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Space

Playing Ball in Space 302

Posted by CmdrTaco from the hail-mary-2010 dept.
oo7tushar writes "Although most experiments in space seem simple they have profound results. Take this for example, astronauts trying to catch a ball in space. What's so hard about that? Nothing much really, down here on Earth. In space it's a completely different story. Here on earth our eyes see the ball and our brain anticipates it's movement according to gravity. In space the brain continues to anticpate gravity but unlike motion sickness (which is adapted to within days), astronauts continue to anticipate the path of a ball for 15 days (after which they start to show progress). What are the ramifications? The brain must have some sort of internal gravitation model."
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Playing Ball in Space More

Playing Ball in Space

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  • Constants (Score:3, Funny)

    by Jouster ( 144775 ) <slashdot@angel[ ].com ['faq' in gap]> on Tuesday March 26, 2002 @11:18AM (#3228207) Homepage Journal
    But is it 9.80 m/s/s or 32 ft/s/s in our heads?

    Jouster
    • Your brain does not have really have all the information it needs (posititon of the object, current velocity of the object, etc) in numeric form to make precise calculations on the fly. It's probably more of something the brain sees, makes an educated guess about, and fine-tunes that guess as it gathers more information about the event it is seeing.

      Or were you asking whether or not our brain thinks of it in imperial units (e.g. the right way), or metric units (e.g. the wrong way)? ;)
      *ducks an angry barrage of balls being thrown at him*

  • Just like... (Score:5, Informative)

    by niftyeric ( 467236 ) on Tuesday March 26, 2002 @11:19AM (#3228220)
    this [slashdot.org] article. Oh well..
    • This article [newscientist.com] talks about the experiments where people do things like wear mirrored goggles that reverse vision, or flip vision upside down. All the experimentation done so far says people can adjust in about one month. And vision is something that we have done every day, all day, since early life. If we can fix that kind of stuff, catching a ball seems easy as well.

    • ...where the 5th Doctor (Peter Davison) is floating outside a huge spaceship, trying to get to the TARDIS hovering nearby. He's somehow lost his momentum (this is bad physics, unlike what follows).

      His solution: he pulls out a cricket ball, throws it at the spaceship, and catches it on the rebound. Voila...thrust. He drifts on to the TARDIS, and all is good.

      Hey, it's really not off-topic if you think about it.

  • the Guinness effect (Score:5, Funny)

    by tongue ( 30814 ) on Tuesday March 26, 2002 @11:20AM (#3228224) Homepage
    Does that explain why a dozen pints of guinness seems to amplify earths gravity to the point that I can't pick myself up off the bar or floor?

  • Nothing special... (Score:4, Insightful)

    by tom_newton ( 179430 ) on Tuesday March 26, 2002 @11:21AM (#3228227) Homepage
    about us having a "gravitation model" in our heads.
    Surely it's just called "experience"?
    • I would think that the reactions would be based more off of observed behavior and experience than a "hard wired" instinct. It would be interesting to do the test on young children who have the motor skills but do not have the experience level of the adult participants.
    • right...probably related to "muscle memory"... ever try to type at a new keyboard...where the keys might be just slightly misaligned compared to your ol' betsy that you've been using for years?

      Singers also have a type of muscle memory that helps them approximate accurate pitches. I'm not talking about perfect pitch, but perfect relative pitch...it seems logical that, after years of catching a ball in earth's gravity, you continue to react as you had been conditioned to on earth.
    • I agree.

      It's been long known that the cerebellum, those two lobes at the back of the brain, is where complex motions are learned and "hard wired." My neuroanatomy professor expressed his awe at how well our brains can learn exactly how far to swing and where to grab, or precisely how to swing a bat, or balance on ice skates... and all without conscious control. It's done mostly in the cerebellum, and is established only through practice, practice, practice.

      Now, when it comes to catching a ball, that's something that a child learns early in his or her life, and it is generic enough that we get lots and lots of practice, so it becomes very firmly entrenched. No wonder it's hard to "unlearn."

      This experiment proves nothing except that our brains are adapted to learn and adapt further. It would have been better if they had taught the astronauts a new skill a few weeks before launch, and then measured how quickly they could relearn it after arriving on station.

