Three of the fundamental forces were theoretically unified in a theory called GUT (Grand Unification Theory). In nature, this unification would happen only at a very high temperature; only the electromagnetic-weak unification has so far been experimentally observed, in collisions with an energy of about 100 to 1,000 GeV (giga-electron-volts). A further unification of the electro-weak force with the strong force has been supported theoretically; but a final unification with gravity is an unsolved problem even theoretically. Even Einstein could not solve it, although he worked on it for many years.

According to an article in Scientific American, August 2000 (by Nima Arkadi-Hamed et aI, pp. 62-69), gravity and GUT cannot be reconciled by present methods, because gravity operates in a 4th spatial dimension in addition to our usual 3. The writers speculate that our 3-dimensional universe may be “plastered” on the wall of a 1 mm diameter curled-up cylinder of the 4th dimension. This 1 mm cylinder diameter is called “large”, since curled-up extra dimensions usually have a diameter of the order of 10 to the minus 35 millimeters, which is the Planck dimension. What we observe in our universe is similar to what was suggested people would see on the walls of Plato’s cave – not a faithful representation of the real world; only a projection to a lower dimension.

Large-scale paradoxes, such as extra dimensions of space, combine with the small-scale paradoxes of string theory of sub-atomic particles; the latter also assumes many dimensions, sometimes 26, sometimes 10 or 11. String theory and cosmology combine to give us these alien and almost incomprehensible views of the universe at extreme size scales. Our brain evolved for survivability, to which extra space dimensions are of no value. Quantum theory has several other examples of such “meta-evolutionary” concepts: non-locality, entanglement, complementarity, superposition, collapse of the wave packet. While our senses and imaginations cannot picture these realities, our symbolic capability can reason about them mathematically. We have some reach toward ultimate reality, even though it escapes our experiential grasp.

Another speculation in the article is that gravity, which of course normally increases when distances get smaller (since it varies inversely with the square of the distance between massive objects) actually increases much faster at distances such as prevail in atomic nuclei and between quarks. Conventional theory would have gravity increase to infinity at Planck distances (10 to minus 35 mm), where it would meet the absolute impenetrability of all fermions (the Pauli exclusion principle). An infinite force would meet an immovable obstacle. However, it is postulated here that gravity increases much faster at small enough dimensions, so that it actually reaches a maximum at only 10 to minus 19 mm, where it is counteracted by the strong nuclear force between protons, neutrons and quarks.

What does this mean for negative gravity (“quintessence” or the cosmological constant), postulated elsewhere, in an article on the accelerated expansion of space? I see three possibilities: 1. The “strong plus” of gravity at ultra-small dimensions may flip to a “strong minus” at infinity (change of attraction to repulsion), like paramagnetic temperature does. 2. Real particles (or only fermions) have positive gravity (attraction), while virtual particles (those that flicker in and out of existence because they have only borrowed energy from the vacuum field) have negative gravity (repulsion). 3. It is “fermion pressure” (generated’by the Pauli exclusion principle) that creates the repulsion, which is even stronger at ultra-small distances (above I called it “absolute”) than strong gravity.

I prefer the third alternative. Fermion pressure would be even greater than strong gravity or the strong nuclear force at ultra-small distances. As virtual particles are continually created (and destroyed) in inter-galactic space, their fermionic repulsion would constitute the quintessence that makes space expand exponentially with time, as intergalactic space itself expands.

Incidentally: if virtual particles continually arise in open space, would they include whole protons? Could extra matter be constantly created in space, in the form of hydrogen, as Fred Hoyle once proposed? (It would mean the conversion of virtual to real protons.) The Big Bang theory replaced Hoyle’s continuous creation theory, but maybe they will eventually be found complementary.

Note that “repelling” means “creating space”. Early “inflation”, soon after the Big Bang, was probably caused by the quintessence force – the fermionic pressure that caused the Big Bang in the first place, after the supersymmetric transformation, which I have postulated in the essay “Eons of the Universe”. In that sense, “attraction” leads to the Big Crunch. Love = Crush? Maybe…

Is the Universe “infinite in all directions”? (Title of book by Freeman Dyson.) Only in 4 dimensions, 3 of space and 1 of time. The other dimensions, tightly (more or less) rolled up into cylinders, are infinite in another sense: you could keep going around and around forever, like going around the Earth either East or West, withou ever coming to the end (Finis Terrae).

Now in the film “The Truman Show”, Truman, who lived in a virtual world to provide entertainment for the television audience (without knowing it), finally touched the canvas at the limit of his Finis Terrae, his constructed world, after barely surviving an (artificial) storm at sea. Then he stepped into the real world from the virtual, and decided to stay real. But just how real is our real world? Is some TV audience (in the 4th dimension?), watching us struggle, for the thrills?