Discovering what lies behind a hill or beyond a neighborhood can be as
simple as taking a short walk. But curiosity and the urge to make new discoveries
usually require people to undertake journeys much more adventuresome
than a short walk, and scientists oft en study realms far removed
from everyday observation—sometimes even beyond the present means
of travel or vision. Polish astronomer Nicolaus Copernicus’s (1473–1543)
heliocentric (Sun-centered) model of the solar system, published in 1543,
ushered in the modern age of astronomy more than 400 years before the
fi rst rocket escaped Earth’s gravity. Scientists today probe the tiny domain
of atoms, pilot submersibles into marine trenches far beneath the waves,
and analyze processes occurring deep within stars.