lets discuss dimensions! Preferably extra ones.

[bhavv]

There is often a lot of interest and discussion about dimensions which I find fascinating. In Sci fi the term is supposed to refer to the idea of extra planes of existence outside of our own, with the multiverse theory being a very popular application of this hypothesis.

But then there is also the idea of extra spatial dimensions, imagined from drawing extra points out from 3D starting from 4D objects such as tesseracts and beyond.

Maybe the extra planes in the first idea could exist within the extra spatial dimensions of the second.

Discuss.

 

[warpus]

I have personally walked through the first 4 dimensions, so I have some things to say about the subject.

The first dimension is length and I've found it to be quite useful. Width is a bit less useful, but I think I'm looking at things from not quite the right perspective; with enough practice width could very well become as useful as length.

Height is a familiar yet completely unexpected take on the whole thing. It rises above the other dimensions in more way than one.

Time is the fourth dimension and the most useful of all - or at least the most interesting to me, since it allows me to move through the other dimensions at will.

Extra dimensions are probably going to be weird. A guy could have a butt that just floats there - but in reality it's 1 solid object that you just aren't seeing the right way.

 

[bhavv]

I do not accept time as a dimension.

 

[Terxpahseyton]

Humans seem to be incapable of imagining something beyond 4 dimensions. That is - anything beyond that which seems to come down to abstract predictions or images forced down to a plane of our comprehensions.

 

[bhavv]

That's why I find it fascinating. I've been trying to figure out how extra spatial dimensions would work, but my human brain is incapable of such things.

 

[Terxpahseyton]

You got mathematics. Or physics. I can understand your fascination. But if none of the two will satisfy you - nothing will.

 

[Kouvb593kdnuewnd]

Well you can use color as the 4 dimension in a x,y,z graph and the 5 dimension could be the form of the point in the x,y,z graph.

 

[El_Machinae]

I found Smolin's book on Quantum Gravity really helped me in my envisionings of extra dimensions. It certainly wasn't an easy book, though.

I find it tough to figure out how to assist the progress with these advanced physics questions.

 

[strijder20]

I do not accept time as a dimension.

You're actually not allowed to have an opinion on the subject.

Our speed through space and time is fixed; displacement through space per second (also known as velocity) (v) and time displacement per second (can be seen as 'aging relatively to an observer with v=0') (t) can be expressed as such:

x² + t² = c²

This means that the faster we go, the slower we relatively age; moving at near-lightspeed means we're basically fast-forwarding the rest of the world. Time and space are intertangled; whether that makes time a dimension or not I don't know, but I'm pretty sure subjective interpretation has little to do with it.

 

[warpus]

I do not accept time as a dimension.

You might as well not accept height as one either.

 

[bhavv]

But this is clearly the fourth dimension:

Not time.

 

[BenitoChavez]

Special/General relativity has already shown that space and time are separate parts of the same thing, namely spacetime. So however many dimensions space has, time is another dimension of spacetime, whether you want to call it the 4th, 5th, ... , or nth dimension doesn't really matter as long as there are n-1 spacial dimensions.

Whenever I try to comprehend a 4-D object I imagine what a 3-D object would look to a 2-D creature. For example a sphere intersecting with a plane would look like a point or a circle to a 2-D creature living on the plane. So in the 3-D world we would only see some cross section of a 4-D object. Like in the picture bhavv posted we would only see the inner cube of the 4-D Hypercube.

 

[El_Machinae]

Are you bhavv, in some ways, the same person you were yesterday? Is there continuity between the 'you' of today and the 'you' of yesterday?

 

[strijder20]

But this is clearly the fourth dimension:

Not time.

Yours is the fourth spatial dimension, so much is clear.

Imagine a snapshot of the universe taken every Plank second and then all those spheres lined up in a row. That's basically the same as the picture you posted (well, aside from it not being a cube), and that's how time can be imagined as a dimension (in the classical interpretation you are using).

You might argue that time is really different from the other three spatial dimensions, but that's only how it feels. Besides, the main reason we perceive that is because the three spatial dimensions are similar - automatically making time the odd one out. If we lived in an one dimensional line-land and if we were automatically (since that is how time feels) moving into a second dimension, we'd call that dimension time - but the only difference between the two is that we're automatically moving in one of them.

(Even in our own universe, this isn't entirely true - we aren't forced to move forward in time - you just have to move in either time or space - see the formula I put in the previous post)

The difference between the two dimensions in this picture is negligible.

 

[bhavv]

I am perplexed by your question.

 

[strijder20]

I am perplexed by your question.

If you say time isn't a dimension you are basically saying you're not connected to your past (and future).

Imagine that height weren't a dimension - it means your feet wouldn't be connected with your brains (or any 'slice' of your body with any other slice') which means you wouldn't be whole.

 

[bhavv]

I meant the question above your post sorry, we posted at the same time.

 

[Samson]

The difference between the two dimensions in this picture is negligible.

Surely there are some real differences between time and the spacial dimensions? For a start, the spacial dimensions have nothing like the 2nd law of thermodynamics to give them an inherant direction. Also the "non-specifiability" of the spacial dimensions, eg. up for you is different than up for me, and we can plot a 45 degree angle between up and left. We cannot plot a 45 degree angle between up and the future.

 

[uppi]

Yours is the fourth spatial dimension, so much is clear.

Imagine a snapshot of the universe taken every Plank second and then all those spheres lined up in a row. That's basically the same as the picture you posted (well, aside from it not being a cube), and that's how time can be imagined as a dimension (in the classical interpretation you are using).

You might argue that time is really different from the other three spatial dimensions, but that's only how it feels. Besides, the main reason we perceive that is because the three spatial dimensions are similar - automatically making time the odd one out. If we lived in an one dimensional line-land and if we were automatically (since that is how time feels) moving into a second dimension, we'd call that dimension time - but the only difference between the two is that we're automatically moving in one of them.

(Even in our own universe, this isn't entirely true - we aren't forced to move forward in time - you just have to move in either time or space - see the formula I put in the previous post)

[...]

The difference between the two dimensions in this picture is negligible.

The difference between the two dimensions in this picture is negligible.[/QUOTE]

It is true that time is the fourth dimension. But it is wrong to think it to be similar to a fourth spatial dimension. Time not only feels different, but it is different. If you would add a fourth spatial dimension, you would calculate a distance in that space as

d=sqrt( (dx1)^2 + (dx2)^2 + (dx3)^2 + (dx4)^2)

where dxn is the distance in the nth dimension.
However, time is different: In special relativity you calculate a distance as (with c=1):

d=sqrt( (dx1)^2 + (dx2)^2 + (dx3)^2 - (dt)^2)

Notice the minus there? This makes the resulting space quite different form a "normal" (i.e. Euclidean) 4 dimensional space.


Here is a useful fact about extra spatial dimensions: The volume of an infinite dimensional sphere is equal to its surface area. (And yes, there is physics where this fact is indeed useful)

 

[bhavv]

I still cant consider time a dimension simply based on how the first to third dimensions work, I cannot correlate time to also being a dimension.