Does it not seem odd that the universe should be exactly right for us? No, because we are here to see it, so it would look that way, wouldn’t it? And if the machinery for fashioning universes out of nothing, or almost nothing, made enough of them – this is the multiverse argument – then of course one would pop up with exactly the conditions for stars, planets, water, life and even a House of Lords.
But, says Rees, look at it another way: suppose instead that you were the intended victim of a firing squad and every bullet missed you, wouldn’t you be inclined to wonder if something special had been arranged on your behalf, that, somewhere in the Looking Glass world of modern physics, there might be some deeper reason for the providential value of these six numbers? And if there were, would we be smart enough to see it?
- The balance between the nuclear forces and the power of gravity, giving us N, a huge number involving 36 zeroes. Were gravity not almost exactly 1036 times weaker then we wouldn’t be here.
- The density parameter Ω (omega), which one second after the big bang could not have varied from unity by more than one part in a million billion or the universe would not still be expanding, 13.7bn years on.
- D for dimension to equal three. Had there been four dimensions, gravitational and other forces would have varied inversely as the cube of the distance rather than the square. Any orbiting planet that slowed for whatever reason in its orbit would swiftly plunge into its parent star; any planet that increased its speed would spiral into the dark. Under the inverse square law, however, a planet that speeds up ever so slightly – or slows down – simply shifts to a very slightly different orbit.
- Q, the one part in 100,000 ratio between the rest mass energy of matter and the force of gravity. Were this ratio a lot smaller, gas would never condense into galaxies. Were it only a bit smaller, star formation would be slow and the raw material for future planets would not survive to form planetary systems. Were it much bigger, stars would collapse swiftly into black holes and the surviving gas would blister the universe with gamma rays.
- The measure of nuclear efficiency, ε for epsilon, has a value of 0.007. If it had a value of 0.006 there would be no other elements: hydrogen could not fuse into helium and the stars could not have cooked up carbon, iron, complex chemistry and, ultimately, us. Had it been a smidgen higher, at 0.008, protons would have fused in the big bang, leaving no hydrogen to fuel future stars.
- The cosmological constant λ for lambda is a number so small that the puzzle is that it is not zero. This value with 120 zeroes after the decimal point – seems to dictate the whole future of the universe. It seems just strong enough to push the most distant galaxies away from us at an unexpected rate. Were it much stronger, there might be no galaxies to accelerate anywhere.