4th Dimension.. anyone know?

Question

Anybody know what the 4th dimension is supposed to be? Like, what do you do? 3rd dimension is 3D. I know that so, what's 4D do?

Answer 1

What you are asking is about a fourth EUCLIDEAN dimension. Euclidean geometry is the study of shapes, angles, lines and planes that work just like you have always imaged them to work.

When people talk about "time as the 4th dimension" they're really talking about something else completely different. In a simple physics/math problem, you can input all kinds of independent variables including things like height, width, depth, and the time it takes for the train to get from one station to another... thats the sense in which time is a fourth dimension. This is to use "dimension" and "independent variable" as interchangeable terms. In fact, Einstein's work was not about time being an independent variable, but actually a DEPENDENT one in this sense... but thats a whole 'nuther can-o-worms!

The sense that YOU mean 4D is much simpler. Imagine the difference between a line and a square. A line has length only, and a square has area. To pick a point on a line, you need only specify it's distance from a reference point. It is this quality of the line that makes it one dimensional. To specify a point on the surface of your square, however, you need to specify its distance in two directions from a reference point, like "2 inches north and one inch east from the lower left corner." It is this property that makes the square 2D where the line is not.

When we specify a coordinate system to map points on a plane, we typically use a reference grid formed of "orthogonal" axes. Orthogonal means "at right angles". Any two lines would work, right angles or not, but things are neater and simpler when defining things like "distance" if the axes are at right angles.

3D space is simply that which requires specification using 3 axes that are all orthogonal to each other. X, Y, and Z axes with X perpendicular to Y and X perpendicular to Z and Z also perpendicular to Y. It sounds complicated but you can see, if you hold three pencils in your hand, that you can easily make three lines come together with all right angles.

4D would then, of course, be that which would require specification of points using 4 orthogonal axes. You can see right away that if you try to make a 4th pencil be orthogonal to your other three, it just can't work.

Of course it can't! You're merely 3 dimensional!

An author named Edwin Abbott wrote a nifty little novel about this, where he describes how difficult it would be for an imaginary flat creature who lived in a flat world to understand a 3 dimensional space. In the same way you can understand how mind bending it is to try to contemplate a 4 dimensional space when you live in 3 dimensions. The book is called "Flatland - A romance of many dimensions" and he wrote it in 1880!!! It's minimally mathematical, a very quick read, and actually quite funny. I highly recommend it.

Answer 2

Think about this way, if you were to meet someone you pick a place (the 3 dimensions) and a time. without the time you may never meet, but once time is added (as a fourth dimension) the actual meeting is set.

Answer 3

The forth dimension is the change brought about in three dimensions. It has to do with mass acceleration. As a mass begins moving, mass is being converted into energy. This energy is described in a particular manner. It is mk = hf. Mass kinetic energy is equal to Planck's constant times the frequency of the mass. Because mass is composed of electromagnetic energy, it acts as does that form of energy. As it moves, in the direction of acceleration the mass density becomes greater in that direction, thus the length of the mass shrinks to accommodate the greater hf. At the speed of light the mass would convert into electromagnetic radiation, and all that would exist would be electromagnetic energy moving in a single dimension - the 4h dimension of time. There is a short writing at http://360.yahoo.com/noddarc that answers your question in greater detail. It is entitled "The Problem and Repair of Relativity". You may have to scroll down a bit to find it.

Answer 4

Einstein's two theories of relativity treat time as a fourth dimension. The Kaluza-Klein theory (since discredited) hypothesized a fourth spatial dimension. Current string theory hypothesizes a host of additional dimensions (I think the current total is 11). In most of them it's impossible to get a decent pint of Guinness.

Answer 5

The fourth dimension is time. An object can be at X, Y, and Z-coordinates. Then another object can be at the same place, but at a different time, and they do not interact. Put both objects at the same three coordinates at the SAME TIME (fourth dimension) - and they collide-!

Answer 6

Traditionally, Time is considered the fourth dimension.

Answer 7

time is the 4th dimension

Answer 8

Some say it is time.