Notwithstanding the Millenium Falcon’s ability to jump to hyperspace, travel at the speed of light, or faster than the speed of light, is not possible according to the theory of special relativity. It turns out that Star Wars is just fiction.
There are two reasons light speed travel is not possible under the theory of special relativity. This IFOD is a bit on the long side, but it’s a complex answer.
First, because of the equivalence of mass and energy (E=MC^2), the energy which an object has due to its motion will add to its mass. In other words, it will make it harder to increase its speed. This effect is really only significant for objects moving near light speed. For example, at 10 percent of the speed of light (which is still really fast – much faster than we send rockets into space) an object’s mass is only 0.5% more than normal, while at 90% of the speed of light it would be more than twice its normal mass. As an object approaches the speed of light, its mass rises ever more quickly, so it takes more and more energy to speed it up further. Any object with mass can never reach the speed of light because its mass would have become infinite, and by the equivalence of mass and energy, it would have taken an infinite amount of energy to get there. For this reason, any normal object is forever limited by special relativity to move at speeds slower than the speed of light. Only light, or other waves that have no mass, can move at the speed of light.
Second, according to special relativity objects don’t just move thru space – they also move thru time (i.e. “spacetime”). An object at rest (relative to another object also at rest) is just moving thru time. If the object moves away and begins moving thru space then that object’s movement thru time will slow (as compared to the other object at rest). As the speed thru space speeds up the movement thru time slows for the moving object. For a beam of light the math of special relativity says that time stops. So, if you could attain a speed greater than the speed of light time would reverse according to the math. That means that a traveler traveling at faster than the speed of light would observe the temporal order of events for other people or objects to be reversed. In other words, you would observe people answering a message BEFORE it was sent. This isn’t suggesting that the images are carried to the traveler in the wrong order, but rather that when you correct for how long it took the light to reach the traveler, you STILL find that the answer came before the message. This sort of occurance doesn’t seem to be possible because one of the basic ideas behind special relativity is that the laws of physics should be the same for all observers. If there were an observer going faster than light, then cause and effect would appear reversed in some cases for that observer, and so the laws of physics must look different to him. This violates the basic premise of special relativity, so it is a deep logical problem, not just a practical one of getting enough energy to move an object with infinite mass at the speed of light..
Now some of you may say that classical newtonian physics has been supreceded by relativity and quantum mechanics. That we didn’t think the sound barrier could broken by an airplane. That a bunch of physical laws have been overthrown.
All true. Maybe relativity is wrong. BUT – every experiment for over 100 has shown that special relativity is correct. We have used IMMENSE amounts of energy to send super small sub-atomic particles thru colliders just below the speed of light and we cannot achieve light speed (and these experiments have shown that mas increases as the energy behind the particle increases – exactly inline with the theory of relativity). We have confirmed via experiment that time slows as the speed moving thru space increases. The energy/mass equivalence of E=MC^2 has worked exactly according to the equation.
So, while it is possible that special relativity is wrong it also seems highly unlikely. I guess time will tell (pun intended).