What is the 4th dimension?

the fourth dimension is TIME

The first three dimensions are experienced by the human stance: front/rear, left/right, up/down. As we measure objects, we distinguish length, height, and width.

We exist within a context of other matter arranged in three dimensions around us. We perceive ourselves in the center of three dimensional space.

Freeze the three-dimensional frame: there is a volume of atoms arranged just so, each with a fuzzy quantum probability spread of where it going to be next.

But you can't freeze the frame. It's always unfolding, at any scale of time you try to measure. It is unfolding into a fourth dimension, Time.

Unlike the three dimensions of space, we can't control our movements through time. We, with everything around us, are "unfolding" into the future at what seems to be a common and constant rate. It is as if all of our three-dimensional space is just the "skin" of a four dimensional expanding bubble.

Inside the bubble is the empty past, outside the bubble is the empty future. The bubble grows as the world unfolds into the fourth dimension, time, the future. All of the quantum interactions of all the atoms of our Universe reach out with fuzzy probability into the infinite vacuum of the future. As quantum probabilities interact and resolve, a new "Now" is created at the leading edge of the old one dissolving behind it.

In each moment, there are things that are possible and things that are not possible for the next moment. Of the infinitely many things that are possible, some are very probable and some are very unlikely. The present "now" conditions the future but does not define it. Quantum probability leads to real world probability; quantum uncertainty leads to real world uncertainty. The future is not random, nor determined; it is probabilistic.

Time became more accepted as a true dimension once Einstein's theories of Relativity were accepted. By these theories, the dimensions of space and time truly are stitched together into "spacetime".

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This is wrong. Mathematically and physically there can be an infinite number of spatial dimensions. Time is completely separate and is only used as a 'fourth' dimension for the purpose of graphing and calculation of motion in our observable universe. It is interestingly quite easy to construct a representation of a four-dimensional universe in three-space: it's a tetrahedron with its vertices connected in the centre. Intriguingly if you flatten it to two dimensions then it becomes a pentacle! 'Flatworld' - a novel about life in two dimensions - is well worth reading in this respect.

'Spacetime' is a useful tool but not a definition of multidimensionality.

Jan Rockett

First answer by Munnings1729. Last edit by Janrockett. Contributor trust: 1 [recommend contributor]. Question popularity: 63 [recommend question]