Close to Critical

by Hal Clement
Reviewed date: 2007 May 8
Rating: 3
190 pages
cover art
cover art

Hal Clement is a worldbuilder. He writes stories grounded strongly in actual science, about strange alien planets. In Close to Critical, the planet is Tenebra: a hot world (400 degrees) with a heavy atmosphere (800 Earth atmospheres of pressure) where the density of liquid water is almost identical to the density of gaseous water.

There is intelligent life on Tenebra. The dominant species is a race of many-limbed creatures roughly as smart as a man, who are in a state roughly akin to Earth's Stone Age. Their biggest natural threats are the poisonous floaters, and rain.

Rain on Tenebra comes in the form of huge, thirty-to-fifty foot bubbles of liquid water that float gently and silently out of the sky. Anyone caught in a raindrop (or in the vapor of a recently-evaporated raindrop) will immediately fall asleep due to lack of oxygen. This in itself is not fatal to the Tenebrans--they can go dormant for days without oxygen--but leaves them susceptible to predators.

To protect themselves from the nightly rains, Tenebrans light fires and evaporate the incoming raindrops. This is small help, though, because the vapor of an evaporated drop is just as dangerous as the liquid water--and less visible.

In a freak accident, two children--a human and a Drommian--crashland on Tenebra in an experimental bathyscaphe. Scientists rush to try to rescue them, coordinating with a group of natives on the planet's surface.

The characters are not Clement's strong suit. In particular, none of the Tenebran natives have a distinctive personality. The main character--Nick--acts like a loyal dog, running to help the humans at every chance. The other Tenebrans--even Swift, the leader of the antagonistic tribe--act conveniently to advance the plot.

I find it amusing that the Tenebran native is named Nick Chopper by his human friends. The name tickled my memory, but I couldn't place it until I noticed one of the other Tenebrans is named Dorothy. Nick Chopper is the name of the Tin Woodsman from The Wizard of Oz.

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