  • What a bunch of crap (Score:3, Insightful)

    by yatest5 ( 455123 ) on Tuesday March 26, 2002 @11:23AM (#3228238) Homepage
    What are the ramifications? The brain must have some sort of internal gravitation model."

    Er, no, maybe it has some capacity to learn the way things move, which surprisingly, after 30-odd years of the same observed behaviour, proves a little hard to unlearn.

    The ramifications? Well, people are going to, like have to, like, train for the new environment! Quick, call the cops!

    • I agree completely - it's a little stupid to expect decades of muscle memory to change within 15 days. Frankly, I think the real lesson is that it only takes 15 days for such massively ingrained learning to start being corrected!

      Sure, they learned to deal with naseau within 3 days - that's 72 hours of constant, unremitting weightlessness, awake and asleep, that they are adjusting to. I'll bet the 15 days of playing catch was more like 15 or 30 hours, spread out over the two weeks, so there's no comparison.

    • You beat me to it -- in fact, you used the exact subject I was going to use. :)

      Try throwing a ball to a small child and see how naturally they compensate for gravity.

      Sheesh, if you ever doubt that scientists follow the same idiot/smart ratios as the general population, take a look at something like this.

      • You beat me to it -- in fact, you used the exact subject I was going to use. :)

        I think it's because our brains have some form of 'slashdot post subject writing model' - the fact we both came up with the same idea *proves* it :).

    • Re:What a bunch of crap (Score:5, Funny)

      by JordanH ( 75307 ) on Tuesday March 26, 2002 @12:04PM (#3228529) Homepage Journal
      • The ramifications? Well, people are going to, like have to, like, train for the new environment! Quick, call the cops!

      A much more serious ramification is that researchers are noting that children exposed to gravity seem to have a much greater facility with walking down staircases than those who aren't. It's a mutation!

    • Exactly. I doubt the brain is doing any complex calculations simply just taking into account the thousands of other times it's seen projectiles and guessing based on that data where this one is going to go. I've been trying to teach my young children to catch for years and they still have trouble figuring out where the ball's going to go every time. They simply don't have the experience to pull from in every case yet.

    • Er, no, maybe it has some capacity to learn the way things move, which surprisingly, after 30-odd years of the same observed behaviour, proves a little hard to unlearn.

      Sounds reasonable, but I think you're wrong.

      I recall reading (sorry, no cite due to faulty memory) that we don't have to learn to catch; it comes automatically as soon as we can control our limbs properly. Sure, we get better with practise, but we can do it without.

      It was assumed that this was due to our "excellent" hand-eye co-ordination, but this experiment seems to show that instead we're predicting the motion in a gravity field. It shouldn't have taken 15 days for the astronauts to learn to adjust if they were really following the movement of the ball.

      An example given in the brief article was that a baby placed on a glass table became distressed even though it should know it was going to fall.

      The guy doing the experiment is a neuroscientist. I think he would have considered the simpler explanation first, don't you? Just because the article doesn't give a complete account doesn't mean that work wasn't done.
      • It was assumed that this was due to our "excellent" hand-eye co-ordination, but this experiment seems to show that instead we're predicting the motion in a gravity field. It shouldn't have taken 15 days for the astronauts to learn to adjust if they were really following the movement of the ball.

        You are jumping to conclusions there. Even if you are right about the ability to catch being inherent rather than learned (I have doubts that it is. Don't believe everything you read.) it would have little bearing on this experiment. To test what you claim is true, you would need to have people who have not been catching under earth's gravity for the past X years try to catch in zero G. It is entirely possible that catching is inherent, yet because these scientists have been exposed to it for so long, they have also learned what to expect, and that may be why it took them longer to re-learn to catch. Someone with no experience catching under gravity may have been able to learn it more quickly.
    • The ramifications? Well, people are going to, like have to, like, train for the new environment! Quick, call the cops!
      Wish I had some mod points - this comment nails it (so to speak).

