No lack of courage here. The authors plunge right into the big questions: Who are we? Where did we come from? Where are we going? Are we alone?

Two astrophysicists, John Gribbin, a science journalist, and Eric Chaisson, an associate professor at Harvard, draw on the dramatic progress in the past few decades in physics and biology to astonish us with immensities. Both began with the "singularity" before space, before time, before matter. Gribbin's sequence moves from the origins of the universe to our galaxy, our solar system, the origina of the earth, of life, of species, of diversity, to human rights and "destinations."

Chaisson moves from particles -- the "moment," if one dare refer to time, when matter began uncoupling from radication; to galaxies and the hierarchy of cosmic structures; to stars, forges for elements; to planets as habitats for life. The "primordial soup" may have been a time of "chemical evolution," when more complex compounds were gradually built up by catalysis and energy from that friendly star, our own sun. This resulted in life, says Chaisson: that is, matter plus energy. His chapter on culture shows evolution at work, leading from the first faltering steps toward intelligence to human technology.

Man has always looked up at the stars and wondered. And he has tried to see the patterns and connections. The modern difference, and the reason such speculation has moved beyond philosophy, is that technology has given us powerful tools for observation and measurement. The same human curiosity, the need to know, that built Stonehenge and the precise alignments at Fajada Butte, motivate cosmologists like Carl Sagan -- and the millions of us transfixed by "Cosmos," or even "2001."

The beautiful myths and the imaginative fables of creation have given way to newer models. But like the old, they are attempts to understand, to create order, to see cause and effect. The new models assume that the physical laws we can observe here on earth and relatively close by, operate in the same way throughout the universe. They enable us to recreate in general terms, as in Nobel laureate Steven Weinberg's brilliant book, "The First Three Minutes" after the big bang. They predict what we might see as we gaze into deep space and deeply in time -- the halos and auras, the drifting dust and glowing gas, the clusters of galaxies, and the shapes they assume -- pinwheels, pancakes, spirals with arms, kaleidoscope of whirlpools and vortices.

"The scenario of cosmic evolution," says Chaisson, "is a human invention." It is "a grand scenario" that strives to integrete the big and small, the near and far, the past and future, into a unified whole." Simple -- and beautiful.

This is cosmic drama that could have been invented by Tolkien: red giants and white dwarfs, black holes, blazing supernovas, and complex curves of time and space, like an Escher painting or a Mobius strip of eternal dimensions.

And here we are, bits of star stuff, "brothers of the boulders, cousins of the clouds," as Harlow Shapley put it, "residents of an undistinguished hunk of rock, circulating about an average star, someplace in the suburbs of the Milky Way Galaxy."

The view from space is humbling. But it is also challenging. Gribbin and Chaisson emphasize that we respond to the same few fundamental physical laws as the most distant quasars. But the universe is also characterized by diversity and randomness.

Man's intelligence and his tools present him with the potential to shape his own destiny. "Technology," says Chaisson, "enables life to begin to control matter . . . We are more than products of the Universe, more than life in the cosmos. We are agents of the Universe -- agents of the Universe commissioned by it to probe itself."

But this same potential gives us the power to destroy. Chaisson singles out over-population, the self-destruction of nuclear warfare, genetic degeneration, and the possibility that "silicon-based circuitry" may someday subjugate us.

These two books are compelling. Bronowski is richer in human detail, Asimov has a wider range. Although Gribbon is the professional journalist, Chaisson is the better writer -- and his judgments are often more soundly based. But speculations like these will never cease, nor should they. They're what being human is all about.