perceiving acceleration and g-forces

[Nithel]

I'm wondering if humans have any build in mechanism for detecting acceleration and g-forces? I've never heard of something like it, but I can't imagine that it would be very hard to evolve some kind of accelerometer, and it would be extremly usefull too. On the other hand, you can easily trick the mind with a flight simulator, so I'm not sure what to think. Oh, and somewhat related, what causes butterflies in the stomach when you fall?
Anybody knows anything about this?

 

[Inferno]

Well I don't know a lot about it either plus I don't quite understand your question, but:
I can perceive if something is falling, if it is accelerating and even how fast. This doesn't mean that I can say "this falls at 5km/h and accelerates with 15km/h", but it does mean that I can track the pathway of an object and predict when and where it will fall. And I can catch that object, too. That's all one would need, wouldn't it?

As to the butterflies... Your stomach or your intestines being pressed upwards and since that's not a normal occurrence, that's what causes that weird sensation?

 

[televator]

Aren't you pretty much talking about existing organs? Our eyes and inner ears: http://en.wikipedia.org/wiki/Motion_sickness I think the inner ear in particular looks somewhat like an accelerometer....but of course all it translates into for us is "feeling" or "sense" and not arbitrary measuring units.

 

[Master_Ghost_Knight]

Before going any further, what are you asking is a physical impossibility in a uniform field. You can't tell the diference between falling due to the effect of gravity or just being suspended because every part of your body is acelerated equally and thus they will allway share the same relation in space. You would only feel if the aceleration is caused by pressure, as one extremety is bieng pushed while the other isn't, the pressure of one extremety will have to be transfered to the rest of the body (and thus you are able to feel it as you get compressed).
The only way you could feel is if your feet are being accelerated at a different rate then your head (which is the way everything really is) but the gradient for something like the earth is so small that it is almost as if you were in a uniform field.

 

[Nelson]

explanation

This.

But, I'll expand just a little. GR explains how gravitational fields can be thought of as a curvature of space-time. The "most natural" or free-fall path through this space is following the curvature. If we jump from a plane and fall toward the surface of the earth, we are following this curved path (neglecting air resistance). In general, we can't tell the difference between free-falling toward some massive body or sitting almost motionless far from any massive bodies. As long as we are following this free-fall path, we will feel weightless.

The forces that we feel are a result of interactions with objects that resist our motion along this free-fall path. I feel heavy on the surface of the earth, because the surface itself prevents me from following the shortest path through this space, which is straight toward the center. The cool thing is, we can take this a step further. In fact, as far as we know, there is no way to to distinguish between sitting on the surface of the earth in a gravitational potential that imparts an acceleration of 9.81 m/s^2 at this distance, and moving through some empty bit of space with this same acceleration. Any sort of physical experiments you perform in these two separate reference frames, will give the same results.

I apologize if I've derailed the original topic a bit, but I felt this bit of information was worth clarifying so that we could get a better understanding of what sort of ability you are asking about.

 

[televator]

I think I misunderstood the question. I thought he was talking about detecting changes in G forces do to "acceleration" AKA a change in motion in relation to body that we find ourselves spinning along with.