      My thought is that there must be an amazingly powerful adaptive learning mechanism built into the brain if it can reprogram itself to compensate for zero G (no, I won't say "microgravity". Nor "Shuttle" without an article, nor "liftoff" instead of "blastoff". Take that NASA!) trajectories in 15 days. I started playing catch with my boys when they were 8 months old or so - something burned in that deep and the brain can still adapt. Amazing.

      sPh

  • Encoding Specificity (Score:4, Interesting)

    by Transient0 ( 175617 ) on Tuesday March 26, 2002 @11:24AM (#3228246) Homepage
    An internal gravitation model would be theorizing far more than is necesarry to account for the data. In cognitive science, there has long been an understanding of encoding specificity. This simply means that data, including skill knowledge, is best retrieved from human memory under the same conditions which it was learned.

    An example from the real world is underwater welding. When underwater welders were first being trained, the companies tried to simply train professional welders in all the ways that underwater welding was different from normal welding. But, in diong this, they found that when they were underwater, the welders had serious trouble calling on those skills which supposedly transferred over unchanged. As a result, they had to be entirely retrained in skills they had apparently already learned.

    Similarly, if you lose your keys while you're stoned and then can't find them the next day. Psychological evidence shows that your best chance to find them is to get stoned again and then look for them.

    Any number of other controlled psychological experiments have been performed to domonstrate this same effect(memorizing words under different lighting conditions, etc.). I don't see why gravitation would be any different.

    • Re:Encoding Specificity (Score:4, Interesting)

      by sunhou ( 238795 ) on Tuesday March 26, 2002 @11:48AM (#3228426)
      Re: learning welding underwater -- when I visited Australia, driving was a somewhat similar experience (driving on the opposite side of the road from what I was used to).

      At first, it was hard because everything was the opposite of what I knew. But within a few days, I simply learned to reverse my innate responses, since I knew that those responses were backwards, and so it got easier. But after a couple of weeks, I had started to get accustomed to the new configuration, and so some of my natural responses were correct. That meant I could no longer just "do the opposite of what felt natural", and it actually got harder again and took more thought; I always had to think "is my gut feeling about what to do an old gut feeling from the US, or a newly acquired gut feeling from the past couple of weeks in Australia?"

      I was there for about 4 or 5 weeks. When I got back to the US, within a day, I promptly drove on the wrong side of the road. (It was a small road with no traffic, so fewer cues, and I did catch myself within a few seconds before causing any major havoc.)
    • An internal gravitation model would be theorizing far more than is necesarry to account for the data. In cognitive science, there has long been an understanding of encoding specificity. This simply means that data, including skill knowledge, is best retrieved from human memory under the same conditions which it was learned.

      All true, but how does this apply in this case? If your theory is that astronout fails to remember how one correctly responds to falling balls in space because he has not learned that skill in that environment, that is also theorizing far more than data suggests. Also that theory will have hard time explaining why non-motor skills related to gravity does not suffer likewise in space.

      OTOH, assuming having expectations about how the world and objects in it will behave without resorting to a native bias for that expectations can be easily justified. Under this assumption, astronouts inability to efficiently catch those balls simply results from failure to correctly foresee how objects will behave, gravity-wise. They learn slowly because of a negative interference from long term behavior they enjoyed on Earth. They relearn in Earth's gravity quickly because of the experience's deep roots from childhood.

      But this is also a simple to understand layman's theory, requiring no expansive speech to express. So I understand why it is unpopular among us, the cognitive scientists.

  • Or... (Score:3, Interesting)

    by ruiner13 ( 527499 ) on Tuesday March 26, 2002 @11:24AM (#3228247) Homepage
    It could be that a baby born in space would not have such models. I'm guessing that is a learned response of the brain, not an inherited one. I took a Psychology of learning class in college once, and i learned many interesting things. For one, spacial perceptions depend a lot on the environment in which you are raised. For instance, if you live in a rectangular type house, you can generally make good guesses as to the dimensions of other rectangular shaped rooms. If you bring that person into a round room, the estimations are way off. It works in reverse, too. If you live in a round hut your entire life, you won't be able to make good guesses about rectangular rooms. Seems kinda analogous to the gravity story. I say we get some randy astronauts to give birth on the space station, and kinda have a truman show in space. We'll see how that baby will catch a ball then.

