# Life in the Fourth Dimension

• Ploegman
Now imagine a three-dimensional person. She is standing on a surface, looking up. Now imagine a four-dimensional person. She is looking down, and can see all of the other directions at the same time. Imagine a five-dimensional person. She can see all the other directions and all of the other people at the same time. Imagine a six-dimensional person. She can see all the other people, all the other directions, and all the other surfaces at the same time. Imagine a seven-dimensional person. She can see all the other people, all the other directions, all the other surfaces, and all the other time periods at the same time. Imagine an eight-dimensional person. She

#### Ploegman

I would like to start off by introducing myself, my name is Jonathan Ploegman from Long Island, New York. I am 18 years old and I am new to the physics world, however I am very interested and eager to learn all that I can.

I was wondering what life in the "fourth" dimension would be life. I am not talking about the fourth dimension as time, but as the fourth dimension of space.

I read that we could walk through walls, and do all kinds of stuff nearly becoming God-like.

Anyway, I am just curious about the fourth dimensional world.

Have a great day everybody!

Welcome, Jonathan.

Well, yes, higher dimensions offer incredible abilities that defy many of our laws of physics. But there is a flaw. Usually when we refer to the next higher spatial dimension, we use the 5th, accepting time as the 4th. Now, a theory that holds up to date to the superstring theory is that the universe began in 10 dimensions, but some disturbance caused all the matter to flow into and remain in 4 dimensions, space-time. The other 6, without any matter collapsed into a nearly impenetrable size, the Planck length. To probe it, it would require incredible amounts of energy we cannot harvest just yet.

This is from the book hyperspace, imagine a man that lives in 2D, and is somehow exposed to the 3rd dimension and is floating through it. His vision is limited to be able to conceive only 1 dimension. We, as 3 dimensional beings can observe only 2 dimensions at once without rotation. Now, he would be floating through space, and let’s say he encountered an apple. What he would see is a red line, that becomes progressively larger, then smaller, and then it turns brown and disappears. He would be seeing the apple in 1 dimensional cross-sections. Apply that to our 3 dimensions. We can only conceive 2 dimensions at a time, but supposedly a higher being, to visualize a hypercube for example; we should be able to conceive all 3 dimensions at once to be able to visualize higher dimensional movement. But we can’t do so without rotating the figure.

So let’s say we were floating through a higher dimension and we encountered a hyper-sphere or a hyper-apple to suppose. What we would see is a 2D view of the sphere, and as we progress through the cross-sections of the sphere, we would see the sphere appear out of nowhere, get bigger, then smaller, and then disappear.

What you’re speaking of, regarding walking through walls is often used in mystical sciences, to explain the movement of ghosts, spirits, etc. Take the same 2D person, and draw a box around him on a piece of paper. His vision is limited to the paper; he cannot visualize or move up and down as we have it. No matter which way he would move, he would not be able to escape. Now, take a prison cell for example, and place a higher dimensional being into it. Being able to move through a higher spatial dimension, he would be able to move ana or kata, the motions defined for the next spatial dimension, and go around the walls and appear back on the other side by reversing the motion.

Some argue though that we do exist in all dimensions, but being that the dimensions are so microscopically small and looped, if we do move through them, our motion is limited past what we can observe. But that is another idea behind tunneling, where a particle can move from point to point through any barricade under a certain probability. Whether that fits under the Schrödinger wave function or that is up to the rest. But a higher dimensional being will not exist if there isn’t room for it in the shrunken higher dimensions, unless we are actually are those beings.

The fourth spatial dimension is a hard concept to visualize but u can infer its properties by comparing the other dimensions...for instance take a square ABCD (A up-left, B down-left, C down-right, D up-right)...now how many vertical lines can u draw like AB, between the side AB and CD...infinite...

The same is with a cube...how many vertical squares exist between the 2 faces of the cubes...infinte...so we can go on to say that there are infinite number of cubes between the two opposite faces of a hyper cube...thats another way of imagining...Funkee included all the cool ideas...

Welcome to the PFs, Ploegman . How do you pronounce "Ploegman"?

