WHAT IF THE MOON DIDN’T EXIST?, by Neil F. Comins, HarperCollins, 291 pages, $20.

Anyone who has raised children is familiar with the question that begins “What if?” It was incessant “What if” questions from his son that spurred Neil Comins, a professor of astronomy at the University of Maine, to write this highly readable and informative book.

Each chapter speculates on the conditions to be found on a hypothetical planet that could be the Earth if the formation of the solar system had taken a different path. In the first chapter, Comins describes the conditions on Solon, a planet just like Earth except the moon never formed. Some fascinating possibilities emerge such as the fact that the endless high winds caused by the rapid rotation of the planet would make speech virtually impossible.

Comins proposes that mental telepathy, a sense undeveloped in the hearing inhabitants of Earth, might become the favored means of communication. Birds on Solon would have to be heavier and more muscular to cope with the winds while animals would be more streamlined and have thicker coverings to cut down on wind resistance and protect against flying debris.

Even the life cycles of salmon would be affected, according to Comins. Salmon are hatched in fresh water, migrate to the salty oceans to grow, and then return to their native rivers to spawn. At the river’s entrance to the ocean, the salmon’s cellular biochemistry has to make the adaptation from fresh to salt or they would die. But, writes Comins, this happens only when the moon is new, so salmon on a moonless Solon would have to find another biological adaptation.

Successive chapters deal with what would happen if the moon were much closer to the Earth, if the Earth were only one-quarter of its true size, if the sun were much larger, if the planet had a different tilt with respect to the sun, and even what would happen if a supernova occurred in our vicinity or a black hole passed through the planet. In each case, Comins explains how the tides, length of the day, weather, and evolution of life forms would differ from those on Earth.

On Lunholm, where the moon is much closer to the Earth, huge tides would surge for many miles inland altering the entire coastal environment while on Granston, where the sun is much larger than Earth’s, a runaway greenhouse effect would give conditions much like those now existent on Venus. Comins supplements his speculations with enough basic astronomy to help readers understand how the differences between Earth and his hypothetical planet come about.

In the last chapter, Comins leaves the realm of speculation to deal with a serious possibility, that of an Earth minus its protective ozone layer. The consequences for life in terms of a depleted food chain, increased risk of cancer, and rapidly changing weather patterns are grim.

Anyone who has retained a child’s “What if” curiosity about the planet and its workings will find that Comins has employed his teaching skills to write a book that is enjoyable and instructive, a rare blend. A bibliography and glossary are included. In essence, the book will prove a “good read” for those with a scientific bent and an active curiosity about the world around them.

Clair Wood is a science instructor at Eastern Maine Technical College and the NEWS science columnist.