01 March 2011

Cosmological Numerology

A study released late in 2010, revealed that the estimate of the share of matter in the universe that is ordinary matter, as opposed to dark matter, was low by a factor of three, because the proportion of ordinary matter relative to dark matter in ellipical galaxies was underestimated. The estimated total amount of matter in the universe is unchanged, because that comes from mass measurements based on the lensing effect of entire galaxies on light that measures total mass rather than from estimates of the total number of individual stars and planets in galaxies multiplied by the estimated mass of each one.

The old estimate was that the universe was 4.6% ordinary matter, 23% dark matter, and the remainder "dark energy." Those are pretty weird numbers and no one has ventured a credible guess about how that came to be.

The new estimate comes up with some numbers that are quite different: 13.8% ordinary matter and 13.8% dark matter. Thus, the amount of ordinary matter and dark matter are almost exactly equal - a remarkable coincidence that wouldn't be hard to infer from a scenario in which energy from the big bang condenses into matter (called baryogenesis and leptogenesis) by a process by which half of matter created is in the ordinary sector, and half is in the "dark" sector, for example, from particles predicted to exist by supersymmetry. We already know, for example, that to the extent permitted by available mass-energy, the weak forces W boson has an equal chance of transforming into any available possible output fermions.

Another of the great unanswered questions of physics is "why is ordinary matter almost entirely made up of matter, rather than anti-matter?" A potential answer could be that almost all of the anti-matter, which we would otherwise expect to make up 50% of the mass in the universe, somehow turned into dark matter.

The fact that the weak force interacts with particles that have left partity, but not right parity, ignoring half of all the particles of matter in the universe, provides another 50-50 division of the matter in the universe that might drive a process that creates 50% ordinary matter and 50% dark matter in the universe.

The ratio of the total amount of matter in the universe to the total amount of dark energy in the universe is also an interesting number. Within the margin of accuracy of the measurement that ratio is "e", the exponential constant, which is often rounded to 2.78. I'm not aware of any specific theory in physics that predicts that ratio, but the equations of physics are awash with dimensionless fundamental constants like "e" and the expansion of the universe with which dark energy is associated is an exponential expansion process, so the ratio wouldn't be a terribly surprising one to fall out of the relevant equations.

Is this scientific proof? No. It is pure speculation of a basically numerological nature about the way that a theory that does have real meaning could produce numbers like these. But, it is an interesting observation, nonetheless, about a question, "why do we have the percentages of matter, dark matter and dark energy in the universe that we observe?", which could be relevant to answering those questions. In the ordinary case, science looks for relationships in emperical data first, and then comes up with hypothetical theories that could explain what could be causing those relationships. This kinds of observations advance that cause.

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