The Relative and Absolute of Buddhism and Theoretical Physics

Rather than viewing the modes of inquiry of these two great traditions as incompatible, it may be more fruitful to regard them as complementary. Like focusing two eyes on the same reality, with the integration of these two perspectives, we may discover a deeper and more encompassing vision than either tradition has achieved on its own.

— Physicist Allan Wallace

The purpose of this post is to demonstrate a remarkable similarity between Buddhism and theoretical physics. In Buddhism, the absolute can be referred to as the dharmadhātu, dharmakaya, tathagatagarbha, or Universal Mind, just to name a few. While in physics, the absolute nature of reality is described by mathematical frameworks like the unified and quantum field. After unpacking these ideas, we will see how they can be understood as merely two different pedagogical strategies used to evoke the same one understanding of realitySo, with an eye poised on such an all encompassing comprehension, let us begin the discussion.

To work our way up to the more complicated concepts in physics, we ought to start with Einstein’s comparably simple theory of General Relativity and the Spacetime model of the universe. According to Einstein, space and time are interwoven into a single fabric called spacetime. Massive bodies, like earth, warp and twist their local spacetime. This curvature gives rise to gravity. In mathematical terminology, Einstein-Minkowski spacetime is made up of three spatial dimensions x, y, and z, and one time dimension t. Spacetime is commonly thought to be the history of the entire universe, containing every “event” that ever happens. A “world-line” is the history of an object in spacetime.

One way to represent four-dimensional spacetime in a two-dimensional image is by drawing height, width, time, and leaving off depth. The resulting diagram is something called a light cone. The image above represents how a light cone corresponds to a world-line. The difference between the two representations is that the world-line depicts the future as determined and fixed, while the other depicts it as a collection of undetermined possibilities. These interpretations of spacetime correspond to deterministic or infinitely probabilistic views of the universe, which will become relevant in our later discussion of quantum mechanics.

Einstein’s equations for relativity were assumed to describe the universe in its entirety, being applicable at every possible level of analysis, from the microcosm of subatomic particles to the macrocosm of planets, solar systems, and galaxies. However, physicists soon discovered that this was not the case. Around 1926, they began to observe the fact that electrons could only occupy orbitals with discrete, quantized, energy values. This is where quantum mechanics gets its name; “quanta” means a discrete, invariant, amount.  Quantum mechanics is the science of phenomena that take place at this level of reality. It regards the behavior of matter and its interactions with energy on the scale of atoms and subatomic particles. Classical physics, on the other hand, is the science of phenomena which take place from the scale of atoms all the way up to galaxies.

For simplicity’s sake we can condense this understanding of reality into two domains: the quantum and the physical. As we shall see, different “rules” govern each of these domains of existence.

The phenomena of the quantum domain exhibit properties which break the fundamental laws of our physical domain. Such properties as these include: the wave-particle duality of photons, quantum superposition, quantum entanglement, quantum tunneling, non-locality, and uncertainty. Wave-particle duality is a property exhibited by subatomic particles which allows them to exist simultaneously as an abstract wave of probabilities and as a discrete unit of matter. Superposition is a related property, which allows quantum particles to exist simultaneously in two or more locations at once. Quantum entanglement refers to pairs of particles being “synced up” such that  they can “communicate” with one another instantaneously, regardless of the distance between them — thus violating the speed of light. Heisenberg’s uncertainty principle describes the fact that it is impossible to simultaneously know a particle’s position, “where it is,” and its momentum, “where it’s going.” Once one is measured, the other becomes necessarily uncertain. Contrast these properties with something from the physical world, like an apple, and the absurdity of it all is made plain.

The existence of quantum phenomena demonstrates the error inherent in our conventional way of looking at the world. On our side of reality, the physical world, things are solid and objects have definite properties. If you look at a clear drinking glass, you will observe either that it contains liquid or that it contains no liquid. Never will you observe both situations at once. Yet that is precisely the kind of thing that “takes place” in the quantum world.

Perhaps the discrepancy between the quantum and physical domains is due to a fundamental flaw in the human mode of perception. Maybe the world brought to us by our senses and scientific instruments really is all just an illusion, what the Buddhists and Hindus call maya. Yet even if this is true, if existence is all just an elaborate kind of dream, shouldn’t we still be able to reconcile our scientific descriptions with one another. After all, they supposedly would exist entirely inside the world of illusion. Having stemmed from our humanly perceptions, they could never themselves reach beyond the realm of maya. The loop must close somewhere in sight.

To close this loop, let us reconsider physics’ two main descriptive frameworks: general relativity and quantum mechanics. Physicists have been trying to reconcile these two theories for years. It is thought that these theories must both be correct because they’ve both withstood some of the most rigorous experimental testing in the history of science. There have been many attempts to unify relativity and quantum mechanics, but despite half a centuries worth of theories, none of them seem to be able to account for one of the most well known concepts in all of science: gravity. Perhaps the problem of unification can be solved if we first consider the fundamental limits of our universe. This brings us to the work of physicist Max Planck.

The Planck Scale is the level at which the smallest measurements of spacetime can ever be made. If you zoom down to smaller and smaller levels of the physical word (e.g. from a hand, to skin cells, to molecules, to atoms, to protons, to quarks, etc.) eventually you will reach a point where no more zooming in is possible. You would hit wall, for it would be impossible to measure any length smaller than this. This is called the Planck length. Physicist discovered the existence of this absolute length by extrapolating from the already known universal physical constants (e.g. the speed of light). And just as there is an absolute smallest length, there is an absolute smallest unit of time, and an absolute smallest unit of mass.

