The theory of everything is the idea that all of the main physical forces in the world around us: gravity, strong and weak nuclear forces, and electromagnetism, can be worked into one all-encompassing theory.
As of right now, physics theories solve one or two of the interactions of these forces, but no single one explains them all together, yet. Physicists are revising an experiment proposed by Richard Feynman in 1957 to hopefully find a uniting theory of everything.
The researchers from Oxford University and the University College London (UCL) have successfully found a theory that combines electromagnetism and the weak nuclear force, but none to connect all of them. Steven Weinberg, a theoretical physicist on the team and a Nobel Laureate, is leading the research.
Einstein's laws of general relativity and the theories of quantum mechanics do a fantastic job of explaining the world when they're kept in their own domains. However, they fall apart if you use the ideas therein to explain physics that the theory doesn't govern.
In order to grasp what the theory of everything would mean for Physics and the work that's going on to revitalize Feynman's ideas, first we need to understand the full scope of a "theory of everything."
What is the Theory of Everything
The theory of everything, or TOE, is in brevity a single all-encompassing framework that links every aspect of the universe together, from relativity to quantum mechanics. The theory of everything is not a theory in and of itself with fully fleshed out ideas, but rather a term to describe the potential theory that may come to connect all the dots in the physical world.
The search for finding a TOE has been going on for some time now in the world of physics. String theory, a more common quantum physics theory, has been presented as a possible theory of everything in the past; M-theory being another. Both of these theories sit on the ideas of general relativity and quantum mechanics. Though these are theories themselves that don't overlap in their fields.
One of Richard Feynman's most famous quotes is “I think I can safely say that nobody understands quantum mechanics.”
Contextually that may seem confusing, understanding that Feynman was one of the greatest minds to live in the last 100 years. However, it was a great representation of what he thought of the field, that it couldn't be easily presented through metaphors or through relation to observable reality. The way that quantum mechanics works is so different from common sense physics that it takes a unique perspective to even begin to grasp.
Feynman was unique in the way that his brain worked to understand things. His biographer, James Gleick, noted that Feynman found it difficult to understand why everyday humans needed theories related back to them in tangible means.
He was able to seemingly grasp and understand nature just by reading and observing equations and mathematics. Feynman was also blisteringly good at taking highly complex topics and explaining them simply, a skill he noted was only present if you really truly understood something.
Feynman worked on some incredible experiments and theories in his time, even going on to win the Nobel Prize in 1965. Perhaps one of his most valuable contributions to the field of science was that of quantum electrodynamics, the idea of interaction between all light and matter, linking both quantum mechanics and special relativity together.
Following this he proposed something known as the path of integral formulation, a theory that took into account all potential trajectories of any given particle between any given two points.
The physicists state that if they are able to detect gravity on quantum particles, on the quantum level, then they would be better able to understand why gravity has such a strange interaction with the quantum realm. Feynman had the idea to test for quantum gravity around quantum superposition, or the idea that a particle exists in all potential states before you measure it, at which point it's only in one state.
Feynman believed that utilizing quantum entanglement, you could take a mass, put it in a gravitational field, and cause it to become entangled on a quantum level. Then by utilizing finely tuned sensors, the observer would be able to detect the field's interference. The interference of the gravitational field would cause the mass to take on a specific location. This would allow the researchers to detect and measure quantum gravity.
This experiment proposed by Feynman is what the teams of researchers are working to replicate and flesh out. Researchers from Oxford are worried that since Feynman's initial experiment had no way of directly measuring quantum entanglement, they wouldn't be able to definitively draw a connection to quantum gravity.
That said, the researchers have come up with a way to quantize two masses and entangle them, which would allow them to detect quantum gravity definitively. Each of the masses would in a state of superposition and be connected through quantum entanglement to a quantum gravity field.
The experiment is being developed and could lead to an even better path to a theory of everything. However, there's no guarantee that the experiment will work and quantum gravity could end up being much harder to detect than once thought.
All this said, intense research is still continuing across the world to discover a working theory of everything, which would lead to a completely new understanding of how the universe fits together.