Just Six Numbers, by Martin Rees

N = 1,000,000,000,000,000,000,000,000,000,000,000,000

This number is how many times stronger the electrical force (the attractive force between the negative electron and the positive proton) is compared to the gravitational force.  If this number had a few less zeroes the universe would be smaller and stars would burn hotter and be shorter lived…not allowing enough time for higher lifeforms to evolve. Plus, if gravity were stronger, life would not be able to evolve much larger bodyforms than insects. Gravity is amazingly feeble compared to the electrical force, but it is additive, so that on large scales it becomes the organizing force in the universe, while the electrical force is the organizing force on small scales.

E = .007

This is the percentage of mass that converts to energy when hydrogen combines to form helium (the energy source for stars). This number is derived from the strength of the strong force binding the protons together in the atomic nucleus.

If E were less than .006 hydrogen would not bind into helium…let alone helium combining to form the higher elements…and the universe would contain only hydrogen. If E were greater than .008 because no hydrogen would have survived the big bang and there would be no fuel for stars. This number is tuned just right for star formation and star lifespans long enough for life to evolve.

Omega = nearly one

This is the ratio of the actual density of matter in the Universe to the critical density. The critical density is the density whereby the universe would neither quickly collapse on itself (density too much, gravity too strong) nor expand too quickly. At the present time this ratio seems to be nearly one…which is super remarkable since any deviations from one would have amplified themselves over the last 13 billion years. It must have been almost exactly one at the big bang. And here’s the thing. At each point there is theoretically (for the possible exception see the next number) a balance between the kinetic energy of expansion and gravity. If the actual density had been too little the Universe would have expanded so fast that neither stars nor galaxies could have formed. If it had been too large the Universe would have quickly imploded.

Lambda = well, very small!

This is the antigravity force…still controversial…which controls the expansion of the Universe (also known as Einstein’s blunder). This, if it even exists, is extemely small and operates at extremely large scales. Physicists have invoked this because there does not seem to be enough matter and energy to keep the Universe from collapsing on itself…though if it werent very small the Universe would have expanded too rapidly and galaxies and stars would never have formed. This is the number I understood the least…probably because scientists also understand it least.

Q = .00001

This is the ratio of the energy necessary to break up the largest structures in the Universe (clusters and superclusters of galaxies) to their total rest mass energy, mc^2. But what it is a representation of is how grainy the Universe is. Imagine an Earth where the height of the ripples on the surface were .00001 the total radius (about 60 meters). This non-uniformity would have been imprinted very early in the big bang. And it really is quite small, meaning the Universe is rather homogeneous…ripples of only 60 meters on the earth surface would still make the Earth seem fairly smooth from far away. However, this amount of graininess is crucial. If it were even smaller the Universe would be inert and structureless. If it were any bigger (more grainy) the Universe would be dominated by black holes.

D = 3

This is the number of extended spatial dimensions in the Universe. Although it seems impossible to imagine any other type of Universe, mathematicians have no trouble dealing with Universes of different dimensions. In fact, according to string theory there may be six additional non-extended dimensions (dimensions that circle back on themselves)  through which these strings vibrate. But three extended dimensions seems to be crucial for the existence of life. If there were only two, networks like digestive or circulatory tracts would bisect the critter. At four dimensions, the inverse square law governing the strength of forces like gravity would become the inverse cube law. This would make things like planetary orbits extremely unstable.

Posted on January 1, 2012, in Book Reviews. Bookmark the permalink. Leave a comment.

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