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For the medieval astronomer/astrologers the Universe was a small place, the
Earth was the center, and events in the heavens were orderly and designed to
benefit humanity. The only change that was deemed appropriate was cyclic change
such as the (mostly) orderly motion of the planets on the sky or the daily
travel of the sun around the heavens, for cyclic change returns one to the
starting point and so is not really change at all. In Europe of the Middle Ages
this belief was elevated to the level of religious dogma, and one dared
challenge this worldview at considerable personal peril.
However, the Copernican revolution began a long process that changed
completely our perception of the heavens and humanity's place in the Universe.
Beginning in the 16th and 17th centuries and continuing until today,
observations and increased theoretical understanding demonstrated that the
Universe is enormous, that it has existed for periods that dwarf human
lifetimes, and that we do not occupy the center of the Universe (for there is no
center). Probably less appreciated is a change with antecedents in events
observed hundreds of years ago, but that has accelerated at breathtaking pace
over the last 30 years. As observational astronomy at wavelengths other than
visible light (Radio-Frequency, X-Ray, Gamma-Ray, Ultraviolet, ...) has become
more commonplace, we have begun to appreciate that the Universe is party to
scenes of unimaginable violence. Far from an orderly stage for stately and
gentle physical processes, the Universe at various times and various places
undergoes violent cataclysms releasing energy on a scale to numb the mind of
even the most analytic physical scientist.
The medieval natural philosopher would perhaps have had even greater
difficulty accepting this insight than accepting the Copernican hypothesis that
the Earth was not the center of the Universe, for it would have destroyed the
strongly held belief that the Universe existed as a nurturing cocoon for
humanity. However, it is supremely ironic that these violent processes that on
the surface seem hostile to the place of humanity in the Universe are in fact
essential to the production of the present Universe. In particular, our modern
understanding is that there would be no matter as we know it, no life as we know
it, and no humanity to contemplate these questions, in the absence of violent
processes that would, of themselves, destroy all life within countless light
years.
The development of these ideas has been a truly remarkable odyssey in the
history of human thought. These lectures represent an introduction to how this
modern worldview has come about, and a survey of the often beautiful, sometimes
astonishing, but never dull, Universe described by these evolving ideas.
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