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Math Science

A Unified Theory of Animal Locomotion 229

Posted by ScuttleMonkey from the how-much-wood-can-a-woodchuck-chuck dept.
Roland Piquepaille writes "You probably already know that there is a master equation for all life processes based on metabolism. Now, physicists from Duke University have applied the so-called 'constructal theory' to explain how running, flying and swimming modes of locomotion are similar even if they're apparently unrelated. This single unifying physics theory explains how fast animals get from one place to another and how rapidly and forcefully they step, flap or paddle in relation to their mass. In other words, these scientists argue that the characteristics of animal shape and locomotion are predictable from physics."
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A Unified Theory of Animal Locomotion More

A Unified Theory of Animal Locomotion

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  • Real animals only (Score:3, Funny)

    by MarkusQ ( 450076 ) on Monday January 02, 2006 @10:37PM (#14381831) Journal

    the characteristics of animal shape and locomotion are predictable from physics

    They must be using real animals only. I know for a fact that the Pegasus's shape (to cite just one famous example) isn't predictable from physics.

    --MarkusQ

  • Roland Piquepaille (Score:5, Interesting)

    by Anonymous Coward on Monday January 02, 2006 @10:38PM (#14381833)
    Roland Piquepaille and Slashdot [slashdot.org]

    • Re:Roland Piquepaille (Score:2, Funny)

      by Anonymous Coward

      In related news, scientists also discovered the unified theory behind the ratio of Roland Piquepaille accepted articles to submissions. Applying the so-called 'covetousness theory,' these scientists developed the formula describing the miraculous amount of articles from a single submitter, regardless of merit or ripped-off content. The answer, contrary to popular belief is not 42 but rather one. This ratio therefore implies that every article submitted has been and will be accepted. The reasons for this

    • My guess is that Roland is an alter ego of a /. staffer, or a /. staffer's buddy, and that /. staffer is getting kickbacks.
    • What YOU can DO:

      1. Mark rpiquepa [slashdot.org] as foe.
      2. Send mail to CowboyNeal (Jonathan Pater) complaining about Roland Piquepaille [mailto].
      3. Profit!

    • Re:Roland Piquepaille (Score:4, Insightful)

      by ajs ( 35943 ) <ajs.ajs@com> on Tuesday January 03, 2006 @07:39AM (#14383474) Homepage Journal
      I'll point out that the primary concern that you cite in your journal is that this guy is driving traffic to his site instead of to the sites of the source information, and yet this article's primary link goes directly from Slashdot to Duke University.

      It's sad when a canned reply that consists of a single link to an off-topic journal is modded up to a 5. Makes me think of the days when anti-Katz postings would be modded through the roof for no particular reason other than spite.
  • This is question I have asked my daughter from time to thing about... Are Bird and Fish the same or different?

    This article starts to show that yes they are.

    For me thought the answer is yes they are. They both can move 3 dimentally in they fuild mediums... Air and Water. Just one is just more dense then the other.

    Best example of this is Penguin. They "fly" in water.

    • Re:Swimming Fish = Flying Bird? (Score:5, Funny)

      by Anonymous Coward on Monday January 02, 2006 @10:46PM (#14381856)
      Yes, they are the same or different. I could have told you that without a research paper.

    • Re:Swimming Fish = Flying Bird? (Score:5, Insightful)

      by Murphy Murph ( 833008 ) <sealab.murphy@gmail.com> on Monday January 02, 2006 @10:47PM (#14381862) Journal
      Forget the penguin for a moment.

      Are birds buoyant in their fluid?
      That right there is a big difference.

      • Re:Swimming Fish = Flying Bird? (Score:2, Insightful)

        by Anonymous Coward
        Of course they are, just not nearly enough to stop them from plummeting downwards.

      • Re:Swimming Fish = Flying Bird? (Score:5, Funny)

        by dsanfte ( 443781 ) on Monday January 02, 2006 @11:00PM (#14381913) Journal
        You have obviously never hooked a bird up to a tank of hydrogen. I assure you, they're quite buoyant before they explode.
      • Are birds buoyant in their fluid?
        That right there is a big difference.

