AFTERWORD 603O
ur journey together is over; but, before we part
company, let’s ponder one fi nal time the primary
theme of this book—humanity’s place in the physical
universe. Astronomy gives us some comprehension of the work-
ings of stars, galaxies, and planets, but its greatest value lies in
what it teaches us about ourselves. Now that you have surveyed
astronomical knowledge, you can better understand your own
position in nature.
To some, the word nature conjures up visions of furry rabbits
hopping about in a forest glade. To others, nature is the blue-
green ocean depths, and still others think of nature as windswept
mountaintops. As diverse as these images are, they are all Earth-
bound. Having studied astronomy, you can see nature as a beau-
tiful mechanism composed of matter and energy, interacting
according to simple rules, forming galaxies, stars, planets, moun-
taintops, ocean depths, forest glades, and people.
Perhaps the most important astronomical lesson is that
humanity is a small but important part of the universe. Most of
the universe is probably lifeless. Th e vast reaches between the
galaxies appear to be empty of all but the thinnest gas, and stars
are much too hot to preserve the chemical bonds that seem nec-
essary for life to survive and develop. It seems that only on the
surfaces of a few planets, where temperatures are moderate, can
atoms link together in special ways to form living matter.
If life is special, then intelligence is precious. Th e universe
must contain many planets devoid of life, planets where sunlight
has shined unfelt for billions of years. Th ere may also exist plan-
ets on which life has developed but has not become complex,
planets where the wind stirs wide plains of grass and rustles
through dark forests. On some planets, creatures resembling
Earth’s insects, fi sh, birds, and animals may watch the passing
days only dimly aware of their own existence. It is intelligence,
human or alien, that gives meaning to the landscape.
Science is the process by which Earth’s intelligence has tried
to understand the physical universe. Science is not the invention
of new devices or processes. It does not create home computers,
cure the mumps, or manufacture plastic spoons—those are engi-
neering and technology, the adaptation of scientifi c understand-
ing for practical purposes. Science is the understanding of nature,
and astronomy is that understanding on the grandest scale.
Astronomy is the science by which the universe, through its
intelligent lumps of matter, tries to understand its own
existence.
As the primary intelligent species on this planet, we are the
custodians of a priceless gift—a planet fi lled with living things.
Th is is especially true if life is rare in the universe. In fact, if Earth
is the only inhabited planet, our responsibility is overwhelming.
We are the only creatures who can take action to preserve the
existence of life on Earth; ironically, our own actions are the most
serious hazards.
Th e future of humanity is not secure. We are trapped on a
tiny planet with limited resources and a population growing
faster than our ability to produce food. We have already driven
some creatures to extinction and now threaten others. We are
changing the climate of our planet in ways we do not fully
understand. Even if we reshape our civilization to preserve our
world, the sun’s evolution will eventually destroy Earth.
Th is may be a sad prospect, but a few factors are comforting.
First, everything in the universe is temporary. Stars die, galaxies
die; perhaps the entire universe will someday end. Our distant
future is limited, and this assures us that we are a part of a much
larger whole. Second, we have a few billion years to prepare, and
a billion years is a very long time. Only a few million years ago,
our ancestors were starting to walk upright and communicate. A
billion years ago, our ancestors were microscopic organisms liv-
ing in the oceans. To suppose that a billion years hence there will
be beings resembling today’s humans, or that humans will still be
the dominant intelligence on Earth, or that humans will even
exist, are ultimately conceits.
Our responsibility is not to save our race for all eternity but
to behave as dependable custodians of our planet, preserving it,
admiring it, and trying to understand it. Th at calls for drastic
changes in our behavior toward other living things and a revolu-
tion in our attitude toward our planet’s resources. Whether we
can change our ways is debatable—humanity is far from perfect
in its understanding, abilities, or intentions. However, you must
not imagine that we, and our civilization, are less than precious.
We have the gift of intelligence, and that is the fi nest thing this
planet has ever produced.We shall not cease from exploration
And the end of all our exploring
Will be to arrive where we started
And know the place for the fi rst time.
—T. S. Eliot, “Little Gidding”Excerpt from “Little Gidding” in Four Quartets, copyright 1942 by T. S. Eliot
and renewed 1970 by Esme Valerie Eliot, reprinted by permission of Harcourt,
Inc. and Faber & Faber, Ltd.