The Order of Time by Carlo Rovelli (Pt 1 of 3)

Having read Stuart A. Kauffman's magnificent Humanity in a Creative Universe, and the late Steven Hawking's best-selling A Brief History of Time, I am thankful to my father for buying me another excellent pop-science book, Carlo Rovelli's The Order of Time. For those to whom the name is unfamiliar, Prof Rovelli is the author is the Seven Brief Lessons on Physics (a million copies sold, translated into 41 languages); my father is reading this right now (so I look forward to reviewing it next month).

Compared to Prof Hawking's book about the same subject, The Order of Time has two advantages. One is it was written 30 years later, and science has advanced somewhat. The second is that the author, being a historian and philosopher of science as well as a purely theoretical physicist, places the science into a broader context of human wisdom.

Divided into three parts, Prof Rovelli strips away our perceptions of time as something that flows uniformly from the past, through the present and into the future at a regular rate. Einstein proved, over a century ago, that time contracts and stretches, being affected by mass and velocity. Time passes more slowly the nearer one is to a massive object than further away; time passes more slowly the faster one is travelling. Today for a few thousand dollars, says Rovelli, you can buy a timepiece accurate enough to show the difference in time between sea level and mountain peaks, and between a stationary observer and one flying at supersonic speed. So there is no objective 'universal' time; spacetime is stretchable. The reason that we don't notice this is down to scale. We see the sun as it was over eight minutes ago, the moon as it was 1.3 seconds ago. It doesn't make any difference to our lives unlike international time zones, an artificial construct.

Rovelli doesn't mention (as it is as yet inconclusive) the notion of information being passed between entangled particles instantly - faster than the speed of light, stuff that Kauffman touched upon. A large-scale experiment conducted this month seems to confirm Einstein's worries about 'spooky action at a distance'. If confirmed, it suggests that information can travel at superluminary speed - question can that happen at interstellar distances?

Entropy, the key to understanding time

Rovelli brings to our attention the idea that Rudolf Clausius's equation for entropy change (ΔS ≥1) is "the only equation of fundamental physics that knows any difference between past and future. The only one that speaks of the flowing of time." Indeed, ΔS ≥1 is the only equation in the book's main text (much like the only equation in Hawking's book is E=mc². ). This is because it is significant in the age of quantum mechanics; other equations are reversible, whereas if you leave a glass of hot water in a cold room, the water will only tend to get cold. It is here we can witness the passage of time. But again, there's a notable gap - like Hawking (who at least mentions it), the role of dark energy pushing our universe apart at an accelerating speed - isn't mentioned by Rovelli.

The quanta of time attract Rovelli's attention. Just as light is both particles and waves, so time is fluid and yet granular. The shortest unit of time is Planck time; a hundred millionth of a trillionth of a trillionth of a trillionth of a second (That's ten to the minus 44th). In other words, you cannot have 'half a Planck time'; Plank Time is indivisible. Similarly, out there at the subatomic end of spacetime, Planck length ("the minimum distance below which the notion of length becomes meaningless") is a millionth of a billionth of a billionth of a billionth of a centimetre. Down at this level, electrons have no precise position, everything is a blur - until observed by the conscious observer.

Essentially, Rovelli is tearing down everything we instinctively feel about time and its passing. He asks us to imagine the moment Copernicus watched the sun set and having the insight that it is not the sun descending below the horizon, but rather him sitting on a planet that's spinning backwards as it orbits a stationary star. What this paradigm shift means for science - and for philosophy - I will cover tomorrow in Part 2 of this three-part review.

This time two years ago:
Brexit and Trump - a political fiction

This time six years ago:
The law of diminishing returns disappears up its own fundament

This time seven years ago:
A night at the Filters (Museum Night 2011)

This time eight years ago:
Warsaw's Museum Night

This time nine years ago:
Exploring my anomalous memory events