A Theory of Everything is a theory that explains, well, everything: every force, every particle, every bit of matter and energy in the universe. The problem with theories of everything is that they have to reconcile so many different theories into one.
Individually, we have a good idea of how matter works and what it is made from. This is called the Standard Model of particle physics. We also have the theory of gravity which explains the universe as a geometric structure that curves to create gravitational effects.
These two ideas are largely incompatible.
It is possible that if Albert Einstein hadn’t been in the picture, if he had been content to worry about problems like Brownian motion and the photoelectric effect, we might have ended up with a very different theory of gravity, perhaps one that is more inline with other particle theories.
We’ll never know.
The problem now is that there is only one serious contender for a theory of everything: string theory.
String theory isn’t one theory either. It is a collection of related theories, any of which could be true or none of them. This article isn’t about string theory, but about the lack of any paradigmatically different approach to a theory of everything.
While there are many, many theories of quantum gravity that attempt to reconcile Einstein’s theory with the Standard Model, few are as ambitious as string theory to attempt to integrate all forms of particles into one: strings, which create the different particles by vibrating in multidimensional spaces.
It is no wonder that so many thousands of papers have been written about it.
Isaac Newton wanted a theory of everything and so spent literally decades of his life trying to understand what stuff was made from. Unfortunately, he lived at a time when chemistry didn’t even exist and wasted his time on alchemy, a mystical art that had as much to do with science as astrology.
Lucky for us that we are smarter than that.
Or are we?
Perhaps endeavors like string theory are little more than a modern form of alchemy, couched in the language and practices of science but ultimately more about ourselves and the narratives we tell about the world as about reality.
More hardheaded types might say that we don’t need a theory of everything. Perhaps there is no such thing. Science is often messy and ugly. Look at the three-body problem of Newtonian mechanics — another problem Newton wasted a lot of time on. It is unsolvable in any closed form and admits chaotic solutions. How could that be? How ugly.
But beauty and ugliness are not as important as truth in science. The three body problem is a good example for it shows our hubris in that we look for order and call it beauty when a universe as vast and complex as ours also admits chaos, which has its own beauty.
While string theory has many things going for it mathematically that make it more compelling than other ideas, I wonder that it perpetuates a 20th century viewpoint of physical processes that needs to be overturned.
Consider that it posits an object, a string, which moves in a space, e.g., Calabi-Yau microspacetime. It also accepts quantum field theory as is without modification as providing the statistical background of the theory.
Thus, it perpetuates the 20th century viewpoint of modern physics: quantum fields, representing particles, moving in spacetime manifolds. It modifies the view considerably with strings and multidimensional spaces, but it hardly changes the paradigm. Perhaps this, not its lack of predictions or its complexity, is its greatest shortcoming.
19th century physics suffered its own flaws, many of which have been forgotten. It focused largely on bodies in Newtonian fashion rather than fields. It failed to understand the power of general covariance and equated coordinate systems with reality. It traded in absolutes in time and space.
Are we doing better?
A string’s existence is a type of absolute reality, no matter how dynamical it is.
Could it be that the 21st century might eliminate absolutes? To allow for a reality that can be dynamically shaped in every possible way?
I don’t know what that theory looks like, but I know it will be completely general. It will not posit a thing exists in the world to create reality; rather, it will only posit that a world exists and thereby makes itself real. It will have no absolutes: no strings, no quantum field theory, nothing but, perhaps, shape, infinitely malleable, and underlying that shape, perhaps nothing, i.e. no thing. For to posit a theory of every thing requires that one not start with a thing, or you arrive at infinite recursion.
What, if not a thing, underlies all things?
When contemplating what is not a thing and yet is important to physical law, I think of energy. Energy can be like a thing as when it becomes mass. Or it can be expressed as frequency of light, movement, heat, or potential for something to happen. Fundamentally, energy is just one of many similar quantities such as momentum, but it is not a thing.
I am not necessarily saying “all is energy” but rather all is akin to movement, like energy, but there is no thing moved because movement underlies all things.
This could be like a pregeometry such as an algebra as David Bohm proposed or some other way of representing that which underlies geometry.
What is clear to me is that whether string theory pans out or not, we will have no theory of everything until we have a theory that has no things in it, including strings.