# THE forth Dimension

1. Sep 1, 2004

### bayan

HI. I was wondering if anyone can tell me a bit about the forth dimension?

Any comment is welcome

2. Sep 1, 2004

### jcsd

Time is often called the fourth dimension, but be careful as it is not a dimension of space, it is a dimension of spacetime which has four dimensions (usually by convention it is actually the zeroth dimension of spacetime, but this is only a convention), the other three being the normal three spatial dimensions. In spacetime each 'point' is known as an event and is specified by four coordinates: (t,x,y,z).

The reason why choose to describe physics using spacetime comes from special relativty. In special relativty how someone views space and time is dependent on their motion (I'm sure that you have heard of the phenoumna of time dialtion and length contraction in special relativty), however evryone views spacetime pretty much the same (a different veelocity is equivalent to a different coordinate system in spacetime). This means that spacetime is a powerful tool for describing the world around us using relativty.

3. Sep 1, 2004

Seeing the world in a grain of sand

I agree that the 4th dimension is considered to be time in relativity. Like the gentleman before, he states that time is not an isolated dimension but entwined with the trhee spatial dimensions.
The 5th dimension is the age of aquarius. If you are not familiar with 60s music you will not understand my joke.

The astrophysicist Paul davies once asked if mathematics is built into nature or if it is just an abstraction of human thought. With this in mind you must ask if geometry (which is what dimensions are) really exist or is just a concept of man. Does our mathematical and geometric constructions accurately describe the universe or is geometry a depiction of reality, like a photograph of your family. Is geometry and mathematics just a depiction of nature, like a topographical map of the Earth (such as a globe)?

I believe there are no dimensions to the universe. Time and space are illusions. Physicist David Bohm (along with many others) believe the holographic model of the universe, which is caused by wave interference. If you take a picture of an apple on a piece of holographic film, you can cut the piece of film in half. If you expose that half piece of a picture of the apple to a laser, you still get a whole picture of the apple but the size of the apple will be reduced by 50%. What this says in general is that all parts of the film has information about the whole (if you were to keep cutting the picture of the apple into smaller and smaller pieces the image would become very distored and unrecognizable). From the perspective of a holographic model, in a sense the whole universe is contained in every part of the universe. The whole universe is contained in each subatomic particle if one subscribes to a holographic model.

4. Sep 2, 2004

### bayan

that was a very nice ending. lol

5. Sep 2, 2004

### chroot

Staff Emeritus

- Warren

6. Sep 3, 2004

### Mk

That's pretty cool.

If you were a 4 spatialy dimensional being you would be God to 3 dimensionalers.

But of course you wouldn't need money...

What sorts of things would happen if they were to try and attack you? Would you feel pain? Only the two dimensional parts of the atoms touching the ground would be hit?

Last edited: Sep 3, 2004
7. Sep 3, 2004

### Tide

Most of the folklore about the fourth dimension is due to Abbott who wrote a cute and whimsical story years ago called Flatland. It was a fantasy but has contributed to the misguided view many mathematicians and physicists have of "the fourth dimension." There just one problem with it. If there are hidden dimensions (i.e. we 3-D people can't see into the fourth dimension) then there is absolutely no reason to believe that it's not reciprocal (i.e. those 4-D people shouldn't be able to see into OUR 3-D world!)

If there are extra degrees of freedom out there then certainly some components of either "universe" would have taken advantage of them.

8. Sep 3, 2004

### Chronos

Time is a necessary component of a universe that submits to being described by physics.

9. Sep 3, 2004

### Mk

We can't see in 3D? I think not.

You could take several sides:

We wouldn't know if they did, they'd do it so often that it would be normal.

Besides why would they want to tinker with inferior us?

Maybe they got tired with us, that's why God doesn't intervine all the time, like in the bible...

Maybe no creatures exist in higher dimensions?

What about the tea garden-carp-scientist-hyperspace analogy?

Last edited: Sep 3, 2004
10. Sep 3, 2004

### 4newton

Bayan:

Almost everyone has tried to make the fourth dimension strange and mysterious. In mathematics multiple dimensions have no strange properties. All dimensions are the same. If all dimensions are the same then the difference between the three spatial dimensions and the time dimension must be what is going on in the time dimension. The only thing you can do in a dimension is move, or transition. We therefore perceive time because we are transitioning in the time dimension.

We know that time is perpendicular to all the spatial dimensions because we are able to plot movement in the spatial dimension against time. We find that time is always perpendicular to motion in any direction. This is called velocity.

It is also only possible to plot this function up to the speed of light. At this point we run out of time base. You run out of time base if you are moving at the same rate as the time base. We must therefore be moving in the time dimension at a rate equal to the speed of light.

As you can see it is all very simple.

11. Sep 3, 2004

### Tide

Well, there may be exceptions! ;-)

12. Mar 21, 2010

### Evelia13

Really, we can't see in 3-D. If you look at something you see it as a 2-D plane, just as in the 2-D you'd see things as lines (1-D).
In addition, there is a 4-D all around us. In Flatland, a book that had been sited many a time here, the square points out that even after he is pulled into 3-D he is incapible of moving up and down. On pondering this, I came to the idea that perhaps there are two (or more) direstions inwhich we cannot move.
What say ya'll? (Wow, that was the best transision from intelligent to hick ever.)

13. Mar 21, 2010

### AUK 1138

excellently correct.

14. Apr 19, 2010

### Evelia13

Here's an idea, have we ever stoped to consider the effects of gravity in a 2-D world? That really hung me up before. I didn't undersatnd how in Flatland the creatures propelled themselves about without traction in the nothingness "below" them. It was then that I realized that the creatures in "spaceland" didn't abide by any laws of gravity. Long story short, I find easier to invision a world without width instead of the traditional lack of height. It's as if the world were a circle rather than a sphere, if that makes sence...

Last edited: Apr 19, 2010
15. Apr 19, 2010