        The article explains that swimmers still have to fight gravity proportional to their body size, because the water they push out of the way while swimming effectively raises the surface of the fluid. I don't know that I entirely understand this, but that seems to be the authors' argument that it isn't such a big difference at all.
        • Look at it this way:


          |
          |
          |
          #
          |

          Say the | is water and the # is a fish. Now let's assume (this simplifies the situation, but it is still quite accurate) that one | weighs the same as a #. Now consider that somehow that system moved on to this state:


          |
          #
          |
          |
          |

          There is no energy difference between the two systems. The only thing the fish had to work against was friction (and building up his own inertia). He doesn't fight the gravity of the water--well he does but for each bit he fights he is pushed up by an equivale
          • I don't disagree, but the article does -- it devotes seven (short) paragraphs to saying that in the process of moving between states (or just moving forward), the fish actually has to raise the water level. I think it's saying that when a fish pushes itself from point x to point y, the water it displaces from y doesn't just zap directly into x, but actually moves upward against gravity. The linked article doesn't attempt to explain the researchers' evidence for this, so I don't think there's much room for
        • Have you seen images of submarines where they still cause a bit of a bow wave when slightly submerged? Pushing against the water in front creates a bit of a ripple, and even though the total volume of the water is the same, part of it is at a raised height. Due to gravity, this ripple requires some energy that has to be exerted - just like the bounce in running.

    • Re:Swimming Fish = Flying Bird? (Score:4, Informative)

      by Ruff_ilb ( 769396 ) on Monday January 02, 2006 @10:48PM (#14381868) Homepage
      As far as I'm aware, fish have gills and lay squishy (scientific term) eggs, while birds lay solid eggs and have lungs. Birds also have feathers, and I'm not aware of any feathered fish.

      And heck, if you're going to define our atmosphere and our ocean as a fluid medium, then you're saying that ALL animals are the same - name a single animal that travels through a completely SOLID medium.

      • Re:Swimming Fish = Flying Bird? (Score:5, Funny)

        by BorgCopyeditor ( 590345 ) on Monday January 02, 2006 @11:03PM (#14381925)
        name a single animal that travels through a completely SOLID medium

        The Horta [ericweisstein.com]?

      • Penguins don't have feathers and they are birds. Just something to think about there ;)

        And worms travel through a solid medium!
        • See what I said earlier: "Moles and related animals create holes in the solid medium to move through - they don't travel through the solid medium, they make room for them to travel and then they travel through the empty room."

          Even if you don't buy that, the medium becomes a liquid by definition if the earthworm/mole/whatever can move through it. I know what you're thinking: "But dirt isn't a liquid!" - True, but earthworms couldn't move through dirt if it were JUST dirt, i.e. no air. The air allows it to ac

        • Re:Swimming Fish = Flying Bird? (Score:4, Informative)

          by 1u3hr ( 530656 ) on Tuesday January 03, 2006 @12:13AM (#14382153)
          Penguins don't have feathers

          Penguin FAQ [penguin.net.nz]
          "Penguin feathers are short, overlapping and densely packed. The outer part of the feather is waterproof while the inner down section traps an insulating layer of air, keeping the penguin warm in the sometimes freezing water."

      • And heck, if you're going to define our atmosphere and our ocean as a fluid medium, then you're saying that ALL animals are the same - name a single animal that travels through a completely SOLID medium.

        You're missing the point. He's not saying they're related because they move through fluids, he's saying they're related because they have three dimensional control of where they are.

        And to some extent, that is something exclusive to them. Land animals have to do a lot more work than them in order to move in
        • That is a good point - it makes me wonder how much dynamic 3d control an average bird, say, a swallow (That is, an unladen, European swallow) can exercise as compared to say, a goldfish.

          How would one measure that, anyway?
          • My somewhat educated guesses are as follows:

            1. In general, I'd say fish have more control than most birds
            2. Fish can pretty much stop if they like and move very little; almost no birds can (I think the hummingbird may be the only one able to hover)
            3. Birds can dive very quickly because they have gravity to assist them; fishs' climb and descent speeds will be a lot more equal
            4. A fish needs to expend energy to move forward; some birds have very very high glide ratios and can soar for quite some time while ra
            • So it basically comes down to density and coef of viscosity, no?

              And what if we're comparing a fish to a bird to an earthworm or a mole?

              Could we say

              1. In general, I'd say fish have more control than most birds, but less than moles
              2. Fish can pretty much stop if they like and move very little; almost no birds can (I think the hummingbird may be the only one able to hover), but moles can stop dead whenever they like
              3. Birds can dive very quickly because they have gravity to assist them; fishs' climb and descen
              • It does seem like there's a qualitative difference in how they move. You yourself argued in other threads [slashdot.org] that the motions of a bird and fish are different than a mole, because the latter digs. I would add to your distinction the observation that the holes left behind by a mole are permanent in the short term, while the "holes" behind the bird and the fish refill pretty much instantly.

                You can take this point further and say that once a mole digs out a nice house, almost all his motion is constrained to the
        • Land animals have to do a lot more work than them in order to move in anything but the "plane" of the Earth.

          But they can still do it (for instance moving down through the ground can be easier then moving up, but in some cases it can be easier to move up then down, and near cliffs or other walls it is just as easy to move up or down, then it is to move forward or side to side).
    • Stingrays "fly" in water too (I mean the larger kind that have "wings", not the smaller ones that look like fish frisbees). They are very interesting to watch. They're also very curious...they don't act like fish at all. They act more like puppies than fish actually.
    • This is question I have asked my daughter from time to thing about... Are Bird and Fish the same or different?

