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.
Many of the newest areas of scientifi c research involve objects or places
that are not easily accessible, if at all. Th ese objects may be trillions of miles
away, such as the newly discovered planetary systems, or they may be as
close as inside a person’s head; the brain, a delicate organ encased and protected
by the skull, has frustrated many of the best eff orts of biologists until
recently. Th e subject of interest may not be at a vast distance or concealed
by a protective covering, but instead it may be removed in terms of time.
For example, people need to learn about the evolution of Earth’s weather
and climate in order to understand the changes taking place today, yet no
one can revisit the past.