The Anthropic Principle: Evidence from Gravity

Consider gravity. Gravity is one of the four fundamental forces of the Standard Model of Physics. What is the nature of gravity? Is it caused by the mass of an astrological object bending spacetime as General Relativity claims? Or is it a theoretical particle having no mass and no charge that carries a gravitational force as Quantum Physics suggests?

Currently, the only theory experimentally verified is the model proposed by General Relativity. Physicists would very much like to unify General Relativity and Quantum Theory, but as of today, this has not been accomplished.

What we do know about gravity is that if it were too strong, stars would burn too quickly and collapse under their own weight. Additionally, Black Holes would form too often and, essentially, devour all the matter of the Universe before life could form.

On the other hand, if gravity were too weak, the stars would not have compacted enough to the to produce nuclear fusion. Without fusion, heavier elements (such as carbon!!!) would not have formed preventing life as we know it from forming.

The fact that we exists proves that gravity is tuned just right to support life. The question that begs an answer is why does gravity seem so finely tuned to support the existence of a Universe capable of sustaining life?

The anwers seem to boil down to three:

1. The existence of an infinite number of physically real universes (a “multiverse”, if you please) guarantees that at least one of them will support life.

2. A designer hypothesis that created the Universe for life.

3. Pure coincidence. The fine tuning of gravity is in appearance only and implies nothing.

Number 3 can be immediately rejected, I think, because leaving fine-tuning unexplained leads to the acceptance of complicated, inelegant theories without good reason to do so. If a more elegant theory can account for the available data, then it is to be preferred as the more reasonable theory. I am, after all, appealing to reason from the available experimental data.

The problem with number 2 is that the existence of multiple Universes has not been empirically verified. Sure, proponents point to the inflation of the Universe and a non-zero Cosmological Constant, but at best, these provide the foundation for speculation - not hard evidence.

That puts miltiverse supporters on very shaky ground. Moreover, since the theory hasn't been verified, multiverse proponents are actually in a weaker position than their Intelligent Design opponents (although I don't think the existence of multiverse reality prevents the existence of a Designer).

Intelligent Designers, at the very least, have the weight of emperical evidence to support their reasoning and why I believe number 2 offers the most reasonable case. Multiverse proponents have no hard evidence to support their theory. Until they do, it is not incorrect to suggest the multiverse theory be regarded as metaphysical, and therefore, unfalsifiable.