Book Reviewed: Hidden In Plain Sight 3: The secret of time by Andrew Thomas

Book Reviewed: Hidden In Plain Sight 3: The secret of time by Andrew Thomas

Physics and philosophy of time: Is time an illusion?

Our understanding of spacetime has advanced in the last couple of years which has led to new thoughts about spacetime and physical reality. Some physicists suggest that space is an illusion and time is real; but others propose that time is an illusion and space is real. The key to this question is to understand the nature of physical reality: How matter (and energy) formed our universe in spacetime? Is it strictly guided by the laws of physics, a set of universal constants and four natural forces? How spacetime is treated in classical and quantum physics? In this book the author tries to address some fundamental questions about time. There are ten chapters and only two chapters (5 and 10) address the question of time directly. The concept of time is discussed mainly from the point of second law of thermodynamics which states that the entropy (chaos) of the universe is increasing (transitioning from order to disorder). Hence this sets the arrow of time, going from past to future. This explains why in our common experience, when a glass of water is dropped on to the floor, it breaks, but it does not reverse itself (to re-assemble) to form the glass with water, because that would be going from an disordered to an ordered state. The author does not go into details of underlying physics but uses a highly simplified approach to the concept of time. The book falls short of a good discussion on time.

According to relativistic physics, time is stitched together with space to form four-dimensional space-time. The passage of time is not absolute - no cosmic clock ticks away the hours of the universe. Instead, time differs from one frame of reference to the next, and what one observer experiences as time, another might experience as a mixture of time and space. In this spacetime concept, the past, present and future all exist together. Space-time is a frozen fabric that does not evolve. Our own existence, from birth to death, is set out in space-time in a timeless way. There is no time flow and no place for now. The concept of time might be similar to that of integers (whole numbers). All numbers exist simultaneously, and it would be insensible to think that the number 1 exists before the number 20.

In quantum physics time plays a key role, keeping track of the ever-changing probabilities, and the wave function of the universe evolves over a clock residing outside this universe. In this scenario the universe is split into two parts: the quantum system being observed and the classical world outside. In this fractured universe, a clock always remains outside the quantum system. According to physicist Carol Rovelli’s thermal time hypothesis, time emerges as a statistical effect, in the same way that temperature emerges from averaging the behavior of large groups of molecules. Most physicists believe space and time are quantized at the most fundamental scale and perhaps exists as atoms; grainy in nature just like the quantum nature of matter (and energy.)

Recently well-known physicists like Lee Smolin and Sean Carroll have provided an in-depth look at the concept of time. For interested readers, I recommend the following books:

From Eternity to Here: The Quest for the Ultimate Theory of Time by Sean Carroll
Time Reborn: From the Crisis in Physics to the Future of the Universe by Lee Smolin
The End of Time: The Next Revolution in Physics by Julian Barbour