Total solar eclipse of August 11, 1999 seen in France (via Wikipedia).That's one of the many curious facts about solar eclipses you can check out at a web site I came across the other day, the Eclipse page of NASA. Solar Eclipses: Past and Future features a catalogue of eclipses over five thousand years, from 2000 BCE to 3000 CE. And there is a web interface, the Solar Eclipse Explorer, which allows to search for solar eclipses visible between 1500 BCE and 3000 CE from any given location on Earth - that's how I've found the Waterloo eclipse.
Path of the October 26, 2144 Solar Eclipse over Ontario, Pennsylvania, and New York, as seen by Google Maps (Eclipse Map and Predictions by Fred Espenak and Jan Meeus, NASA's GSFC).One can even have a look at the path of the Moon's shadow: The band of totality runs from Waterloo to the Southeast and ends in the Atlantic ocean - the centrality line just misses the southern tip of Manhattan. Eclipse data are plotted using Google Maps.
I wonder how Theodor Ritter von Oppolzer would feel about this treasure trove of eclipse data. The Austrian astronomer is the author of the Canon der Finsternisse (Canon of Eclipses). This work, which appeared in 1887, one year after Oppolzer's death, contains exact data of 8,000 solar eclipses and about 5,200 lunar eclipses of the period from 1208 BCE to 2161 CE.
To accomplish all the necessary calculations, Oppolzer had enlisted the help of ten "computers", as these assistants were called at the time. Half of them were volunteers, half of them were paid by Oppolzer's private money - the payment for the calculation of one eclipse was about the daily wages of a plumber. Each eclipse was worked out independently by two groups, and only matching results were accepted, in order to minimise computational errors. The Canon was supplemented with maps showing the centrality lines of the solar eclipses. However, these paths were only approximate: A circular arc was fitted through the eclipse locations at sunrise, for the mid-point, and for sunset - it was just way to laborious to calculate more point.
A map from Oppolzer's Canon of Eclipses, showing approximate centrality lines of solar eclipses for the late 20th/early 21st century. [Sheet 153 of Canon der Finsternisse, Denkschriften der kaiserlichen Akademie der Wissenschaften in Wien, Mathematisch-Naturwissenschaftliche Classe 52 (1887), from "Schwarze Sonne, Roter Mond".]Oppolzer's Canon, which "stands as one of the greatest accomplishments in computational astronomy of the 19th century", was mainly intended as a reference work for historians. It was the authoritative collection of eclipse data before the advent of electronic computers. A translation into English was prepared as late as 1962, and 1966 saw an extension of the calculation of future solar eclipses up to March 2510, computed this time by an IBM 1620 and printed by photo-offset from the original computer printout to exclude typesetting errors.
The Theodor Oppolzers of today are called Jan Meeus and Fred Espenak - they are the heads behind the NASA eclipse data base. But not only has the speed of computation exploded since Oppolzer's time - there has also been an increase in precision of the formulas used to calculate eclipses. An eclipse calculation requires very precise coordinates of the Moon and Sun on the celestial sphere as a function of time. For Oppolzer, the factor limiting the precision of his Canon was the orbit of the Moon. Today, this is not a problem anymore - instead, the largest remaining uncertainty in the eclipse predictions is caused by tiny fluctuations in the Earth's rotation.
So, I can trust the prediction that on September 7, 2974, at 13:31 in the early afternoon, there will be a total eclipse of the Sun where now is Frankfurt am Main, Germany. But who knows how the place will look like that will be cast in the Moon's shadow for 4 minutes and 21 seconds - and if anyone will be around to be fascinated by this spectacular event?
PS: Concerning the more forseeable future, there will be a total eclipse of the Moon in two weeks, in the night from February 20 to February 21, 2008. It will be visible in Europe, Africa and America; mid-eclipse is at 04:26 Central European Time (in the early morning of Thursday, February 21), or 10:26 Eastern Standard Time (in the evening of Wednesday, February 20). More details (... you guess it) at Fred Espenak's NASA Eclipse site.
This is no time to be sitting on your hands!
ReplyDeletehttp://en.wikipedia.org/wiki/Allais_effect
http://science.nasa.gov/newhome/headlines/ast06aug99_1.htm
Apply for grant funding, assemble a battery of (isolated) towering Foucault pendula and a few atomic fountains, and do it,
Stefan,
ReplyDeleteInteresting post, although for me to count on still being around in 2144 would be somewhat optimistic. There will be one April 8th 2024 passing through Hamilton On. With a little luck I might make that one.
Regards,
Phil
One strange thing about Oppolzer's Canon of Eclipses is that he had the Hawaiian Islands in the wrong place on the base map that was used for all the northern hemisphere eclipse paths. It shows, for example, the island of Oahu at about 148 deg west, when it's actually at 158 deg west. This might not have mattered in Oppolzer's lifetime, but it certainly makes a difference for the July 11, 1991 solar eclipse, which was total at Mauna Kea on the big island, while Oppolzer shows the central line crossing the island chain at Oahu about 300 km away.
