Everett and the Anthropic Principle

Everett and the Anthropic Principle

The Everett approach could explain how life developed in the first place. English physicist Paul Davies argued that it is very unlikely that life arose from classical theory. He stated that "simple calculation shows that it would take much longer than the age of the universe, even if all the matter in the universe consisted of pre-biotic soup, for even a single protein to form by chance. So the classical chance hypothesis seems unsatisfactory" (Davies, pp.75). The Everett approach resolves this problem by providing a new interpretation of the anthropic principle.

The anthropic principle was devised to explain why the universe appears to be perfectly designed for our existence in a way that seems deeply improbable. The weak anthropic principle, first suggested by American physicist Robert Dicke in 1961 states that this is a selection bias as we could not observe any world incapable of containing life. The strong anthropic principle, first suggested by Australian physicist Brandon Carter in 1968, implies that life is somehow needed for the universe to exist.

English writer Douglas Adams illustrated the problem with the strong anthropic principle as follows; "Imagine a puddle waking up one morning and thinking, 'This is an interesting world I find myself in, an interesting hole I find myself in, fits me rather neatly, doesn't it? In fact it fits me staggeringly well, must have been made to have me in it!' This is such a powerful idea that as the sun rises in the sky and the air heats up and as, gradually, the puddle gets smaller and smaller, it's still frantically hanging on to the notion that everything's going to be alright, because this world was meant to have him in it, was built to have him in it; so the moment he disappears catches him rather by surprise. I think this may be something we need to be on the watch out for" (Adams, 1998).

The universe can be described by a number of ratios that appear to be finely tuned so as to produce life (Rees, 2000). The first ratio describes how massive things need to be before the force of gravity overpowers the nuclear strong force. If gravity were much stronger than the strong force then everything would be smaller because objects would get heavier more quickly. Stars would not need to be as massive in order to radiate and everything else would shrink in turn. If life forms did exist, then they too would have to be tiny. Even creatures the size of insects would have to have thick necks to hold their heads up. If gravity were stronger still then the universe would be a tangle of black holes as everything would fall in on itself.

The second ratio describes how energy is related to mass and so determines how much energy is given off in nuclear reactions. The fusion of two hydrogen atoms results in a small loss of mass, but the amount of energy released is multiplied by the square of the speed of light. This amount is so large, in comparison to the amount of mass lost, that this process is capable of powering the Sun. If the amount of energy were smaller, then stars would not be able to produce the elements that we need to live. If it were larger, then gravity would be important at smaller sizes and, again, everything would be too small for life to evolve.

The third ratio is between the rate at which dark energy is accelerating the expansion of spacetime and the rate at which the universe would otherwise collapse due to gravity. Dark energy is small enough so that it did not push galaxy clusters apart before they had time to form but is not so small that the universe stopped expanding and fell in on itself again.

The evolution of life is also reliant upon quantum fluctuations that occurred during the inflationary epoch of the early universe. If there were no fluctuations then everything would be equally dispersed and so mass and energy would drift apart before it could become gravitationally bound. If the fluctuations in symmetry were too vast, however, then everything would be distributed too closely together, creating a universe full of black holes.

The finial important factor for any universe which contains life is the number of dimensions that we experience. If we lived in a world with only two spatial dimensions, then any holes in our body, such as the tubes that carry our food, oxygen and blood, would cut us in half. If we were to experience four spatial dimensions however, then the force of gravity would be proportional to the cube of an object's mass. This would mean that stars would be too heavy to last very long and life would not have time to evolve.

The weak anthropic principle explains that the universe must be the way that it is because we would be unable to observe it if it were any other way. Yet there is something unsatisfying about this response, it would be like saying to someone who survived certain death that they did so because they wouldn't be here if they hadn't. This still doesn't explain what happened.

Everett's interpretation provides a natural extension of the weak anthropic principle by suggesting that there are an infinite amount of worlds and so, however improbable our existence is, we know that life must exist somewhere. This is analogous to the explanation that the person in the above example survived because one in every million people do and a million people had already faced certain death that day. An unusual event occurred because it had a non-zero probability and a vast number of trials were run.

References

Adams, D., 1998, 'Speech at Digital Biota 2'

Davies, P.C.W., 2004, 'Does quantum mechanics play a non-trivial role in life?', BioSystems, Vol.78, pp.69-79

Rees, M.J., 2000, 'Just six numbers: the deep forces that shape the universe', Basic Books