To help you visualize life in the fourth dimension, I suggest getting/borrowing a copy of "Journey Through the Tenth Dimension", by Michio Kaku. It's on audio tapes, and is a lecture that he gave in 1989.

An example of the illustrations that he uses would be this:

Imagine a two-dimensional person. She is absolutely flat. Her skin has formed "all-around" her, but, to us, it looks like a flat outline. You see, to other two-dimensional people, it appears that you would have to pierce through the skin, in order to see her insides. However, if you look at it from the third dimension (as we could) you would see both the outline, and the insides, at the same time! This is what it is like for someone that lives in the fourth dimension, even with regard to us (three-dimensional people). You see, you may think that you are covered "all around", but to a person in the fourth dimension, it is just an "outline", and they can see both it and the "insides".

There is much more in the lecture, and I highly recommend listening to it.

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That sounds like a wonderful lecture! I think I'll listen to it.

Anyway, in a 4D world, are there 4 spatial demensions? The 4th demension is perfectly active in our demension. So, in a 4D world, what would it be like, in the sense that 4D is time, which is defined as the increase of entropy? Would people themselves be increasing in entropy? I know how silly that sounds! but I can't help but guess(note I didn't say infer!)

Originally posted by MajinVegeta
That sounds like a wonderful lecture! I think I'll listen to it.

Anyway, in a 4D world, are there 4 spatial demensions? The 4th demension is perfectly active in our demension. So, in a 4D world, what would it be like, in the sense that 4D is time, which is defined as the increase of entropy? Would people themselves be increasing in entropy? I know how silly that sounds! but I can't help but guess(note I didn't say infer!)

Yes, it is a really fantastic lecture. If you are really interested in this whole 4th dimensional viewpoint, I also recommend the books, Flatland and Sphereland.

Yes, Majin, that's what they mean when they talk about life in the 4th dimension. Basically, when one theorizes about spatial dimensions, other than those that we are accustomed to (note: Prof. Kaku also briefly discusses why we are only used to three of the spatial dimensions), they "push 'time' up a notch" - so to speak. e.g. In ten-dimensional theory, time is the 11th dimension.

re: time is the 11th demension to 11D theory
How so?(do expand)

I, too, seem to be a bit lost.

10 dimensional string theory explains that there is a total of 10 dimensions, due to quantum symmetry, and that even change (time) can alter symmetry, so time itself is within the 10. One popular idea supports that the universe split when all matter was confined to only 4 dimensions, while the 6 other collapsed to smallest measurement in each dimension that any matter can have.

For instance, take a sheet of paper. Draw a person on it. The 2D person is confined to the dimensions only when using the dimension to describe a part of an object. Not when you try to describe the object in the dimensions.

For you see, the man on the paper truly has a height(3rd dimension) when describing the man itself, and in that we do in fact use our 3, if not 4 dimensions. The point is, that any particle will have a measurement in higher dimensions, but it is supposedly the absolute minimal that any matter can have, which is the Planck Length.

If the object were to cease to have any properties in higher dimensions, no matter how infintessimaly small, the object would cease to have values in other dimensions and cease to exist. That means, that all matter does have a property and value in every higher dimension, including time, because even change can be symmetrical.

Originally posted by Funkee
I, too, seem to be a bit lost.

10 dimensional string theory explains that there is a total of 10 dimensions, due to quantum symmetry, and that even change (time) can alter symmetry, so time itself is within the 10. One popular idea supports that the universe split when all matter was confined to only 4 dimensions, while the 6 other collapsed to smallest measurement in each dimension that any matter can have.

Oh, you mean like branes?

For instance, take a sheet of paper. Draw a person on it. The 2D person is confined to the dimensions only when using the dimension to describe a part of an object. Not when you try to describe the object in the dimensions.
The person is confined to the dimensions because it does not have dimensions that exceed 2.

For you see, the man on the paper truly has a height(3rd dimension) when describing the man itself, and in that we do in fact use our 3, if not 4 dimensions. The point is, that any particle will have a measurement in higher dimensions, but it is supposedly the absolute minimal that any matter can have, which is the Planck Length.