      Enjoy that playful moment while you can, for one day the question will be about the Birds and the Bees, at which point you'll want to quickly say "Game Over" and pretend the lawn needs mowing.
    • No. Fish receive most of their vertical support from hydrostatic buoyancy; if a fish doesn't move a muscle, it will neither rise nor sink very quickly. All the muscular energy it expends goes into overcoming the drag that resists its forward movement.

      Birds have to expend some energy just to stay aloft, plus more to travel. If a bird doesn't move a muscle, assuming it's holding its wings in the gliding position, it will continuously lose altitude. Its drag has two components: parasite drag which resists it

    • Are Bird and Fish the same or different? This article starts to show that yes they are.

      Is the meaning of your comment easy or hard to decipher?

      I'd say that yes, it is.

    • As another poster pointed out, fish are boyant in water. They take advantage of this through an organ designed to control positive and negative boyancy (gas bladder). They use it to ascend and descend in depth without swiming. That's quite a major part of how fish move in water that's vastly different from how birds fly.

      That's not to say that fish and birds aren't similar in how they move through fluids, but to say they're the same is a vast misunderstanding of fish and birds.

    • [Ahem]

      I have to type in some non cap letters here, otherwise the server won't let my quote pass. It is not my fault it's all in caps. That's the way it was written the first time!

      So, without further ado, the quote, courtesy of that haven of IRC gems, bash.org:
      YES IS NOT AN ANSWER TO "A OR B?" [bash.org]

    • On a similar vein are all fish rear wheel drive?

      I know on the land animal front most are, with exceptions such as the elephant (4-wheel drive) and the hyena (I believe has a strange and unique front wheel drive motion).

  • Science gibberish (Score:5, Funny)

    by Piroca ( 900659 ) on Monday January 02, 2006 @10:42PM (#14381845)

    these scientists argue that the characteristics of animal shape and locomotion are predictable from physics

    I wonder who could expected the outcome to be the other way around.

    • I for one did indeed expect that physics would be predicted by characterics of animal shape and locomotion :)

    • Re:Science gibberish (Score:5, Funny)

      by jackb_guppy ( 204733 ) on Tuesday January 03, 2006 @12:00AM (#14382120)

      I wonder who could expected the outcome to be the other way around.

      Intelligent Design?

  • and how rapidly and forcefully they step, flap or paddle in relation to their mass.
    Can't we do that already, as in... Oh look, the animal weighs 100 lbs and has two legs on the ground at any given point, so each leg has an average of 25 lbs of force on it?
    • "Can't we do that already, as in... Oh look, the animal weighs 100 lbs and has two legs on the ground at any given point, so each leg has an average of 50 lbs of force on it?"

      *Fixed*

      Sorry.
      • Okay, that's find and dandy until they move. Now, as you run, what are the various stresses that your leg endures? Is there any point at which your full weight is on just one foot? More than your full weight? Is there any point it which there is almost no weight on a foot? What is the range of weights? How 'bout for a bird's wings? How much does a bird have to flap its wings in order to hover (for birds that can) in relation to the range of fores on the wing? Fly forward? What about for a fish?

  • Wow, I never would have guessed that you could predict the charactaristics and shape of an animal by the physics. When's the last time you would have guessed a bird was shaped like a cube? Or maybe a fish shaped like a donut? I hardly think it is amazing that you can predict the shape of an animal from it's physics. But hey, maybe these guys don't get out much...

  • Some robot guys already discovered that (Score:4, Insightful)

    by Anonymous Coward on Monday January 02, 2006 @10:48PM (#14381867)
    Robotics researchers already knew that something like 'animal' locomotion could be implemented based on the principles of physics. ie. given the right mechanical setup, locomotion is almost automatic and takes no supervision by a computer.

    Actually, it's what you'd expect. Animals would naturally evolve to move in an efficient manner. It would give them an evolutionary advantage. What the bleep did these guys expect?

    www.sciencenews.org/articles/20050806/bob8.asp
    • Actually, it's what you'd expect. Animals would naturally evolve to move in an efficient manner.

      I be they were pretty funny to watch before they started moving in an efficient manner.

      Watching my dog chase its tail gives me a glimpse of what it must have been like.
      --
      Q

    • Famously, Pixar's first film Luxo Jr is based on the same principle. They set up the armature, and then did a global optimisation process to minimise the energy expended for the lamps to hop around.

      (BTW, for the would-be pedants present: André & Wally B was not technically a Pixar film, since it was made while everyone was still at Lucasfilm.)

  • It is the same thing, swimming through a liquid, just many orders of magnitude different in viscosity.
    • It is the same thing, swimming through a liquid, just many orders of magnitude different in viscosity.


