Book Reviewed: The Order of Time, by Carlo Rovelli

Time is an Illusion, says physicist Carlo Rovelli

Physicists calling time an illusion is not a new idea. Julian Barbour, in his 1999 book argued for the same hypothesis. Contrary to this idea, physicist Lee Smolin proposed that time is real. He suggested that laws of physics are not fixed in the universe but evolve over time. The principle argument in support of his theory is that mathematical models provide an abstraction of reality and ignore time dimension. Carlo Rovelli observes that since theory of general relativity assumes spacetime is smooth and continuous, and quantum theory describes matter and energy in discrete quantities which implies that spacetime is also quantized. i.e. they exist in discrete quanta. These two realities are unconnected because quantum physics cannot deal with the continuous spacetime, and general relativity cannot reconcile with quantization of space and time. In fact, space, time and gravity are suggested as emergent properties of a system. Emergent properties are not identical with, reducible to, or deducible from the other physical properties. Examples include, temperature, pressure, viscosity, spacetime and gravity. Therefore, the author concludes that Isaac Newton’s picture of a universally ticking clock, and Albert Einstein’s relativistic space-time that bends so that local times differ depending on one’s relative speed or proximity to a mass is an over simplification. According to Rovelli, the time; the sequences of past, present and future is an emergent phenomenon of thermodynamics.

One of the principal arguments Rovelli advances is the Wheeler-De Witt equation which describes quantum gravity, but it has no time variable associated with it. Quantum mechanics and general relativity, taken together, imply the possibility of quantum superposition of different spacetimes. But the Wheeler-de Witt equation, which is based on a wave function Ψ[q] over geometries offers new perspectives.

In this book, Rovelli often muses about metaphysics, poetry and spirituality but fails to convince the reader that his idea is on the right track. It reminds me of Einstein’s famous saying that “God does not play dice,” Which makes me believe that if time is an illusion, then space would also be an illusion. There is a beauty and symmetry in the universe, and time alone could not be an illusion without space. Elon Musk, founder of SpaceX and Mars explorer suggest that this universe is a computer simulation on someone’s computer. And black hole physics suggests that the information in 3D world could be described in 2D dimension, in fact reality is a hologram. In quantum reality, the wave functions of a reality must be collapsed by physical observation (conscious observers), until then the reality is smeared out in spacetime. In fact, reality is in the eyes of beholder. Taken together, reality of matter and energy in spacetime could be an illusion (Maya), as interpreted by the Vedanta School of Hindu philosophy.