Geography Reference
In-Depth Information
In the second place, geography is about exploration and discovery. People have always asked, “What's
over that mountain?” and “Who lives on the other side of that lake?” Even if the motives have often been
greed or the desire to dominate the next-door neighbors, there is no denying that wanting to know about
the places we can't see has been the prime mover throughout history. With fewer unexplored places left on
earth, moving beyond the bounds of earth's gravity represents the last and greatest “frontier” and perhaps
the most potentially rewarding realm of undiscovered riches.
And finally, if geography is simply about where we are in the world, it makes sense to understand where
our world is in relation to all those heavenly bodies that we see at night, and the big one we see by day
that keeps the earth alive—the sun. The secrets held by the universe about the creation of the earth, the
beginnings of life, and the fate of the earth are being examined as we look to space to see where humanity
will head next, and to seek an answer to one of the Really Big Questions: “Are we alone?”
How Big Is the Universe?
While astronomy has rightfully been called the first science, it might also be safe to call it the worst sci-
ence. But it is not for lack of trying or general stupidity on the part of astronomers. On the contrary, it is
astonishing to realize how
right
astronomers have been, given the tools they had to work with. For centur-
ies, it was like using a kitchen knife to do brain surgery, and with the lights turned off.
Until fairly recently, astronomers were the scientific equivalent of the proverbial six blind men trying
to describe an elephant by feeling different parts of its body. One felt its tail and thought it was a snake.
Another grasped its leg and said it was a tree trunk. They just couldn't get the whole picture, so they were
left to grope around the separate parts and imagine what the rest of the elephant looked like.
But a burst of extraordinary discoveries during the 1980s radically transformed our notions of the
universe. It's not that today's astronomers have been given smart pills. They've just been given better
tools—or more specifically, better eyes. It is a little daunting to imagine what Galileo, Kepler, Newton, or
Einstein might have come up with if they had had the information and the technical wizardry astronomy
has in its workshop today. And in the new century, a new generation of space-based and earth-based instru-
ments, capable of seeing things science could never see before, will provide some of the missing pieces in
the immense jigsaw puzzle called the universe.
One of the most basic notions the astronomically untutored must contend with is the idea that looking
at space means looking at time. The light we see in the stars of deep space is light emitted long, long ago.
In that ancient light are the clues that science hopes will answer many of the most basic questions people
have asked since they started to crane their necks upward at the sun and the stars.
Ancient ideas about the size and shape of the universe coalesced in the writings of Ptolemy, whose
notion of an earth-centered universe lasted for some fourteen hundred years. This notion was gradually
challenged, first by Copernicus and then nudged along by Tycho Brahe and Johannes Kepler. Finally, Ga-
lileo raised papal eyebrows by stating that the earth was not the center of the universe at all, but only one
smallish planet revolving around the sun, along with several others.
Earth is one of the nine planets—even that number is now in question; Pluto may actually belong to
another solar system—that are held in the gravitational thrall of our life-giving star, the sun. Counting out
from the sun, there are four
inner planets.
Rocky and smallish—on the cosmic scale, that is—they are also
called the
terrestrial planets.
Mercury
Slightly larger than the earth's moon, Mercury is too small to have its own atmosphere.
Without an atmosphere to trap heat, Mercury is very cold, even though it is the planet nearest the sun.
