[Delvo]

Garrett Lisi, with consultation together with John Baez and Lee Smolin, has come up with what seems to be a solution to a few long-standing conundrums of physics. It's described in a paper titled "An Extraordinarily Simple Theory of Everything". I waited to see whether this would promptly fizzle away as another failed bit of physics quackery, but it hasn't, and it's causing the most excitement and buzz in the physics & math communities that any one thing has in decades.

THE MYSTERIES OF PHYSICS WHICH THIS NEW THEORY ADDRESSES

One thing they've been struggling with has been why the known particles should have exactly the traits they have instead of some other traits. Their actual traits can be figured out one case at a time, but there hasn't seemed to be any "big picture" in which they fit together and make sense overall instead of just being arbitrary and independent.

There's also the matter of "force unification". It's been thought for a while that the electromagnetic and "weak subnuclear" forces were related, as if they were different reflections of the same underlying thing. But joining them to the "strong subnuclear" force is much harder or impossible, and so far getting gravity in on the group has been nowhere near even seeming even faintly possible by any stretch of the imagination. Nobody knows why some forces would be unifiable and others not, so there's been a quest to try to figure out just how many separate fundamental forces there truly are and which ones can be unified... or to unify all of them, figuring out how they're really all just one thing.

And pretty much the biggest problem physicists have been struggling with is how to define gravity. Relativity describes it in terms of curvature of space, but quantum mechanics doesn't have curved space. It might even have space that's divided into separate little pieces like the pixels on your computer screen. In particle physics as usual, forces are carried by particles, like the photon for electromagnetism and the gluon for the force that makes quarks stay together in protons and protons stay together in atomic nuclei, so gravity should be like that too, since forces carried through particles are the the only way for massive particles to interact... but there's essentially no role played by gravity in the known interactions between particles, no variable or operation corresponding to it in their equations at that level, so it's like gravity's not even there, so they can't call it a "force" at all or precisely describe its hypothetical carrier particle (graviton), and that particle has never been observed. The problem is that these conflicting views of gravity (a curvature of space or a particle-based force) come from theories that both seem to be right according to every test that's been done, because so far we've only been able to test sitautions that one of them doesn't give predictions about, not situations in which they give conflicting predictions.

So the big challenge in physics is to figure out which view of gravity is really right or find a third, new option that's really right... and then explain the test results that have made it look as if the wrong one(s) were right too. A theory that could do that, unifying the seemingly incompatible quantum mechanics and relativity, would be a "theory of everything" because it would encompass the areas of physics that have been separate from each other so far. String theories have been a set of attempts at a theory of everything, but they've made no testable predictions, and have made things much more complicated and difficult to do basic calculations on, including giving us various numbers of spatial dimensions greater than 3 and other such oddities that seem to have no place anywhere else in physics.

The new theory that they've been talking about contains answers for all of the above puzzles.

THE THEORY: A MODERN COUNTERPART TO MENDELEEV'S PERIODIC TABLE

The new theory that they've been talking about is, for particle physics, roughly the equivalent of the Periodic Table of the Elements for chemistry, so I'll start there to describe the new theory by analogy...

When people had figured out what a bunch of the elements were (isolated them from compounds) and started measuring their traits, Dmitri Mendeleev saw certain patterns among them: put them in order of how strongly they acted as chemical "reducers" or "oxidizers" or by certain measurable physical traits like melting points, and you'd end up with groups of elements that behaved similarly but were heavier or lighter than each other, with the amounts of weight difference between members of a group being about the same in each group; put them in order by weight instead, and you'd end up with a list that cycled through strong and weak reducers and oxidizers and increasing/decreasing melting points and such, in the same order, at about the same interval, several times. The table was just a way of combining and displaying the information to make both of those statements at the same time. Other people had noticed certain elements' similarities to each other and progressive patterns between/among them before, and tried to group them by other methods like a Law of Triads and a Law of Octaves, but one thing that made Mendeleev's table stand out and succeed was that, instead of trying to find a pattern consisting of only the known elements and nothing else, he left holes in it where the strict numerical patterns seemed to say there should be other elements that nobody knew about.

