"Time" not a dimension.

[lilphil1989]

You can't, look at the twins paradox.

As far as the twin travelling at light is concerned time feels normal and any clock on the spacecraft will show the same. But as far as his brother is concerned he has slowed right down.

In the theory it is usually considered that time(as a seperate demension) has slowed down.

The twin paradox isn't a paradox. It arises from a naive formulation of the problem as symmetric between the the earth twin's frame and the travelling twin's frame. The problem is that in order to return to earth, the travelling twin has to make a lorentz boost to move to the frame in which he returns, so that there are 3, not 2 relevant frames in the problem, and you can't just claim that each sees the others time dilated by an equal amount.
What happens then is that the travelling twin "sees" the home twin age very quickly when he turns around, because his definition of simultaneity with the unmoving twin changes when he lorentz boosts to the return frame. The travelled twin will be younger than the twin that stayed on earth.
This is confirmed experimentally: New Scientist, Feb. 1972

But it could be equally said that the physical interactions have been stretched out(a bit like red shift)

So it only appears that time has slowed down.

I'm not quite sure what you mean by this.
What would be the difference between the two empirically?