ReplyDeleteHi Stefan,
ReplyDelete“To accomplish all the necessary calculations, Oppolzer had enlisted the help of ten "computers", as these assistants were called at the time.”
I was fascinated when I first learned that the term computer was actually something that related to a human occupation. I first became aware of this when I read a book about Allan Turing several years ago. It is strange that what we commonly refer to as computers is not called synthetic computers or some such thing. I can remember using slide rules and log tables and yet until recently only thought computers referred to machines. I noticed in the Wikipedia piece about Oppolzer he was known to have memorized 14,000 logarithms. I wonder if there is anyone alive today that would know anymore then a few if any.
I have also often wondered if our dependence on computers has perhaps actually stunted in some way our abilities to conceptualize mathematically. I certainly sense a general difference in terms of my generation and younger ones. What I’m actually referring to is the spatial sense of proportion and weight in this regard, for as you know these abilities are extremely useful in the physical sciences, engineering and what not. Do you think such reliance could actually prove to diminish the general global aptitude and thereby progress in such areas?
Regards,
Phil
Thanks for the link to the NASA calculator. There's a good partial eclipse of the sun (91.4% of Solar diameter covered by moon) in London on 12 August 2026, reaching its maximum at 18:13 (GMT, presumably, thus the time will be 19:13 allowing for Daylight Saving Time, but it is still quite light at that time in mid-August).
ReplyDeleteHello,
ReplyDeleteif one looks back or forth on a geological
scale of time, we live in a rather short
period of "just" total eclipses.
Back in Archaicum the moon was much closer, eclipses "bigger", whereas in future there will be no total eclipses
at all, only ringshaped ones, and
even later, no more eclipses at all.
So, is there someone who arranged things
in favor of Einstein, because he was
in need of total eclipses for light
bending measurement? :=)
Phil:
I dont know about "computer" as an
occupation, in Germany the title was
"Rechner" at least in optical industry.
Abbe (Zeiss) payed for dozens of them.
I think that Bausch & Lomb maybe
had some "calculators" on their payroll.
Best Regards
Georg
Hi Georg,
ReplyDelete"So, is there someone who arranged things in favor of Einstein, because he was in need of total eclipses for light bending measurement? :=)"
Good point yet I suspect if left to the future we could look to the actual visitation of a neutron star for black hole. Then the question is could this be accomplished without knowledge of GR or what in a limited sense (limit) this may turn out to be ;-) And Plato said that there was no truth to be discovered in the shadows. This is one time that this mentor of mine had it wrong at least in this respect :-)
“..in Germany the title was "Rechner" at least in optical industry.”
Also interesting, are computers (electronic) called Rechner in Germany? I found it curious that the singular and the plural of this word are the same, so I suspect it is defined in terms of context.
Regards,
Phil
Hello phil,
ReplyDeleteyes, in German "Rechner" is used as a
term for computers. Plural and Singular are
identical for this word.
I think only few Germans are aware today that
a "Rechner" might be a profession. I know this
by chance, because I happened to read some
books about optics from the 20/30ties.
More popular was the word "Rechenknecht"
(calculator slave) for someone doing boring
calculation work. But this was before the days of computers.
Best Regards
Georg
Hi Georg,
ReplyDelete“More popular was the word "Rechenknecht" (calculator slave) for someone doing boring calculation work.”
I like this word! I wonder what those who do the data input these days are referred as. How about Datentyp-knecht ? :-)
Stefan,
I apologize for having eclipsed the subject. Pun implied yet not intended.
Best,
Phil
Hallo Stefan,
ReplyDelete"'schuldischung!"
Because the subject was an eclips
at Waterloo, Ontario, I did not
switch on brain...
BTW "Waterloo", did You know, that the
German word is "Belle Alliance"? :=)
I watched the 99 eclipse in the nortern Elsaß,
although clouds obscured the main event,
I found it very impressive.
The "night" with some faint illumination
by stray from horizon is something one cant describe .
It was worth some hundred miles of driving.
Regards
Georg
Re PS:
ReplyDeleteHallo Stefan & Sabine. Lustig, der 21. ist genau der vorausberechnete Termin für die Geburt unserer Tochter. Vielleicht kommt sie ja gerade waehrend der Mondfinsternis...
Hi Phil,
ReplyDeleteThere will be one April 8th 2024 passing through Hamilton On
thanks for pointing out that one - here is the path on google maps. I guess there will big a gigantic traffic jam on the roads to Niagara ;-)
For the Waterloo eclipse, I had in fact started searching for the ones furthest away in the future, I had not expected at all to find one in that near future.
Hi Sam,
One strange thing about Oppolzer's Canon of Eclipses is that he had the Hawaiian Islands in the wrong place
That's curious, indeed. Now that you mention that, I cannot spot at all Hawaii on the map. But that may be because the figure is taken form a reproduction of a map from the Canon in a book about ecplises...
