The second part of Duncan’s book deals with the origin of the green children . The author speculates that a matter transmitter could have been responsible for their accidental arrival on Earth and the unusual number of strange astronomical events recorded by contemporary chroniclers and observers are suggested as possible side-effects of the use of such a transmitter.

Duncan uses the green girl’s description of her home as the starting point for suggesting the kind of planet she has come from. Her sparce  descriptions of a land perpetually in twilight, but with a bright sunlit country visible across a river , seems a tall order to fulfill, but the author , by a dextrous use of his scientific knowledge and an imaginative speculation , presents us with an ingenious solution   to explain these strange facts.

He suggests that the planet in question must be one in a locked orbit   ( i.e. one whose rotational period around its   star is the same length as its day, like the Earth-Moon situation, so the same hemisphere always faces its star.

He speculates that an advanced alien intelligence could have created a valley, by means of asteroid impact , which followed the planet’s terminator along all or some of its length. Duncan discusses in great detail the terraforming processes which would be needed to accomplish this and to furnish the valley with a river and breathable atmosphere.

For me, the really brilliant touch is his suggestion that the inhabitants are placed on the side of the valley nearest to the sun-side , sheltered by towering clifs behind them and lit only by the reflected sunlight from the opposite valley cliffs, which would always be in direct sunlight. Thus we have a land always in twilight , but with a bright sunlit land always visible across the river .

The book contains a great deal more, including the speculation that mass abductions of people from the Earth took place in the twelfth century . He goes on to present a theory that the authorities in Europe at the time had knowledge of this activity , and that such alien activity was intimately bound up with the crusades and later, the knights Templar. Duncan also goes on to speculate as to what use the aliens might have had for such abductions and works out in detail the ecology and possible technological possibilities of this valley-world.

“ Children from the sky”, although not an easy read is an exhaustive and ingenious speculation  which combines the discipline of science with the imaginative extrapolation of the sci-fi writer.  Skipper prossitt