h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

This thought came to be a while ago, so I will share it here.
According to traditional ideas:
* in a 1-dimensional world an object can travel relative to a single axis only - it can travel left or right only.
* in a 2-dimensional world an object can travel relative to two axese only - it can travel in any direction you can draw on a piece of paper.
* in a 3-dimensional world an object can travel relative to three axese - it can travel in any direction you can point with your finger.

We are taught at school that time is the 4th dimension as you can travel in any direction you can point with your finger and at any time.
HOWEVER, this is not strictly true. You can only travel in that direction at some point in the future, you can not now decide you want to go south-west two weeks before last Moday. It's simply too late.

Put another way, objects can travel through time in one direction only - forwards. Relativity shows us that it can go at a different rate relative to another object, but it can never go backwards.

Based on this, it seems appropriate that it actually comes in the scale BELOW the 1-dimensional model.


(Theory also suggests that if an object passes a black-hole's event horizon, this 0th and the 1st dimension swap around - you can travel backwards in time but you can only move in the direction of the singularity, never away from it!)

Speaking of dimensions and time in such a fashion is difficult, I have on occasion thought on this matter.

The reason I started writing this reply is that all measures of motion; velocity, acceleration and so on use time in their definitions, so to talk of movement in 1 dimensional space, with the specific intent of relating this to time seems illogical.

However now I've gone to the effort of registering and starting this i may as well add my own thoughts. To play devils advocate, while it is clear that we travel though the dimension of time in one diection, and at the fixed rate of 1 second per second, it is not concievable that this is a restriction on us (or rather I should perhaps say our concious perceptions), rather than on all energy and matter.

However, since the universe and time started at the Big Bang, when the expansion of the universe ends and everything starts to implode doesn't this mean that time will also start to go in reverse? If, as I've read, this universe is a 1 in a billion event, with carbon based life occuring on formed planets might not time be different in other universes? it need not go from A to B but B to A or in loops or in a circle. Time is seen to be passing because things 'happen' but what if nothing happens? If the universe were static or empty would time pass?