Well, I agree that, since the piece of paper which the object is drawn is influenced by time, it can have a 4th demensional property.
But other than that, I don't see your point, since you seem to be missing a very important prospect: you need to know what a "higher" demension is in order to incorperate it to an object.

If the object were to cease to have any properties in higher dimensions, no matter how infintessimaly small, the object would cease to have values in other dimensions and cease to exist. That means, that all matter does have a property and value in every higher dimension, including time, because even change can be symmetrical.
So you believe that a demensional value is what dictates existence? Please explain.

I'm sorry for the confusion, I didn't expect that. Well, then, let me try to explain.

When Einstein was developing Relativity, he was only making reference to the three spatial dimensions that we commonly discuss/affect. These are represented by the x, y, and z coordinates. Time is supposed to be another dimension/coordinate, and is thus number four. Einstein thought that this was complete. However, hyperspacial theories dictate that there may be many more spatial dimension than Einstein thought. Now, the numbering doesn't really matter, but string theorists refer to time as the 11-th dimension (and the other ten are spacial). If it were discovered that there were in fact 11 spacial dimensions (instead of 10, like string theory postulates) then time would be the 12-th dimension. Does that make more sense?

Ploegman: Pronounced = Plue (like "glue") add a "g" sound, like in the beginning a glue, Plueg ... min, like mint. Pluegmin.

Originally posted by Mentat
I'm sorry for the confusion, I didn't expect that. Well, then, let me try to explain.

When Einstein was developing Relativity, he was only making reference to the three spatial dimensions that we commonly discuss/affect. These are represented by the x, y, and z coordinates. Time is supposed to be another dimension/coordinate, and is thus number four. Einstein thought that this was complete. However, hyperspacial theories dictate that there may be many more spatial dimension than Einstein thought. Now, the numbering doesn't really matter, but string theorists refer to time as the 11-th dimension (and the other ten are spacial). If it were discovered that there were in fact 11 spacial dimensions (instead of 10, like string theory postulates) then time would be the 12-th dimension. Does that make more sense?

Why does time have to be the last demension in any number of demensions? Is it because time is always the last demension relative to spatial demensions? if so why?
whats the difference between spatial dimensions and non-special demension? i.e., what makes a non-spacial demension non-spacial? How in the world do you visualize this?

If you're really interested about learning all that stuff, i would recommend the book "Hyperspace" by Michio Kaku. I read it when i was 14 and since then i decided to orient my studies in physics. It really explains well, even without much mathematical concepts which is good if you are not familiar with advance math (and is not as fantastic when you actually know the math after and you wish he'd talk more about that). Anyway, it's a classic, and all the libraries i know have it so you don't even need to buy it to take a look. Hope you'll find it interesting.

You know, Max Born is an excellent author too. But a PhD physicist recommended his books; this must have been in the 70's...

So Michio Kaku's books are all basically on m-theory and string theory?

The ordering doesn't matter at all; it's just convention, ie what order you write stuff in. Actually time is usually written first, so an event's coordinates are given as (t, x, y, z).

A spatial dimension is just another one like the 3 we have now. A line is 1-D, a plane 2-D, and regular space 3-D. Higher spatial dimensions just add more independent directions. You can't really visualize more than three -- at least I haven't met anyone who could, except for maybe a topology professor or two -- so you have to just use the math.

A non-spatial dimension would be another time dimension, I suppose, though it's hard to imagine how there could be more than one.

Originally posted by pi-70679
If you're really interested about learning all that stuff, i would recommend the book "Hyperspace" by Michio Kaku. I read it when i was 14 and since then i decided to orient my studies in physics. It really explains well, even without much mathematical concepts which is good if you are not familiar with advance math (and is not as fantastic when you actually know the math after and you wish he'd talk more about that). Anyway, it's a classic, and all the libraries i know have it so you don't even need to buy it to take a look. Hope you'll find it interesting.

Michio Kaku is an excellent physicist, and an extraordinary author. He helps people visiualize/comprehend the more advanced concepts of string/M- theory, whether they have an advanced knowledge of math and science or not.

I second the recommendation of Hyperspace, but I would like to add Beyond Einstein, also by Prof. Kaku.

