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[Phys-L] Re: Light from fireball visible?



At 22:21 -0500 2/9/06, Hugh Haskell wrote:

. . . given that one
time zone is approx. 1700 km, and Shanghai is only 800 km from
Nagasaki, and given the time of detonation at Nagasaki, the sun
should have been well risen in Shanghai by that time, so I doubt that
a reflection would have been sufficiently brighter than the
background to be noticed, even if it could be detected.

It's been a long day, and I'm not thinking to well. Of course, at 32
deg. N lat. a time zone won't be 1700 km--that's the equatorial
distance, but its not a whole lot less at that latitude, maybe 1450
km. In any event I took the trouble to look at a map, and noted that
both Nagasaki and Shanghai are at about 32 N, and Nagasaki is at
about 130 E while Shanghai is at about 121 E, meaning that the sun
will be only about 9 degrees lower in the sky at any time than it is
in Nagasaki (in the early morning, that is). According to the website
of the 509th bomber group, Fat Man detonated at 12:02 PM at an
altitude of 1840 ft ASL (that number is probably based on a
calculated fall distance from the drop point, which was measured with
an altimeter setting of 29.92 in. Hg. So it may have been lower if
the local pressure was lower than standard that day, which may
account for the difference between this HOB and that quoted by BC
earlier.

But it is clear that the sun would have been approximately overhead
in both cities at the time of the explosion. Still more evidence that
the fireball or any other immediate evidence of the explosion would
not have been seen in Shanghai.

If I learned anything from this little exercise, it has been some
geography. I had completely forgotten that Shanghai is a coastal
city, and I was also unaware that it was that close to the main
islands of Japan. This does give me some understanding of why Japan
is so nervous about the Chinese gaining a nuclear missile capability,
even if it is not very long range--it doesn't have to be with much of
Japan less than 2000 km from likely launch points in China.

Hugh
--

Hugh Haskell
<mailto:haskell@ncssm.edu>
<mailto:hhaskell@mindspring.com>

(919) 467-7610

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