Originally Posted by

**geordief**
I know some (was it Lorenz?) have said that we can no longer think of space (ie distance) and time separately but only entwined. So can we disentangle space and time after all (just not in the spacetime model itself)?

Here's how I envision the 4th dimension spacetime -- although I'm the first to admit the concept is way beyond my puny brainpower.

You know that light moves at the speed of light, C, 186,000 mi/s right? And you know how as one APPROACHES the speed of light, time slows down? In effect that means that photons exist everywhere along their path of travel simultaneously. From a photon's point of view, leaving a distant star and arriving at your retina are

* simultaneous events*.

Therefore,

**time** -- in effect --

**moves at the speed of light.** If you could travel in any direction at the speed of light you would, from your viewpoint, arrive at your destination instantaneously. Everything around you would progress in normal time, at the rate of 1 second per second (unless traveling at a significant percentage of C) but from your viewpoint, traveling at C, there would be no time passage at all.

THAT is the 4th dimension. That is what "spacetime" is. At the speed of light, there is no distance between two points in space, there is no passage of time. You just exist everywhere simultaneously -- a 1-dimensional line -- along the path of your travel from Point A to Point B.