      I'm no physicist, but intuitively I'd think that the fact that air is compressable (and water is not) would have some effect on the process...

    • From TFA, the point was that most motion involves:
      1) A vertical gravity component (the bounce in running or the lift/glide in flying)
      2) A horizontal motion/friction component.

      At first glance, swimming only has #2, but they realised that in swimming the fish has to displace some water as it moves. The sides and bottom of the water body are constrained (lake etc), however the top is not, so a slight ripple on the surface is crated. This may be inpercievable as it can be spread out over an entire lake, but i

  • "From simple physics, based only on gravity, density and mass, you can explain within an order of magnitude many features of flying, swimming and running," added James Marden, professor of biology at Penn State. "It doesn't matter whether the animal has eight legs, four legs, two, even if it swims with no legs."

    I'm pretty sure that my own running speed is within an order of magnitude of almost anything with legs, regardless of its mass. That leaves a lot of biological interest within these simple physical

  • DURR (Score:5, Funny)

    by ClamIAm ( 926466 ) on Monday January 02, 2006 @11:07PM (#14381942)
    This single unifying physics theory explains how fast animals get from one place to another

    Well if they're fast animals, and they're going from one place to another, perhaps they do it by moving quickly? Ever considered that?

  • For doing software simulations of walking creatures or robots, I've used the Yobotics Simulation Construction Set [yobotics.com]. It's reasonably easy to get started, given the complexity of physics simulations. Also, they have a free trial download, so it's great if, like me, you just want to play around.
  • Science fiction writers! Yes, SF writers, never again hand me your alien in the form of a flaming flying football, or a man crayola'd green with spikes taped to his ears, or an 80-ton katydid. If you have one of those, it belongs in the *fantasy* section. In science fiction, I should be able to picture the whole chain of evolution for the species, and if it's sentient, I should be able to marvel at it's natural design and be able to appreciate how it must have become the dominant species on it's planet.

  • Dinosaurs (Score:2, Interesting)

    by samkass ( 174571 )
    I'm curious what his equations would reveal about dinosaur locomotion. I've seen a lot of people claim that dinosaurs could never move under today's Earth gravity, or that pterodactyls could never fly. Wouldn't this guy's equations tell us not only whether or not they could, but how fast they'd likely travel and what they're walking, swimming, and flying capabilities might have been?

    • Re:Dinosaurs (Score:3, Insightful)

      by Stevyn ( 691306 )
      Gravity? I could understand if the atmosphere was thicker back then it may help the pterodactyls fly, but how was the gravity different? I'm not saying you're wrong, I've just never heard of this idea.
      • I remember this assinine theory. A couple years ago there was a /. story, one of the precursors of the torrent of shit science we see today, about some "respected" professor who believed that gravity on earth was somehow weaker in the past. I don't recall if he had any theories for why on his website (Did the gravitational constant suddenly change? Did earth's mass increase dramatically? Nothing makes sense), but the real gem was the way in which he inferred this, and even better defended it.

        There was so
    • but this could give more insight into what the muscles would have to look like to power the size frame.. draw better pictures or learn more abou how they lived. you can get close looking at other animals, but more info is always better.

      The "REAL" reason this is newsworthy right now is that Will Wright has been putting serious inquery into just this thing for his next game Spore. One of the hooks of that game is defining general geometry of a creature an letting the computer figure out what it's supposed t

  • And here we go again: another rule of thumb and back of the envelope calculation that biologists used to perform anyway gets reified and turned into a fundamental theory.

    This is, perhaps, is the most universal law of the 21st century: ideas that didn't use to count as sound scientific theories or engineering principles have become acceptable as such.

  • Giant ant overlords are scientificly impossible? (Score:3, Insightful)

    by craXORjack ( 726120 ) on Tuesday January 03, 2006 @01:38AM (#14382455)
    "Our finding that animal locomotion adheres to constructal theory tells us that -- even though you couldn't predict exactly what animals would look like if you started evolution over on earth, or it happened on another planet -- with a given gravity and density of their tissues, the same basic patterns of their design would evolve again," Marden said.

    So giant ant overlords could only evolve on a planet with less gravity or intense pressures? Or maybe have bouyancy like at the bottom of our oceans. Maybe we should worry about giant lobstermen.

    I would like to know how this applies to humans in space. Will I somday be able to fly under my own power in a lunar gymnasium like in an old Heinlein story I once read?

  • Take that, arrogant scientists (Score:3, Funny)

    by 0xdeadbeef ( 28836 ) on Tuesday January 03, 2006 @10:09AM (#14383980) Homepage Journal
    You have finally proven what God knew all along. Could a random process be self-optimizing? This is yet more proof of His infinite wisdom.

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