Elements corresponding to his table's "holes" were discovered later, with the traits that had been predicted for them based on the surrounding trends in the table. Today, the Periodic Table is used to teach points about the structure of nuclei and electron levels because it illustrates them well, but in a sense, they're not what it represents, because nobody knew about them in Mendeleev's time. In fact, it's a big part of what would later lead to theories of atomic structure and particles, by showing physicists what the theories they were working on would need to be able to explain and giving them a source of new predictions to test from any theory they came up with. Despite its maker not having known this, the table represents the true underlying nature of how atoms are made so well that more information has turned out to be contained in it than even he imagined. For example, it was based on organizing the elements along two dimensions, horizontal and vertical, but it also reveals other patterns if you look at it through the angles from corner to corner, such as increasing/decreasing atomic radius, which could never have been predicted from the data in the horizontal or vertical dimension alone.

Lisi's new theory in the physics world is essentially a periodic table of the particles, both of matter and of forces. It's just a bigger, funkier-looking table, with 57 basic dimensions instead of 2. (Notice that these are NOT dimensions of space; they're just dimensions in which information is represented.) And just as you can find more patterns hidden in Mendeleev's table by looking at it across a diagonal, Lisi's also can be turned at different angles, adding up to a 248-dimensional pattern describing the 57-dimensional object's various symmetries and reflections and diagonals. This pattern, called E8 (don't ask me why), has been known to mathematicians for a while before Lisi used it, just like the basic idea of grids and rows and columns had been known for years before Mendeleev used it for his Periodic Table. Obviously, no human can actually picture all of those dimensions, but they're just a mathematical abstraction having nothing to do with dimensions of the universe, and a computer can do the calculations for it.

Like Mendeleev's table, the geometric relationship between two positions in the figure tells you how the two things there will interact with each other. Also like Mendeleev's table, at least in Mendeleev's time, Lisi's has a place for every known item (elements for Mendeleev, particles for Lisi) but also some empty spots where a "new" one can be predicted and even its exact traits can be calculated before it's observed, so Lisi's table gives predictions that we might be able to test for their accuracy.

HOW IT FITS INTO MODERN PHYSICS AND ANSWERS THE MYSTERIES

On the apparent arbitrariness of the particles' unique traits (charge, mass, spin, and so on): each known particle now has its own place in the figure, where its position says exactly what those traits must be, so the figure describes all possible configurations of the traits of particles and shows how all of the different particles of matter, energy, and force are all really just complex reflections of some basic principles in the background that make them all what they are... just as Mendeleev's table described all possible types of atom and revealed how they were all made what they are by the same fairly simple background principles (which turned out to be numbers and arrangements of protons, neutrons, and electrons). No such pattern relating one particle's traits to another's has existed before, although smaller and less precise ones have which only put small groups of particles together.

The position-dictated particle traits and relationships between groups of points in the E8 figure also describe all of the fundamental forces of nature, unifying them all as if they're reflections of a single force just acting differently through different angles in the figure between differently-positioned particles. And that includes gravity because some of the positions in the figure describe particles that would, based on how they fit into the big picture, be gravitons. So Lisi's E8 gives an answer to the question of what gravity is: it's just another force, carried by another particle, like electromagnetic force is carried by photons. (That means it's not a curvature of space.)

And it does all of the above without any of the complications like new phenomena or particle behaviors or extra dimensions, beyond 1 for time and 3 for space, that burden string theory. (The phrase "extraordinarily simple" in the title of Lisi's paper is even a couple of math puns meant as little digs at the string theory folks, which are now the big critics of his theory and the one group of people who would be the most threatened by it if it's right.) Instead of complicating things, it makes them simpler by bringing everything we know together in one place, from which everything's role in the system can be derived with the right mathematical procedures. And unlike string theory, it makes predictions that can be tested: the points in the figure where particles with certain predictable traits should be even though we haven't seen them before. The search for some of these "new" particles will presumably be one of the first tasks to which the Large Hadron Collider will be put to use when its construction is finished in several months.

Even if it is right, something which will have to be done next, other than the recording of some of its predicted particles, is some explanation of how relativity fits into the picture now, because this thing says gravity is a force instead of a curvature of space but some of relativity's other predictions have been accurate anyway. And if as many more hidden relationships and patterns can be revealed by turning it in various different directions as its high number of dimensions suggests, like the way the diagonals in Mendeleev's table contain real information, then all the extra dimensions in this thing might contain more new discoveries for years to come.