    • Re:Or... (Score:2, Interesting)

      by Shalda ( 560388 )
      There is really no question that this is a learned response. However the article belies a basic understanding of how atletic actions work. Most notably, when you catch a ball, you don't actually look at the ball as you catch it. You anticipate the path of the ball and keep your gaze steady.

      This is further complicated by the lack of gravity. You move your arm and it torques the rest of your body out of position and throws off your reference frame too. I want to get paid to write stupid papers like that. Oh, wait, I'm getting paid right now...

    • Re:Or... (Score:3, Interesting)

      by Peyna ( 14792 )
      Yeah, reminds me of "The Forest People", by Colin Turnbull. He took a pygmy out of the forest where he lived and up on this mountain, and the guy thought that everything he saw was miniature versions of what they really were. His eyes had never had to look at anything more than 15-20 feet in front of him in the forest, and he had no clue what things looked like when they were that far away.

  • illusion (Score:2, Insightful)

    by alanak ( 451478 )
    isn't this more or less just like another optical illusion. Our brains are "wired" or just merely used to seeing things one way, so when something suddenly goes wrong, our brain simply pretends everything's normal. Internal gravity mechanism? hmmph, just call it millions of years living on a planet with constant gravity.
  • Well, doh! Those astronauts are all-American boys who know how to play ball in gravity. Probably made some sort of ball sports team. Of course they're going to have trouble in zero-gee. They'll have to unlearn all the trajectory compensations they learned in practice. I'd expect someone who who didn't make the team and doesn't know throwing/catching to do alot better. Habits are harder to unlearn than to learn.

  • This means that Quidditch must be an even harder game than I thought.

    Just more kudos to Harry Potter, who can catch that Snitch even though it seems completely unaffected by gravity.

    Now I think would be a good time to propose a Quidditch Module to be added to the International Space Station. Then all the funding countries could make teams and send them up.

  • It's a remarkable parallel to playing the game of badminton. The air resistance of the shuttlecock is much higher than that of a normal ball, so the flight trajectory is not what a person used to playing other games would expect. As a result a novice player has an adjustment period before he can really anticipate where a shot is going to go.

  • Maybe it isn't the gravity... (Score:4, Funny)

    by qurob ( 543434 ) on Tuesday March 26, 2002 @11:26AM (#3228267) Homepage

    Whenever the jocks threw balls at the geeks at school, they never caught them either :)

  • If fluids in the ear are what help us for balance and orientation, why _wouldn't_ it be able to compensate for gravity? Once the nausea has been overcome for lack of gravity, all of your other orientation skills (ie gravitational compensation for prediction of a ball) should follow suit. The nausea stage is where you're body is trying to adjust, I'd assume that the mind is doing the same.

  • but tacos link goes to his home page, insted of his e-mail. Oh well, as long as hits on his web page are more important, then i dont feel guilty about karma whoring.

    http://slashdot.org/article.pl?sid=02/03/18/2055 25 9&mode=thread

  • Or you could read this article... (Score:5, Funny)

    by pwagland ( 472537 ) on Tuesday March 26, 2002 @11:28AM (#3228282) Journal
    also on Slashdot... [slashdot.org]

    And again, I say, so what? It takes the human body a while to accustomise yourself to a new environment, this is hardly breaking news!

    Any SysAdmin who has gone from Solaris to AIX could tell you exactly the same thing! :-)

  • its easy. For anyone who has been totally wasted, you know that all sense of gravity seems to be scewed. That way the only thing working against you is keeping from passing out, and the mental capacity of maybe 1/10th your normal capacity. So other then the fact that when you hurl it won't be as easy to find (It doesn't just go down and hit the ground) You would have a great advantage over everyone else in your allstar baseball-in-space .... right? right?

  • Isaac Asimov used this for a SF story (Score:5, Interesting)

    by Seth Finkelstein ( 90154 ) on Tuesday March 26, 2002 @11:31AM (#3228308) Homepage Journal
    Isaac Asimov wrote a prescient short story [earthlink.net] "The Singing Bell", about this effect. The plot hinges on proving that a man has recently been to the moon, by catching him off-guard in catching something as if he was on the moon (i.e. he had adapted to the lunar gravity in terms of ball-catching). Absolutely great science-fiction story.

