Saturday, March 17, 2007

Retrocausality

Physicist Paul Davies, the author of many fascinating books on cosmology and the origin of life, has come up with a novel explanation for how the universe could be so exquisitely fine-tuned for life without having to invoke the dread concept of a Creator God. Davies hypothesizes that the precise calibrations of dozens of cosmic parameters were set during the Big Bang by a phenomenon called "retrocausality":

If retrocausality is real, it might even explain why life exists in the universe -- exactly why the universe is so "finely tuned" for human habitation. Some physicists search for deeper laws to explain this fine-tuning, while others say there are millions of universes, each with different laws, so one universe could quite easily have the right laws by chance and, of course, that's the one we're in.

Paul Davies, a theoretical physicist at the Australian Centre for Astrobiology at Macquarie University in Sydney, suggests another possibility: The universe might actually be able to fine-tune itself. If you assume the laws of physics do not reside outside the physical universe, but rather are part of it, they can only be as precise as can be calculated from the total information content of the universe. The universe's information content is limited by its size, so just after the Big Bang, while the universe was still infinitesimally small, there may have been wiggle room, or imprecision, in the laws of nature.

And room for retrocausality. If it exists, the presence of conscious observers later in history could exert an influence on those first moments, shaping the laws of physics to be favorable for life. This may seem circular: Life exists to make the universe suitable for life. If causality works both forward and backward, however, consistency between the past and the future is all that matters. "It offends our common-sense view of the world, but there's nothing to prevent causal influences from going both ways in time," Davies says. "If the conditions necessary for life are somehow written into the universe at the Big Bang, there must be some sort of two-way link."

In other words, since causality is not limited by the laws of physics to only one direction, it's theoretically possible, Davies argues, that sentient life was able to somehow reach back to the Big Bang and calibrate the forces of physics and the expansion rate of the universe and a host of other values. Billions of years later intelligent beings would arise which had the ability to retroactively create their own universe.

This sounds bizarre even for a cosmologist, suggesting as it does the notion that the universe is the creation of its own inhabitants. Davies' theory is interesting, however, for what it implies. First, it's a tacit admission by Davies that the universe is inexplicable apart from having been tinkered with by an intelligent mind, and second, it illustrates the philosophical contortions some people will put themselves through in order to avoid the conclusion that the intelligent agent responsible for the universe is God.

HT: Telic Thoughts

RLC