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The Anthropic Principle

anthropic principle: is life here because it has to be?
The fact that we are living and can observe the universe, implies that the fundamental constants must be "just right" to produce life. There is an element of circular reasoning here, because if the constants were not "just right", we would not be here to observe the universe. However, the fact is that the universe does not seem to be a random or chance event. We can postulate a many universe scenario, in which only one or some universes produce life, but we cannot validate that scientifically because we only live in one of those universes.

A life-giving factor lies at the centre of the whole machinery and design of the world." John Wheeler "everything about the universe tends toward humans, toward making life possible and sustaining it" Hugh Ross "... the Anthropic Principle says that the seemingly arbitrary and unrelated constants in physics have one strange thing in common--these are precisely the values you need if you want to have a universe capable of producing life." Patrick Glynn

The Anthropic Principle was first suggested in a 1973 paper, by the astrophysicist and cosmologist Brandon Carter from Cambridge University, at a conference held in Poland to celebrate the 500th birthday of the father of modern astronomy, Nicolaus Copernicus. The Anthropic Principle is an attempt to explain the observed fact that the fundamental constants of physics and chemistry are just right or fine-tuned to allow the universe and life at we know it to exist. (see Cosmic Matters). The Anthropic Principle says that the seemingly arbitrary and unrelated constants in physics have one strange thing in common--these are precisely the values you need if you want to have a universe capable of producing life. The universe gives the appearance that it was designed to support life on earth, another example of Paley's watch.

  • Gravity is roughly 1039 times weaker than electromagnetism. If gravity had been 1033 times weaker than electromagnetism, "stars would be a billion times less massive and would burn a million times faster."
  • The nuclear weak force is 1028 times the strength of gravity. Had the weak force been slightly weaker, all the Hydrogen in the universe would have been turned to helium (making water impossible, for example).
  • A stronger nuclear strong force (by as little as 2 percent) would have prevented the formation of protons--yielding a universe without atoms. Decreasing it by 5 percent would have given us a universe without stars.
  • If the difference in mass between a Proton and a Neutron were not exactly as it is--roughly twice the mass of an electron--then all Neutrons would have become protons or vice versa. Say good-bye to Chemistry as we know it--and to life.
  • The very nature of water--so vital to life--is something of a mystery (a point noticed by one of the forerunners of anthropic reasoning in the nineteenth century, Harvard biologist Lawrence Henderson). Unique amongst the molecules, water is lighter in its solid than liquid form: Ice floats. If it did not, the oceans would freeze from the bottom up and Earth would now be covered with solid ice. This property in turn is traceable to the unique properties of the Hydrogen atom.
  • The synthesis of carbon--the vital core of all organic molecules--on a significant scale involves what scientists view as an astonishing coincidence in the ratio of the strong force to electromagnetism. This ratio makes it possible for carbon-12 to reach an excited state of exactly 7.65 MeV at the temperature typical of the centre of stars, which creates a resonance involving helium-4, beryllium-8, and carbon-12--allowing the necessary binding to take place during a tiny window of opportunity 10-17 seconds long. Taken from God the Evidence by Patrick Glynn

Here are some definitions, first from Barrow and Tipler:

Weak Anthropic Principle (WAP): The observed values of all physical and cosmological quantities are not equally probable but they take on values restricted by the requirement that there exist sites where carbon-based life can evolve and by the requirements that the universe be old enough for it to have already done so.

Strong Anthropic Principle (SAP): The universe must have those properties which allow life to develop within it at some stage in its history. Because:

  1. There exists one possible universe 'designed' with the goal of generating and sustaining 'observers'. Or...
  2. Observers are necessary to bring the universe into being (Wheeler's Participatory Anthropic Principle (PAP)). Or...
  3. An ensemble of other different universes is necessary for the existence of our universe (which may be related to the Many_Worlds interpretation of quantum mechanics).


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