Hi george,
we live in a rather short period of "just" total eclipses.
true - that's a very nice coincidence :-)
BTW, Einstein may have been impatient to wait for eclipses for experimental corrobation of light bending - in that 1913 postcard to Mount Wilson astronomer Hale, he asks if it is possible to measure light deflection in plain daylight, without eclipse.
did You know, that the German word is "Belle Alliance"?
Oh, thanks - no, I didn't know that. Obviously, it was not a really successful idea of Blücher to suggest a very French name to commemorate the victory over Napoleon ;-)
BTW, I had seen the 1999 eclipse with friends from a place near Saarlouis, close to the French border, and we had been very lucky with the weather - the clouds had dispersed shortly before totality. Very impressive! The place where I have grown up was just inside the totality strip, and I remember that when I was still a small kid, my uncle had told me about the eclipse, which was, for me, in the very very far future at that time.
Best, Stefan
Hi Phil, george,
ReplyDeleteyes, the word "Rechner" is used in German to denote an electronic computer - after all, it's the literal translation of the Latin "Computator", and I guess it has the same roots as the English word "reckoner", as in Sand Reckoner. The French have "introduced" the word "ordinateur" because they considered the name "computer" too restrictive to do justice to the many uses of an electronic computer beyond mere numerical calculations, and I think they have a point there.
I think only few Germans are aware today that
a "Rechner" might be a profession.
May be true.. I knew a very charming old lady who actually had worked as a computer at the Göttingen observatory.
I have also often wondered if our dependence on computers has perhaps actually stunted in some way our abilities to conceptualize mathematically.
I don't think so - maybe even to the contrary, computers can help to visualise mathematical concepts. I mean, understanding mathematical concepts and the ability to do complex calculations are somehow related, but they are not the same thing. But I agree, kids who don't know the multiplication table probably won't end up as mathematical geniusses.
Bes, Stefan
Hallo Andi,
ReplyDeleteLustig, der 21. ist genau der vorausberechnete Termin für die Geburt unserer Tochter. Vielleicht kommt sie ja gerade waehrend der Mondfinsternis...
Ob das mal ein gutes Zeichen wäre? ;-)
Aber ein ganz besonderes schon - die nächste totale Mondfinsternis ist erst wieder im Dezember 2010!
Hi Stefan,
ReplyDelete“I guess there will big a gigantic traffic jam on the roads to Niagara ;-)”
I never thought of that, can you imagine a total eclipse at Niagara Fall’s. It will be a zoo for sure. Imagine they have 16 years to plan the marketing campaign. They could turn the night lights on the falls at the height of the eclipse for a first in the daytime.
“But I agree, kids who don't know the multiplication table probably won't end up as mathematical geniusses.”
You certainly have that right! Have you ever been in a fast food place with the equipment down? No one knows how to even make change anymore (which only requires counting up). Calculators should not be allowed in schools until at least the 9th or 10th grade.
Regards,
Phil
Hi Andi,
ReplyDeleteVielleicht solltet Ihr den Namen in Monda Luna aendern ;-)
Sabine
Hallo Sabine,
ReplyDeletebetreffs:
"Vielleicht solltet Ihr den Namen in Monda Luna aendern ;-)"
könnte dieser Link interessant für dich sein:
http://de.uncyclopedia.org/wiki/Kevinismus
Gruß
georg
Hi Georg:
ReplyDeleteAchjeh. Die Deutschen sehen das mit den Namen viel zu eng, die Amis sind da viel kreativer. Ich mein, April find ich zB einen ganz schoenen Namen, ueber Sydney und Brooklyn kann man streiten. Sundance macht sich auch gut. Ich hab mal ein Buch gelesen ueber ein Geschwisterpaar names 'Occasional Rain' und 'Partly Cloudy', benannt nach dem Wetter am Tag der Geburt. Ich find das nett. Allerdings hat man in USA den Vorteil, dass man den Namen, wenn er einem denn nicht gefaellt, auch leichter wieder aendern kann. In Dland brauchts vermutlich einen jahrelangen Gerichtsprozess gegen die eigenen Eltern oder so. Gruessli,
B.
There was a famous Texan philanthropist with the very creative name Ima Hogg, although her parents supposedly named her without realizing that her name sounds like a sentence in English. (See the Wikipedia entry.) And -- to change the subject back to eclipses -- I seem to have incorrectly blamed Theodore Oppolzer for misplacing Hawaii. As Stefan pointed out in an email, the erroneous eclipse maps were in an English-language canon of eclipses. I'm not sure which one, though; either a translated edition of Oppolzer, or someone else's canon.
ReplyDeleteHi Sam,
ReplyDeleteI seem to have incorrectly blamed Theodore Oppolzer for misplacing Hawaii.
But it seems that you can indeed blame Oppolzer for completely ignoring Hawaii at the first place and not putting it on the map at all ;-).
When I find some the time, I'll try to get a glimpse at one of the original Canon maps in the library.
Best, Stefan