The Physics of Star Trek By Lawrence M. Krauss FORWARD (by Stephen Hawking) • Science Fiction like Star Trek is not only good fun but it also serves a serious purpose, that of expanding the human imagination. We may not yet be able to go boldly where no man (or woman) has gone before, but at least we can do it in the mind.. • We can explore how the human spirit might respond to future developments in science and we can speculate on what those developments might be. • There is a two-way trade between science and fiction. Science fiction suggests that ideas that scientists incorporate into their theories, but sometimes science turns up notions that are stranger than any science fiction (black holes, for instance). • It is very interesting and important that Star Trek has focused on “faster than light” travel (which the special theory of relativity apparently forbids, but the special theory might allow through “space warp”. If this were not possible if the Enterprise were to take a trip to the center of the Galaxy (~1 million light years / 2, though only several years would pass on the Enterprise, 80,000 years would pass on Earth., with all its implications. • To confine our attention to terrestrial matters would be to limit the human spirit. PREFACE • I (the author, Lawrence M. Krauss) did not want a book that ended up merely outlining where the Star Trek writers went wrong. • What really makes Star Trek interesting to its followers is “charting the unknown possibilities of existence.” Ch. 1: Newton Antes • The image of a poker games from the fact that this is a popular pastime on the Enterprise. The three chapters in Section I are engaged in a poker game, bet, in that each participant offers something that he believes is the most valuable, starting with Newton, then Einstein, Hawking and at last Data. • Even though much of Star Trek involves subjects related to the frontiers of science, like space-time cosmology and quantum mechanics phenomena, the “old” ideas of Isaac Newton still apply and always will, in spite of what a lot of popular writers say (in order to sell more books). • Newton's major contributions: universal theory of gravitation, calculus, the three laws of mechanics, and optics (diffraction of light, color, and nature of light as a particle). • This physics was developed at a time when the fastest speeds were those of fine steeds (horses), the microcosm remains to be explored and the cosmos is far bigger than anybody imagines. In short it is a world of the human size and speed. The science reflects these dimensions. • But, one of the most important aspects of this chapter is to point out that the Newtonian (classical) laws of physics are still completely valid and must be considered even in space on board the Enterprise. Through several illustrations this is made completely clear. • Laws of motion: - A body (mass) remains at rest or in a state of constant motion unless a force acts on that body (mass). - The acceleration of an object is proportional to the applied force and inversely proportional to the mass of the object: a = f/m - For every action (force) there is an opposite and equal reaction (negative force): reaction force = - applied force • When the star ship Enterprise accelerates (using the fusion reaction in the “impulse drive”) to warp speed there is tremendous force and resulting acceleration to do this within a reasonable time. Thus, there is a reaction force due to statement 3 above. This would turn the human body into “salsa sauce” • The ships acceleration is due to spitting gas and particles, producing the reaction. • In order not to be pushed back into the seat with a force greater than 3 G (maximum before passing out), force must be less than this value. But at 3 G it would take 5 million seconds, or 2 1/2 months, to reach 150,000 km/sec, or half the speed of light. • Pilots in hot jet aircraft use special suits to keep blood flowing properly. • To allow rapid acceleration on the Enterprise the concept of “inertial dampers” was invented, which produce and opposite, opposing, gravitational field, so that those on the ship feel very little force during acceleration. • This must be produced almost instantaneously, shorter 60 milliseconds, or 60 / 1,000 second. Imagine being hit on the head by a hammer or running into a brick wall at full speed (about 10 miles per hour). The reaction systems would have very little time indeed to take effect. • Another “classical’ effect involves the ”tractor beam”, which is used to pull or push objects. • In empty space it the object is being pulled, perhaps it would be the star ship moving if the pulled object is much more massive. This would not make much difference, since the result would be the same. Consider using a device to turn a bolt; which would move? • But it WOULD mater if the Enterprise were trying to pull some object out the war of a renegade star. • Enterprise needs to apply a negative impulse engine pulse when using the tractor beam. Ch. 2: Einstein Raises • Thousands of years ago some cultures thought the basic elements of the universe - Earth - to be earth, water, air, fire and either, such as some of the ancient Greek philosophers. All objects would be made from combinations of these. • Ether was considered to be the mostly refined material and to exist in the heavens. Fire would be the stuff of stars; thus, a fire on earth leaps to the sky in an effort to return there. And air and water would be less refined and earth the most base material. • Also, thousands of years ago people noticed interesting properties of some materials, now called the electric force and magnetic force. Static electricity can easily be produced by rubbing some materials together, and allowed one to pick up small objects, like paper and cloth. • Some metallic ores were found to produce a “magnetic force” which acts differently. They would tend to point in certain directions and interact with each with a force. • There was absolutely no understanding of how these forces come about. • Not much more was learned about the nature of these materials and their properties until about the 1600s in Europe. Scientific investigation was starting to evolve at this time, which greatly accelerated after Isaac Newton developed the laws of mechanics. • Scientist scholars were studying mechanics, optics, thermodynamics, electricity, magnetism and light. • At this time there was thought to be no relation between electricity, magnetism and light, all having seemingly different properties. • During the 1600s, 1700s and 1800s much progress was made through both experimental and theoretical investigations, resulting in mathematical equations that expressed the characteristics of these phenomena while producing an ever greater amount of related and other technology. • A great turning point in the evolution of science took place when in 1864 the Scottish theoretical physicist James Clerk Maxwell combined and manipulated the various equations of electricity and magnetism, and came up with a startling result: • Light is an “electromagnetic wave” that travels at a speed of 300,000 km/second. Suddenly, light, electricity and magnetism were deeply related entities. • The only problem was that waves need a medium within which to propagate. Then how could light get to earth from the Sun and other stars separated by a vacuum? • The ancient Greek word vacuum was used to define some unseen and detected material that fills the universe and allows the propagation of the electromagnet light wave. • The famous subsequent Michaelson Morley experiment, which was conducted to prove the existence of an ether, surprisingly to almost everyone, showed that there is no such thing. SPECIAL THEORY OF RELATIVITY • At about the same time Einstein was contemplating the nature of space and light, and decided that the only way that all physics could be consistent would be that nature operates in such a way that ALL OBSERVERS SEE LIGHT TRAVELING AT THE SAME SPEED UNDER ALL CONDITIONS. • This is rather hard to believe, since tradition and commons sense would say that the situation would be the same as a boy throwing a ball on a train. Within the train all observers would see the ball move at some speed v. But, outside of the train observers on the ground would see the ball move at speed v + V, the speed of the train!! • As a result of Einstein’s statement and that physics is the same everywhere in the universe, he was able to derive several remarkable equations, and concepts: 1) Energy and mass are equivalent: E = mc2 2 2 1/2 2) Mass is dependent on speed: m = m0 / (1 - v /c ) 2 2 1/2 3) Time intervals differ based on speed: ∆t = ∆t0 / (1 - v /c ) (called time dilation) 2 2 1/2 4) Length differs based on speed: l = l0 (1 - v /c ) (called length contraction) • As can be seen from 1) and 2), the speed of light (c) is the speed limit of the universe; nothing can go faster, since to accelerate an object past C would require infinite energy. • Also mass, time and length are no longer constants and the same for all observers, a revolutionary idea. • BUT, these equations are only significant as the speed of an object approaches C, meaning that in our everyday lives we can not see or feel any obvious effects. • BUT, these equations have giant implications for space travel: 1) C is the speed limit of the universe making space travel very difficult due to the very large distances involved.