Via Radley Balko, a couple of articles in the Daily Telegraph about the prospects for a Theory of Everything --- this is a technical term --- piqued my interest. The first, a personality-driven piece about a semi-employed surfer who happens to have a Ph.D and has spent years working on a ToE that was inspired by correspondences between the E8 polytope and the workings of nature, is notable for confirming that work done at the apex of theoretical physics looks rather like an artistic project. Take a look at how Garrett Lisi, the theoretician, was moved to his conclusions:

E8 encapsulates the symmetries of a geometric object that is 57-dimensional and is itself is 248-dimensional. Lisi says "I think our universe is this beautiful shape."

What makes E8 so exciting is that Nature also seems to have embedded it at the heart of many bits of physics. One interpretation of why we have such a quirky list of fundamental particles is because they all result from different facets of the strange symmetries of E8.

Lisi's breakthrough came when he noticed that some of the equations describing E8's structure matched his own. "My brain exploded with the implications and the beauty of the thing," he tells New Scientist. "I thought: 'Holy crap, that's it!'"

You can see something similar in The Double Helix: At least if James Watson is to be believed, he and Crick realized, prior to testing, that the double helix had to be the shape of DNA simply by modeling the shape and observing the simple beauty of it. Not to get too sentimental, though, Lisi will need to demonstrate the existence of 20 heretofore unobserved particles to grant his ideas evidential credence.

Second comes this article on the ongoing work of USC physicist Itzhak Bars, who began work on the applicability of gauge symmetries to M-theory as early as 1995 --- very, very briefly, a physical symmetry is a system whose features do not undergo observable change in spite of mathematical transformation, such as a circuit whose electric potential is raised uniformly at all points, so that no change in voltage differential occurs and hence no change in the operation of the circuit; and M-theory, according to which there are 10 dimensions of space and one of time, is the current de rigeur theory on the spacetime maniforld --- and proposed a two-dimensional (2T) time. Apparently, Bars is not only ready to propose a 2T hypothesis, but to test it. (Subscribers to the New Scientist can read more here.)

What actually caught my eye from the Bars piece is the following:

Changing our picture of time from a line to a plane (one to two dimensions) means that the path between the past and future could loop back on itself, allowing you to travel back and forwards in time and allowing the famous grandfather paradox, where you could go back and kill your grandfather before your mother was born, thereby preventing your own birth.

The idea seems to be that Bars' hypothetical gauge symmetry resolves grandfather paradox-like problems by proposing a manifold of plain old vanilla 3+1 spacetimes, each subsumed within a broader 4+2 framework. Well, here's the thing. There's this temptation that high-powered physicists are often unable to resist, and journalists who write about high-powered physicists are simply incapable of resisting, of going beyond the bounds of data modeling and prediction, and playing around with speculative metaphysics. And the result is usually something that makes philosophers cringe.

So while I have no reason to doubt that Bars' work is a novel and potentially groundbreaking insight into the dimensionality and shape of spacetime, it's sort of laughable that he (and the author of the piece, who doesn't have a byline) seems ingenuously worried that the mathematics of temporal dimensionality could pose insuperable philosophical problems. In fact, no doubt in part because metaphysicians tend to grok science fiction, the problems and paradoxes of multi-dimensional and/or multi-directional time are a fairly well-worn subject in metaphysics, and the current going theories resolve such problems as there are in ways that defuse wild-eyed wonder over Back to the Future scenarios.

The ur-text here is David Lewis' "Paradoxes of Time Travel," from which I'll quote freely for a moment:

Consider Tim. He detests his grandfather, whose success in the munitions trade built the family fortune that paid for Tim's time machine. Tim would like nothing so much as to kill Grandfather, but alas he is too late. Grandfather died in his bed in 1957, while Tim was a young boy. But when Tim has built his time machine and traveled to 1920, suddenly he realizes that he is not too late after all. He buys a rifle; he spends long hours in target practice; he shadows Grandfather to learn the route of his daily walk to the munitions works; he rents a room along the route; and there he lurks, one winter day in 1921, rifle loaded, hate in his heart, as Grandfather walks closer, closer,....

Tim can kill Grandfather. He has what it takes. Conditions are perfect in every way: the best rifle money can buy, Grandfather an easy target only twenty yards away, not a breeze, door securely locked against intruders, Tim a good shot to begin with and now at the peak of training, and so on. What's to stop him? The forces of logic will not stay his hand! No powerful chaperone stands by to defend the past from interference...By any ordinary standards of ability, Tim can kill Grandfather.

Tim cannot kill Grandfather. Grandfather lived, so to kill him would be to change the past. But the events of a past [or any -- DK] moment are not subdivisible into temporal parts and therefore cannot change. Either the events of 1921 timelessly do include Tim's killing of Grandfather, or else timelessly they don't...The events of 1921 are doubly located in Tim's (extended) personal time, like the trestle on the railway, but the "original" 1921 and the "new" 1921 are one and the same. If Tim did not kill Grandfather in the "original" 1921, then if he does kill Grandfather in the "new" 1921, he must both kill and not kill Grandfather in 1921...It is logically impossible that Tim should change the past by killing Grandfather in 1921. So Tim cannot kill Grandfather"...

