Gravity Hard-Coded Into The Brain

guiding_knight writes: "A study by French scientists suggests that gravity is imprinted in the human brain. Interesting article, tells of human ability to calculate effects of Earth-normal gravity and how difficult it is to adapt to another model."

Comments

So you mean...

[psicE]

with a little genetic engineering, we can all go around floating?

juggling

[DeadSea]

As a juggler, I would be very suprised if the earth's gravitational constant was totally pre-implanted in your brain. One way to teach people to juggle is to use handkercheifs or some other object that falls slowly due to air resistance. Learning to juggle when stuff moves more slowly is much easier, and people have no trouble catching handkerchiefs.

Also look at computer games which can have arbitrary G constants. People playing video games can get very very good at predicting when their character hits the ground no matter what G is thrown in.

Upon reading the article, it looks as though they have found evidence that we are attuned to normal earth gravity but they have proven nothing. Their experiments are all done with people who, after having grown up in normal gravity, are thrown off by less gravity. I don't think they have much in the way of nature/nurture on this. Better experiments would involve raising a kid in space and seeing how he could catch a ball.

I would not be suprised if we somewhat expect earth's gravity after years of evolution (the same way we are easily get phobias of snakes but not much more dangerous things like cars and electricity), but humans obviously have wide skills with other acceleration constants. This study is hardly conclusive from the summary of it in the news article.

Learning with and without gravity

[martyb]

It's one thing to try and do something WITHOUT gravity, that I had originally learned how to do WITH gravity. That's what this experiment was attempting to do.

I'd be more interested in how well they did learning, for example, to play hacky sack (passing a small, bean-filled leather bag using only your feet). if they had no prior experience with the game, I'd be interested in seeing how well they did, learning it in zero-G; compared to others learning how to do it with normal gravity. That would be a more valid experiment in my book.

Re:Learning with and without gravity

[martyb]

It's a bit hard to play it at all in zero-G

Though I have no first-hand experience in zero-G (man, don't I wish!), I would expect it would be difficult to play hacky sack there. Then again, It was hard for me to learn how to play hacky sack in normal gravity. ;^)

But, that was not the point. The article contended that gravity may be hard-coded into the brain. My concern is that the experiment they used does not clearly test that hypothosis. This could simply be a learned response, that happened to have been learned under the influence of gravity.

The point is to have people learn a skill which they had never done before, some under the influence of gravity, and others in zero-G. I just used hacky sack as an example that did not require the individuals to UNLEARN something they already had gained some measure of expertise while in earth gravity. Feel free to use some other coordination challenging task that could involve gravity. Hacky sack involves hand-to-FOOT coordination which I discovered was much more difficult than I thought it would be. Not because it is that difficult, but because I was that inexperienced.

So, whether or not it's hacky sack, pick some coordination activity other than one in which the participants are already well-versed. Use the same instrumentation as was used in the article's experiment to monitor muscles, timing, feedback, and the like. Then, compare the results between the zero-G participants and the earth-bound participants. If the brain were really wired for gravity, then I would expect there would be clearly perceptible differences in the abilities, and the learning curves, of the two groups.

Re:What a ridiculous notion

[taion]

Indeed, what a ridiculous post.

First, your figure of "100 million years" seems to have been completely fabricated. Care to back that up?

Your number for day length of 100 MYA is also rather off. Day length change is approximately 2 milliseconds per century, meaning that even 100 MYA, the day could not have been more than 2000 seconds (considerably less than 6 hours) shorter than it is currently. The actual day length was actually longer than what these quick calculations indicate, given changing rates, but your numbers are completely out of the ballpark.

In addition, your very concept of gravity seems to be off. Gravity is the attraction of two bodies with definite mass, and is equal to G_c*m_1/d^2. Rotational speed doesn't affect gravity at all -- only mass does.

Heck, you even contradict yourself, not to mention practically all scientific knowledge we have. A weaker gravitational force means a lower gravitational acceleration constant, which is rather inconsistent with your figure of 15.2 m/s^2, which is rather more than the 9.8 m/s^2 we have now!

Article says it is NOT hardwired

[m_evanchik]

Despite its title, the article states the scientists are unsure of how "hard-coded" gravity is in the brain:

It's possible that the astronauts did adapt to 0-g, and then readapted back to 1-g again. It's also possible that the brain is able to learn and retain multiple models of acceleration. In different situations, it might simply choose which one to apply. That, in fact, is what McIntyre and his colleagues believe is going on.

In other words, like on Slashdot and other publications, the headline writers didn't read the article, or deliberately misstated its conclusion in the interest of an exciting headline.

Re:TROLL!

[taion]

I didn't mention centrifugal force because it had no relevance to debunking what the original poster stated. The original post gave a value of 'g' of 15.2 m/s^2 if the Earth rotated faster, corresponding to INCREASED gravity.

Of course, this has no grounding in fact, as gravitational force relates only to the masses of the objects in question and the distance separating them, and neither the mass of the Earth nor its radius has changed significantly enough to change the value of g to only one decimal place.

Presumably, the original poster was referencing the apparent force felt by objects on the Earth. Assuming the presumed increased centrifugal force to be significant, that would mean that g would instead be less than its current value --- the exact opposite of the larger value of g that the post gives.

Now then, if we wish to calculate the effect of centrifugal force... F_c = mv^2/r, so a_c = v^2/r, where v is the velocity, and r is the distance from the centre of the circle. v is proportional to 1/t, so using 86400 s and 84400 s, we get a change of less than 5% as a rough figure.

Now, calculating a_c, we use the Earth's rotational velocity and the radius for v and r. At the equator, these are approximately 460 m/s and 6378.1 km, respectively. Using the formula for a_c, we obtain a figure of approximately 0.03 m/s^2 at the equator, and values that decrease the further we get from the equation. A 5% change on 0.03 m/s^2 gives us less than 0.002 m/s^2, which is hardly even detectable without highly sensitive instruments!

The estimated change in centrifugal force at the equator from 100 MYA is less than 0.02% of g --- which is hardly even noticeable!

What about catching a frisbee on the ground?

[phr2]

If someone throws you a spinning frisbee, it flies level at about constant speed--aerodynamic lift prevents it from accelerating downward. Yet you can catch it as accurately as a baseball.

I think a more valid conclusion from that experiment might be that free fall makes you clumsy.