Originally posted by damgo
The ordering doesn't matter at all; it's just convention, ie what order you write stuff in. Actually time is usually written first, so an event's coordinates are given as (t, x, y, z).

Why x,y,z? Why not abc or something?

usually, the last half of the alphabet is reserved for variables and the first half for constants. It's just by convention.

hmm...

The 4th dimension is something i have never understood. Time, is it not just an invention of man? The speed of time is relative, is it not? I have often thought that if an object could reach the speed of light, time would stand still for that object. To me, there are only 2 limits in the universe. The speed of light, maximum kinetic energy, and absolute zero, minimum kinetic energy. I know we have come within a billionth of 0 kelvin, but i believe we are no closer to that than we are the speed of light, neither of which i believe man will ever reach. I probably sound like a complete idiot, but 10th grade doesn't teach much physics.

The fourth spatial dimension gives one amazing perceptual abilities, among other things of course. He could read an entire book without turning a single page, escape from closed rooms, be able to see the sun at all times of day. Instead of painting is masterpieces on planar canvases, he would do so on and inside cubes. He may even be able to travel through space at alarming speeds...

Originally posted by The_oMeGa
The 4th dimension is something i have never understood. Time, is it not just an invention of man? The speed of time is relative, is it not? I have often thought that if an object could reach the speed of light, time would stand still for that object. To me, there are only 2 limits in the universe. The speed of light, maximum kinetic energy, and absolute zero, minimum kinetic energy. I know we have come within a billionth of 0 kelvin, but i believe we are no closer to that than we are the speed of light, neither of which i believe man will ever reach. I probably sound like a complete idiot, but 10th grade doesn't teach much physics.

This post is about a 4th spatial dimension. However, I find it necessary to say that time is not just an invention of man. Time is a property of the universe as absolute (in existence) as something such as light. And you can't say man invented light, or for that matter, energy, space, gravity, etc.

BTW, I'm in 10th grade too and the problem with is it is that other kids just care more about getting drunk on prom night than learning things. Sadly, this deters us all.

Originally posted by The_oMeGa
The 4th dimension is something i have never understood. Time, is it not just an invention of man? The speed of time is relative, is it not? I have often thought that if an object could reach the speed of light, time would stand still for that object. To me, there are only 2 limits in the universe. The speed of light, maximum kinetic energy, and absolute zero, minimum kinetic energy. I know we have come within a billionth of 0 kelvin, but i believe we are no closer to that than we are the speed of light, neither of which i believe man will ever reach. I probably sound like a complete idiot, but 10th grade doesn't teach much physics.

What??! I was looking forward to 10th grade (and high school) 'cause I thought you'd learn physics more physics. so much for high school.

Anyway, time is just the increase of entropy, and a coordinate. It tells when something existed. That's a simple definition. What part of time do you not understand?

Nope...Most people only take like physics accel in high school and that's it...All our school has is regular physics and then AP B and AP C...theres no classes about 20th century physics or anything specific... u got to take those in college...

Ok..well...the increase in entropy is an AFFECT of time, is it not? I mean...for our universe i guess it could define it..but yea..Its more complicated than that..Yea.. i don't know what I am talking about

Lol, no, you've missed the point. Time is the increase of entropy. But to make it a little easier to understand, I'll describe it using coordinates:
Code:
     time l
l
l
l        x
l____________space
MV

The x, is let's say 12:00pm. MV is someone somehwere at 12:00pm. this is what I mean by 'time tells when something exists".

do you follow?

alright...lets make the question clear...has the geometry of higher spatial dimensions been developed already?

I believe so. m-theory has the geometry for higher demensions. See my thread "A Brane New World"

alright...lets make the question clear...has the geometry of higher spatial dimensions been developed already?
Yes; it's generally known as Riemannian geometry. Actually, for plain-old "flat" space -- Euclidean space -- it's rather simple: instead of points being described by (x,y,z) with a distance sqrt(dx^2+dy^2+dz^2) you just have, in n-dimensions, points described by:

(x1, x2, ..., xn) with distance sqrt(dx1^2+dx2^2+...+dxn^2)

The properties of this n-dimensional Euclidean space are fairly obvious and well-known. For fancier spaces -- like higher-dimension analogues of the surface of a sphere -- Riemannian geometry is used. This is the basis upon which General Relativity and some portions of string/m-theory are built.