    Sig: What Happened To The Censorware Project (censorware.org) [sethf.com]

    • Asimov wrote another cute little short story called "Belief" in which a scientist was able to levitate simply because he believed he could. (I think it first started happening in his sleep, and then he was able to do it awake.)
    • A shame that the Good Doctor wasn't around to hear of this. Anyone who hasn't read his Wendell Urth short stories or his other SF mysteries should hasten to a book store; they're great fun.
      • &ltheresy>I've always found Asimov's novels slow, the characters flat, and the style dry.&lt/heresy> But, his short stories are execellent. The same style that makes his novels tedious make his shorts amazingly satisfying. A science fiction story doesn't need incredible depth of character, it gets by entirely on an idea and its presentation. And Asimov's ideas, I won't deny, were truly excellent.

        My favorite story of his, by far, is The Billiard Ball, wherein a scientist kills the engineer who has been leeching off his work for decades by potting a billiard ball through the zero-mass field the engineer has built. Very nice story.

  • This is a really flawed argument. Since every single human they've tested with was conceived, born, and grew up subjected to gravity, a *model* is hard wired?

    I think before he can claim this, we'd need to see the results of testing on space-born and -bred animals.

  • Dogs, calculus, and fetch. (Score:5, Funny)

    by B1 ( 86803 ) on Tuesday March 26, 2002 @11:32AM (#3228324)
    Has anybody else read Dirk Gently's Holistic Detective Agency? (Douglas Adams)

    In one passage, I believe Dirk is explaining that we don't give credit to dogs for their ability to perform complex calculus in realtime.

    For example, when you play fetch, your dog is able to analyze the trajectory and velocity of a thrown ball. Based on his observation of the throw, he solves a complex three-dimensional physics problem involving a system of differential equations based upon the underlying physics. He does this fast enough that he is able to position himself to catch the ball.

    Of course, that's *most* dogs...our dog wasn't so good at catching things. I think he was more of an "arts" dog. :)
    • A Bowwoofwoof cluster of them! :^)
    • ... in one of the "future history" series. I forget which one -- but it was one of the lunar stories. The Rolling Stones? The Moon is a Harsh Mistress? The Menace from Earth? I remember one of his Knockout-Nobel-Laureate-Who-Just-Wants-To-Make-Bab ies women talking about it...
    • I've read that book, and yes, you're correct. That was the first thing that came to mind when I read that article.

      BTW, that series is really good if all you've read of his books is the Hitchhiker series.

  • Eyesight.... (Score:2, Informative)

    by davidfsmith ( 81296 )
    IIRC there is some study about eyesight that seems to think that the brain adjusts within about 2 weeks as well... an experiment was done where people wore glasses that inverted vision, however after 2 weeks the brain had "corrected" this and vision appeared returned to "normal"

    IIRC this also led to the conclusion that babies see updside down for the first 2 weeks of there lives before the brain "fixes" the problem....

    ;-)

    of course i could be making it all up
  • ... and you learn to deal with motion issues later in life.

    This would be especially true with astronauts. A lot of them learned to deal with motion issues as adults during pilot/aviation training in previous careers. For the rest, you learn to deal with motion issues when learning to drive a car or ride a bike.

    Contrast this with learning about gravity and trajectory. One learns to catch and throw at a relatively young age (say 1 1/2 to 3 years old). Such learning is deeply embedded and may well take longer to "unlearn."
  • With people I think it's easy to ascribe this to learning, rather than built-in gravity models. A more interesting example is with animals.

    My neighbor's dog (an Australian cattle dog) is fantastic at catching tennis balls. If you throw one, he can go running, look up over his shoulder, and catch the ball in midair over the shoulder. If you throw farther and he gets there too late, he's very good at knowing where it will go on the bounce and doing a flying leap to catch it off the bounce.

