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Attack of the alien robot tripods

Q. You may be on the wrong track with your objection to the three-legged aliens in "War of the Worlds," when you write, "Three legs are inherently not stable." Amateur carpenters are advised to build three-legged stools rather than four-legged stools. Why? Because, even if the seat is not level, all three legs will be in contact with the surface.

The real problem with the machines in the movie is that they have a very high center of gravity, so high that any rapid locomotion is likely to tip them over, especially when they stop or change direction. Mike Barnas, Chicago

A. Seeking an expert opinion, I contacted Jessica Banks, a Ph.D. candidate at the MIT Computer Science and Artificial Intelligence Lab, whose thesis involves a robot with one point of contact. She consulted her colleague Dan Paluska, a Ph.D candidate at the MIT Media Lab, an expert on robot-legged locomotion, who was featured on the cover of Wired magazine.

They began by pointing out, "Your comment, 'If evolution has taught us anything, it is that the limbs of living things, from men to dinosaurs to spiders to centipedes, tend to come in numbers divisible by four' is wrong and misleading. Numbers of limbs are divisible by two, due to the principle of bilateral symmetry to which nature adheres."

I meant of course to write "two" instead of "four" but was attacked by a brain cloud. My online review has been corrected. Banks and Paluska continue with a fascinating discussion of the functions of three legs among both living and mechanical creatures, which I am printing in full on Here are some bullet points:

  • "A three-legged chair or table is very stable when it is still. However, the answer isn't so easy when one considers three-legged locomotion. Things have a right and a left, a front and a back. This has to do with the fact that animals tend to travel in a certain direction, facing forward when doing so. Having an even number of legs allows animals to be balanced as they travel forward."
  • "There is a rhythm to walking and running that may be difficult to achieve with a three-legged machine. A kangaroo is the closest thing to a three-legged animal because it uses its tail. However, its tail is not the same as its legs and the tail does not touch the ground when the kangaroo is hopping."
  • "The argument that nature didn't 'come up' with such a creature doesn't hold much water. Nature didn't come up with the wheel for locomotion, either. We could, for instance, imagine a three-legged creature that stood still and upright for the vast majority of its life. However, it would be hard to imagine such a robot being efficient at locomoting over any significant distances."
  • "The height of the tripods and the fact that they are top-heavy makes it plausible that one would fall if one of its legs was damaged, especially if the alien was in motion at the time of injury. This doesn't really say that much, though; considering the fact that if you were to kick one of my legs while I was running or even give it a forceful unexpected blow when I was just loitering about, I would most likely fall to earth as well."
  • "So who knows if it is practical or not for a robot to walk on three legs? Ultimately, it would all depend on the system as a whole (speed, passive stability, simplicity, energy consumption, navigability, human-exterminating-ability, etc.), the available technologies (sensors, computation, actuators, etc. ), the environment in which the robot was supposed to perform, and, well, who was funding it."

  • Q. I am disappointed that you have not actually read The War of the Worlds by H.G. Wells. If you had read it, you'd know all the answers to the questions you posed. George H.W. Bush, Norman Schwarzkopf, George W. Bush and Karl Rove did not invent the strategy of "shock and awe" to cow your enemy -- Wells did, and they stole shamelessly from him without knowing this either.

    The aliens have a whole strategy of invasion, capitulation, domination, colonization, Martian-forming and domestication of Earth. Humans are ancillary to their plans and quite inconsequential. Wells' book is quite remarkable. It's the first literary treatment of the hostile indifference the universe, which points up our own relative insignificance, literally played out in the Martians' callous annihilation. You seem to have missed this. Kevin Mequet, San Jose, Calif.

    A. I did read the book, when I was 10. But if the explanations aren't in the movie, they aren't relevant, because the movie creates its own closed system.

    Q. Are the couple standing on the mother's stoop in Boston, at the end of "War of the Worlds," Gene Barry and Ann Robinson, the leads from the 1953 version of the movie? Tony McFadden, Singapore

    A. Yes.

    Q. I was pleased and disappointed to read your assessment of silent film comedian Harold Lloyd in your latest Great Movies installment; pleased by a piece on the neglected Lloyd and disappointed you didn't treat the great comic more favorably. It is tiresome to read another lament over Lloyd's inferiority to Chaplin and Keaton, especially when you admit that you had never seen a Lloyd film until "Safety Last."

    You fault Lloyd for his "ordinariness," yet fail to note that Lloyd's naturalistic characterization was a big first for film comedy, and paved the way for hundreds of romantic comedies to come. Or that Lloyd's feature films combined the emotional resonance of Chaplin with the cinematic virtuosity of Keaton.

    It was none other than Orson Welles who lobbied for Lloyd's genius years ago: "Harold Lloyd -- he's surely the most underrated of them all. The intellectuals don't like the Harold Lloyd character -- that middle-class, middle-American, all-American college boy. There's no obvious poetry to it, and they miss that incredible technical brilliance. ... Someday he'll get his proper place -- which is very high."

    I envy you. You have many Harold Lloyd films ahead of you, and Lloyd has many tricks up his sleeve to surprise you with, whether in the formal cinematic beauty of "The Kid Brother," the uproarious surrealism of "Why Worry?" or the sheer crowd-pleasing fun of "The Freshman." I urge you to watch these comedies with an open mind. Let Lloyd's brilliance come to you on his own terms. Yair Solan, Brooklyn, N.Y.

    A. So I will. The Lloyd films were very hard to see for many years, and are now in national release in art and repertory theaters in preparation for DVD editions.

    Q. People seem to be blaming the movies for the slump in the box office this year. I feel it's the actual experience of going to the theater that makes people stay away. When I saw "War of the Worlds," the projection was slightly off and fuzzy, and certain scenes weren't framed properly. That was nothing compared to the theatergoers who were talking and directing glib remarks to the screen. One answered his phone and started talking loudly.

    Going to the movies is my favorite thing in the world. But now incidents like that happen about four out of five times I go. Isn't there anything theater chains can do to promote quiet screenings and make going to the movies fun again? Mark Donahue, Philadelphia

    A. I've received a lot of feedback just like yours. People are also angry at the commercials they're forced to sit through. I've heard from people who now mostly attend "art theaters," not because they dislike commercial films, but because they know the audience behavior will be more appropriate.

    Q. The animated feature "Madagascar" has two illogical scenes where the male lion gets kicked from the front between his back legs and doubles over like a man kicked in the testicles.

    Problem: A male lion, like all cats, has his testicles located on his back side, and there is no way they could be kicked by standing in front of the lion, who is "rampant" on his hind legs. I suspect that you noticed this error, but were too politically correct, or lacked the cojones, to point this out in your review of the movie. Michael L. Stoianoff, Anchorage, Ala.

    A. Just ignorance on my part, actually. This info could be a life-saver.

    Roger Ebert

    Roger Ebert was the film critic of the Chicago Sun-Times from 1967 until his death in 2013. In 1975, he won the Pulitzer Prize for distinguished criticism.

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