Holographic Universe and Extra Dimensions: Two Faces of the Same Coin?
Within cosmology there are strong suggestions that the universe has more than the four dimensions we observe (3x space + 1x time). When theoretical physicists extended the formulae from Quantum Mechanics with those of General Relativity (to try to understand what gravity is at a quantum level), it lead them to multiple possible “string theories”. All of these theories need additional dimensions in order to be mathematically consistent. We are a long way from being able to test which of these versions of string theory is the closest depiction of reality. We are so far from understanding the possible permutations that its almost meaningless to us. At one point superstring theory suggested 10 dimensions, but when you add an 11th dimension, you get M-Theory. M-Theory appears to be our best bet so far of what things are like beyond the already poorly understood quantum world (although there are more useful theories such as Loop Quantum Theory) . The one dimensional strings that it describes as the cause of all phenomena in the universe are beyond anything we can really test or even really conceive at this point, but we’d be sloppy to ignore the non trivial existence of some form of additional dimensions.
There are other good reasons to believe that there are extra dimensions. Gravity is a fundamental force, but unlike the other forces its extremely weak. When you lift something off the ground you’re overcoming the weight of the earth, something you could never do with the other forces. Try to imagine pulling a spanner off an earth sized magnet. One explanation for this extreme difference in the order of magnitude is that gravity applies across extra dimensions. In this case gravity would be normalised to expected levels (in Bayesian terms) within formulas, rather than standing out as oddly weak.
There are other hints of extra dimensions. Quasicrystals exist in nature, but the only way to describe them mathematically is as projections of higher dimensional latices. This is not in any way evidence of extra dimensions, but it does point to unexpected dimensional aspects of the nature of matter.
Complex numbers contain impossible “imaginary numbers” based around the square root of -1. Normal numbers go up and down the Y axis with 1,2,3… upwards, and -1,-2,-3… downwards. On the X axis are the imaginary numbers that can’t exist according to fundamental maths. However complex numbers are needed all the time by physicists and engineers to describe the world. The symmetry of maths seems fundamental to nature, so what does this X axis describe? Again, not evidence of any correlation, but a hint that nature is more than what seems obvious on the surface.
According to the WMAP probe results on the cosmic microwave background radiation left over from the big bang, the stuff we know about in the universe is less than 5% of the totality. There are theories for what the rest of it may be, but they are pure speculation at this point. Definitely not evidence of extra dimensions, but a fairly blank slate in our knowledge.
On the other side of the coin, there are also hints that aspects of the universe are holographic. The holographic principle comes from the physics of black holes, and looks at the universe in terms of information rather than matter and energy. When you do this, the information contained in any given part of the universe is described by its surface area, rather than its volume. The conclusion from this is that volume is an illusion, that three dimensional space of the universe is in fact a projection of a two dimension hologram. The universe itself is a hologram, a bit like some gigantic film being projected from ‘outside’.
When you look at quantum physics, its clear that at the smallest level, things are not here or there. Particles don’t exist at any point in space until they ‘collide’ with something. Entangled particles somehow can be separated by miles, yet when you measure one, not only does it change in measurement, its partner immediately changes to match this measurement (as its opposite). This suggests that despite separation in space, these particles are still somehow connected. How can this be possible unless there is some kind of direct connection that transcends space, as if the spacial dimensions are at some level illusory.
There is also good reason within physics to believe that time itself is illusory. I won’t go into the detail here, but if you’re interested in this The End of Time by Julian Barbour is worth reading (although the first few chapters are enough to get the idea!).
…. we have two apparently conflicting views of the nature of the universe. In one, the universe has hidden dimensions. We don’t know whether they are like our spacial dimensions, or more like temporal dimensions, or something else we just can’t imagine, but it does seem that there is more than we can detect with our senses or instruments. In the other, the dimensions that we do observe seem to be – in some fundamental way – illusory and intangible.
From a string theory perspective this is not really a problem, as all the dimensions are phenomena that emerge from fundamental one dimensional strings. Despite the fact that we have no conceptual understanding of this, its probably the only way we can make sense of these apparently opposing views. We are very used to thinking about space and time as fundamental realities, and the only instances of their species. Our evolved reptilian and mammal parts of our brain, combined with our senses, have resulted in this being deeply ingrained. In reality, its a bit more like we’re in a cinema watching a film, one that’s become our reality due to our absorption in it. When the film is over, our experiences during the film are still real, and carry over inside us, but we re-realise something far bigger. Plato’s analogy is that our experience of reality is like we’re watching shadows on the back of a cave. Its very difficult to get a good idea of the world outside, when all you’ve ever seen are black and white shadows.
The one consistent fundamental in these analogies is the living, conscious observer, with a mind and a will. Life and consciousness are arguably even bigger mysteries than time, space and their cousins, the only things we really know about these are the signs of their presence.
Anyway … that’s enough speculation for tonight!