It’s always a nervous moment when, as a scientist, you discover that a documentary has been made on one of your favourite topics. Science journalism is rather hit and miss. So it was when the Australian Broadcasting Corporation (ABC), our public TV network, aired a documentary about the fine-tuning of the universe for intelligent life as part of their Catalyst science series. (I’ve mentioned my fine-tuning review paper enough, haven’t I?).
The program can be watched on ABC iView. (International readers – does this work for you?). It was hosted by Dr Graham Phillips, who has a PhD in Astrophysics. The preview I saw last week was promising. All the right people’s heads were appearing – Sean Carroll, Brian Greene, Paul Davies, Leonard Susskind, Lawrence Krauss, Charley Lineweaver. John Wheeler even got a mention.
Overall – surprisingly OK. They got the basic science of fine-tuning correct. Phillips summarises fine-tuning as:
When scientists look far into the heavens or deeply down into the forces of nature, they see something deeply mysterious. If some of the laws that govern our cosmos were only slightly different, intelligent life simply couldn’t exist. It appears that the universe has been fine-tuned so that intelligent beings like you and me could be here.
Not bad, though I’m not sure why it needed to be accompanied by such ominous music. There is a possibility for misunderstanding, however. Fine-tuning is a technical term in physics that roughly means extreme sensitivity of some “output” to the “input”. For example, if some theory requires an unexplained coincidence between two free parameters, then the “fine-tuning” of the theory required to explain the data counts against that theory. “Fine-tuned” does not mean “chosen by an intelligent being” or “designed”. It’s a metaphor.
Ten minutes in, the only actual case of fine-tuning that had been mentioned was the existence of inhomogeneities in the early universe. Sean Carroll:
If the big bang had been completely smooth, it would just stay completely smooth and the history of the universe would be very, very boring. It would just get more and more dilute but you would never make stars, you would never make galaxies or clusters of galaxies. So the potential for interesting complex creatures like you and me would be there, but it would never actually come to pass. So we’re very glad that there was at least some fluctuation in the early universe.
Paul Davies then discussed the fact that there not only need to be such fluctuations, but they need to be not-too-big and not-too-small. Here’s the scientific paper, if you’re interested.
The documentary also has a cogent discussion of the cosmological constant problem – the “mother of all fine-tunings” – and the fine-tuning of the Higgs field, which is related to the hierarchy problem. Unfortunately, Phillips calls it “The God Particle” because “it gives substance to all nature’s other particles”. Groan.
Once we move beyond the science of fine-tuning, however, things get a bit more sketchy.
Leonard Susskind opens the section on the multiverse by stating that the multiverse is, in his opinion, the only explanation available for the fine-tuning of the universe for intelligent life. At this point, both the defence and the prosecution could have done more.
Possibilities are cheap. Sean Carroll appears on screen to say “Aliens could have created our universe” and then is cut off. We are told that if we just suppose there is a multiverse, the problems of fine-tuning are solved. This isn’t the full story on two counts – the multiverse isn’t a mere possibility, and it doesn’t automatically solve the fine-tuning problem. (more…)