there aren't many subjects more interesting to me than the concept of time. before i get into it, my disclaimer is that my wording may not be technically correct, but i think you'll still be able to get my point. maybe someone who knows the details better can explain it more precisely. anyway, here goes.... everything constantly travels through spacetime at the speed of light. you are right now. the more motion you have towards the speed of light, the less is available in the time dimension. therefore, time slows the more motion you have towards the speed of light. at the speed of light, all of the motion is used up and therefore there is no room for time. so time doesn't exist at the speed of light. bottom line, there is no "one" time; time is relative. if you could travel close to the speed of light for a few minutes and come back to earth. it would feel like a normal few minutes for you, but the people on earth would have aged significantly. btw, don't think that because of this you can live forever or something. how long you live would still feel the same to you, but you could fast forward into the future. i don't think there is a way to go in the past, however. THINK OF HOW AMAZING THIS IS...AND IT IS REAL. much of what i say comes from reading "the elegant universe" by brian greene. i would HIGHLY recommend reading this book if you are even remotely interested in what i just said. you don't need to be a genius to read it, either. i'm no genius. here are a few quotes from the book to give some substance to what i said: "einstein found that...the sharing of motion between different dimensions--underlies all of the remarkable physics of special relativity, so long as we realize that not only can spatial dimensions share an object's motion, but the time dimension can share this motion as well. in fact, most of an objects motion is through time, not space." "when an object moves through space relative to us, its clock runs slow compared to ours. that is, the speed of its motion through time slows down. here's the leap: einstein proclaimed that all objects in the universe are always traveling through spacetime at one fixed speed--that of light." "the speed of an object through space is thus merely a reflection of how much of its motion through time is diverted." "...the maximum speed through space occurs if all of an object's motion through time is diverted to motion through space. this occurs when all of its previous light-speed motion through time is diverted to light-speed motion through space. but having used up all of its motion through time, this is the fastest speed through space that the object--or any object--can possibly achieve." "...something traveling at light speed through space will have no speed left for motion through time. thus light does not get old; a photon that emerged from the big bang is the same age today as it was then. there is no passage of time at light speed." "...nothing can travel faster than light speed. you may have wondered, for instance, why we can't take some object...[boost it up to] 99.5 percent of light speed--and 'push it a bit harder,' getting it to 99.9 percent of light speed, then 'really push it harder' impelling it to cross the light-speed barrier. einstein's formula [e=mc^2] explains why such efforts will never succeed. the faster something moves the more energy it has and from einstein's formula we see that the more energy something has the more massive it becomes...the more massive an object is, the harder it is to increase its speed...it would require a push with an infinite amount of energy to reach or to cross the light barrier. this, of course, is impossible and hence absolutely nothing can travel faster than the speed of light." SCIENCE RULES, RELIGION SUCKS!