get a bit more complicated if the day is defined as the interval between two sunrises or sunsets as they then also depend on the latitude and the season of the year. However, if the day is taken as a calendar day the issue is more complicated as at a given moment two or even three calendar days can be simultaneously in progress on the terrestrial globe, all dated by the same (Gregorian) calendar. This of course has to do with the International Date Line (IDL) where the calendar date makes awkward jumps. A given calendar day, when measured in UT, starts at -12 hours when it is midnight in the time zone immediately to the West of the IDL (for instance Kiribati) and is already 12 hours old when the day starts at midnight in Greenwich. It lasts until 24 + 12 hours UT when it finally becomes midnight in the time zone immediately to the East of the IDL (for instance Samoa). So in ordinary circumstances each (Gregorian) calendar day in fact lasts 48 hours though during half of the time it is either a day earlier or later somewhere else on the globe. When Summer Time applies for countries bordering on the IDL, things get even more complicated. During the summer months on the southern hemisphere, the New Zealand Dependencies adopt a Summer Time arrangement that puts them 12 hours 45 minutes ahead of Greenwich. During that period a calendar day can thus last 48 hours and 45 minutes before it winks out of existence on the globe. And this still not the longest possible day! During the last winter, the island republic of Tonga adopted a time zone 13 hours ahead of Greenwich to which they added another hour of 'Summer Time', putting them 14 hours ahead of Greenwich. Thus the New Year's Day of 2000 (erroneously claimed by the media world wide as being the first day of the 3rd millennium) lasted from 10h UT on 31 December to 12h UT on 2 January, or 50 hours in total. * Robert H. van Gent * Tel/Fax: 00-31-30-2720269 * * Zaagmolenkade 50 * * * 3515 AE Utrecht* E-mail: [EMAIL PROTECTED] * * The Netherlands* * * Home page: http://www.phys.uu.nl/~vgent/homepage.htm *
