What is 4-D?

Question

What on earth is 4-D and how is it different from 3-D? What is the fourth dimension?

Answer 1

The first answer is correct, but here's more.

Dimensions are simply a mathematical framework for working problems. The most common framework is called the Cartesian Coordinate system. This is the framework frequently defined as having width, length, and height, which are three dimensions; therefore, we call it 3 dimensional or, simply, 3D. Another way to designate 3D is x, y, and z, which are called variables because we can vary their values.

Now, 3D is just fine for describing, say, the size of something not moving. For example, we can say a box is 3 by 4 by 5 and that nicely describes the size of it by its width, length, and height. And, in fact, if we multiply the values for these three dimensions, we can find the volume of that box. So the three dimensions are useful for doing math problems. But what if we try to describe something that is moving?

For example, what if we want to specify the location of an airplane? We can say it's at a point (x,y,z) 10 mi east of a north-south line drawn through SFO, 5 mi north of an east-west line also drawn through SFO, and 2 mi above the point (10,5) = (x,y). In which case, we'd draw a north-south line on a map 10 east of the airport, then an east-west line 5 mi north of the airport, and then imagine the airplane 2 mi above the place where the two lines intersect. And we can write the position, relative to SFO as the zero point (0,0,0), as (10,5,2) for the three distances along the three, x,y,z dimensions.

But wait a mintue...this airplane is traveling at 500 mph. So it will clearly not be at (10,5,2) for long. What to do, what to do? Ah, we add time, the fourth dimension. So we can now describe that position by a 4D point (x,y,z,t); where t is time. Now we can say the airplane is at (10,5,2,1200) the original position given, but at 12 noon (1200). And later, we can say the plane has moved to (10.2,5.3,2,1203), which is 10.2 east, 5.3 north, and still at 2 mi altitude at 12:03 PM. And that's about it, we need that fourth dimension to fix moving objects over time.

And we also need that fourth dimension to describe their motion. Look at this, speed is defined as a change in position over a lapsed period of time. In math talk, this is often written as v = (S1 - S0)/(t1 - t0); where S0 is the original position at time t0 and S1 is the revised position at time t1. For example, if S1 - S0 = 60 miles and t1 - t0 = 1 hour, then the speed v = 60 miles/1 hour or, simple, sixty mph, which is speed.

So, to answer your question, 4D differs from 3D by the addition of time as the fourth dimension. I hope the other information I added helps you understand why the fourth dimension was needed. There are a lot more reasons for it, including, but not limited to: momentum, acceleration, and the theory of relativity. They all need that fourth dimension.

Answer 2

How is the term being used? 4-D means four dimensions instead of three dimensions, (as our space has.) Einstein's theory of relativity treats time as another dimension, so it is sometimes refered to as 4-D.

Sometimes it is useful to create hypothetical mathematical "spaces" to solve equations in, which may have any number of dimensions. This can simplify the math used to solve various complex systems in physics, meteorology, or even economics, to name a few applications.

Answer 3

The fourth is usually time.
Usually, 4D is referred to a three dimensional reference through time. Often done as an animation or video.
Often said about 3D videos of baby ultrasounds.

Answer 4

4 Dimensions. Humans cannot visualise it, it's a concept; it is to 3D what 3D is to 2D (and what 2D is to 1D).

The fourth dimension, as in space-time, is the dimension of time.

Answer 5

The American Indians conceived of 7 directions: up,down, norht, south, east, west, and inward. If the pairs up, down, etc. are seen as the x,y and z axes of 3D, then the 4th D is inward. What is 90 degrees from everything else?

Answer 6

the normalspace is called 3-Dand any point in it can be represented by coordinates(x, y,z)in a three-dimensional rectangular coordinate system.
in relativity theory another dimension - time is also cosidered. then ,it becomed 4-D space described by (x,y,z, ict.)c= velocity of light in vaccum.

Answer 7

(d^4)(d^5)^3 <--multiply the 5 and three to get 15 because it really is a ability raised to a special ability (d^4)(d^15) <--upload the 4 and the 15 to get 19 because it really is a ability cases yet another ability (d^19) <--answer :)

Answer 8

mri related, procedure developed by canadian scientists which enables a medical professional to observe human organs life-sized from any possibe angle, a tremendous boost for diagnosis. basically virtual reality