July 7, 2009
Q Is For Quantum And ‘Q-life’
As the world celebrates Charles Darwin, who was born 200 years ago, physicists can be forgiven a certain jealousy at the spotlight being placed on his profound legacy. But physicists have in fact had a huge impact on biology "“ no more so than in helping to discover the structure of DNA and in developing medical-imaging techniques like MRI. The July issue of Physics World marks those achievements and examines at some of the ways in which current ideas in physics are still changing biology.
Features in this issue include a close look at how physics is informing our understanding of cells and of the brain, while Paul Davies, a physicist, astrobiologist and director of BEYOND: Center for Fundamental Concepts in Science at Arizona State University, suggests there are tentative signs that life itself may have arisen as a result of physicists' long-cherished theory of quantum mechanics.
Many of the pioneers of quantum mechanics, such as Niels Bohr, Werner Heisenberg, and Erwin Schrödinger, hoped that their theory, which proved so successful in explaining non-living matter, could one day explain living matter too. But although quantum mechanics can explain the sizes and shapes of molecules -- and how they are bonded together -- no clear-cut "life principle" has emerged from the quantum realm.
Still, Davies points to increasing, albeit controversial, evidence that suggest that fundamental quantum processes like quantum tunnelling and quantum superpositions can play a fundamental role in biology.
In particular, researchers think that quantum mechanics could lie at the heart of the mechanism by which the European robin can navigate over spectacularly long distances by means of the Earth's magnetic field. Others, meanwhile, think that quantum mechanics is essential to the process of photosynthesis.
Davies also asks whether some form of "quantum replicator", or "Q-life", could provide a solution to the challenge of understanding the origin of life itself. Most researchers suppose that life began with a set of self-replicating digital-information-carrying molecules or a self-catalyzing chemical cycle but, Davies argues, they key properties of life -- replication with variation and natural selection -- does not logically require structures to be replicated. "It is sufficient," writes Davies, "that information is replicated, which opens up the possibility that life may have started with some form of quantum replicator."
The advantage of copying information is that it would be much faster than building duplicate molecular structures, while quantum fluctuations provides a natural mechanism for variation and coherent superpositions could let life Q-life evolve rapidly by exploring an entire "landscape" of possibilities at the same time.
As Davies writes, "Life has had three and a half billion years to solve problems and optimise efficiency. If quantum mechanics can enhance its performance, or open up new possibilities, it is likely that life will have discovered the fact and exploited the opportunities."
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