Strange Horizons Aug ’01
Strange Horizons
CONTENTS:
Article: What the Light Said by Brian Tung
Interview: Andy Duncan by Mack Knopf
Article: Under the Daddy Tree by Heather Shaw
Article: Vikings in America, by Arturo Rubio
Fiction: One-Eyed Jack by Connie Wilkins
Fiction: Right Size by M. L. Konett
Fiction: Toaster of the Gods by Randall Coots
Fiction: In a Mirror by Kim Fryer
Poetry: In the Shade of the Tree of Knowledge by Michael Chant
Poetry: On Mars by David Salisbury
Review: Terror for the Thoughtful Reader by Amy O’Loughlin
Review: Moore and O’Neill’s The League of Extraordinary Gentlemen, reviewed by Bryan A. Hollerbach
Review: Two Novels of Speculative History reviewed by Christopher Cobb
Review: Ben Bova’s Jupiter, reviewed by John Teehan
Editorial: Blood, Death, and Dismemberment by Susan Marie Groppi
What the Light Said
Do we really understand the way that space and time operate?
by Brian Tung
8/6/01
And then black night. That blackness was sublime.
I felt distributed through space and time:
One foot upon a mountaintop, one hand
Under the pebbles of a panting strand,
One ear in Italy, one eye in Spain,
In caves, my blood, and in the stars, my brain.
—Vladimir Nabokov, Pale Fire
In early January 1999, a 57-year-old man driving his BMW in Caputh, Germany, drove into the Havel River. Upon questioning, he revealed that he had been following the driving instructions relayed to him by his car’s satellite navigation computer. The computer directed him across the river to his destination, but neither he nor his computer realized in time that the only way across the river was by ferry. Fortunately, the man was not injured; unfortunately, the same couldn’t be said of his car.
“Normally, accidents like this shouldn’t happen,” said a Caputh police spokesman. “This sort of thing can happen only when people rely too much on technology.” In other words, one runs into trouble by reasoning that, “If the computer says so, it must be true.”
One is reminded of the statement made by the English countess and pioneer of computer theory, Lady Ada Lovelace (1815-1852): “The [computer] has no pretensions to originate anything. It can do whatever we know how to order it to perform.” Special conditions often result in strange behavior.
On the other hand, a Swiss-German patent clerk decided to take the strange behavior of light at face value. “If the light says so,” he might have said to himself, “it must be true.” His name was Albert Einstein (1879-1955), and what the light told him led him to, among other things, the special theory of relativity.
Special relativity looks, at first blush, like nothing so much as a bundle of contradictions. It predicts that objects change shape when they move close to the speed of light, that they change mass as well, that the nature of space and time is intimately related to where we observe them from. Part of the reason that special relativity is so counterintuitive is that light travels so darn fast: very nearly exactly 300,000 km/s, about a million times faster than any man-made object at the time. It was very difficult to listen to what the light said.
So let’s not start with light. Let’s start with a tennis ball.
Suppose you’re sitting in a boxcar in a train. Say that the boxcar is 9 feet wide. You sit on one side of the boxcar, and idly throw a tennis ball off the other side, 9 feet away. It bounces back to you. If you throw the ball at 45 feet per second (about 30 mph), the ball takes 0.2 seconds to reach the other side, which we’re able to calculate very easily, based on the following simple formula:
(1) t = d / v
which simply states that the time t that it takes an object to travel a distance d is simply d divided by the speed or velocity, v. We’ll use this formula a lot. In this case, the time taken is 9 feet, divided by 45 feet per second, or 0.2 seconds. Then it takes 0.2 seconds to bounce back to you—the whole thing takes 0.4 seconds.
Now let’s start the train in motion. Suppose it gets up to a rate of 60 feet per second (40 mph). Anyone who has ever played dodgeball with a sibling in the back seat of the family station wagon knows that the speed of the train won’t affect the behavior of the ball. It continues to travel 18 feet round trip, taking 0.4 seconds to do so.
Consider, however, a stationary observer sitting by the side of the track. He agrees that it takes 0.4 seconds from the time you throw the ball to the time you catch it again. On the other hand, he doesn’t agree that the ball only travels 18 feet round trip, because to him, the ball doesn’t travel straight forward and back. Instead, he sees it take a zig-zag path, as shown in Figure 1.
Figure 1. Path of ball as seen by outside observer.
In the 0.2 seconds that it takes the ball to travel from one side of the boxcar to the other, the train travels 12 feet. The distance that the ball travels, from the point of view of the stationary observer, is the length of the diagonal of the right triangle, which is sqrt(92 + 122), or 15 feet. The ball then travels another 15 feet on the way back, again from the point of view of the stationary observer. To this observer, therefore, the ball travels 30 feet in the same 0.4 seconds, and 30 feet divided by 0.4 seconds equals 75 feet per second (50 mph). From the point of view of someone on the ground, that’s how fast the tennis ball is moving.
There’s nothing terribly peculiar about this. The thing it depends on is the Newtonian principle that time is absolute. If you clock the round trip time of the tennis ball at 0.4 seconds, then so does everyone else, no matter how fast they’re moving. In the everyday experience of Newton and his contemporaries, there was nothing to contradict that common sense rule.
In 1873, the Scottish physicist James Clerk Maxwell (1832-1879) formally set down the four equations that govern the transmission of electromagnetic waves through a vacuum. He noticed that if you combined the four equations, you could derive the speed of those waves—it was the square root of the product of two constants, both of which could be measured in the laboratory. Given the then best-known values for those constants, he came up with a speed of just about 300,000 km/s (about 186,000 miles per second).
That is very close to the speed of light, and Maxwell decided that was too much of a coincidence. He concluded that light itself was an electromagnetic wave. But what was waving? Ocean waves are waves in water, sound waves are waves in air or some other sound-transmitting medium, but a light beam can go through a vacuum just as well as it can through anything else—better, in fact. Maxwell couldn’t bring himself to conceive of light waves just “waving themselves,” so he proposed what came to be known as the luminiferous aether. The aether was a mysterious medium, which had no mass, no energy, nothing—except that it was necessary in order for light to move anywhere at all.
For light to get to us from all across the universe, this aether had to be everywhere, in our houses, out in the fields, in buildings, in the solar system, throughout the galaxy—everywhere. Since the aether was the medium for all electromagnetic waves, it made sense to say that the speed of light was 300,000 km/s relative to the aether. In those days, the only massive objects that were known to move an appreciable fraction of that speed were astronomical: stars, planets, galaxies, and so forth. That raised the interesting question: what was our own motion—that is, the motion of the earth—relative to the aether?
In 1887, the American physicist Albert Michelson (1852-1931) and the American chemist Edward Morley (1838-1923) conducted an experiment to detect the earth’s motion through the aether. They set up an intriguing apparatus designed to measure small variations in the speed of light. As the apparatus was rotated, they expected that the instrument would show small changes reflecting the alignment of the apparatus with the earth’s motion through the aether. Light moving with the aether would be faster than light moving against the aether, and light moving across the aether would be somewhere in between.
What they found startled them: no matter how the apparatus was rotated, no change at all was detected. This seemed to imply that the earth was stationary with respect to the aether, or, in other words, that the aether moved with the earth! That seemed completely unreasonable, but it occurred to them that perhaps, just by coincidence, the earth happened to be moving with the aether. Six months later and half a revolution around the sun later, it ought to be moving the opposite direction, and then the results ought to show motion relative to the aether.