Through the use of special effects we retrace the 15-billion-year journey from the big bang to the present. We also hear the tragic story of the martyrdom of Hypatia, the woman scientist of ancient Alexandria. This is the famous episode on nuclear war in which Dr. Sagan argues that our responsibility for survival is owed not just to ourselves, but also to the cosmos, ancient and vast, from which we spring.

Are there alien intelligences? How could we communicate with them? What about UFOs? The answers to these questions take us to Egypt to decode ancient hieroglyphics, to the largest radio telescope on Earth and, in the Spaceship of the Imagination, to visit other civilizations in space. Dr. Sagan answers questions such as: "What is the life span of a planetary civilization?" and "Will we one day hook up with a network of civilizations in the Milky Way galaxy?"

The brain is the focus of this fascinating portion of our journey as Dr. Sagan examines another of the intelligent creatures with whom we share the planet Earth — whales. Then we wind through the maze of the human brain to witness the architecture of thought. We see how genes, brains and books store the information necessary for human survival.

Dr. Sagan leads us on some awesome trips — to a time when galaxies were beginning to form, to India to explore the infinite cycles of Hindu cosmology, and to show how humans of this century discovered the expanding universe and its origin in the big bang. He disappears down a black hole and reappears in New Mexico to show us an array of 17 telescopes probing the farthest reaches of space.

Using computer animation and amazing astronomical art, Dr. Sagan shows how stars are born, live, die and sometimes collapse to form neutron stars or black holes. We then journey into the future to witness "the last perfect day on Earth," 5 billion years from now, after which the sun will engulf our planet in the fires of its death throes.

A voyage to see how star patterns change over millions of years is followed by a journey to the planets of other stars, and a look at the possibility of time travel. This takes us to Italy, where a young Albert Einstein first wondered what it would be like to ride on a beam of light.

Humans once thought the stars were campfires in the sky and the Milky Way "the backbone of night." In this fascinating segment Dr. Sagan takes us back to ancient Greece, when the basic question "what are the stars?" was first asked. He visits the Brooklyn elementary school of his childhood, where this same question is still on students' minds.

Dr. Sagan compares the exhilaration of 17th-century Dutch explorers who ventured in sailing ships halfway around our planet in their quest for wealth and knowledge to an inside view of the excitement around Voyager's expeditions to Jupiter and Saturn. The newly acquired treasures of our present golden age of exploration are the focus of this episode.