If we really want things to get confusing, there are situations where time itself slows down, and that would include light slowing down to the perspective of an outside observer. Suppose, for example, that we situated a number of laser-emitting relays near the event horizon of a black hole (outside the event horizon, but very near it.).

Then we hit one of them with a laser, triggering it to light up and then fire a laser beam at the next, which lights up and fires a beam at the next.... etc. To a distant observer, I think these relays would appear to be receiving their signals from each other at a speed much slower than C.

I don't know that it is really different to say "time slows down in a gravitational field" than it is to say that "all speed uniformly diminish (including C), in a gravitational field."

Originally Posted by

**GiantEvil**
Its not possible to travel at the speed of light. There is no way of achieving it.

What about photons? But even without considering photons, can you Mr Roberts explain why it is not possible for object's with mass to accelerate =>c?

Your inertial mass increases as you gain energy. Velocity is energy as well. As you approach the speed of light, your inertial mass begins to approach infinity. Once your inertial mass reaches infinity (at the speed of light) you become in immovable object. (Well, unacceleratable object, anyway. You're still moving at C.)