Why we can't feel gravity in a free fall situation

[elminah]

Hello,

 

I was wondering why we can replicate imponderability by free falling an airplane (the standard way they do it). And why the force of gravity cannot be felt inside this airplane - why it does not keep the objects on the earth side.

[Boerseun]

Actually, you do!

 

The airplanes they use for these exercises can do it for between 20-30 seconds, then they reach their airodynamic 'terminal velocities' - and then they have to pull up again, gain altitude and repeat the process.

 

You, as a passenger, are accellerating with the plane towards the earth at 10m/s^2, which happens to be the speed at which the Earth pulls at you. So, you float in mid-air, with respect to the airplane. When the airplane reaches its 'terminal velocity', which means it cannot fall faster through the specific medium without a power assist, it stops accellerating. You, inside, are 'falling' towards the earth inside a tube of air which is falling with you (the atmosphere inside the plane). So your airodynamic terminal velocity would be measured against the air falling with you - and you're static with respect to it, until the plane reaches its terminal velocity. Then you'd start falling towards the cockpit. But at this time, the pilot have already pulled the craft up to gain altitude for the next 'hop'. They do this because in trying to maintain 'weightlessness' inside the aircraft by opening the jets is virtually impossible - there's no way to get the jets to accellerate at exactly 10m/s^2.

[elminah]

I see it like this:

 

It shouldn't be possible not to feel anything - the sensation of weightlessness this close to a planet should be impossible to obtain.

You should feel a drag - acceleration of the plane or the gravity.

What happens in reality is that the sensation in that kind of plane is identical to the one on the orbit. It's like you can consider that the earth is falling towards you.

[sanctus]

Well this is why you call it microgravity and not zero gravity (as gravity is still ver present).

The drag you feel until you have the maximum speed reached as Borseun pointed it out.

[Guest chendoh]

I see it like this: It's like you can consider that the earth is falling towards you.

 

 

I'm not sure if you misspoke when you wrote this, but if you said that while an astronaut or engineer was present, I feel that they could give you a strong argument as to the opposite of that statement.

 

 

It’s to my understanding that weightlessness either in parabolic flight or in orbit is the same.

What’s bothersome are your visual references, one you’re in a padded cargo hold, the other the vastness of near space.

Skydiving is somewhat different….You were doing fine until you stepped off the plane weren’t you?

 

Nowadays, it takes a rocket of some design to lift objects into orbit.

Once that propulsion is gone that object starts to fall to earth.

Even your plane would start to fall. Though a ship based on Magnetic propulsion would fit the bill.

 

 

Now maybe, IF you were bigger than the Earth....Then the Earth would fall towards you. ;)

 

 

[elminah]

Maybe i haven't explain properly.

The gravity force does not really exist - it does not manifest like a force.

You don't feel the drag like when you accelerate in a sports car.

Gravity is more like an inertial modification of things - when objects are close to a planet (large object) the inertial resistance to acceleration makes the object accelerate towards the planet without feeling any drag. Einstein explain this by curvature of space - but this is like saying that space really exist - like ether.

Curvature of space in my understanding is more like a guideline for movement - the movement of objects in proximity of other objects is different than the Newtonian linear movement (conservation of moment).

My understanding of gravity is like this - gravity is not a force, it's just a rule of how relative object movement occurs, possibly an illusion determined by another phenomena that we don't understand.

 

Maybe theories like the accelerated expansion theory should not be dismissed before a better explanation is found.

[Dracontes]

elminah: I don't know, but it seems to me you're confusing the normal (as in surface reaction), tensional and compressional forces one feels on the surface of a planet as a concomitancy of gravity and a hard substrate with gravity itself.

 

One's always being accelerated, it's only the ground that stops one from going any further. Lacking that, or having enough distance between the mass in question and oneself, one's accelerated to the fullest extent of the law (of gravity). That one feels weightless is just a consequence of one's sensory devices, habituated to a world were whole-body acceleration is trumped by sundry surfaces, thus having various resulting forces to sense. Those devices the vestibular system in the inner ear and the stretch receptors in muscles.

 

I hope that was helpful and sufficiently intelligible.

