Why is time called a dimension when time is always now?

This is another question posted on Quora, which attracted 100+ answers, apparently, of which mine is a modest contribution.

I’m not presenting anything new here that I haven’t discussed before. But there is a benefit in polishing one’s ideas so that they are more succinctly expressed and, hopefully, easier to follow.

I should point out that, aside from my exposition on Einstein’s theories of relativity, these ideas are not orthodox: specifically, my views on QM and ‘now’.



This is a good question that I’m sure will garner a variety of answers. Even among physicists, the nature of time and our experience of it is a debatable topic. Einstein’s theories of relativity changed our understanding of time irrevocably, but possibly created more mysteries than they resolved.

The most significant revelation from Einstein’s mathematical formulations is the link between time and the finite speed of light. If the speed of light was not finite (i.e. instantaneous) then everything would happen at once. The speed of light, c, turns light into a 4th dimension (by ct) and in combination with the 3 dimensions of space creates a metric called spacetime. Whilst time and length can appear different to different observers in different frames of reference, the metric of spacetime is invariant.

You can see the dimension of time by looking at the night sky, because the stars you see are light years away. In the southern hemisphere (where I live) if you can get away from city lights, on a clear night, you can see the Magellanic clouds with the naked eye, which are over 150,000 light years away. In other words, you are looking at least 150,000 years into the past, and, in that context, time becomes a 4th dimension that you can actually see.

Because the speed of light is finite it means that everything you observe has already happened, which is why we never see the future. Einstein believed that the dimension of time was just as fixed as space and therefore the future already existed. This is called the ‘block universe’ interpretation, but quantum mechanics (QM) doesn’t support this view.

In fact, Freeman Dyson argues that QM can only describe the future, which would explain why we never actually observe a wave function (ψ), because it’s always in our future, and why we can only determine probabilities from a range of so-called superpositions. Note that only one of the superpositions becomes reality when the wave function collapses (or decoheres).

Erwin Schrodinger, in his book, What is Life? made the observation that consciousness exists in a constant ‘now’, and I contend that it’s the only thing that does. Everything else immediately becomes the past as soon as it happens, which is demonstrated every time someone takes a photograph.

In summary, the finite speed of light ensures that everything we observe is in the past which can be measured as a dimension of time. If consciousness is the only thing that exists in a constant present, then, it not only provides a continually changing reference point for past, present and future, it also explains the effect that everything is passing us by.