"What's Dexter talking about?"
Simultaneous events only appear simultaneous to us because of the error margins of our senses, our ability to process information, and our close proximity to one another.
Imagine you stand in the middle of a train car and you are looking at a set of mirrors that reflect the front and back of the train car, where there are red and green lights.
Both lights are turned on at the same time and you see them both come on at the same time.
Move your mirrors so they are only a foot away from the red light at the front, turn on both lights at the same time, and they still appear to be on at the same time. This is a problem of perception, however.
If you slow down the speed of light to walking speed, though, you will see something quite different. Light ambles down the aisle from front and back to the middle and the mirrors at the same time, is reflected and arrives at your eyes simultaneously. You would say the lights were turned on simultaneously.
Someone else one foot away from the front says the red light came on first, then some time later the green light came on.
You would both be looking at the same "simultaneous event", but you would disagree about what happened first or second, or at the same time. Someone at the back of the train would say the green went on first.
A similar effect comes into play if the speed of light is back to what it is in reality, but the train is traveling close to the speed of light.
Check out Sixty Symbols' treatment of this topic!http://www.youtube.com/watch?v=kGsbBw1I0Rg