    If we built a little enclosed park with atmosphere on the moon, I wonder how long it would take him to adapt the model in his brain to calculate the new trajectories? (I guess I believe that even in dogs, it's learned -- of course there weren't any tennis balls bouncing around over evolutionary time scales, and probably not a whole lot of birds falling out of the sky and bouncing in parabolic trajectories either.)
  • <imagines the shape of breasts for the colonies of women that grow-up in low grav>

    *homer gurgle*

    (Forgot to escape my symbols :P)
  • Perhaps they did the experiment with the nerdiest batch of astronauts. I can hear the new phrase now... "Ha ha! You throw like an astronaut!"

  • Wha? (Score:2)

    by sporty ( 27564 )
    That doesn't make sense. If someone lob's a ball to me, I can anticipate that it will curve and will land in a certain place.

    If someone pitches a ball at me, then I know its not going to curve as much.

    I play v-ball, if someone spikes a ball, it ain't curving.

    Yes, there is some learning in terms of catching a ball, but I just think those guys up there can't throw/catch.
  • I find it hard to believe that it took 15 days for the astronauts to acclimatize to projectile motion without gravity. Any video game veteran has learned that instinct by interacting with Descent: Freespace, XWing, or even 3D Pong. These video games serve as excellent simulators; the astronauts must have never played any of them.

    If aliens invade, I pray that Defender becomes standard training for our fighter pilots.
    • Video games are a far cry from reality my friend. Pressing some buttons does not equal duplicating the actual physical motion. I agree 15 days seems a lot, but don't compare it to using a joystick.
      • But the researchers are arguing that it's a matter of how the brain predicts motion in a 3D space. The physical training is not supposed to be the issue here. The researchers are blaming the eye part of the astronauts' eye-hand coordination, and that's something that video games can train.

        I'm left with two conclusions, both of which are likely: That this research conclusion is either seriously flawed, or these astronauts have never played video games in their lives. :)
  • The brain must have some sort of internal gravitation model.

    It's not a model, it's just a reaction. You live all of your life under the earth's gravity, so your brain is used to how things react in that system. The brain doesn't come with, or even learn, some sort of function to calculate gravitational effects, the brain just gets used to the way things happen.

    In other words, your brain doesn't see a ball coming at you and do this:
    Ball approaching at 40 mph and presently 12 ft altitude.
    Based on calculations of gravity and wind resistance, ball will arrive at 35 mph and 4 ft altitude
    Move hand to location

    It's more like this: Ball approaching. Based on the millions of times I've experienced this, the ball will arrive at about right here (hand goes into place)

    • "The brain must have some sort of internal gravitation model." -- You live all of your life under the earth's gravity, so your brain is used to how things react in that system.

      Speaking as a neuroscience grad, I'm going to say this once: The second sentence above says the same thing as the first. "Internal model" is a fancy way of saying that the brain will predict the behavior of something. No more, no less.

      In other words, your brain doesn't see a ball coming at you and do this:
      Ball approaching at 40 mph and presently 12 ft altitude.
      Based on calculations of gravity and wind resistance, ball will arrive at 35 mph and 4 ft altitude
      Move hand to location

      Calculations dont have to be in base 10, or involve digits at all, in order to be calculations. Analog computers are still computers.

      It's more like this: Ball approaching. Based on the millions of times I've experienced this, the ball will arrive at about right here (hand goes into place)

      There's a big "at this point, a miracle happens" moment in that sentence. Unless you claim that you can only catch balls that travel in exactly the same trajectory as balls you'e seen before, you're going to need to generalize their behavior a bit. Once you generalize the behavior, you've got an internal model.
  • The article does seem incredibly counter intuitive. The human brain learns through experiance, when learning to play badminton or tennis your brain builds a mental model of how the ball will travel to you.

    IT also builds a mental model of how the ball will travel away from you when struck.

    This just takes exposure and practice. (However I could believe that the brain has developed the ability to learn patterns of motion)

    During our lives we watch leaves fall, we play ball games, we do the thing out of aliens with the knife. All of this allows our brain to predict how things will happen around us.

    Maybe the scientists are right (I really have no educational basis for what I say) but I feel that too often people have a theory, they do an experiment and then merrily claim that the experiment proves the theory. Without exploring the alternatives. (I apologise to scientist types, I do not meen to generalise and I only refer to the "weird" experiments that make it into the main stream press) Cheers.

