Physics of Space Travel
We measure the distances to the stars in units called “light years.” A light year is the distance that a beam of light travels during one Earth year. Though it makes a conveniently large measure of distance, approximately equal to 9.47 E 12 kilometers, it has little relation to travel time between the stars.
For more than two centuries, the physics of Isaac Newton explained all the observable phenomena in our Solar system. Yet by the end of that period, physicists had observed a number of things that didn’t fit Newton’s theories and how they relate to the physics of space travel. While trying to measure the speed of light, they noted that all observers measured the same speed, regardless of how they were moving relative to the light source. Newton’s theories said velocities add linearly. The orbit of the planet Mercury also exhibited perturbations that Newtonian physics could not explain.
Albert Einstein resolved these dilemmas by rejecting two ideas implicit in Newton’s physics; the existence of an absolute inertial frame and the notion that simultaneous events can be simultaneously observed. Einstein accepted the commonsense idea that the laws of physics can be formulated so they are the same for all observers, no matter how they are moving through space. After all, the Earth rotates on its axis and travels about the sun, and the sun orbits the galactic center, and the galaxy in turn moves through space along with thousands of other galaxies. Where then, is the absolute frame of reference that Newton postulated? Starting with these new assumptions, Einstein re-derived the laws of physics to arrive at some startling conclusions. His reasoning is too complex to describe here, but his conclusions are important to the physics of space travel. Einstein showed that an observer in motion relative to an object will observe that object to be shorter than he would if he were at rest relative to the object. Such differences can’t be detected when speeds are low relative to the velocity of light, but at the speeds of interstellar spaceships they become significant.
Let’s say that a space traveller gets into a space ship and heads for the planet Genesis about 44 light years away. If the ship accelerates to 95 percent the speed of light, Genesis now appears only 13.6 light years away. To travellers on board the ship, the trip appears to take just 14.3 years, but to observers watching from Earth or Genesis (all the planets have low velocities relative to each other), the trip appears to take three times as long. This simple example illustrates why travelers aboard a starship perceive that the trip takes less time than the people waiting for them on the planets. The effects of acceleration further complicate the computation of travel times, but the results, calculated by computers, are indicated in the data tables for each colony planet.
Unfortunately, Einstein’s theories went on to predict that no material object could reach or exceed the speed of light relative to another object. Einstein calculated that as the relative speed of an object increased, its mass and therefore its resistance to acceleration would increase too. Experiments with atomic particle accelerators in the mid-20th century verified his calculations with stunning accuracy. Thus as the space age opened, and people began to send their first feeble probes to the other planets of the Solar system, the distances to the stars still seemed overwhelming. Even if technology could have developed new propulsion sources that would enable ships to approach the speed of light, the nearest stars would still have taken decades to reach.
Despite this dismal conclusion, Einstein’s theories did much to advance the cause of space travel, for he predicted that matter could be converted into energy. The inefficient chemical rockets that powered early space vehicles could not possibly have reached the stars. Only direct conversion of large amounts of matter into energy could propel spaceships near the velocity of light. Before the next great breakthrough in physics, the theories of Einstein had formed the basis of the laser fusion drive that propelled Captain Jan De Wyze and the Freedom 4 to Alpha Centauri and the discovery of Wyzdom. The round trip of just 8.6 light years required more than thirteen Earth years of travel time. Yet to the crew of the Freedom 4, the trip seemed to take five years each way. During that time they aged three years and four months less than the people waiting for them on Earth!
Thirteen years after the return of the Freedom 4, a young physicist named Raymond Krauchunas again rocked the scientific world with a new comprehensive theory of space travel physics that unified the previously discordant concepts of matter, electricity and quantum mechanics. His theories encompassed all data that supported the theories of Newton, Einstein, Maxwell, and Planck, and went on to explain new data gathered during the voyage of the Freedom 4 and other, early, nearlight-velocity spacecraft. The singularities of mass and energy predicted by Einstein’s theories bothered Krauchunas. Singularities are mathematical concepts of infinity or “infinitesimalness” that never in fact occur in nature. In the past, simple theories predicted the force of an elastic impact or the stress before a crack to be infinite. Yet more refined observation and analysis showed these predictions to be imprecise.
