# Space-time dimensions

I was having a look at Seeing the fifth dimension and I was thinking the following.

A dot is 0-dimensional entity. A dot "living" in an 1-dimensional world would be a moving dot along a pipe of some sort. The dot would perceive the dimension as time.

Again, a line in a 2D-world would again perceive the second dimension (y-axis) as time for travelling around the 2 dimensions.

The above 2 examples is our analogy of being 3-dimensional entities living in a 4D-world that we perceive time as the fourth dimension.

Are the above analogies right?

Mathematically, all the above are valid explanations, but am I thinking in the right way as far as Physics is concerned?

• I would say all of those are wrong mathematical analogies. Spacial dimensions allow back and forth Time does not. Spacial dimensions can be interchanged with each other but not with time. In general, thinking of time as "one of the dimensions" is not a valid expression. – userLTK Feb 11 '17 at 4:18
• Historically, the kind of thinking you're doing was formalized as Minkowski space, and also described as the block universe by the less mathematically-inclined. Henri Poincaré discussed the merits of this perspective in his essay, The Measure of Time (1898). – Nat Feb 11 '17 at 7:29
• I'd add that this sort of thinking goes into a lot of modern theoretical models, e.g. string theory. Time reversibility occurs along world lines. – Nat Feb 11 '17 at 7:53
• Thanks Nat for the resources, they are very helpful. Would you mind posting them as an answer, so that I can accept it? – Alexios Tsiaparas Feb 12 '17 at 9:44