Day 3 Cambridge: cosmology

This morning started with a talk by Katherine Blundell ‘God and the Big Bang’. Katherine is a Professor of Astrophysics at Oxford and this was definitely an astrophysicist’s view of cosmology, with plenty of shots from the Hubble space telescope and much emphasis on the sheer scale of distance and time of the universe. She gave a brief introductory overview of the evidence for the BB, from Hubble’s Law to the cosmic microwave background, before going on the philosophical side of things.
In the second part, Prof Blundell gave a wonderful defence of the scientific method in the context of the criticisms of the creationist Ham, explaining how truth will eventually out in a community bent on proving each other wrong! However, she then drew an analogy between scientific investigation and interpretation of scripture which I for one found a bit unconvincing…

Interestingly, Katherine seemed quite skeptical about Dark Matter and quite taken with MOND as an alternative (see post on DM last month). I was quite surprised at this as I have always understood the MOND gang to be very much in the minority. Plus, I think many physicists are excited by last year’s ‘galaxy collision’ evidence for DM, while MOND has received a few setbacks in recent years..

Katherine’s talk was succeeded by a full knobs-on review of modern cosmology, inflation and the multiverse by Prof Paul Shellard , a colleague of Stephen Hawking at DAMTP, Cambridge. This was a joy for the physicists, a spectacular overview of today’s cosmology with a thorough review of inflation, eternal inflation, the multiverse and the landscape. Shellard went through the WMAP evidence, explaining that the evidence for some sort of inflation was very strong, but the mechanism under-determined (his word, glorious understatement -he showed a hilarious slide listing all possible flavours of inflation)…

Shellard’s discussion of eternal inflation and the multiverse was thorough but accessible, with emphasis on the viewpoint that this may be the price we have to pay for the success of inflation (in explaining the standard BB riddles), yet emphasising also the speculative nature of the multiverse idea…

Inhomogenieties in the cosmic microwave background (WMAP)

If this weren’t enough, the high point of the day for many was ‘Meta-stories of Fine-tuning ‘ by Sir John Polkinghorne. In typical fashion, Sir John gave a succinct overview of the fine-tuning problem from a philosophical viewpoint. In particular, he focused on a choice between the multiverse explanation and the anthropic principle from a philosophical perspective. He was clearly unimpressed with the theory of the multiverse, describing it as meta-physics and probably contrary to the principle of Occam’s razor. Calling on Leslie’s famous example of the firing squad, he suggested that it was a little excessive to suggest that the firing squad engaged in a gigantic number of shootings in order to explain a miss – suggesting that it was more likely that they simply missed by design…

He was also unimpressed with a third possibility (from me) that an unlikely outcome – however unlikely – can simply occur without the need for an explanation. I can’t do justice to John’s persuasive arguments here, but you can get his views on this, and other subjects on the Polkinghorne webpage

Peter Woit of NOT EVEN WRONG would be pleased to note that, along the way, Sir John gave a very terse overview of the opinion of his generation of particle physicists of string theory – not very high!

The day finished with a talk on time by the brilliant philosopher Dean Zimmerman, Professor of Systematic Philosophy at Notre Dame. Dean spoke of his A-theory of time, a theory in which the ‘priviliged present’ has  special properties over other tenses, and his work to reconcile it with the special and general theories of relativity. I’m not sure how much I really understood, but it was great to get a glimpse of how modern philosophy is reasoned out in the context of modern physics. Afterwards, it struck me that if he overcomes the apparent conflict with relativity, Dean’s A-theory might have some useful insights to offer concerning the ‘arrow of time’ problem in physics.

Dean in full flight – note the SR cone on the chart!