Bad Astronomy: Misconceptions and Misuses Revealed, from ...

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A Dash of Seasons:
Why Summer Turns to Fall
S ome
examples of bad astronomy are pernicious. They sound
reasonable, and they even agree with some other preconceived
notions and half-remembered high school science lessons. These
ideas can really take root in your head and be very difficult to get
out.
Perhaps the most tenacious of these is the reason why we have
seasons.
Seasons are probably the most obvious astronomical influence
on our lives. Over most of the planet it’s substantially hotter in the
summer than in the winter. Clearly, the most obvious explanation
is our distance from the Sun. It’s common sense that the closer you
are to a heat source, the more heat you feel. It’s also common sense
that the Sun is the big daddy of all heat sources. Walking from
underneath the shadow of a shade tree on a summer’s day is all
you need do to be convinced of that. It makes perfect sense that if
somehow the Earth were to get closer to the Sun, it could heat up
quite a bit, and if it were farther away our temperatures would
dip. And hey, didn’t you learn in your high school science class
that the Earth orbits the Sun in an ellipse? So sometimes the Earth
really is closer to the Sun, and sometimes it’s farther away. This
logic process seems to point inevitably to the cause of the seasons
being the ellipticity of the Earth’s orbit.
Unfortunately, that logic process is missing a few key steps.
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