With human footprints on the moon, radio telescopes listening for messages from alien crea

tures (who may or may not exist), technicians looking for celestial and planetary sources of energy to support our civilization, orbiting telescopes' data hinting at planetary systems around other stars, and political groups trying to figure out how to save humanity from nuclear warfare that would damage life and eliminate on a planet-wide scale, an astronomy book published today enters a world different from the one that greeted books a generation ago. Astronomy has broadened to involve our basic circumstances and our mysterious future in the universe. With eclipses and space missions broadcast live, and with NASA, Europe, and the USSR planning and building permanent space stations, astronomy offers adventure for all people, an outward exploratory thrust that may one day be seen as an alternative to mindless consumerism, ideological bickering, and wars to control dwindling resources on a closed, finite Earth.

Today's astronomy students not only seek an up-to-date summary of astronomical facts: they ask, as people have asked for ages, about our basic relations to the rest of the universe. They may study astronomy partly to seek points of contact between science and other human endeavors: philosophy, history, politics, environmental action, even the arts and religion.

Science fiction writers and special effect artists on recent films help today's students realize that unseen worlds of space are real places—not abstract concepts. Today's students are citizens of a more real, more vast cosmos than conceptualized by students of a decade ago.

In designing this edition, the Wadsworh editors and I have tried to respond to these developments. Rather than jumping at the start into murky waters of cosmology, I have begun with the viewpoint of ancient people on Earth and worked outward across the universe. This method of organization automatically (if loosely) reflects the order of humanity's discoveries about astronomy and provides a unifying theme of increasing distance and scale.

This passage is most probably taken from

A．an article of popular science.

B．the introduction of a book of astronomy.

C．a lecture given by the author to astronomy students.

D．the preface of a piece of science fiction.