Findings: The 'Simple Theory of Everything'
“Surfer Dude Stuns Physicists with a Theory of Everything,” writes The Daily Telegraph. Further down, a caption below physicist Garrett Lisi’s picture reads “Dude, where’s my theory?” — a likely reference to the Ashton Kutcher comedy about two stoners called Dude, Where’s My Car?
Lisi holds a Ph.D. in theoretical physics from University of California, San Diego, so perhaps he deserves a little more respect than this. Despite lacking any university affiliation (or perhaps because of it), Lisi spends his days surfing the waves in Hawaii and, along the way, discovered a theory of everything.
Fallible or infallible, we can safely agree that this is an ambitious and admirable feat. Thus, we will look at Lisi’s theory of everything — aptly titled “An Exceptionally Simple Theory of Everything.” It should be noted, immediately, that the title of Lisi’s paper is a pun.
The theory proposes to unite the four fundamental forces of nature (the electromagnetic force, the strong nuclear force, the weak nuclear force, and gravity) using a mathematical structure called E8.
The E8 group is a member of a family of mathematical structures called exceptional simple Lie groups (hence the pun) — of which E8 is the most complicated.
While the structure is incredibly difficult to envision and understand, its symmetries are profoundly beautiful.
There is a problem with physics, and Lisi set out to tackle it. The Standard Model of particle physics, which currently describes three of the four fundamental interactions (gravity is not one of them), is a zoo of subatomic particles. Some particles dictate forces. Others particles, like baryons, include protons and neutrons. These particles constitute matter. There are also 24 types of force-carrying particles, or fermions.
Fermions are particles with half-integer spin, and can be distributed among 12 quarks and 12 leptons — each having their own particles and antiparticles.
There are too many particles to begin to list, but a visit to the Particle Data Group (pdg.lbl.gov) can update you on the latest figures. To date, there is no experimentally verified model that ties all of these particles together.
The problem is this: When one applies the concepts of quantum mechanics to general relativity, the results are nonsensical — with the gravitational force, mentioned earlier, being the major fly in the ointment. For example, the force between the particles mediating gravitational interactions (gravitons) becomes infinite. Because of this, the Standard Model cannot unify the four fundamental forces in any coherent way.
This disconnect between quantum mechanics and general relativity — the root of the gravity debacle — is the roadblock toward formulating one robust theory of everything. To put this information within the framework of Lisi’s theory, it is necessary to know that the E8 structure contains 248 dimensions, or “points.” The 248 dimensions of the structure do not imply a 248-dimension universe.
Our physical universe, as described by this theory, will still have four.
Lisi attempted to solve the disconnect between quantum mechanics and general relativity by incorporating the gravitational force into E8’s structure. In Lisi’s model, the points in the structure correlate to all of the known particles in the universe — with only a few holes. The nice thing about Lisi’s paper is that it contains step-by-step diagrams and shapes to illustrate his point.
Toward the end, Lisi writes that his theory is an “exceptionally simple unification of the Standard Model and gravity,” and that there are “a remarkable number of ‘coincidences’ that work exactly right to allow all known fields to be unified as parts of one connection.” In the paper, one can work through Lisi’s idea by following the placement of shapes and colors on the E8 structure.
Red, orange, green, blue, and purple triangles all represent quarks — the constituents of protons and neutrons. Yellow and gray triangles are leptons — a group of particles that includes the electron. Force particles are represented by circles. By way of a gross oversimplification, Lisi connects these points, forming stars.
Out of this emerges a structure that defines force particles and matter particles, via lines and rotations, in a highly specific, and serendipitously accurate, way.
The theory is causing collective unrest among the physics community. Some scientists, such as Lee Smolin, a theoretical physicist and researcher at the Perimeter Institute for Theoretical Physics, are giving Lisi’s paper a chance. In an article in New Scientist, Smolin comments on Lisi’s work. “It is one of the most compelling unification models I’ve seen in many, many years,” he said.
Critiques, comments, and objections from the masses exploded after the posting of Lisi’s paper on arXiv (pronounced “archive”) — an electronic archive of as of yet unpublished scientific papers.
The article in The Telegraph covering Lisi’s theory contains 51 pages of comments. A physics degree is not a prerequisite to chime in on E8.
“Right or wrong, Lisi is challenging accredited physicists to think again. The community has everything to gain and nothing to lose by Lisi’s theories,” one poster wrote.
“I did this with my spirograph when I was 6,” stated another, referring to the E8 structure.
There are some serious critiques as well. Many scientists view Lisi’s idea as nothing more than a particle physicist’s attempt at a theory of everything — namely, classifying particles in a coherent and mathematically sound way. Some feel that it is simply a piecing together of several other scientists’ work.
A major issue with the E8 system involves the combining of force-carrying particles (fermions) and matter particles (bosons) in a way that is somehow inconsistent. At the end of his paper, Lisi humbly added that his theory will either succeed or fail spectacularly. Recently, the fervor over the paper seems to have died down — although Lisi and Smolin continue to work on it. In the April 2008 issue of Scientific American, Smolin maintained that the media misrepresented the paper as a finished work.
“In reality,” he said, as quoted in the magazine, “almost every new theoretical proposal is first presented in a way that is flawed and incomplete, with open issues that need to be filled in.... While Lisi’s proposal has exciting aspects, this is the case with it as well.”
I, for one, hold Lisi in exceptionally high regard. Success or failure, his contributions have forced many of us to rekindle the lost art of thinking for thinking’s sake.
From a college student’s standpoint, developing a theory of everything in between catching waves is also an exceptionally spectacular use of spare time.