Which would be your two dimensions (directions?). Length and breadth? Then where would you fit in depth?
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Originally Posted by Fredrick  The commonly known three dimensions are in reality the three directions, and not the three dimensions. When the word dimension is used, something is implied with a (time-)spatial aspect.
A single direction is something that cannot exist all by itself, and can therefore not display anything dimensional.
Something that has two directions, such as a screen (though the screen has a thickness, too), can be used as a medium on which something dimensional can be portrayed that itself is not based on thickness, just on left-right and up-down, like a projected movie (thickness of a movie is not part of the dimensional experience, though there can be some in the plot). It is easy to show that this dimensional feature is fake/art. Nevertheless, it is dimensional.
Something that has three directions can always be considered as dimensional because it can not only be experienced as such, but unlike the two directional experience of dimension it can also be measured in three directions.
I do not know why the word dimension was ever used as if it were the same as direction. My guess is that in the enlightment one tried to capture our reality in packages, and the directions and the dimensions were too much related for people to question any distinction between both. I do know that scientists tend to not have the best sense of language, and many words that scientists use get their own explanation in dictionaries as such, next to the usual explanations.
You may find it interesting that the word dimension is based on Latin for to measure out. Direction and 'to measure out' may appear the same, but they are only similar, not the same.
In as far as the three directions are concerned, they do not portray dimensional reality in a complete way, though they can get close. The dimensional aspects of a round object, say the earth, is not captured fully by 3 directions, for it does not state anything about density of layered material from which the earth is build up. Gravity also has a dimensional aspect that is not captured either by 3 directions (similar though not the same to the example of the round object). Inward and outward, an experience one can call dimensional (see Latin root), is not captured by the 3 directions (except as a very complex state, while in reality it is very simple as the action of 'to measure out' already shows).
I have no objections to you using the word three-dimensional, and when communicating with others I conform to the common use, but we live in a world where a single direction never exists by itself, so for me two spatial dimensions is all there is (unless when also talking about time). |