Over the past few centuries, scientists have delved deep into the structure of physical reality, inspecting it on ever-smaller scales. This incredible journey has resulted in a towering structure of scientific theories. At the top, we have biology, which relies on chemistry, which in turn leans on atomic physics, which stands on nuclear physics, ultimately resting on particle physics. Particle physics is the study of elementary particles, such as the quarks within protons and neutrons and the electrons orbiting them—the basic building blocks of atoms.
Thousands of scientists have spent lifetimes uncovering this formidable intellectual tower. It begs the question: How tall is this tower? Will it end somewhere? Is there a final theory that halts this reductionist probing, or do layers upon layers of theories continue infinitely? The exploration of whether there’s an endpoint for this scientific voyage to understand the nature of reality is riveting.
One school of thought argues that this tower of scientific theories must be finite. To grasp this, let’s consider the process of measurement. Any measurement involves interaction—a probe observes an object, whether that probe is a photon, an electron, or even a tennis ball. At low energies, space-time curvature is negligible. However, as we probe shorter distances, higher energy probes are required. At very high energies, the space-time curvature created by the probe’s energy can form a black hole, making further measurement impossible. This implies a fundamental limit to how short a distance we can measure, known as the Planck length.
The Planck length is 1.6 x 10^-35 meters, incredibly tiny—ten orders of magnitude smaller than a proton. This suggests that the tower of scientific theories likely ends here. Without the ability to measure beyond a certain length, having theories that can’t be tested becomes nonsensical.
Even though we acknowledge limitation in measurement, it doesn’t automatically imply nothing exists beyond that scale. Our theories can only be guided by the information accessible to us. Science has already unified several seemingly disparate theories into a greater whole. For instance, the electric and magnetic forces were unified into electromagnetism, and then the electromagnetic force was combined with the weak force into the electroweak force. This pattern hints at the possibility of further unifications, perhaps leading to a theory of everything.
Currently, we manage two overarching theories: Einstein’s general relativity for gravity and the Standard Model for electromagnetic, weak, and strong forces. A problem arises because the Standard Model employs quantum field theory, while general relativity remains a classical field theory. Bridging this gap is key to unlocking a unified theory. Many research initiatives aim to develop a quantum theory of gravity.
Several candidates for a theory of everything have emerged, such as string theory and loop quantum gravity (LQG). String theory proposes that everything is made up of one-dimensional strings vibrating in multiple dimensions. Meanwhile, LQG attempts to quantize space-time itself. Another contender, lesser-known but intriguing, is Quantum Holonomy Theory (QHT). Pioneered by Jesper Grimstrup and Johannes Aastrup, this theory aims to end reductionism by basing everything on incredibly simple principles.
QHT begins with the concept of empty three-dimensional space, focusing not on objects within it but on the motions through which space gets defined. The idea revolves around gauge fields, which represent recipes for moving particles from point A to B, capturing the interactions and forces in the process. The infinite array of these “recipes” forms a configuration space with its own geometry.
This theory’s elegance lies in its ability to derive known physics from the basic principle of movement in space. QHT manages to encapsulate the mathematics of the Standard Model and potentially beyond. One significant implication is why the universe is quantum mechanical—if the simplest description of the universe involves quantum movements in 3D space, then the math dictates the universe must be quantized.
Additionally, QHT provides answers to several thorny issues, such as the non-quantization of gravity, the absence of singularities, and potentially effective resolutions to questions about the Big Bang.
While profoundly complex, QHT’s foundation on principles of movement in three-dimensional space means its math is intricate. This non-commutative geometry is not widely understood, which keeps QHT relatively obscure.
In the grand scheme of things, if QHT holds, it offers a cohesive and comprehensive framework that simplifies the myriad complexities of the universe into a singular, easy-to-understand form—movement through space.
And that’s a wrap on this dive into the potential end of our towering scientific quest.
