You are in Geometry/3D (space) section

Welcome in our Geometry/3D (space) section. You must read the Geometry/1D (line) and 2D (plan) sections.

As we have seen: in a 1D-world we can only move following a line or a direction; in a 2D-world we can only move following a two main directions (in a plan). What happen in a 3D-world? In a 3D-world we can move following three main directions.

Example:

You are in an outdoor area, in a backyard of your house. Considere your feet. First, if you move alone a line, we say that you are moving in a 1D-world. If you move in any direction on the ground of your backyard we say that your feet are moving in a 2D-world. If you repeat your movement in any direction on the ground and you jump in the air sometime during your movement we say that your feet are moving in a 3D-world. In a 3D-world your degree of liberty (or freedom) is following a three main directions (you are moving in a space or if you prefer throught the space). In the real world (on earth) we live in a 3D-world ! As three-dimensional person in three-dimensional space, we have freedom of movement in any direction !

Examples of things in a 3D-world:

- a box;

- a house;

- indoor environnement of a house;

- outdoor environnement of a house;

- a school book;

- a pen;

- the earth, the moon, the space, a car, ... and you !

What is the mains directions in a 3D-world?

Considere a box. We can defined geometrically a box by the length, the thickness and the height. This is the three main directions of the box or an object, if you prefer, in a 3D-world.

Remember:

- the first dimension (1D-world) is : length;

- the second dimension (in a 2D-world) is : width;

- the third dimension (in a 3D-world) is : thickness or height.

Is there another dimension (i.e. higher dimension) ? Yes there is. As we have seen we live in a space world. But more specifically we live in a space-time world. In this 4D-world the time (clock) is the other dimension. To "feel" this fourth dimension we must travel at a higher speed than we usually use on the earth, like travelling near the speed of the light ! or be near or if you prefer in a great gravitationnal field like a big star. This is why it is difficult to us to understand this because here on the earth we live more in a 3D-world (travelling in a space at low speed in a low gravitationnal field (gravity)) than in a 4D-world and we don't "feel" the effect of the fourth dimension. But we can retain that there is a fourth dimension and in a 4D-world the fourth dimension is the time. This mean that the time, in a 4D-world, is not "fixed" like it appear on the earth. The time has a dependance upon the speed and/or the gravity. The mesurement of the time (with your watch) is relative and not the same for all. May be we will explain all of this, simply, later in our web site. Just retain that it is possible to move in a space-time (4D-world) environment like in a 3D-world, a 2D-world, ..., and on the earth we live in a 3D-world !