From: Henry Spencer <henry@zoo.toronto.edu>
Newsgroups: sci.space.tech
Subject: Re: EARTH'S ORBIT ABOUT THE SUN
Date: Mon, 10 Jun 1996 03:46:49 GMT

In article <4p01pp$153@news13.erols.com> Larry Brunson <lbrunson@erols.com> writes:
>I have a question about why our hot season starts with the summer 
>solstice.  It would seem that it should be centered about it...
>...Somehow it sounds like a pat 
>answer to say that the initial 3 months of northern hemisphere sun serve 
>to heat the earth so that the latter 3 months feel hot because of latent 
>heat...

It may sound pat, but it's true.  At the end of winter, there is a lot of
cold air, and cold ground, and cold water, in the northern hemisphere.
It takes quite a lot of accumulated heating to warm all that up, especially
since the heating effect doesn't immediately go full blast at the vernal
equinox.  Try swimming in a reasonably large and deep lake (Lake Ontario
is a good example) in May if you want proof that things warm up slowly!

>It seems inadequate because the sun never gets any higher than 
>23deg north, and we're at 50...

If you compute the difference in solar energy, per square kilometer of
surface, between winter and summer, you'll find that it makes a large
difference.  What with the higher sun and the much longer days, we get a
lot more heat in summer. 

>Also, we have to wait well after the 
>summer solstice (until August) (even though the sun keeps getting farther 
>away from our latitude) to get our blistering heat.  What gives?

Thermal inertia, pure and simple.  The heat input is weakening, but it's
building on the cumulative results of a whole summer of heating.
-- 
If we feared danger, mankind would never           |       Henry Spencer
go to space.                  --Ellison S. Onizuka |   henry@zoo.toronto.edu