[Cosmology on television - closely related to cosmetology?]
I just watched a lecture given at UC Berkeley appropriately enough on April 1, 2010. It is titled "Particle Physics in the 21st Century". Professor Sivas Dimonopoulos is the inventor of super-symmetry which is now part of the Standard Model. Which means that he is a serious physicist. one of those who has defined, and is defining, the mainstream. He is also a charming lecturer.
I had long thought that the concept of multiple universes was just empty speculation and a way to sell glossy magazines like Scientific American, Astronomy, and Hustler. But in this lecture, Dimonopoulos alludes to, albeit obliquely, some reasons why it is not necessarily a crock.
I had heard (on CD) a lengthy bioography of Einstein (eighteen CD's) that the mathematics of general relativity requires not three and not four, but TEN coordinates to specify location. Just as one needs three co-ordinates, usually x, y, and z, to specify a position in 3 dimensional space, and t to specify the position of an event in space-time, so it takes no fewer than ten coordinates to specify how general relativity works. No one knows for sure what the physical significance of the extra six coordinates are, or if there is any physical significance to them.
The question starts out as, "Is the correlation between mathematics and physical reality a coincidence?" Or "Is there a physical significance to mathematical formalisms?". Einstein found in the course of his life that the answers were "no" and "yes". He pissed away most of his later years fighting the significance of these conclusions.
The basis of quantum mechanics is that there is no comprehensible reality distinct from the mathematics describing it. Some would say there is no reality at all, only our perceptions of it. Curiously physics, when pursued to the point of driving it to ground, hunting it like a desperate wild beast, becomes philosophy.
Einstein, the insolent radical when a young outsider, became the conservative coot when middle-aged and established. The generation of quantum mechanics, led by Niels Bohr, Schrodinger, Heisenberg, Born, DeBroglie, Pauli, and others, passed him by. The debate came down to the skeptical empiricist philosophy of David Hume versus the positivist philosophy of Kant, Leibniz, and Comte. For the past 90 years Hume has been kicking Leibniz' ass.
So too, the question of multiple universes. The philosophical question, according to Professor Dimonopoulos, comes down to philosophical minimalism versus philosophical plenitude. The formulator of minimalism was William of Ockham (1288-1347), inventor of Ockham's Razor. His dictum is that the simpler a proposition is, the better. A chain of reasoning with fewer steps is more likely to be right than one with more steps. There is no way to prove that Ockham is right, it is just intuitively true.
It is the minimalist passion that leads to theories of unification, of trying to show that the four fundamental forces of nature, strong, weak, electromagnetic, and gravity, are really only one force. Which is why Maxwell's equations were such a triumph of 19th century physics. Maxwell showed that light, electricity, and magnetism were all the same thing. He simplified. He minimaliized. Ockham ruled.
On the other hand, there are philosophers like Kant and Liebniz who argue that every possibility is realized, that the universe is complex and multifarious. If there can be one world, there can be many like it. Variation and replication are the favored rules of nature.
Reasoning by analogy from the progression from the belief in only one planetary globe like this one, to belief in several, and from the belief in only one solar system to belief in vast numbers of them, Dimonopoulos argues that there are many universes.
He argues that just as multiple parallel two-dimensional universes can exist in a three dimensional space, similarly, many three dimensional universes can exist in a space with four, five, or ten dimensions. While it is hard to visualize, it is also hard to disagree.
Some of the arguments for other dimensions and other universes comes from the mathematics of string theory and some of it is expected to come from the Large Hadron Collider (the LHC) in Geneva.
Dimonopoulous as an aside answers the question about the possibility that the LHC could create a mini-black hole which could devour the earth in an instant. The theoretical physics of such a black hole is that, if such a thing could form, it would instantly evaporate in a tiny puff of (Stephen) Hawking radiation.
The practical physics of it is that the earth has been undergoing bombardment by cosmic ray particles at much higher energies than the LHC can generate, for the past five billion years. If such high energy particle collisions can indeed generate proton-sized black holes and if such black holes could devour the planet, it would have long since have been devoured. Good to know.
It turns out that one argument and philosophical position is not just as good as another, and we are not entitled to take our pick according to our preference. They aren't and we aren't.
I didn't exactly understand why it mattered, but the question of whether there were more likely to be many universes or only one depends on the energy of a vacuum. I admit I have only a vague understanding of vacuum energy (the sum of the virtual mass-energies of the virtual particles that are forever coming into existence then going out of existence before they can violate the Heisenberg uncertainty principle limits) but it is apparently somehow measurable. If it is low, then there is likely only one universe. If it is high, there are likely many.
In the 1990's they measured it. It was high.
So not only does the universe not exist in any comprehensible way, but there are probably lots of others just as diaphanously almost real as this one.
Now Leibniz has his foot in Ockham's ass.
Here is a link to Professor Dimonopoulos' lecture: (Click on the clackboard icon with the blue arrow at upper left)