(dx^2+dy^2+dz^2)

does x=1demension, y=2d, z=3d?

That formula is for 3D -- x,y,z are just any three mutually orthogonal directions. x could be measured east-west, y north-south, and z up-down.

In 2D, you have points described as (x,y) , often (horizontal,vertical) just like on graph paper.

Originally posted by pi-70679
If you're really interested about learning all that stuff, i would recommend the book "Hyperspace" by Michio Kaku.

Yes, I have ordered that book a few months back and have been reading it since. Takes me a while to get through books usually. :)

if we can see lower dimensions then show
me a 1 or 2 dimension object or thing.
i don't know much about physics but that was
just a question i was asking myself.
And technically is it possible for a human
being to advance to a higher dimension.

thanx all

Originally posted by jlorino
if we can see lower dimensions then show
me a 1 or 2 dimension object or thing.
i don't know much about physics but that was
just a question i was asking myself.
And technically is it possible for a human
being to advance to a higher dimension.

thanx all

1 and 2 dimensional objects don't exist in our 3D world, every piece of mass that exists has 3D measurements to it.

The idea of moving in the 4th dimension certainly creates interesting possibilities. Sure, a being capable of seeing in 4d can see both the outside and inside of a 3d object at once, given it fits into his/her visual scope. A 4d being can, however, not walk through 3d walls (only 'over'), but his/her 3d shadow (or rather projection) will seem to perform this wonderfull feat. If the 'light source' causing the projection can be moved, then the 3d projection can even appear to fly.

But, if you believe that the above possibilities are real, then you have not discovered the truth about science yet. The rest of this post might help you on your path.

A 0-dimensional space can not be seen by us because it is infinitely small and has a zero measurement in all dimensions. A 1-dimensional space (commonly referred to as a line) can also not be seen by us, because, although it has a measurement in 1 dimension, it is infinitely thin. A 2-dimensional space (flat surface) can not be seen because it is infinitely thin. I assume that a 4d person will not be able to observe a 3d space, because it is infinitely 'thin'. These facts should make you wonder a little. But, let me continue...

You might believe that 3d space is described by 3 mutually orthogonal axes (directions). But, in fact, 3d space can be described by an infinite number of arrangements of axes, as long as there are 3 of them and they are at angles greater than zero with respect to each other and they intersect. The same holds for 2d space (and, of course, 4d space).

Our universe is not 3 dimensional. Our universe is only described by a 3 dimensional coordinate system. The reality: there is no 4th spatial dimension. Dimensions are only units of measurement. We require 3 measurements of length to describe a position in our universe (we also need a reference position, of course). Measurements of time, temperature, etc. are also dimensions. All along you have stared yourself blind at vocabulary.

This brings me to the true nature of science, something you should never forget:
Science does not tell us what our universe is, but rather, it tells us how our universe functions. Science uses the language of mathematics to describe the universe, and the notion of spatial dimensions is just another mathematical tool.

I'm not saying that 'hyper space' wormholes (which would allow us to use the shortest possible path in 'hyper space' to travel between two 3d coordinates) does not exist, or cannot be created. What I am saying, is that we only use mathematics to describe the mechanics of the wormhole, not what or where the wormhole is. If, indeed, our mathematical tools can describe reality closely enough, then maybe we might be able to someday create those funky wormholes.

I have to admit, that I came to this forum looking for ideas of what would be possible in 4d space. But, as I carefully thought it through, I came back to the truth of science, and as I remembered it, everything suddenly made sense again.

So, remember that a 2d space (flat surface) is not a physical thing. It is only a mathematical description of the face of a piece of paper. Also remember, that we, as '3d' beings, can not see in 3d. What we see, is a stereoscopic image (providing the sense of depth) built up from two 2d projections of the world onto our eyes.

I hope my words could bring you some enlightenment, and may you always practice science truthfully. :-)