Planck Length (hG ÷ c3) 1/2: This is the quantum of length, the smallest measurement of length that has meaning. It’s equal to 10-35 meter and is about 10-20 times the size of a proton.

Planck Time (hG ÷ c5) 1/2: This is the quantum of time, the smallest measurement of time that has any meaning. It is also sometime referred to as the “Planck second.”

Planck Mass (hc ÷ G) 1/2: This is small by everyday standards, but 1019 times the mass of a proton, and would be contained in a volume roughly 10-60 times that of a proton. This represents an enormous density that has not occurred naturally since the big bang.

All of these units combine to form what we call the Planck scale. The existence of this scale leads us to conclude that there is indeed a discernible “limit” or “boundary” to the physical world.  Beyond this horizon is the mysterious and ineffable Absolute. It is here, at the edge of spacetime, where the unification of general relativity and quantum mechanics can take place, and where the wisdom of Buddhism shines through.

In order to understand how this is so, we should first be familiar with field theories. Thus far, physicists have developed two main types of field theories: those concerning the world of classical physics and those concerning the world of quantum physics. Because of the different properties of these domains of reality, classical and quantum field theories are incompatible with one another. However, there is a growing effort among physicists to describe a “unified field,” which would unite the classical and quantum into one coherent framework. If successful, this would unify all the known forces and particles, including gravity, into one glorious mathematical theory of everything. This framework would thus be the most fundamental description of the known universe, reflecting the horizon beyond spacetime itself.

The concept of such an all pervasive field at the horizon beyond spacetime is also evoked in Buddhism. Depending on the sutra and the context of utterance, this ineffable essence of existence is known as: Universal Mind, the dharmadhātu, dharmakaya, alayavijnana, or tathagatagarbha. These are all merely different designations for the same one thing, different fingers pointing at the same moon.

However, we must acknowledge that the unified field is only a hypothetical framework. We shall, therefore, discuss the absolute aspect of reality as if it referred to the quantum field instead of the unified field. The distinction between the types of fields in this case is almost irrelevant to our purposes, for both rely on the same fundamental understanding of the universe as a field. But in reviewing the science, we ought to follow the roads most paved. This brings us to quantum field theory (QFT). Now we will briefly explore this and the related concepts of quantum vacuum fluctuations and quantum foam.

In QFT, the field state with the lowest possible energy is called the “vacuum state.” When there is a temporary change in the amount of energy in the field, it is an “excitation.” These excitations give rise to particles. Another term for such an excitation is “quantum fluctuation,” or to be more precise “quantum vacuum fluctuation.” And according to physicist John Wheeler, the totality of all the quantum vacuum fluctuations gives rise to the “quantum foam.”

The idea of quantum foam views all the waves and particles of the physical world as simply fluctuations on the surface of the quantum field. The metaphor of a body of water and the waves on its surface comes in handy here; only instead of waves, imagine the white foamy surface that sometimes arises in a pot of boiling water. Quantum foam is to be thought of as the fabric of our universe, and as mentioned earlier, one of the best ways to think of this “fabric of the universe” is with the concept of four-dimensional spacetime. Thus, the foam on the surface of the quantum field corresponds to our physical world of spacetime. Its quantum nature is manifest in the fact that our future exists merely as an abstract mathematical wave of probabilities. The unification of the physical and the quantum is seen at the Planck scale. The planck second can perhaps be thought of as one frame in the movie of our spacetime world-line, i.e. our life.

Now, if we take all of the ideas discussed thus far together, we may more clearly see the correspondence between Buddhism and theoretical physics. Einstein’s theory of spacetime and general relativity deals with the physical world, and corresponds to what many Buddhist traditions call Relative Truth, as opposed to Absolute Truth. In Buddhist terms, this theory could be said to describe samsarathe world of birth and death, of change and suffering, and of an ego that experiences the passage of time. On the other hand, quantum mechanics deals with the quantum world and could be said to correspond more with what is called Absolute Truth. For when we examine the aspect of reality where quantum phenomena occur, our conventional understanding of the world breaks down. Instead of observing an electron at one location or another, we find that it is both everywhere and nowhere. The quantum world is the realm of pure potentiality and possibility, and such words have also been used to describe the nature of nirvana. Fluctuations in this level of reality foam up and manifest in the physical world of spacetime, samsara.

Furthermore, consider the relation between descriptions of Universal Mind and the underlying quantum field which guides the unfolding of the universe. The metaphor about quantum foam, which saw of the physical world as nothing more than excitations on the surface of an ocean, is the very same one used in Zen Buddhism to explain the ultimate nature of reality. One of the primary Zen sutras says, “Universal Mind is like a great ocean, its surface ruffled by waves and surges but its depths remaining forever unmoved.” Neither the Universal Mind or quantum field are literally oceans, but using these comparisons is the greatest way we have to understand such difficult concepts.

Hopefully this brief review of conceptions of the absolute in Buddhism and theoretical physics has demonstrated how they can be seen as merely two different pedagogical strategies used to evoke the same one understanding of reality.