Just Six Numbers: The Deep Forces That Shape the Universe

The sun has adjusted its structure so that nuclear power is generated in the core, and diffuses outward, at just the rate needed to balance the heat lost from the surface-heat that is the basis for life on Earth.

Our universe, extending immensely far beyond our present horizon, may itself be just one member of a possibly infinite ensemble. This ‘multiverse’ concept, though speculative, is a natural extension of current cosmological theories, which gain credence because they account for things that we do observe. The physical laws and geometry could be different in other universes, and this offers a new perspective on the seemingly special values that the six numbers take in ours.

[The fine structure constant] ... defines how firmly atomic nuclei bind together and how all the atoms on Earth were made. Its value controls the power from the Sun and, more sensitively, how stars transmute hydrogen into all the atoms of the periodic table.

A measure of the strength of a body's gravity is the speed with which a projectile must be fired to escape its grasp. It takes 11.2 kilometers per second to escape from the Earth. This speed is tiny compared with that of light, 300,000 kilometers per second, but it challenges rocket engineers constrained to use chemical fuel, which converts only a billionth of its so-called mass 'rest-mass energy' (Einstein's mc^2) into effective power. The escape velocity from the sun's surface is 600 kilometers per second-still only one fifth of one percent of the speed of light.

More energy is needed to rise a millimetre above a neutron star's surface than to break completely free of Earth's gravity. A pen dropped from a height of one metre would impact with the energy of a ton of TNT (although the intense gravity on a neutron star's surface would actually, of course, squash any such objects instantly). A projectile would need to attain half the speed of light to escape its gravity; conversely, anything that fell freely onto a neutron star from a great height would impact at more than half the speed of light.

The Sun contains about a thousand times more mass than Jupiter. If it were cold, gravity would squeeze it a million times denser than an ordinary solid: it would be a 'white dwarf' about the size of the Earth but 330,000 times more massive. But the Sun's core actually has a temperature of fifteen million degrees-thousands of time hotter than its glowing surface, and the pressure of this immensely hot gas 'puffs up' the Sun and holds it in equilibrium.