by John Realpe
Contents
II. What is the difference between classical mechanics and quantum physics?
III. What are the different interpretations of quantum mechanics?
I. Introduction
Science & Wisdom LIVE promotes the dialogue between science and the wisdom traditions. We are particularly interested in how this conversation could positively impact our lives and helps us address some of society’s biggest challenges. But could there be any middle ground between science and the contemplative traditions to begin with?
Both science and some contemplative traditions try to reach an objective understanding of reality via experimentation and logical reasoning. Yet they tend to differ in their focus and mode. Science mostly focuses on the external or material world and is usually quantitative. Contemplative traditions mainly focus on the internal or mental world and therefore tend to be qualitative. In spite of this, they offer similar insights about “among other things“ the quantum nature of reality. What are these insights? What do they tell us about the relationship between mind and matter, between consciousness and the physical world? Would this have any impact on our lives at all?
We plan to write a few blog articles that will explore some of these questions in more detail. In this current blog, we will set the stage for the overall discussion.
II. What is the difference between classical mechanics and quantum physics?
Science & Wisdom LIVE recently hosted several events on quantum theory and its interpretations. But how does quantum theory differ from classical physics? What is the difference between these two descriptions of reality, and why does it matter?
Classical mechanics
Classical mechanics was mainly built out of concepts formed via our everyday intuition. When we look at the world, we see many separate objects that exist ‘out there’ , separate from us. We experience them as independent from the mental processes needed to perceive them. If we see an apple falling from a tree, we clearly see that there is a tree, on the one hand, and an apple, on the other. Those two objects appear to exist completely independent of each other. Never mind that the apple needed the tree for it to come into existence and the tree was born from an apple’s seed. Moreover, we tend to assume that trees and apples exist exactly as we humans perceive them.
Classical mechanics sought to explain what we see in day-to-day life in terms of the so-called fundamental particles and their interactions. In doing so, classical mechanics projected on these concepts some of our everyday intuitions. In other words, such fundamental particles and their interactions were not unlike the collection of separate objects described above: here you have a particle, there you have another, in between you have an interaction, and none of these has anything to do with the process of observation.
Quantum Physics
Quantum physics has shaken this view. It shows that, on a very small scale, matter behaves in puzzling and counter-intuitive ways. It presents a view that is hard to reconcile with our everyday intuition. For instance, measuring first the position and then the velocity of a particle in general gives different results than measuring first its velocity and then its position. It is as if measuring the position of a particle disturbs its velocity and vice versa — something we do not usually see in our everyday life. Other examples are particles that seem to instantly influence each other no matter how far apart they are, cats that appear to be simultaneously alive and dead as long as we do not observe them, and objects that sometimes behave as particles and other times as waves depending on how we observe them – even though waves are somehow the opposite of particles.
But what is the core message of quantum physics, and what does it say about the nature of reality?
III. What are the different interpretations of quantum mechanics?
Trying to make sense of those puzzling and counter-intuitive behaviours, physicists have come forward with many different interpretations of quantum physics.
The Copenhagen interpretation of quantum mechanics
The Copenhagen interpretation emphasises that “unlike classical phenomena“ quantum phenomena cannot be separated from the whole experimental arrangement. The experimental arrangement for, say, measuring the position and velocity of a particle would be generally different depending on which quantity is measured first. Therefore, obtaining different results would not be unexpected. However, this interpretation leaves the experimenter out of the experimental context in an attempt to avoid the intrusion of subjectivity into the fundamental laws of nature.
David Bohm and the Implicate Order
David Bohm “and later on Basil Hiley“ believed that the distinction between classical and quantum physics could be narrowed down to a new and very peculiar kind of (potential) energy, a ‘quantum potential.’ This quantum potential contains global information about the environment – for example, about the experimental arrangement. So it collectively influences all the system’s particles accordingly, and that is why it is also referred to as ‘active information’.
Bohm proposes a holistic view of nature, where everything is interdependent and the whole can influence the parts via this new form of energy. He suggests that particles are not like billiard balls that persist and move, but processes in which “certain forms undergoing regular changes manifest again and again, but so rapidly, that they appear to be in continuous existence” (Bohm, 2002). However, active information was not considered information about us, observers, but information about the particles themselves, which led Bohm to suggest that “the particles of physics have certain primitive mind-like qualities” (Bohm, 1990).
The Relational Interpretation
Carlo Rovelli proposes yet another interpretation, that he defines as the ‘relational interpretation’ of quantum theory. According to Rovelli, physical phenomena do not exist intrinsically, in isolation, but only relative to other phenomena. Nothing can exist absolutely, but only relative to something else. In particular, when an ‘observer’ observes a physical phenomenon, such a phenomenon is relative to that ‘observer.’ Importantly, when Rovelli says that an ‘observer’ observes a certain phenomenon, that very fact is itself relative to another ‘observer.’ But for Rovelli, contrary to common wisdom, any physical system “ a star, a rock or an electron“ can be considered an observer. So he, too, carefully avoids the intrusion of subjectivity into the fundamental laws of nature.
QBism
In contrast to all the previous interpretations, QBism explicitly puts the scientist back into science; it brings subjective experience to the forefront (Mermin, 2014). According to QBism, quantum physics is a tool that each of us can use to compute the probability of having a certain experience – for example, seeing a particle in the corner of our room. This probability, in turn, depends on our previous experiences – for example, the experience of seeing that particle moving at 1 km/h. Taking such an agent-centric perspective appears to resolve the conceptual puzzles of quantum physics (Mermin, 2014). However, it does not provide additional insight as to the specific form of the equations that describe the quantum world. Furthermore, it treats scientists as rather abstract entities that follow certain norms, without delving further into their potential cognitive makeup.
But isn’t objectivity the bedrock of science? How can we do any science at all if we allow for the intrusion of subjective experience as QBism seems to suggest? In our next blog we will explore these intriguing questions.
References
- David Bohm (2002). Wholeness and the implicate order. Volume 10. Psychology Press (p. 246).
- David Bohm (1990). A new theory of the relationship of mind and matter. Philosophical Psychology 3, 271–286.
- Mermin, N. D. (2014). Physics: QBism puts the scientist back into science. Nature News, 507 (7493), 421.
