Only two things are infinite: the universe and human stupidity. And I'm not sure about the former
Somehow, it always seem intuitive to people that space is relative, but they just can't grasp the fact that time is relative as well (and that is the whole point - saying that light is relative is nonsense). If you move at relativistic speeds with respect to an observer, your passage of time tends to slow down with respect to that observer. You don't notice that yourself, because every physical process, including those in your brain, is slowed down as well (it's like assuming a fixed frame time even though the computer you're running on is not fast enough to process the frame in that amount of time - the game thinks it's running 30FPS, while in reality it's more like 10FPS ). So you just percieve one second just as being one second, but for that observer, your second might take two of his seconds.So, if someone steps into a rocket and takes a year long journey at near lightspeed and then returns to earth, he has aged a year, but all of his friends and family might have gone to pass. This is what Einstein predicted in his theory of special relativity and has been proven time and time again. This also makes it very feasible to travel into the distant future, the only problem is you probably can't go back. Well, unless you travel far enough into the future for humanity to have actually invented time travel .
Acceleration makes up for an interesting effect as well. It seems that, under an accelerated frame of reference (including a gravitational potential), time is slowed down as well. That is why a clock on earth ticks slightly slower than a clock in outer space. GPS satellites (which as you might know work by simply telling their time and position so a receiver can triangluate his position based on the time difference of the messages he recieved of the different satellites and their actual positions), orbiting earth at a very large distance where there the gravitational pull is lower, need to correct for their faster passage of time. This is what Einstein predicted in his general theory of relativity.
For you to reach light speed with respect to an external observer, you'll need an infinite amount of energy and your passage of time will slow down to a near complete halt. For a photon traveling at light speed, there is no passage of time. So, in a way, from the photon's point of view he reaches his destination instantly, regardless of the traveled distance. That is also why a photon can't decay - there is no passage of time for a physical process to make it decay. And for this very same reason we can detect the muons that are a result of cosmic rays colliding with particles high up in our atmosphere. Even though they decay in a fraction of a second (their mean lifetime is 2.2 nanoseconds - a particle at the speed of light will only be able to travel \~65cm in that timeframe), they move so fast that they are able to reach the surface of the earth because their passage of time is slowed down enough to keep them alive long enough.
But enough about this uninteresting relativity. Let's talk quantum mechanics