  • How long did it take you to learn in gravity? (Score:3, Insightful)

    by weave ( 48069 ) on Tuesday March 26, 2002 @12:18PM (#3228596) Journal
    How long did it take you to learn to catch a ball on Earth?

    My father was never one who was into sports until one day when he felt guilty I guess and bought me a mitt when I was 8 and took me out back to play catch.

    Guess what, I sucked. I don't know how long it took me to learn but I tell you what, once in a while someone tosses a set of keys to me across the room and I still can't catch em half the time.

    So I don't see why this is a big deal. Now if it was a story about the difficulties of re-learning how to have sex in space, then I'd be interested! (No, my dad didn't teach me that either, thank god)

  • So, how would you juggle in a zero-gravity environment?? Has anybody tried it? Or is the very concept void and null?
    -russ
  • I recommend they follow the lead of these firemen [9news.com]. Nothing like fear of negative reinforcement to improve performance.
  • and it was obvious that he picked up standing while holding onto something (i.e. the muscle coordination involved) before he picked up "standing while counterbalancing gravity. He would stand next to his toybox while comptemplating which toy to grab... then he'd let go off the toybox to grab a toy and fall down. You could see that he had *no idea* of why he fell down initially.

    So yes... I find it quite believable that gravity is modeled in the brain separately from kinematics and that therefore new kinematic skills (like learning to catch in 0-g) have a hard time disengaging the gravity model.

  • rat (Score:2, Interesting)

    by Toshito ( 452851 )
    I saw a documentary where there was a rat (I think, or another small furry ball of some sort) that was given a small piece of food. This piece of food was dropped in a hole in front of the animal's eyes and was exiting on the bottom. There was several holes on the top of the box and another row of holes in the bottom.

    The experiment was to drop the piece and see where the animal would expect it to fall. Well, it seems that the animal always expected it to fall from the hole directly under the one it was dropped into, and when it wasn't the case the animal was confused.

    So they found that this animal was expecting the piece of food to follow the law of gravity.
  • by laying on your back and throwing a ball straight up. Once you get the hang of throwing it straight up, which is a challenge in its own right, you will be catching the ball with the same trajectory as the astronauts. It's difficult to throw it straight up for the same reason it's difficult to catch in space: your brain ends up compensating for gravity, so your first several (or several dozen) will probably go back over you head. I discovered this exercise when I was about 10; I was quite surprised at how difficult it was to catch at first.

    I propose that future astronauts perform this exercise for 15 days before their flight. That way, they will be able to play catch right away, with no "warmup period," thus making them more productive. And to think my Mom said I was wasting time!
    • This is a different effect.

      Humans' 3d vision is effective over a very short range. the spacing of our eyes is optimized for accurate depth perception at arm length. It is still usable to several feet -- maybe 10s of feet, but with ever reduced accuracy until it fails us entirely.

      Beyond this limited range, we rely on a number of other cues -- comparing an object with nearby objects of known size, reduced detail at distance, and observed change of anglular direction to a moving object.

      Humans use the latter -- observation of the angle to a moving object, to catch a ball. The effect is easily visible when driving down a road at constant speed. Watch the telephone poles by the side of the road -- they appear to "speed up" as they get closer. It's because they're off to the side, as they get closer even though the car's speed hasn't changed, the rate that the angle to a given pole changes more rapidly until it is exactly opposite you. You could also plot it. If you drive straight at a pole (don't try this at home), this cue doesn't exist, and bifocal vision doesn't help until possibly too late.

      We use this to determine a moving ball's distance. Watch a baseball outfielder. if the ball is coming straight overhead, as he runs back to get the ball he'll actually run to the side, then veer back in to meet the ball. I suspect that when you were throwing a ball up & catching it, you were subconsiously learning how long it takes for a ball to come down for a given force of throw. Had you had the ball dropped from straight above, from a random height, you'd still be unable to accuratly time the ball's arrival & miss the catch.
      • Interesting...

        While I don't agree 100% with your disagreement, you did make me realize one thing: the ball being caught in the "laying on the back" experiment is accelerating, while the ball thrown in space is not. That may be a significant difference.

