hi I read a few other post about this but i'm an engineer, not a physicist, not a genius and didn't get much wiser. And if it's possible try not to use to many technical terms when you answer this, please. As it says in the title "time slows down when you approach the speed of light", it's driving me crazy. I watched a documentary on Discovery about the 100 greatest physics discoveries and it was a bit superficial. They said that... Time slows down when you approach the speed of light If you have a satelite moving at 18000 miles/hour around earth you have to account for relativistic effects Some literature says that it has been exsperimentally confirmed but not how. I just don't understand, maybe because how i think of time... i see time as a man made thing, if humans cease to exist time has no meaning or also cease to exist. This doesn't mean that all the processes in the universe stops. Like lenght for exsample, what's the meaning of a cm or meter if there are no humans or marketing for that matter, etc. So why would the processes in your body slow down (and you would age at a lower rate) just because you're moving extremely fast?