Are all dimensions created equal?

pgrmdave · 12-14-2004

Within the first three dimensions, there is no difference. They are all quite interchangable. While up and left are not the same thing, they are obviously quite similar. If the first three dimensions are the same, should that not hold for higher dimensions? Assuming that the fourth is time, we are moving through time, just like moving forward, or left, or up. If this is true, what information would be lost in thought experiments that reduce all dimensions by one, as in imagining people as two dimensional beings moving through a third dimension they call time?

Tim_Lou · 12-14-2004

dimensions are just a concepts......
there are only 2 dimensions (not the m theory) normally in my opinion, space and time.

they are totally different concepts... defining them as dimensions is just a way for us to understand... (so we can apply math calculation to it)

Tormod · 12-14-2004

Quote:

Originally Posted by pgrmdave

Assuming that the fourth is time, we are moving through time, just like moving forward, or left, or up.

While it is commonplace to assume that the 4th dimension is time, there is really no need to specify it as "the fourth" dimension. We say space-time is 4 dimensional because it works with our models for 3 spatial and one time dimension, but the time dimension is completely different from the spatial dimensions (as Tim implied). The concept of space-time (as defined by Einstein) really tied these different concepts together.

We have discussed dimensions on and off in these forums before, you might want to try to search for dimension or similar keywords.

BlameTheEx · 12-15-2004

Quote:

Originally Posted by Tormod

While it is commonplace to assume that the 4th dimension is time, there is really no need to specify it as "the fourth" dimension. We say space-time is 4 dimensional because it works with our models for 3 spatial and one time dimension, but the time dimension is completely different from the spatial dimensions (as Tim implied). The concept of space-time (as defined by Einstein) really tied these different concepts together.

I am not sure you are right there. Time is different to the other 3 dimensions, but perhaps only to the observer. In an absolute sense there might be no difference between the 4 dimensions (although I am taking a real interest in the idea that there IS a direction within the 4 dimensions that is locally valid as the direction of time, without regard to the velocity of observers).

Observer A travelling at near light speed, as viewed by observer B is time dilated in observer B's opinion, but not as far as A is concerned. Quite the reverse - A considers B to be time dilated. One way of looking at this is to say that both A and B are travelling through what they consider to be time at the same speed, but they each have a direction of time that points in a different direction in the 4 dimensions. A considers much of B's travel through time to be travel through space, and visa versa.

Sigh. This is difficult without diagrams.

Tormod · 12-15-2004

I think the main problem lies in our lack of understanding about what time really is. So there will be many ways to explain how dimensions are related.

pgrmdave · 12-15-2004

I had considered the effect we consider to be time simply a byproduct of the fourth dimension. bring it all down one dimension for simplicity. Imagine there are two-dimensional beings living in a two-dimensional universe. Assume that all of time, past present and future co-exist, but only the past can affect the present and present can affect the future. If every "frame" of time were stacked upon one another, it would become a third dimension. The beings within this dimension would think that there are three dimensions, two spacial and one time. I know this is a bad explanation, but it is difficult without graphs.

Jonahtan · 12-22-2004

I have read and heard that theorists believe that there may be as many as 10 or eleven dimentions. Can anyone provide a link to a website or thread about this topic? Im wondering if any likely dimentions have been conceptualized or considered or anything?

pgrmdave · 12-22-2004

http://superstringtheory.com/experm/exper3.html

Quote:

In string theory, the set of physical quantum states usually contains a graviton that gives rise to gravitational interactions. Therefore, it has been widely assumed that the natural distance scale of string theory should be the Planck scale. However string theories contain many duality symmetries that connect a string theory at one distance scale to a different string theory at a different scale. So the idea of a distance scale itself is not as firm and reliable in string theory as it it normally is in quantum field theory.

I won't pretend to know anything about string theory, but this site seems to explain it well.

Aki · 12-22-2004

Quote:

Originally Posted by Jonahtan

I have read and heard that theorists believe that there may be as many as 10 or eleven dimentions. Can anyone provide a link to a website or thread about this topic? Im wondering if any likely dimentions have been conceptualized or considered or anything?

In the M-theory, aka string theory, Edward Witten suggests that there must be 11 dimensions, in order for a string to stretch into a membrane or "brane". Here is a link to a set of videos,
http://www.pbs.org/wgbh/nova/elegant/program.html, it explains the 11th dimension in the the third hour.