 

Chendoh: Looking at the equation, attraction in gravity is mutual, so it really goes either way (in a conceptual context), though for the average human falling from space, the movement of the Earth towards the hapless person, is nigh to inexistant due to Earth's inertia, while the inverse is a more harrowing prospect

[elminah]

Ok , I understand, but the problem remains - can you make a device to measure gravity pull (acceleration) that is independent from vision in space? ( some accelerometer for gravity). Relatively you can consider that no pull is happening, just the two objects are adjusting their trajectories according to the rules of inertial movement.

I think that when you accelerate in a spacecraft in space you can measure the acceleration, and feel it.

 

I am saying that maybe there is no acceleration to be felt or measured, only because inertia does work different from the way it was postulated.

This can be tested by measuring tension in large objects in space due to gravity differences. Is there any proof that this tension exist?

[Boerseun]

If you're in free fall, your feet experience a higher gravitational attraction from Earth than your head. Same when you're in orbit. If you're floating in the space station with your toes pointing at the Earth, your feet are literally in a lower orbit than your head, and hence will have to move faster than the top of your head in order to maintain the orbit. These small-scale tidal effects are microscopic in its effects, hence we call these and other gravitational artifacts in near-to-earth space 'microgravity'.

[Guest chendoh]

Ok , I understand, but the problem remains - can you make a device to measure gravity pull (acceleration) that is independent from vision in space? ( some accelerometer for gravity).

There are already formulas and devices. I believe that is how engineers measure GForce.

 

 

Relatively you can consider that no pull is happening, just the two objects are adjusting their trajectories according to the rules of inertial movement.

Irrelevant….For now.

 

Somehow you are mixing apples and oranges.....Well, maybe not so much ....I can see where you are going......

 

 

I think that when you accelerate in a spacecraft in space you can measure the acceleration, and feel it.

GForce again….Have you ever seen videos of manned spacecraft launches?

 

NASA - Multimedia - Video Gallery

 

I am saying that maybe there is no acceleration to be felt or measured, only because inertia does work different from the way it was postulated.

This can be tested by measuring tension in large objects in space due to gravity differences. Is there any proof that this tension exist?

We mite be talkin' 'bout the Dark side here.....ergs an mass......

 

 

 

 

 

elminah: I don't know, but it seems to me you're confusing the normal (as in surface reaction), tensional and compressional forces one feels on the surface of a planet as a concomitancy of gravity and a hard substrate with gravity itself.

Agreed........

Chendoh:Looking at the equation, attraction in gravity is mutual, so it really goes either way (in a conceptual context), though for the average human falling from space, the movement of the Earth towards the hapless person, is nigh to inexistant due to Earth's inertia, while the inverse is a more harrowing prospect

 

 

IF you were bigger than the Earth….

If you're in free fall, your feet experience a higher gravitational attraction from Earth than your head. Same when you're in orbit. If you're floating in the space station with your toes pointing at the Earth, your feet are literally in a lower orbit than your head, and hence will have to move faster than the top of your head in order to maintain the orbit. These small-scale tidal effects are microscopic in its effects, hence we call these and other gravitational artifacts in near-to-earth space 'microgravity'.

, And in the Quantum realm we are reminded of MBH……..Mini or Micro Black Holes.

 

Bravo! my Boerseun Friend!

 

 

Magnetic momentum is next!

 

 

 

[Pyrotex]

I was wondering why we can replicate imponderability by free falling an airplane (the standard way they do it). And why the force of gravity cannot be felt inside this airplane - why it does not keep the objects on the earth side.

What you "feel" is NOT gravity, but accelleration. (In this case, the accelleration due to gravity.) There you are, standing on a hardwood floor in an elegant Victorian house, and you "feel" a force holding you to the floor. But think of it as feeling the floor accellerating you upward. This would be more accurate.

 

It is the same as sitting in a bright red, 1988 Ferrari convertible, as the driver stomps on the gas, tires shriek, and you "feel" a mighty force push you backwards against the seat.

 

Gravity creates, as it were, a permanent accelleration, causing exactly the same effect upon you as if the floor of that Victorian house was really the floor of an elevator accellerating upward at ever increasing speed.

