On 04/26/2013 01:35 PM, Scott Holmes wrote:
> Mark Twain used a solar eclipse as a devise to rescue Hank Morgan from
> certain death and establish him as the premier wizard of King Arthur's
> Court.  He posited the date as the 21st of June, 528 at 12:03 pm.  No
> such eclipse occurred so I'm wondering how/where Twain came up with this
> date.  Did he invent this or was it erroneously reported in some almanac
> that may have been in Twain's possession?
> 

   It was probably just invented.  The nearest eclipse to that time was
on August 1, 528 and the difference in dates cannot be attributed to one
source tabulating dates according to the Julian calendar and another
source using proleptic Gregorian dates.  The difference in dates at that
time would have only been 3 days on the two different calendars.

   In any case, the eclipse on August 1 didn't take place at high
noon--it was in the middle of the night for England (02:34 Greenwich
mean time) and was centered on Antarctica.  It wouldn't have been
visible from England.  See:

  http://eclipse.gsfc.nasa.gov/5MCSEmap/0501-0600/528-08-01.gif

   One might try to explain it by saying that "the boy" in the story not
only told Hank the wrong date (he told him it was the 20th) but the
wrong year as well.  Unfortunately, the only solar eclipses that
happened on a Jun 21 in that century were in the years 559 and 578.

   I doubt that Twain got the number out of any almanac, but just chose
a figure.  He was interested in astronomical phenomena, and had a fair
understanding of related facts and figures, but this was probably just
artistic "laziness".  As much as Twain blamed other authors (like James
Fenimore Cooper) for having completely unbelievable characters who could
do totally unreasonable things, pulling the exact date and time of a
solar eclipse in the 5th century from memory is one of the most
unbelievable.

   There's no chance of an almanac incorrectly citing a "near miss"
partial eclipse on that date.  The angular separation between the moon
and sun was in fact 138 degrees at the specified date, and it was nearly
a full moon (86.8% illuminated) on that day.  Quite the opposite of a
solar eclipse.

-- 
  Alan Eliasen
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  http://futureboy.us/