Albert Einstein'sspecial theory of relatively famously leads up to the remarkable conclusion that no object, whether animate or inanimate, can ever, under any means, travel faster than the speed of light.
In order to support these claims, Einstein offered up two equations in his theory, which actually provide four separate, yet wholly interwoven, reasons that this must be so if the theory itself is correct.
These issues revolve around time, size, energy and mass, respectively.
Time
One of the revolutionary feats of special relativity was in initiating the concept of "time dilation," wherein the faster an object travels, the slower its perception of time becomes, in a phenomenon known as time dilation. In order to quantify this behavior, the reader can utilize an expression which has become known as the "shrinking factor:"
D = √(1-(v²/c²))
By plugging in the speed of an object for v and the speed of light for c, the result of the equation will show how much the object's perception of time has shrunk when compared to a stationary object.
Now, how does this prevent light speed travel? Simple. Just plug in a value for v of the speed of light. What is the result?
Zero.
According to time dilation, as an object approaches the speed of light, its perception of time ebbs slower and slower. At the speed of light, time perception goes to zero and slows down infinitely. So, if one was to be able to travel the speed of light, they would probably never be able to slow down again.
Space
The same shrinking factor expressed above which was used there to refer to time dilation, can also be used to define "spacial" shrinking.
A similar principle holds true for the perception of "length" and "distance." From the perspective of an outside observer, as an object travels faster, its size begins to shrink in the direction of its motion (to a very minute degree at first, which is why it is never really noticeable).
As the speed of light approaches and the object's perception of time decreases accordingly, so also will its perceived size from an outside observer. Once the speed of light is reached, however, the object's size will become zero. It will disappear.
Thus, by using the "shrinking factor" equation, one can fairly simply deduce that the idea of both time and space (which after relativity were seen as really being one in the same - space-time) create "cosmic speed limits" for the universe.
Energy
Most people are quite familiar with the other famous equation of special relativity - the equation for mass/energy conversion: E=mc².
What most people don't realize, however, is that this is an incomplete form of the equation. The complete form actually reads: E = mc²/√(1-v²/c²), which, if one looks carefully, contains an expression which is essentially identical to the equation for time dilation.
The more familiar equation can be derived simply by plugging in the value of 0 for v (thus, the traditional equation is useful only for an object at rest).
At other values of v, however, this equation wonderfully demonstrates the interrelated nature of mass and energy, and how they both fluctuate with changes in velocity. As the value of v increases, so also does an object's mass, which requires an even greater amount of energy in order to continue at such a speed.
As an object's velocity approaches infinity, then, the equation clearly shows that an infinite amount of energy would be needed to push it over the threshold. Obviously, there is no known way to achieve infinite energy (though not for lack of trying), and thus there will never be enough energy to push something faster than the speed of light.
Mass
The same equation that demonstrates the energy requirements as velocity increases also demonstrates that the energy added to an object will increase its mass as it travels faster and, true to the pattern developing in these ideas, as an object approaches the speed of light, it would become infinitely massive (which explains why it would require an infinite amount of energy to move it).
So, in the end, for an object (or person) to even think about traveling at or beyond the speed of light, all of these seemingly impossible hurdles would have to be overcome: Infinite time dilation, shrinking to nothing, infinite energy and infinite mass.
Provided these mountains are surmountable, though, time travel would be entirely possible.
References:
The New York Public Library. (1995). Science Desk Reference. New York, NY: Macmillan.
Priwer, S., & Phillips, C. P. (2006). Einstein: Everything you Need to Know About the World's Most Acclaimed Genius. Avon, MA: Adams Media.
Isaac M. McPhee - Isaac McPhee was born as a human child in Mt. Vernon, WA, c. 1982; he currently resides in the bustling heart of New York City where he ...
