No. If I’m not moving, I have no acceleration relative to the ground.
[When astronauts travel into space, they are often seen floating around the interior of their spacecraft and people often refer to zero-gravity. However, the astronauts, such as the ones orbiting in the Space Shuttle never actually get far enough away from the Earth to escape its gravity.
Instead, it is their falling motion in orbit that creates this effect. In fact, this sensation of zero-gravity can be duplicated here on Earth. If you were to stand in an elevator that was free-falling for a significant distance, you would find that you would have a weightless sensation. Astronauts often train in a modified airplane that makes rapid dives. This falling motion also duplicates the weightless effect.](http://library.thinkquest.org/03oct/00181/gravity-t.html)
OK Astral, maybe this will help: Can you feel it if someone puts a 50 pound sack on your shoulders? Could you feel the difference between a 50 pound sack and a 20 pound sack? Of course.
You’re right in that the body can’t really detect the force of gravity directly – if you were in a vacuum, free-falling with no external references, you couldn’t tell whether you were falling in 1G or 0.001 G.
But your body can most certainly detect forces applied to one part of it. When you’re standing on Earth, gravity is pulling your entire body down, but the floor is only pushing back up on your feet. Your feet then push on your legs, your pelvis pushes up on your internal organs, etc.
If the floor stops pushing up as hard-- either because gravity magically lessens, or because the floor falls away because it’s an elevator – then the bottom of your feet have less force on them, your internal organs have less force pushing them up, etc. And if the change is great enough your body can most definitely feel and notice it.
Right, the ground is accelerating upwards, too. And your velocity is in fact changing, relative to a reference frame that’s not accelerating. Compare yourself to a guy who steps into an empty elevator shaft: At the moment he steps in, you have zero velocity relative to him, but then a few seconds later, you have a significant upward velocity relative to him. Ergo, you accelerated upwards.
I got confused about this, but I think The Hamster King is right. Physiologically, I think the feeling you get in your stomach when riding an elevator is due to your stomach pressing down more or less than normal inside your body. Have you ever taken a ride on a pirate ship? You get the strongest feeling of losing your stomach at the top of the swing, where you are stationary and weightless. So, reducing gravity by 5% should give you the same feeling as an elevator accelerating downwards at .05 g. Your stomach is 5% lighter in your body.
On the other hand, the sensations might not be identical, as your sense of balance would not be affected by the lower gravity.
Sorry, meant to say the sense of balance wouldn’t be affected when standing still, it would be affected when moving. The inner ear is filled with fluid, which would rest in the same position at 1g and .95g. Once you started to move in .95 g there would be more slosh.
As a result of this, I don’t think you’d get the same sensations as being in a falling elevator, but I’m not completely confident on this point. I may be misunderstanding how the vestibular system works.
Like I said before, I think what you’ll find provides the mos noticeable feelings is the 3rd and 4th derivitive of postion wrt to time i.e. jerk and jounce. What causes your stomach to press down is that it’s moving at a slightly different speed to the rest of your body. what causes your stomach to move at a different speed is that you have forces acting through your body in a heterogenous way.
With all else being equal, the effects on sensation of being in 95% gravity would be so subtle that the average person would not notice.
I’m not sure why you think this. Consider the most extreme case: freefall. Your acceleration is constant – zero in fact – so there are no higher order derivatives to consider. But you still feel it in the pit of your stomach – hence the nickname “Vomit Comet” for NASA’s freefall training plane.
Your viscera are like an accelerometer – a collection of masses attached to your abdominal cavity by springy connections. When you’re just standing around they’re subject to a constant 9.8 m/s/s upward acceleration. If that changes to a different constant value, the springy bits pull more or less in response. Our guts hang differently inside our body depending on the constant acceleration we’re currently experiencing.
We’ve sent men to the Moon, and I’ve never heard of any problems walking or any intensive training to teach them to walk in different gravity. It isn’t as though tripping and falling is a minor incident for an astronaut. Any tear in their suit is going to be bad news and a potentially fatal incident. I’d expect if it were really difficult to move around or even stay balanced in a less than 1g environment that someone would have mentioned it.
Obviously that’s an extreme situation, What I’m saying is I don’t think 5% difference is enough to cause any majorly noticeable effect to sensation. with 5% your innards are going to be in a simalir postion they would’ve been otherwise and what produces more sensation is actually the jerk and the jounce as rollercoaster designers are keenly aware ofr.