        Your analysis of our use of 3-d observations to catch a ball is interesting, but I don't think that's the whole story. Your explanation is relevent to how we track the ball with our eyes, but it doesn't take into account the timely placement of our hand in a position to intercept the ball. It's not good enough to see where the ball is and put our hand there; we have to put our hand in the right spot before the ball gets there. To do this, I think our knowledge of how gravity affects the trajectory is very important. To use an example from above: a parachute landing. Sure, you can watch the ground and make a pretty accurate judgment about how high you are, but at the very last second you will most likely raise your feet too early because you are used to "falling" at a certain rate of acceleration. Change the acceleration, and your brain no longer knows how to compensate. I did 20 jumps years ago, and I jarred my shins every single time, even though the rate of descent was no greater than hopping of a picnic table.
  • ... that simple ballistics is one of the few instincts we humans are born with (such as holding our breath when under water), an innate ability to judge an object's motion in free-fall. Something that came in handy when we were jumping from branch to branch or throwing stuff at predators. Something akin to the way cats can always land on their feet.

    Of course, I'm not a biologist so I could be wrong...

  • bees, parachutes, & linear thinking (Score:3, Interesting)

    by hawk ( 1151 ) <hawk@eyry.org> on Tuesday March 26, 2002 @02:02PM (#3229419) Journal
    From other seminars I've attended in the past:


    there's a certain amount of linear modeling the brain can do. Note that, for a small enough interval, a linear model can be made "good enough".


    The interesting examples:


    1. Move a beehive by a fixed amount each day while they're out gathering. The bees adjust to this (e.g., 10feet/day), and head to where they know it *will be*. Increase this amount by a fixed amount (10, 11, 12, etc.) and they can't do it.


    2. Parachute landing. Don't look at the ground. You're falling at a rate the brain can't handle; if you watch, you compensate incorrectly, and often hurt yourself. (so hear the brain seems to expect the gravity induced quadratic, whereas you're moving at a linear rate?).


    hawk

  • I'm sure this has been mentioned before... but what about throwing a frisbee? A good frisbee will travel exactly horizontally from source to target and us humans have no problem catching it.

    I'm trying to imagine what I would do in space. I can see myself trying to anticipate the not dropping ball and messing up. I can also see myself catching a frisbee with few problems in space. Maybe our brains have learnt from experience that balls tend to drop and frisbees don't as much
  • Doesn't sound like they's a built-in gravitation model at all.

    With motion sickness, it's a psyiological reaction to having the brain seeing senses (typically sight and balance) out of sync by a bit.

    With catching a ball, that's not a reflex, but a learned behaviour. Throw a ball at a baby or even a toddler, and there won't be much projection of a gravity model going on. It's simply that through repetition and observation we learn what to expect. And such learned behaviour is harder to modify, especially once it becomes ingrained (and somewhat sub-conscious).

    The autonomous nervous system, on the other hand, has the ability to bring things into sync in a few days, to help people get over motion sickness.

    So to me, it just seems like different core parts of the brain, and greatly different function, not that there's any inherent gravity model in the brain, other than what is learned through experience.

    -me
  • To understand this, don't look at humans, who are born with the brain unfinished. Look at animals that are ready to go as soon as they are born, such as horses and Guneau pigs.

    Newborn foals usually stand within half an hour of birth. And they do it right the first time, even though getting up on those spindly legs is hard. Within two hours, they're stable on their feet. They can run with the herd the day they are born. At speed, over rough terrain, without falling. The visual, balance, and locomotion systems are fully functional at birth. With minimal calibration, they're ready to go.

    This observation blows away the "brain comes up blank" school of development. It gives some insight into what's built in and what's not. And it gives some insight into the control algorithms that have to be in the brain.

  • Remember being tiny. You stood up. You fell down. Often when you fell down it hurt. You decided Hurt was bad, balance was good. Remember learning to catch a ball. You were afraid of the ball. People laughed at you. You caught the ball with your face. It hurt. You decided it was always better to catch the ball. Gravity is just the crucible for you follies.
  • According to neuroscientist Joe McIntyre of the College de France,
    Holy shit! Looks like at least one of the New Kids had some talent after all!

  • This sounds much more like Real Life 3D Pong.

    If astronauts can play 3D pong without a computer, then I also want to!

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