Much of what is known about the universe came from the study of
celestial shadows. This book looks in detail at the way eclipses and
other celestial shadows have given us amazing insights into the nature
of the objects in our solar system and how they are even helping us
discover and analyze planets that orbit stars other than our Sun. A
variety of eclipses, transits, and occultations of the mooons of Jupiter
and Saturn, Pluto and its satellite Charon, asteroids and stars have
helped astronomers to work out their dimensions, structures, and
shapes - even the existence of atmospheres and structures of exoplanets.
Long before Columbus set out to reach the Far East by sailing West, the
curved shadow of the Earth on the Moon during a lunar eclipse revealed
that we inhabit a round world, a globe. More recently, comparisons of
the sunlit and Earthlit parts of the Moon have been used to determine
changes in the Earth's brightness as a way of monitoring possible
effects in cloud coverage which may be related to global warming.
Shadows were used by the Greek mathematician Eratosthenes to work out
the first estimate of the circumference of the Earth, by Galileo to
measure the heights of the lunar mountains and by eighteenth century
astronomers to determine the scale of the Solar System itself.
Some of the rarest and most wonderful shadows of all are those cast onto
Earth by the lovely "Evening Star" Venus as it goes between the Earth
and the Sun. These majestic transits
of Venus occur at most two in a century; after the 2012 transit, there
is not a chance to observe this phenomenon until 2117, while the more
common sweep of a total solar eclipse creates one of the most dramatic
and awe-inspiring events of nature. Though it may have once been a
source of consternation or dread, solar eclipses now lead thousands of
amateur astronomers and "eclipse-chasers" to travel the globe in order
to experience the dramatic view under "totality." These phenomena are
among the most spectacular available to observers and are given their
full due in Westfall and Sheehan's comprehensive study.