Krauchunas again reexamined the basic postulates of Einstein’s physical theories and found in them subtle, hidden assumptions. Krauchunas rejected the notion that space-time need be described by any finite number of dimensions and postulated the existence of hyperspace. He went on to show how a space ship, or any self-propelling matter, could travel between points in Einstein’s space-time continuum by taking a short cut through hyperspace. Since the object no longer transverses “real” space and time, no time need elapse during the course of the trip.
An analogy may be helpful in understanding hyper-light travel. Imagine two ants walking along a piece of cloth that has been dropped casually on the floor. The cloth is wrinkled and folded back on itself, and the ants are walking on the folded surface. As they walk, one ant makes a tiny hole in two overlapping pieces of the cloth and crawls through it. He emerges at another point on the cloth several inches from the other ant who does not pass through the hole but keeps walking along the surface of the cloth. The second ant doesn’t reach the point on the cloth that the first ant has reached until some time has passed. Meanwhile the first ant has continued along the cloth and remains several inches ahead of the second ant.
In a sense, the first ant traveled faster than the second ant, but in another sense, the first ant did not travel through the same space as the second ant; so it becomes illogical to speak of his velocity relative to the second ant. Einstein envisioned space as a multidimensional analogy of the folded cloth. Krauchunas envisioned a way that people could make holes in the cloth to cross vast distances of “normal” space in no time at all. The path through hyperspace relates in a complex way to both the acceleration and the first derivative of acceleration, known as “jerk,” at the instant of departure from real space-time.
Twenty-five years passed between the publication of Krauchunas’s unified field theory and the launching of the first starship capable of hyperspace travel. The Albert Einstein, launched in 2112, made the round trip to Wyzdom in only thirty-eight months. Time aboard ship measured less than eighteen months. After the Einstein’s return, the ICSE constructed a much larger vessel, the Christopher Columbus, to make a fifteen-year exploration of eight nearby star systems. Yet even though the concept of hyperspace flight was proven, the first pioneers used conventional sublight ships to transport the first permanent colony to Wyzdom.
Though the development of hyperspace travel (sometimes called “space warp”) brought the stars within reach, reducing travel times to a matter of weeks required a second major scientific breakthrough. Prior to this, interstellar travel had been limited by the fact that Humans can tolerate no more than 1.3 g of acceleration for extended periods. Consequently, it took almost nine months for space ships to accelerate to the near light speeds needed to make the jump through hyperspace and another nine months to slow down again. Thus despite the advent of space warp, the minimum interstellar voyage took one and one-half years of Earth time (though the time seemed shorter to the passengers). Development of the artificial gravitational field allowed starships to attain much higher acceleration levels than those achieved in the early days of interstellar travel. These higher acceleration levels shortened trip times appreciably, and the g-field protected passengers and crew from the large acceleration forces undergone in the transition to hyperspace. The g-field also gave ship designers greater freedom to design their vessels, since the field could be used to resist acceleration forces that would tear the ship apart.
Within the confines of the ship, the artificial gfield creates a gravitational field identical in all respects to the gravitational field of a planet. It maintains this static field despite wide swings in the acceleration of the ship itself. Therefore, the gfield generators are not static devices but highly complex automatic equipment. Adjustments can be made so that the amount of gravity felt within the ship varies. Many novice space travellers believe it would be fun to make their journey in a weightless state, but although most people enjoy the sensation of weightlessness for rather brief periods, the weightless condition becomes rather annoying for the extended periods required by interstellar travel. In addition, people inexperienced with weightlessness can easily injure themselves by bumping into walls and ceilings. The crew adjusts the g-field of the ship during the voyage from the Earth value of 9.8 m/s² to the value of the destination planet. This allows pioneers’ bodies to become gradually acclimated to their new planet’s gravitation.