 

What your inner ear "feels" is not gravity itself, but accelleration. If you could place your body in any set of circumstances where you were NOT subject to any accelleration in any direction at all -- you would "feel" weightless, or in "free fall".

 

Well, gravity is everywhere around a planet (such as Earth), and there is no getting away from it. But you can jump out of an airplane. For about 8 seconds, you "feel" as if you are falling, because you are literally accellerating downward. Then you reach "terminal velocity" (about 120 MPH) because of wind resistance, and the feeling of falling disappears. Yes, that's what I said. You no longer "feel" that you are falling. You are totally supported on an "air mattress" -- that is, a 120 MPH "wind" that is generated by your descent. Your speed is constant, there is no accelleration, there is no "sense" of falling. Which means, you "feel" gravity once again.

 

Now this can be confusing because in that Victorian house, on that motionless hardwood floor, you "feel" your weight, which is just another way of saying that you "feel" accelleration. (They are, in fact, the same.) No literal accelleration is involved as your vertical speed is zero and stays zero. Gravity generates a "virtual accelleration". The reason for this is arcane and esoteric, but basically is due to the fact that time flows slightly slower within a gravitational field. Objects with mass will always have a lower energy if they can move where time flows slower.

 

So, forget gravity. Think of accelleration. There is literal accelleration, like the Ferrari kind. There is virtual accelleration, like the gravitational kind. As far as the math is concerned, they work very much the same. When you are in a free fall situation:

 

1. you ARE literally accellerating downward (for 8 seconds anyway) which, if there were no gravity, would make you feel as if there were a force pushing you downwards (like the Ferrari).

2. if you were stationary (or at a constant speed), you would feel the virtual accelleration of gravity, which would make you feel as if there were a force pushing you upwards.

3. in free fall, these two accellerations (one virtual, one literal) cancel each other out.

[TheBigDog]

I see it like this:

 

It shouldn't be possible not to feel anything - the sensation of weightlessness this close to a planet should be impossible to obtain.

You should feel a drag - acceleration of the plane or the gravity.

What happens in reality is that the sensation in that kind of plane is identical to the one on the orbit. It's like you can consider that the earth is falling towards you.

You only feel a force if there is a resistance to that force. Inside the plane there is not wind resisting the gravity pulling you down, so you feel nothing while you and the plane are falling toward the earth at the same rate. Remember also that you are not just falling at a 130 mph or so, you are traveling laterally at more than 400 MPH, why don't you question the fact that you don't feel the lateral motion?

 

Bill

[Qfwfq]

...and hence will have to move faster than the top of your head in order to maintain the orbit..

...would have to, you mean. They can't fall down, if your centre of mass is OK, unless you cut them off.

 

:hihi:

[Boerseun]

...would have to, you mean. They can't fall down, if your centre of mass is OK, unless you cut them off.

 

Aw damn...

 

...you should at least feel a bit of a stretch, or sumtin'... albeit a miniscule stretch...

[Qfwfq]

Of course!

 

But it would take one mighty heck of a stretch to tear them off...

[Agen]

The way I see it is that you cant feel it because the earth "pulls" every single atom/molecule in your body t words itself at the same speed. Thus there is no pressure administered to the body or much of anything else in that matter, so you cant feel the pull.

[Tormod]

The way I see it is that you cant feel it because the earth "pulls" every single atom/molecule in your body t words itself at the same speed. Thus there is no pressure administered to the body or much of anything else in that matter, so you cant feel the pull.

 

The reason we don't feel it, is that evolution has taken care of it. 1G is perfectly normal to us. Go to the moon and you'd instantly feel a difference. Spend a few weeks or months on the space station and you'll feel like a heavy (soft) rock when you come back down.

 

The Earth is a gravity well and and easy way to test it is to stand on a table and jump. Do you fall up or down? What is the reason you fall down?

 

The Earth does in fact fall up towards you as well, but as someone pointed out above, the relative sizes of the Earth vs You (assuming you are a normal human being) is overwhelming and the effect immeasurable.