The Order of Time by Carlo Rovelli (Pt 2 of 3)

[For Part 1 of the review, click here]

The past is fixed; the future is open. The present, suggests Rovelli, that fleeting intersection between what was and what will be, doesn't exist. "Nothing is. Things happen, they don't exist." Impermanence is ubiquitous. Just as things can be disassembled into their ever and ever smaller components, down to subatomic particles, so events can be taken apart. "A war is not a thing, it's a series of event. A storm is not a thing, it's a collection of occurrences... Things are, in themselves, events that for a while are monotonous"; for example, a large rock or mountain that is constantly shedding molecules under the influence of atmospheric phenomena. At our level, it seems permanent, a thing. Yet at the molecular level, its surface is undergoing continuous change.

A human being? "It's a complex process which food, information, light, words and so on enter and exit... A knot of knots in a network of social relations, a network of emotions exchanged..."

Understanding the world, the universe, on the basis of things rather than events means that you end up ignoring change. Change happens across time; here I feel that Hawking explains the temporal aspects of Big Bang better than Rovelli, who's better at the level of planet Earth than the expansion of the universe 13.8 billion years ago.

The notion that the past, present and future are all equally really, and that the passing of time is merely an illusion is called eternalism; Einstein wrote "People who believe in physics know that the distinction between past, present and future is only a stubbornly persistent illusion". Eternalists have devised the concept of the 'block universe', a single block; all equally real; only the passage of time from its beginning to its end is illusory.

Prof Rovelli is not, however, an eternalist; like Stuart A. Kauffman, he sees the future as being something that isn't predestined; it is unfolding, becoming (both men use these two words to describe the future). Kauffman has the advantage of being an evolutionary biologist. Not a single, set block of time encompassing the entire universe from its beginning to its end, rather something that in itself is creative.

Our languages are inadequate, says Rovelli, to discuss time. When we observe an event upon the face of the sun, we see something that occurred eight minutes and 20 seconds ago, yet we describe it in the present tense. There's no tense that captures the phenomenon of time stretching over distance. Earlier today, the BBC ran a story about the discovery of oxygen in a distant galaxy as it was just 500 million years after the Big Bang (in other words 13.3 billion years ago). The oxygen, the oldest ever found, itself was the result of an even earlier galaxy that existed some 250 million years after Big Bang. And yet it was only just spotted recently; mankind lived in its ignorance until now. Is that oxygen still out there today? We can have no idea. Watch this space for 13.3 billion years!

Moving from language to physics, Rovelli is keen to promote his own field of expertise, namely quantum gravity (where there are several competing theories). Rovelli champions loop quantum gravity (based around something at the Planck-length scale named 'spin-foam'). The other main theory is string theory. Both (and other less well-established ones) aim to unify Einstein's General Theory of Relativity (which places gravity into the context of spacetime) and the other three fundamental forces (electromagnetism and strong- and weak atomic forces). Suffice to say, I am entirely out of my depth when trying to really understand either loop- or string theory, even by way of metaphor. However, the idea that gravity can be quantised - broken down into discreet particles at the Planck level - I grasp. One way or another, the problem of time is central to an understanding of gravity, which is why Rovelli is so fascinated by it.

Equations without time, is what Rovelli is angling at here. "Time and space are no longer containers [of the universe]. They are only approximations of a quantum dynamic that knows neither time nor space. There are only events and relations [between events].

In Part III, Rovelli returns to the human scale, to our understanding of the passage of time, and gets metaphysical.

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This time three years ago:
With Blood and Scars by B.E. Andre - book review

This time four years ago:
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This time five years ago:
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This time six years ago:
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This time nine years ago:
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This time 11 years ago:
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