The understanding of the cosmos described in the last lecture is the
culmination of 500 years of scientific astronomy. But the concerted
study of the sky started long before that. How long? We don't really
know---probably at least 8000 years before. Almost every human
society whose culture we have been able to sample in detail shows some
awareness of celestial phenomena --- if not in the form of written
records then in other ways, such as the alignment of buildings to
In prehistoric times astronomy consisted of simple observations
that any interested person could make. In fact, up to the
nineteenth century most people were well acquainted with the basic
features of the night sky. We are unfamiliar with the sky in modern
times mainly because of the advent of
artificial lighting, which makes it difficult to view the night sky in
urban areas. We no longer need to use the sky as a pathfinder either.
This lecture introduces the basic features of the sky which you can
easily see without telescopes and which are the basis for human
curiosity about the sky. It also discusses constellations and
prepares you for the Constellation Quiz.
1 degree = 60 minutes of arc;
1 arcmin = 60 seconds of arc Don't confuse these angular units with units of time! Always use the "arc" terminology for clarity.
Measuring an angular diameter
[Note: the symbol ~ means "approximately"]
Angular scales of "pan" of Big Dipper
"Hand-y" measuring scale (see illustration):
Click on the image for a QuickTime animation.
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