Theory of Everything
From time immemorial, man has desired to comprehend the complexity of Nature in terms of as few elementary concepts as possible. ~ Abdus Salam
Physicists have long sought an umbrella theory that explains and connects all known physical phenomena, along with the predictive power to anticipate the outcome of any experiment within the physical realm – in other words, the formula to make the world deterministic.
Archimedes was perhaps first in describing Nature by axiomatic principles and using them to deduce new results. The path of theoretical unification has been dreamt by many of his successors: Democritus, Newton, Laplace, Einstein, and others.
Some of the most recent attempts are string theory and M-theory, though those are more particularly oriented toward an approach for producing a unified theory, rather than being a completed theory unto themselves.
A pivotal struggle has been unifying the 3 forces understood at the quantum level (strong, weak, electromagnetism) with gravity, which is incidental at the quantum scale, but long proved tricky to bottle in equation form at that level, owing to the infinities that arise. Relativity reveals a bendable 4d spacetime, whereas quantum mechanics has treated spacetime as unrealistically rigid.
All unification theories suffer from the same philosophical problem: the barrier between the continuity of the field and the discreteness of the quantum. Any quantum-based theory of physical reality must explain everything in terms of the discrete nature of particles, while any relativity-based theory must proceed from the continuity of the spacetime structure. ~ American theoretical physicist James Beichler
The intrinsically quantum phenomenon of entanglement appears to be crucial for the emergence of classical spacetime geometry. Spacetime is just a geometrical manifestation of entanglement. ~ Mark Van Raamsdonk
Canadian theoretical physicist Mark Van Raamsdonk first proposed a way to connect quantum theory with relativity in 2009. The key insight involved entanglement of quantum fields, which has been observed.
Neighboring fields are typically more entangled than those farther away. This relative locality intimates that entanglement plays a role in the geometry of spacetime.
The continuity of spacetime, which seems to be something very solid, could come from the ghostly properties of entanglement. If you change the pattern of entanglement, you also change the geometry of spacetime. ~ Juan Maldacena
In the large, entanglement of quantum fields via flexible spacetime reconciles relativity with quantum mechanics. But explaining entanglement specifically entails synchronicity, which requires an instantaneous channel through spacetime to allow “spooky action at a distance.” Such a shortcut is now known as a wormhole; a term coined by American theoretical physicist John Archibald Wheeler in 1957. The idea of wormholes is older than the word.
Hermann Weyl posited a wormhole theory in 1921, as a way to reconcile relativity with electromagnetic field theory. Einstein and Rosen proposed wormholes in 1935 as a means by which disparate black holes were connected, either in this universe or to other universes. This theoretical observation was an extension of general relativity, which renders the fabric of spacetime riddled with wormholes.
Wormholes act as the conceptual conduit of entanglement. That they exist in actuality has been repeatedly shown in experiments demonstrating quantum nonlocality.
Wormholes demonstrated by quantum nonlocality and hypothetical black hole wormholes are the same thing, just on a vastly different scale. This is simply scale-invariant uniformity; the physics of the universe behaving consistently.
The flexible geometry of spacetime at the macroscopic level emerges from quantum entanglement, which is mathematically characterized as a tensor network. A tensor is a geometric object that embodies a localized locus of relations. Tensor networks are used to describe various systemic entanglements, from quantum mechanics to holographic information storage to brain function. The upshot: entanglement defines the geometry of spacetime.
Our best description of the past is not a fixed chronology but multiple chronologies that are intertwined with each other. ~ American theoretical physicist Jordan Cotler