# Building Blocks of Space

*Most recent answer: 07/13/2008*

Q:

I Read a fascinating article in July 2008 Scientific American entitled "The Self Organizing Quantum Universe." Using their ideas and computer calculations they predicted that, on the smallest scales, space-time has only 2 dimensions but on larger scales it smoothly transforms to 3 then 4 dimensions. Could this mean that Quantum Mechanics applies only to particles that experience < 4 dimensions and Relativity applies only to the 4 dimensional universe. If so there seems to be no point to looking for a mathematical framework joining these two pillars of physics. Your comments please?

- Physics Buff - novice

- Physics Buff - novice

A:

I read the same article, and was able to follow some of it. First off, I should mention that this is just one approach to understanding the nature of space-time. String theory and loop quantum gravity are competitors. All of these are by definition attempts to find a mathematical framework 'joining these two pillars of physics'.

Certainly ordinary General Relativity, a 4-D theory, only emerges at some spatial scale, with a different description applying on smaller scales. That's a pretty general feature of all attempts to integrate relativity and quantum mechanics.

As I understand the article (we'll update if better information comes in from colleagues) the assumption is that quantum rules apply all the way down, in all dimensions. It looks like the choice of 4-simplices as the basic ingredients may put in the large-scale 4-D behavior by hand, although I'm not sure. It also looks like this theory, unlike some hoped-for string results, does not integrate gravity with the other (nuclear and electrical) forces.

Mike W.

Certainly ordinary General Relativity, a 4-D theory, only emerges at some spatial scale, with a different description applying on smaller scales. That's a pretty general feature of all attempts to integrate relativity and quantum mechanics.

As I understand the article (we'll update if better information comes in from colleagues) the assumption is that quantum rules apply all the way down, in all dimensions. It looks like the choice of 4-simplices as the basic ingredients may put in the large-scale 4-D behavior by hand, although I'm not sure. It also looks like this theory, unlike some hoped-for string results, does not integrate gravity with the other (nuclear and electrical) forces.

Mike W.

*(published on 07/13/2008)*