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Archive for April 6th, 2017

I have a small number of physics books in my collection. As far as I can remember Paul Davies’s was the only one till now that I had read right to the end. If I include the one I am about to describe, they span from 1994 till now. I was doing all right on Why does E=mc2? until my reading was interrupted halfway through and I didn’t have chance to pick it up again for over three months, by which time I had forgotten so much of what it said that I couldn’t understand what I was reading.

So, why did I buy Rovelli’s book? Well, it has good reviews (but so did the others). It is short, a mere 234 pages of text. And the print is big.

Even so I’m feeling very smug because I’d read it in a week.

‘It can’t have been very good, then,’ you think.

You couldn’t be more wrong.

Even though I could not follow all his arguments to the last detail, I could get the gist. Not only that, but being able to understand enough made it exciting to read.

Now, I’m not a physicist, in case that is not already obvious, so I am not competent to do a credible review of the physics. All I can say is that what I understood of what he explains gels with the little I have already read and retained.

His basic thesis throughout the book is to explore his perspective that physics has been going through a process of deep simplification, as he illustrates in his last diagram on this theme.

I will just look at the implications that he spells out concerning only one of these transitions into deeper simplicity, and that is the last, the one where space and time have disappeared from the mix. How on earth could that be possible?

Well, not on earth at the macro level as we experience it with our unaided senses.

He believes that the evidence as we best understand it, from a loop theory point of view (he’s not a fan of string theory), is that matter is not infinitely divisible and there comes a point where it cannot be divided anymore at the quantum level. When he is talking about space, the quanta he is concerned with are the quanta of gravity, which constitute space itself (page 148): ‘the quanta of gravity, that is, are not in space, there are themselves space.’ What is crucial is the relationship between particles, their interconnections. He clarifies this by saying (page 150):

Physical space is the fabric resulting from the ceaseless swarming of this web of relations. The lines [between quanta] themselves are nowhere; they are not in a place but rather create places through their interactions. Space is created by the interaction of individual quanta of gravity.

This is how space disappears. Now for time (page 158):

We must learn to think of the world not as something which changes in time but in some other way. Things change only in relation to one another. At a fundamental level, there is no time. Our sense of the common passage of time is only an approximation which is valid for our macroscopic scale. It derives from the fact that we perceive the world in a coarse-grained fashion.

He is aware that much remains to be done before this view of reality is confirmed and widely accepted (page 186):

The theory [quantum gravity] is in its infancy. Its theoretical apparatus is gaining solidity, and the fundamental ideas are being clarified: the clues are good, and concrete – confirmed predictions are still missing. The theory has not yet taken its exams.

I suspect his tongue was rammed into his cheek when he wrote that – ‘solidity,’ ‘concrete’ – unlikely!

He feels (page 203) that the two theories of quantum mechanics and quantum field theory are not contradictory but rather ‘the two theories each offer the solution to the problems posed by the other!’

In his annihilation of infinity, his closing remark paves the way for an interesting discussion later. He writes (page 208) ‘The only truly infinite thing is our ignorance.’

The roots of his concept of science go back at least as far as William James’s pragmatics of uncertainty, which I have discussed elsewhere. As he puts is (page 230):

But if we are certain of nothing, how can we possibly rely on what science tells us? The answer is simple. Science is not reliable because it provides certainty. It is reliable because it provides us with the best answers we have at present.’

While I am not comfortable with his various disparaging references to religious belief and feel that a dose of Plantinga would have done him good, his next point is valid within the sphere of science and also points towards the potential dangers of any kind of fundamentalist and dogmatic certainty (page 132):

We don’t have absolute certainty, and never will have it – unless we accept blind belief. The most credible answers are the ones given by science, because science is the search for the most credible answers available, not the answers pretending to certainty.

Unfortunately his earlier expressed certainty that there is no life after death, which he calls ‘nonsense,’ betrays his message somewhat. However, I still feel his point is valid in the main. He spells out its implications (ibid): ‘the nature of scientific thinking is critical, rebellious and dissatisfied with a priori conceptions, with reverence and sacred or untouchable truth. The search for knowledge is not nourished by certainty: it is nourished by a radical distrust in certainty.’

Even so, if you find his main ideas as exciting as I do, the book is so accessible and stimulating it’s worth buying.

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