# Co-exist dimension

1. Nov 22, 2004

### scilover89

1.Is it possible that different dimensions co-exist?For example:3 dimension space and four dimension space
2.Is it possible that the same type of dimension exist separately in another dimension?(For example:Two 3-dimension space exist together in a higer dimension)
3.Will force in a dimension affect the other if multi-dimension co-exist? (For example:gravity)

Thank you.

2. Nov 22, 2004

Staff Emeritus
1. In our ordinary 3 dimensional world we don't have a fixed separate 2-dimensional space; we can imagine a 2-dimensional plane in any orientation, for an infinite set of possibilities. Just so our 3 or 4-dimensional world can fit into a higher dimensional world in any of an infinite number of ways.

There are two cases in modern physics where dimensions are distinguished from another.

In relativity, time is a distinguished dimension from three dimensional space; the math reflects this by having the time and space coordinates have different signs in the metric.

In string physics the dimensions are distinguished by whether they are compacted or not. Three dimensions of space and one time dimension are uncompacted as we experience, and the other dimensions are compacted to tiny shapes.

2. Yes, if there were a higher dimensional euclidean space, as I said above, a three dimensional space could be "embedded" as they say in an infinite number of ways, and two such spaces could coexist, either parallel or intersecting.

3. This is a well known theory within string physics. Imagine that our spacetime is on the "surface" or boundary of a higher dimensional "brane" (or space). Physics would constrain the three quantum forces (electromagnetism, strong, and weak) to act only within our spacetime, but gravity could also propagate into the "bulk" as the higher space is called. Because gravity also spreads outside spacetime, only a fraction of its strength is available inside spacetime, and this is given as the explanation of why gravitation is so much weaker than the other forces.

3. Nov 23, 2004

### yanniru

"Because gravity also spreads outside spacetime, only a fraction of its strength is available inside spacetime, and this is given as the explanation of why gravitation is so much weaker than the other forces."

Dark matter and dark energy are primarily gravitational effects, at least as we can measure them. Would that suggest that they exist outside of spacetime.

Since dark energy is proportional the volume oif the universe, whereas dark matter is constant regardless of the volume of the universe, I would venture that Dark Energy spreads outside spacetime, but Dark Matter does not.

Any other thoughts?

Richard

4. Dec 3, 2004

### scilover89

Thanks for your reply, but what is dark energy? Is it energy of dark matter?
Anyway, if gravity force can effect other dimension, wouldn't that cause our dimension to crash with other dimension if another dimension exist?

5. Dec 3, 2004

### yanniru

If General Relativity is correct, then gravity creates space, or perhaps is identical to it. So if space is at least controlled by gravity, dimensions cannot come crashing in on other dimensions. In a sense gravity creates the dimensions.

6. Dec 3, 2004

### setAI

the concepts of background independence suggest that the dimensional metrics and physics of a universe are emergent from a web of relationships- so I think there are likely parallel layers of structures that only interact with similar structures- so that what we call spacetime/matter is a lattice/matrix of structures which interact to form and define dimensional metrics/ causal relationships/ matter fields- but an infinitude of OTHER structures forming other such matrices/dimensional manifolds/ branes might overlap each other and never [rarely] interact because structures of these alien realms don't match-up/balance each other due to topology/ wave-frequency/ “dimension” or scale- so that "universes" would interpenetrate but never touch-

I like to imagine that our universe is made of the connections between legos- but there are lincoln log universes and tinker-toy universes overlapping ours- but since they can't connect with legos and the connections are all we are and can see- we don't see those other spaces- [but you never know- every so often a tinker toy stick might get lodged in a lego hole that just happened to be the right size and at the right "place"-]

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

### Burnsys

A black hole maybe???

8. Dec 4, 2004

### scilover89

Perhaps travelling in the higher dimension is the only way to reach the other similar dimension(space)?