Robert Silverberg--Project Pendulum

Robert Silverberg's Project Pendulum, is, unfortunately, a relatively lightweight time travel tale published first in 1987. It's another one of those stories that has an interesting premise, but the author really goes nowhere with it.

The time traveling machine sends twin brothers, one a paleontologist and the other a physicist, on a trip through time that most resembles a pendulum, as the title suggests. Twins were selected because the two travelers had to have similar weights. One twin initially goes back in time while the other goes forward an equal length in time. Then the one going back in time goes forward, while the other goes back. Each "swing" from past to present to past, is longer than the previous stop. Eric first goes back 5 minutes and then moves forward 50 minutes from time zero--the time the experiment began. He then swings back 500 minutes from time zero. Sean, his brother, does the exact opposite--forward 5 minutes, then back 50 minutes, and the forward 500 minutes. Neither stops at the point the other brother stopped on the "outward" leg of the trip. However, they will on the return leg.

This process only allows for a brief period at any stop, though the length of the stop increases as they get further away from time zero. This is the weak point in the story. We really don't get a chance to see much of what each period is like, either going back or going forward. All the reader, and the time travelers get, is a brief glimpse of what that era is like.

I was also surprised that, although they were scheduled to travel millions of years into the past and future, no one seemed concerned about possible changes in the atmosphere. This actually posed a threat to one of the brothers, and presumably will to the other on the return leg, if he isn't killed prior to getting to that stop in time.

While reading the novel, I was almost immediately reminded of another novel, A. E. van Vogt's The Weapon Shops of Isher, first published in the early 1950's, in which van Vogt posits a similar time pendulum. To keep it brief, thousands of years in the future, an energy weapon disguised as a large building is trained on one of the Weapon Shops. The Weapon Shop's energy screen causes the two of them to move through time in opposite directions. A man in 1951 enters the Shop and becomes the focus of the energy beam, and he now moves back and forth in time while the energy weapon building moves in the opposite direction, just as Sean and Eric move back and forth in Silverberg's novel.

Since there is no author's foreward or introduction, I can't say for certain that Silverberg was influenced by van Vogt's novel. In addition, I can't find any internal reference that might suggest Silverberg's familiarity with van Vogt's novel.

Overall, Project Pendulum is a lightweight work, a pleasant but forgettable read. A better introduction to Silverberg's work would be Lord Valentine's Castle, The World Inside, At Winter's End, and Shadrach in the Furnace.