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From: TerryMoselaol.com
Date: Sat, 18 Mar 2006 20:26:54 EST
Subject: Equinox, TV,  2 lectures

Hi all, 
 
1. The Spring Equinox will be 20 March at 18h 26m,  when the Sun will cross 
the equator going Northwards. From then on, we are told,  days will be longer 
than nights, in the N Hemisphere. 
    But even on 19 March the Sun will be above our  horizon for more than 12 
hours! Tables of sunrise and sunset usually give  sunrise as the moment when 
the top of the Sun's disc first appears above  the horizon, and sunset as when 
the top of the disc disappears below the  horizon. But even if one takes the 
rising and setting of the  centre of the Sun's disc, it still  appears above 
our horizon for over 12h 2 minutes on 19 March! How  come? Because of the 
refraction effects of the Earth's atmosphere. When we see  the centre of the Sun on 
the horizon, it has actually already 'set', but the  atmosphere bends its 
light just enough for us to still see it.
   In fact, under most conditions, when the bottom of the Sun's  disc appears 
to touch the horizon, the whole of the  Sun has actually set!
   It's the refraction effect which often makes the Sun's disc  appear 
noticeably flattened when it's near the horizon.
    So the 'observed' Spring equinox actually occurs a few  days before the 
theoretical date. And of course the observed Autumn Equinox  occurs a few days 
late for the same reason.
 
TV:
2. Sun, 19 March, 9.40am, RTE1 TV: Leo Enright's Space  Odyssey

3. Sun 19 March, 5.35pm, BBC1 TV: John Daly visits Armagh  Observatory.

4. Sun 19 March, 8.00pm BBC4 TV: TIME - Michio Kaku discusses cosmic  
possibilities (4/4).

5. Mon, 20 Mar,  7.00pm, BBC4 TV: The Sky at Night - Patrick Moore  looks 
back over five decades.

6. Mon, 20 Mar, 11.05pm, BBC1 TV: John Daly visits Armagh  Observatory 
(repeat).

7. Tue, 21 Mar, 9.00pm, BBC4 TV: TIME - Michio  Kaku discusses cosmic 
possibilities (4/4).
 
LECTURES:
8. The Irish Astronomical Society lecture: "Worlds that Never Were"  (Curious 
Episodes in the History of Astronomy) to be given by the indomitable Mr  John 
Flannery, March 20th in Ely House, Ely Place, Dublin, at 8 p.m. Details on  
www.irishastrosoc.org.
 
9. Talking of the Sun, don't forget: 
IAA Public Lecture, by Dr Miruna Popescu: "The Solar  Wind: from Explosions 
on the Sun to Us", Wed 22 March, 7.30  p.m., Stranmillis College, Belfast, as 
already notified.
 
Clear skies,
 
Terry  Moseley

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