Comets
Comets have fascinated people for millions of years, but until 1994 no
one had
ever had the chance to witness firsthand the destructive power of
these
wanderers. From July 16 to 22, fragments of Comet Shoemaker-Levy 9
smashed into
Jupiter, creating a series of fireballs in the giant
planet's atmosphere. The
string of explosions was awesome, yet the discovery
that comets can wreak havoc
would not have come as a surprise to our distant
ancestors. People of widely
different cultures have long regarded comets with
fear and dread. The
unheralded, unpredictable appearances of these ephemeral
celestial visitors were
believed to be omens of disaster for rulers, realms,
and entire populations.
Comets, it was thought, signaled or caused wars,
revolutions, plagues, and other
calamities. Haley’s Comet made an appearance
in 1066. Modern scientists may
not believe in omens, but they have come to
realize that comets, which are only
mountain-sized bodies, are capable of
causing worldwide disasters as terrible as
any that were imagined of old—and
paradoxically might also be responsible for
our very existence.