The Critics’ Corner

Life Beyond the Speed of c

by Don Webb

Bill Bowler’s The Shepherd of Zakhbaal poses some interesting problems in Relativistic time.

Challenge 461 asks how fast Omar’s spaceship had to travel, on average, to reach the orbit of Pluto, at 40 Astronomical Units, in 8½ hours.

The shortest distance traversed would be 39 AU’s or about 5.2 light-hours. Therefore the ship’s average speed toward the edge of the Solar System is about 0.61c. Assuming steady acceleration, the spaceship was probably traveling at almost 1¼ light-speed when it passed Pluto.

Since the ship’s mass became infinite at the speed of c, it would probably have affected the orbits of any planets in its vicinity. What happens after it exceeds light-speed? That’s pretty much anybody’s guess, but since tachyons need infinite energy to slow down to the speed of light, and they acquire infinite mass if they do so, we may surmise that the ship’s mass begins to decrease once it enters the tachyon realm.

Challenge 462 asks:

The spaceship has traveled 160 light-years in 18 months. Assuming steady acceleration and deceleration, at what speed was it traveling at midway point, i.e. 80 light-years from Earth?

The ship travels 160 light-years in 1½ years. Therefore it averages a speed of almost 107 times the speed of light. Assuming steady acceleration and deceleration, we may estimate it was traveling at about 213c at midway point. That’s quite respectable in science fiction terms. Of course it’s nowhere near Star Trek’s “warp speed,” which means basically “as fast as we need to go.”

From Lyla’s information in Chapter 6, we may surmise that the “Shepherd of Zakhbaal” is none other than the Colonel Shepherd who sent Omar on a one-way trip to Planet X. Assuming, for the sake of argument, that Col. Shepherd left Earth 6 years after Omar, could he have arrived at Planet X 6 years before Omar?

Let’s assume that Col. Shepherd has discovered a wormhole and made the trip to Planet X instantaneously. Here’s the situation:

Omar departs in Earth year +0 and arrives at Planet X a year and a half later, in Earth year +161½.
Col. Shepherd departs in Earth year +6 and arrives at Planet X immediately, in Earth year +166.

Odd questions sometimes arise, for example:

Q.: Since Omar travels faster than light, won’t he be younger upon arriving at Planet X than when he left Earth?

A.: No, he ages normally and is 1½ years older, because that’s how long it took his ship to make the journey. However, he is 158½ years younger than if he had remained on Earth.

Q.: Suppose Omar and the crew turn the ship around as soon as they arrive at Planet X and hightail it back to Earth as fast as they came. Won’t they age precipitously and be dessicated mummies upon their return?

A.: No, since they return to Earth at the same rate as they left, they will be 3 years older. However, everything and everybody on Earth will be more than three centuries older, because Omar and the crew will return in Earth year +323, i.e. (160 x 2) + (1½ x 2).

Traveling at or beyond light-speed is a form of time travel. You can travel into the future of everything outside your own frame of reference, but you can’t time-travel into your own future.

Therefore, Col. Shepherd arrives 4½ years after Omar. The only way he can beat Omar to Planet X by any amount of time is to traverse one of Star Trek’s handy “space-time anomalies” and arrive before he departed.

Otherwise we have to change the assumption and suppose he took a wormhole to Planet X, say, 6 months after Omar. In that case he could arrive about a year before Omar does.

In Joe Haldeman’s classic novel The Forever War, spaceships don’t go very fast; they pass through ubiquitous “collapsars” to travel between stars and even galaxies. As far as the hero, William Mandella, is concerned, the war does seem endless, but in terms of his own time it lasts only a few years.

Meanwhile, the war lasts four centuries on Earth, and Mandella finds Earth becoming increasingly weird from his perspective. By the time he’s promoted to the rank of Major, by dint of sheer survival, he and his troops no longer speak the same language, and they and he find each other’s cultures well-nigh incomprehensible.

The Forever War does for the Vietnam War what Eric Maria Remarque’s All Quiet on the Western Front does for World War I. The Shepherd of Zakhbaal has quite a different purpose: it portrays two outcasts — Omar and Lyla — who don’t have to deal with culture change on Earth but must nonetheless confront the insanity that sent them to Planet X in the first place.