You know, of course, roughly how the story of Tim must go on if it is to be consistent: he somehow fails. Since Tim didn't kill Grandfather in the "original" 1921, consistency demands that neither does he kill Grandfather in the "new" 1921. Why not? For some commonplace reason. Perhaps some noise distracts him at the last moment, perhaps he misses despite all his target practice, perhaps his nerve fails, perhaps he even feels a pang of unaccustomed mercy. His failure by no means proves that he was not really able to kill Grandfather. We often fail to do what we are able to do.

Emphases mine. To boil all this down to a single sentence: Regardless of whether time travel is physically possible --- even assume that it is --- you can't go back in time and kill your grandfather because you didn't. So physicists working on the shape and dimensionality of time have no need to fear that their investigations open up grandfather-type paradoxes, nor is the claim that a particular hypothesis does create time-travel paradoxes a meaningful objection to a physical theory. The laws of physics do not preclude Tim the ideally positioned, would-be avicide, from killing his grandfather, and it would be absurd to suppose that they do. Instead, the fact that Tim will not kill his grandfather is deducible from the fact the he did not --- and on grounds of parsimony, one should assume his failure is due to utterly banal reasons.

On the other hand, what are we to make of the story --- which, if told in an appropriately demonstrative-free, non-haecceitistic manner, is in no way inconsistent --- of the man who steps into a time machine, emerges in what seems to be the time of his grandfather's youth, and kills the individual who seems to be his grandfather? Well, this is precisely the scenario that 2T theories like that of Itzhak Bars open up. The way for Tim to go through with the act of killing is to travel not just backwards in time, but orthogonally to his original position, and kill someone who is qualitatively identical to his grandfather. 2T theories ask us to imagine time not as a line but as a plane, so imagine Tim is originally located at the point (5,0). To be at the correct temporal point to kill his grandfather, he would have to travel to (0,0). Instead, he hops into the Itzhak Bars-patented Model 2T time machine, and travels to (0,1). At this point, he has shifted from one (3+1) spacetime to another. For all we know, this other spacetime is qualitatively identical to our own, except that at a point in time parallel to our own winter day in 1921, someone qualitatively identical to Tim's grandfather --- but not Tim's grandfather --- is brutally gunned down on his way to work.

If Bars turns out to be correct that spacetime is 4+2 (from some suitable God's eye perspective, one supposes), and the obvious engineering problems can be overcome, it will be possible to travel to alternate spacetimes and massacre doppelgangers of our ancestors. But in doing so we would not be brushing up against any iteration of the grandfather paradox, much less resolving it. And if, say, another brand of time machine came out which transported a traveler backwards within our own 3+1 spacetime, in that case we could not murder our forbears, because we didn't.

The Bars 2T time machine permits us an opportunity for something that doesn't really jibe with our intuitions of what time travel is. Really, it's something more like space-travel, in which we visit a world that is very much like our own, but isn't it. To really experience time travel as we understand the concept, we'd need a 1T time machine. But in stepping out on the other side of that machine, the only things we'd succeed at doing are things we already did.

There are a couple of lessons to draw from all this, which go to the way the popular press covers science and philosophy (when it bothers to cover philosophy at all), and most saliently, its tendency to mistake science for philosophy. Science is a process of designing and testing predictive models. It is not simultaneously an interpretation of those models. So when you read an article about some discovery in cognitive science or neuroscience, to which the caption is something along the lines of, "The Mind-Body Problem, which has plagued philosophers for centuries, has finally been solved!", take it with a grain of salt. No amount of increased rigor or detail in mapping correspondences between brain-states and mind-states moves us an inch closer, for example, to a solution to the so-called "hard problem of consciousness", namely, why it should be that physical states give rise to mental states in the first place.

This warning goes quadruple for anything in the popular press about evolution, and why it's so hard to kill off creationist and intelligent design-based attacks on it. The theory of evolution is a cluster of testable and refutable biological models that explain the differentiation of species and predict their patterns of future development and branching. It is neither a moral nor a metaphysical theory, so ostensible objections to it on moral or metaphysical grounds are not actually objections to the theory of evolution. It's a similar story with evolution-denialists who rest their case on a misunderstanding of the meaning of 'theory' in scientific contexts, and worse, reporters who give such misunderstandings anything approaching equal time.

And here we come to one of the great gaping inadequacies of the journalistic profession, namely its dearth of practitioners who actually know anything about science. If there were some, for example, how does one explain the career of Gregg Easterbrook? The most revealing datum in An Inconvenient Truth, in my mind, was not so much the extent to which current and projected atmospheric carbon dioxide levels dwarf anything in the prior history of the earth, but the fact that, while the conclusion that global warming is real and human-caused was unanimous in peer-reviewed journals, opinion was split about 50-50 in the popular press. Small wonder terrorism is supposed to be our biggest threat.