ORIGINS The Lives and Worlds Of Modern Cosmologists By Alan Lightman and Roberta Brawer Harvard University Press 561 pp. $29.95

NASA'S careless failure to test the Hubble telescope's mirrors may seem a minor disaster to many, but to astronomers it was a crushing blow. Revolutionary observations in the past 15 years have thrown cosmologists onto a battlefield where rival theories clash as vigorously as when proponents of the Big Bang and Steady State models of the universe were ridiculing one another. The Hubble telescope could have settled many of the new controversies. Astronomers will now have to wait years before the Hubble can be repaired or a new one launched.

Starting in 1987, MIT physicist Alan Lightman interviewed 27 of the world's top cosmologists about their family background, their early history, their work and their beliefs. Stephen Hawking, Roger Penrose, Fred Hoyle, Steven Weinberg, Dennis Sciama and Robert Dicke are perhaps the best known, but all 27 have made enormous contributions to astronomy. There is no better way to understand their current confusions than by reading this timely and admirable anthology, edited by Lightman and Roberta Brawer, a graduate student in cosmology at MIT.

At the heart of the debates are the "horizon problem" and the "flatness problem." The horizon question is: Why is the universe so homogenized? The microwave background, left over from the big bang, implies a universe with the same overall structure in all directions. The best explanation is an inflationary model which has the universe popping into existence from almost nothing, expanding at an exponential rate before the bang, then settling down to a slow linear growth.

But is the universe really homogeneous? A few years ago Margaret Geller and others, studying red-shift maps, found that the universe is lumpier than anyone suspected. Galaxies lie on the surfaces of monstrous "bubbles" that surround huge voids. Other galaxies form long filaments and flat "walls." To make things worse, some galaxies are streaming the wrong way, against what is called the "Hubble flow" -- the universe's steady expansion. Most of the interviewed cosmologists hope that on vaster scales the universe will be smoothed out. All agree that if peculiar structures and motions persist on still larger scales, the big bang model will be in deep trouble.

The flatness question is: Why is the curvature of space so close to zero? This is the same as asking why the Hubble flow is so nearly balanced by the pull of gravity that only a tiny increase in the amount of mass in the universe would eventually halt the expansion. Lightman likens it to tossing a rock in the air with a velocity exactly enough to let the rock escape earth's gravity. Inflation models solve this problem also, but unfortunately require far more matter in the cosmos than can be observed. Indeed, to make space so nearly flat, there must be 10 times as much matter than can be seen.

There are solid grounds for thinking that the universe contains the required amount of dark (unseen) matter. Vera Rubin and others have shown that galactic motions cannot be explained without assuming this dark matter, but there is no agreement on how much, or what and where it is.

Most cosmologists accept the flatness, and believe that the dark matter will soon be found. A few, notably John Wheeler and Robert Dicke, lean toward enough matter to "close" space-time, halt the expansion and send the universe the other way toward a Big Crunch. The notion that after the crunch it will bounce back again -- the so-called oscillating universe -- is almost ruled out by the lack of known laws to explain it.

Lightman's interviews follow a fairly fixed set of questions about the above problems, and end metaphysically by asking for a reaction to a famous statement by Steven Weinberg in his popular book The First Three Minutes. The more the universe is understood, he wrote, the more pointless it seems.

To me, this is asking whether there is a transcendent Mind behind the universe that gives it a purpose we cannot fathom. I was struck by the fact that a majority of those interviewed were unwilling to make such a leap of faith, and in that sense agreed with Weinberg. Indeed, only four believe the universe has a purpose: Charles Misner, a Catholic; Don Page, an evangelical Protestant; Andrei Linde, a devotee of Hindu theology; and Allan Sandage, who became some sort of Christian convert about 1980. (For a full account of Sandage's distinguished career and evolving beliefs, see Dennis Overbye's forthcoming Lonely Hearts of the Cosmos, from HarperCollins.

Fred Hoyle may also belong to this group even though he did not say so. He is alone in the book in clinging to a steady-state model, rejecting the big bang mainly because he thinks it does not allow enough time for life to evolve. I found it surprising that so many astronomers spoke with regret of having been forced by the microwave radiation to accept a beginning for the universe. Like Aristotle's earth-centered cosmology and Einstein's static first model, a steady state avoids the messy task of explaining how a universe can explode from a quantum vacuum. Several of those interviewed stressed how emotionally satisfying it once was to believe that the universe has always been and always will be just what it is.

Sandage, more than anyone else, spoke of being overwhelmed by the dark riddle of why a universe exists at all, and why it is so beautifully and intricately structured. Let him have the final word:

"The greatest mystery is why there is something instead of nothing, and the greatest something is this thing we call life. I am entirely baffled by you and me. We were both there near the beginning. The atoms in our bodies were made then, yet their sum now, in a living thing, is greater than the whole . . . perhaps the universe is the only way it can be for us to exist."

Martin Gardner is the author of "The New Ambidextrous Universe" and the forthcoming "More Annotated Alice," a sequel to his "The Annotated Alice."