Thursday, April 29, 2010

Fjordman: Superstring Theory and Quantum Gravity

Fjordman has published a new essay about superstring theory and quantum gravity at Vlad Tepes. Some excerpts are below:

Superstring theories are consistent with what we know, but critics, of which there are still quite a few, claim that they are too mathematically abstract to predict anything which can be experimentally tested and verified, as should be possible with a proper scientific theory. Its supporters claim that the theories suggest that there should be a class of particles called supersymmetric particles, where every particle should have a partner particle. CERN, the European Organization for Nuclear Research, recently opened their Large Hadron Collider (LHC), the world’s largest and highest-energy particle accelerator, near Geneva on the border between France and Switzerland. There are those who hope that the LHC will be able to detect signs of supersymmetric particles. If so, this finding will not by itself prove superstring theory, but it would constitute a strong piece of circumstantial evidence in its favor.

Personally, I would still count myself among the skeptical half regarding string theory. The critics who complain that it is unnecessarily complex with precious little experimental evidence in its favor have a point. It does seem rather drastic to go from four to eleven dimensions, thereby nearly tripling the amount of dimensions in the universe. As it is now, the theory contains too many epicycles for my taste. However, just because a theory is complex and seemingly counter-intuitive does not necessarily mean that it is wrong, as quantum mechanics and to some extent the theory of relativity showed us in the twentieth century.
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One humorous illustration of how hard it is to imagine extra dimensions was provided by the English writer Edwin A. Abbott (1838-1926). His satirical novel Flatland: A Romance of Many Dimensions from 1884 is narrated by a being who calls himself “Square” and lives in Flatland, a world populated by two-dimensional creatures with a system of social ranks, where creatures with more sides rank higher and circles highest of all. Women are merely line segments and are subject to various social disabilities. In a dream, Square visits the one-dimensional Lineland, and is later visited by a three-dimensional Sphere from Spaceland. The Sphere tries to convince Square of the existence of a third dimension and mentions Pointland, a world of zero dimensions, populated by a single creature who is completely full of himself.

Perhaps we are all a bit like Square, who finds it very hard to imagine extra dimensions. And most of us have encountered individuals who live in Pointland, occupied only by themselves.

Read the rest at Vlad Tepes.


Zenster said...

Personally, I would still count myself among the skeptical half regarding string theory.

As do I. According to informed sources, if you expand a single atom to the size of our solar system, then − compared to that solar system-sized atom − a string would be the size of a regular atom. This amounts to what is sometimes called a "bucket of sand" theory. Namely, given particles of a sufficiently minuscule size, you can posit just about any sort of theoretical construct with relative, so to speak, ease.

However, this does not necessarily rule out the existence of numerous other dimensions. There are few other ways of explaining such niggling oddities as quantum entanglement and other very small-scale effects that utterly defy classical mechanics. An example is quantum level (versus the angular momentum of oridinary mass level), intrinsic particle spin ½, where in order for said particle to complete one entire rotation, it requires traveling a total of 720 degrees before assuming its original orientation.

Several extra dimensions could prove rather handy as scientists try to explain "dark flow", a new effect attributed to gravitational sources outside of our universe. This arises in an attempt to explain why hundreds of galaxy clusters are streaming at speeds of 3.6 million kilometers an hour in a direction not aligned with typical expansion vectors associated with big bang.

If you believe the current theoretical models, from the Big Bang until 10–43 seconds afterward, a moment which has been called Planck time, all the four forces are believed to have been united as one.

An near way of thinking about quantum time (i.e., non-continuous temporal reality) − whose smallest duration is Planck time − is to imagine a powerful computer that can operate at almost unlimited speeds. In order to increase the processor's speed, more energy must be input into the computing system. With an even faster "cycle time" the processor is then able to divide time into even smaller durations. The theoretical limit is attained when all of the energy in the entire universe is being used to drive the processor. At that point, one would obtain the very smallest incremental duration of time, referred to in some circles as a "chronon". There are many good arguments for the existence of quantum time, despite the difficulty of imagining such a thing.

Perhaps we are all a bit like Square, who finds it very hard to imagine extra dimensions.

Anyone who has programmed computers might be familiar with how to dimension arrays that used in calculations requiring numerical matrices. A given matrix may occupy many more than three dimensions, limited only by the computer's combined storage and processing capacity. If you wish to think in a few extra dimensions, imagine that the temperature of a given 3-D object is an extra dimension. Other properties like color or electrical charge can be used to extend this model. The human mind just happens to be far more comfortable with the usual three dimensions of height, breadth and depth or X, Y and Z.

The more common example is to posit a hyperspatial dimension that lies at right angles to the X, Y and Z axes. In normal orthogonal geometry this poses quite a problem, as exemplified by our mind's stubborn refusal to readily imagine such a configuration.

Finally, there are those who speculate that a successful "theory of everything" might represent a form of predestination in that, given an exact description of the universe's immediate state, all subsequent configurations of matter could be projected, thereby predicting the future. Fortunately, an annoying fact known as "The Uncertainty Principle" precludes obtaining such an exact description in the first place.

Baughn said...

There is a difference between what you say of quantum mechanics and string theory; an important one.

Quantum mechanics is hard to understand because it maps rather poorly to our intuitions, but it is mathematically simple.

String theory is mathematically complex.

Occam's razor operates on mathematical complexity, not on ease of understanding. Higher mathematical (well, Kolmogorov really) complexity means lower prior probability.