Isaac Asimov poses a number of questions:

“The question is: Are we alone?

“Are human beings the only possessors of eyes that probe the depths of the Universe?The only builders of devices to extend the natural senses? The only owners of minds that strive to understand and interpret what is seen and sensed?

“And the answer is, just possibly: We are not alone! There are other kidns that seek and wonder, and do so perhaps even more effectively than we.

“Many astronomers believe this is so, and I believe this is so.

“We don’t know where those other midns are, but they are somewhere. We don’t know what they do, but they do much. We don’t know what they‘re like, but they are intelligent.

“Will they find us if they aer somewhere out there? Or have they found us already?”

Mr. Asimov proceeds to analyze the Universe, life, and intelligence, basing his conclusions on the most recent scientific findings. The size of the Universe, the number of galaxies, the number of stars in a galaxy (300 billioin in our own), and the number of planets (280 billion planetary systems in our Galaxy) provide the setting for determinign whether other civilizations do exist.

We learn why life can form only on a planet. And we learn the requisites for life: proximity to a star (not too close or too far), water, atmosphere, organic compounds, energy, and, in order to develop a civilization similar to ours, dry land as well as oceans.

Despite the huge number of planets, the combination of conditions needed for an advanced technological civilization eliminates so many that the incidence of possible civilizations is relatively slight. Then there is the problem of communication. Distances are so vast and the time for messages traveling even at the speed of light is so immense that messages sent by a civilized community might not reach us for centuries. And then there is the problem of interpreting the messages. Just as man so far has been unable to translate the language of the dolphin into human terms, so the language of distant civilizaitons may pose problems.

There is much to be learned before we will be able to communicate with, and perhaps learn from, the nearest civilizations that undoubtedly exist.

This book is a sine qua non for any Asimov fan, I believe—any science fiction fan, in fact, but particularly fans of the Good Doctor. Interstellar travel was, after all, his bread-and-butter. He’s the inventor of the Galactic Empire. His characters go from one end of the Milky Way to the other with little difficulty—when Arkady Darrell runs away, she dashes down to the nearest spaceport and grabs a ticket to Trantor just as easily as you or I might by one for Paris. (Well, you and I aren’t likely to have enough cash on hand to do that, but that’s why God invented credit cards.)

And so what is this excellent book about? Why, just how implausible interstellar space travel à la Asimov or “Star Trek” really is.

Asimov goes through all the possible scenarios one by one and deflates them. Using black holes as an intergalactic subway? Maybe—assuming you could survive the tides ripping your ship to shreds on the way in and don’t mind the relative impossibility of ever getting home again. Time dilation? Get your ship going fast enough to have relativity dilate time and you’ll be fried to a crisp by interstellar gas. Hyperspace? No evidence for it. FTL via tachyons? No evidence for it, and some good (if controversial) reasons for thinking it impossible. And so on.

Actually Asimov is perhaps a little overly pessimistic here, and it’s nice to have writers like Gregory Benford to correct him on occasion when he needs it. But that’s a quibble, since this is really a terrific book and a lot of fun to read, and it provides a much-needed perspective to the craft of science fiction. It’s nice to see that Asimov, at least, was able to be realistic as to just how plausible his marvelous interstellar romances really are.