Carlo Rovelli – The Illusion of Time – YPO EDGE 2019

The speaker begins by questioning the nature of time, suggesting that it is a sequence of incidents that distinguish the present from the past. They propose a metaphorical picture of time as a long line, representing the flow of moments. This linear view of time is used to illustrate the difference between the past, which we can remember, and the future, which is uncertain and unknown. The speaker also mentions that while this concept is useful for everyday life, it is not entirely accurate in the larger context of the universe.

The speaker discusses the concept of time dilation, where time passes at different rates depending on one's position, particularly in the presence of a large mass. This phenomenon is observed in laboratories using highly precise clocks and is a result of the theory of relativity proposed by Albert Einstein. The closer one is to a massive object, such as a planet or a black hole, the slower time moves relative to a location further away. This has practical implications, such as the need to adjust the timekeeping in GPS satellites to account for the faster passage of time at their higher altitudes.

The speaker explores the idea that the distinction between the past and the future is not inherent in the fundamental equations of physics but emerges from the presence of heat and entropy. They explain that friction and heat are responsible for the arrow of time, as they cause the transformation of mechanical energy into thermal energy, leading to a unidirectional flow from past to future. This perspective is rooted in statistical mechanics and the work of physicists like Boltzmann, who showed that the difference between past and future arises from our lack of detail when averaging out the motion of molecules.

The speaker challenges the notion of a universal 'now', explaining that due to the finite speed of light, events that appear simultaneous from our perspective may not be so when considering their spatial separation. This is particularly evident when observing distant stars or galaxies, where what we see is a snapshot from the past rather than the present. The concept of 'now' becomes complex and less meaningful when considering the vast scales of the universe, leading to a reevaluation of our understanding of reality and existence.

The speaker delves into the complexities introduced by quantum mechanics, where the traditional concept of time becomes even more elusive. They describe how quantum mechanics allows for superpositions of states, which complicates the measurement of time intervals. The speaker shares their experience working on a quantum theory of gravity, where the conventional notion of time is no longer present in the equations. Instead, the focus is on relationships between variables and their changes, necessitating a shift away from the concept of time as we understand it.

The speaker discusses the role of the brain in creating our perception of time through memory and anticipation. They reference the work of neuroscientists and philosophers, highlighting that our experience of time is deeply tied to our emotions and psychological state. The speaker suggests that the brain's ability to predict future events based on past experiences is what creates the illusion of time's flow. They also touch upon the emotional significance of time, noting that it is central to human experience and is closely linked to our deepest emotions, including joy and suffering.

The speaker addresses questions about the practical applications of the understanding of time, particularly in relation to technology like GPS satellites, which must account for time dilation. They also discuss the possibility of time travel, suggesting that while traveling to the future may be possible, traveling to the past is much more complex and likely not feasible with our current understanding of physics. The speaker emphasizes the importance of considering the emotional and psychological aspects of time, as they are integral to our experience and understanding of time.

The speaker acknowledges the individual differences in the perception of time, which can be influenced by various factors including psychological state and level of interest or engagement in an activity. They also discuss the perception of time in different species, suggesting that animals with different processing speeds may experience time differently. The speaker concludes by expressing their pessimism about the current trajectory of humanity, citing environmental destruction and increasing aggression as significant concerns.