# Different Dimensions

#### Brownie

Hi Everyone,

I am a newbie ... i am High School physics student up in canada, and i was wondering if you all could tell me what the different dimensions are ... and what they include ... and any readings i could read that would be easy enough for me to understand.

Thanx

Related Other Physics Topics News on Phys.org

#### lethe

we live in 3 dimensional space. those three dimensions are usually called length, width and height. you can describe space with three axes, usually called the x- y- and z-axes.

sometimes, we speak of spacetime, which is 4 dimensional. the fourth dimension is then time.

some people talk about theories in which there are more than 3 dimensions. this means that in such a space, you could point in a new direction that is perpendicular to the length height and width.

#### dg

The easiest way to develop an intuitive understanding of how dimensions work is to see how adding a dimension change a 2D world into a 3D world (there is a nice book called 'Flatland').

If you want to develop a more solid and formal understading go into linear algebra and study vector spaces on some basic text.

If you have more detailed questions be my guest!

Dario

#### Brownie

I heard one man talk about dimensions like this ...
The first dimension is a basic line, now the second dimension is a rotated version of that so that now we have length and height, then the third dimension is a rotated version of the second dimension so that now we have width.

Am i right in sayin this ... and if so then wouldn't the 4th dimension be a rotated version of a 3-d object?

Thanx guys

#### RuroumiKenshin

I, myself have a hard time* comprehending "the 4th direction", time. BUT, I have two examples that make it easier to understand:
First off, time could be percieved as a coordinate. It specifies when an object is in existence.
Secondly, time could, quite simply be defined as the direction of which entropy increases.

I'm a newbie too, so to speak, so I'm still-a-learnin'. I may be wrong...but I'm 100% sure with what I've said.

#### eureka

for me,

the 4th dimension(time) can't be visualized unlike the x-y-z axis..

#### wimms

Problem with spatial dimensions is that none can actually *exist* without Time. If finite distance is traversed in 0 time, it means that arrival and departure occur simultaneously, or there is no distance to even ponder about. Nothing can exist between 2 points as existance preassumes non-zero time.

Pure 3D-space in math is abstract idea, and even it has problems with time - to *exist* is to be *in* time.
Strictly, there is no length or width or height alone, there can only be length AND time, height AND time, etc.

Therefore I'd say that we live in 3d-spacetime. But usually ignore time for convenience and due to urge to dismantle things and keep them separate.

Time is confusing and mysterious. There seems to exist 2 meanings to time, as coordinate point for chain of states of existence, and as enabler of spatial reality itself.

Any measure of spatial reality needs reference, for that we have velocity of light. As coordinate of existence, we need only fact of change, ordered. Two different states separated by single change can be separated only by single step of time for internal observer, even if either state exists for differing length of time for external observer. Thus intensity of change becomes equivalent to speed of timeflow.

As to imagining spatial dimensions, closest to my braincells I've seen is comparison of displaying 3D environment on your 2D flat monitor. In same way you can transpose imginary 4D environment onto 3D, and then onto 2D monitor. This has actually been done. Looks weird.

I'd personally seek for qualitatively different sense to additional dimensions. Spatial dimensions are complete. Time adds coordinate if you are after one, but to go further, I'd seek for more fancy things, like perhaps universe inside proton, or dimension for curvature of space. But in math, anything like 100 and more dimensions look cool and offer useful models. I'm suspicious about their relation to reality though.

### Physics Forums Values

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving