The theory of relativity and its use in Sci-Fi

This investigation looks in to the different aspects of general and special relativity that has been used in science fiction movies. This report talks about the difficulties and possibilities of travelling at the speed of light (c), the different propulsion systems that could be used and how trecknology has changed the boundaries of physics in Hollywood features. Time travel also features looking at different theories behind it with a number of new ideas. The Foundations of relativity were set out in detail by Albert Einstein. The ‘special' version of the theory, which applies to observers in a uniform relative motion, has led to a number of successful conclusions of a variety of effects. Newton's laws of motion give us a complete description of the behaviour of moving objects at low speeds (speed of objects much less than the speed of light). These laws being thought up in the 17th century, when the classical laws of dynamics where being formulated by other early physicists, these classical laws are themselves subject to a relativity principle. Einstein's special theory of relativity gives the motion of particles moving at close to the speed of light. It actually gives the motion of any particle. This does not however prove Newton wrong; his equations are within Einstein's relativistic equations. Einstein's theory of special relativity is based on two assumptions: 1. All inertial (i.e. non-accelerating) frames of reference are equally valid (i.e. any observations or experiments performed will produce equally valid results). 2. The speed of light is constant for all inertial frames of reference. Given these two statements, Einstein showed how definitions of momentum and energy must be refined and how quantities such as length and time must change from one observer to another in order to get consistent results for physical quantities. Science fiction has for years tried to incorporate the theories that govern the reality of physics within their programmes, to keep those die hard science fiction fans happy. Science fiction has been subject to cult following for many years and in many countries, although no matter how hard they try there are a number of important facts that seem almost popular to overlook, the main one being travelling at the speed of light. Many programmes have some sort of light propulsion, warp drive and travel to other universes. But can this really be done? Many physicists all over the world have tried to find out if travelling faster than the speed of light is possible without violating relativity. We do know that is impossible to accelerate forever, because the closer to the speed of light we get the mass tends to infinity this means that there would need to be an infinite amount of energy needed to push us past this speed barrier; This equation represents what would happen to mass when relativistic speeds are reached. Here, m is the mass, of an object at rest; m' is the value for the moving reference frame. As you get closer to the speed of light the product at the bottom of the equation gets closer to zero so this means that m'/m tends to infinity. If you were to rearrange this equation so to get the value of m' the same results are seen. The increase in mass, however, is best understood not as a change in mass but as a change in the relationship of mass and momentum. Momentum (p) is the product of mass x velocity. Here, p' is the relativistic momentum and m is the rest mass. Once again we can see that the momentum this time will tend towards infinity as we reach the speed of light. Using one of Einstein's most famous equations E = mc2 we can now see that if the mass does tend towards infinity that an infinite amount of energy will be needed to remain at constant velocity let alone accelerate. Time dilation is another consequence of travelling at relativistic speed. We've all heard about the ‘twin paradox' if one twin went on a space journey at 99.5% the speed of light and returned in what he judged to be 4 years the other twin with have aged by 40 yrs! These effects cannot be seen with humans, yet it has been tested and seen to occur with particles at the atomic scale. So any sci-fi movie where the astronauts return home after visiting other galaxies after travelling at the speed of light is clearly impossible, if they had been travelling for any length of time they would have probably come back to their grandchildren. To explain this if you could imagine a spacecraft with a light source perpendicular to the motion; If there were an observer on the spacecraft and the light travelled 0.6m it would take 2 nanoseconds to travel that distance. By using a simple equation speed = distance/ time the light is travelling speed = 0.6 x 2Ãâ€"10-9 = 3Ãâ€"108 ms-1 this should not come to as a surprise as this is the speed of light. However if the observer then was then stationary with the spacecraft moving past them, they would see the light take this direction: Now in pre-relativistic (Newtonian) physics, both observers record the same period of time. Consequently, the velocity recorded by the two observers is different: the Earth-bound observer would record a greater velocity for the beam of light. But taking into account Einstein's assumption that the speed of light doesn't change, and is the same for both observers, the distance for the light to travel doesn't change as it is not in the direction of travel, the time which the light takes obviously changes. Does this then mean there is no such thing as absolute time? The distance that would have been observed for the light to travel would have been 1m so using the equation time = distance / speed, time = 1 / 3Ãâ€"108 = 3Ãâ€"10-9 s, so we can conclude the clock on the space craft is slower than that when stationary. This is given by the equation: If v