Human's sense of falling?

Gravity is a dis-proven theory, and gravitation stands not much better. That gravitation exists in some form, I am prepared to grant.  I never said that gravitation was fictitious. Only that Einstein posited that his own form of gravitation was a fictitious force. Whether you decided to argue in ignorance or just to disagree, I do not care.

Gravity is a dis-proven theory, and gravitation stands not much better. That gravitation exists in some form, I am prepared to grant.  I never said that gravitation was fictitious. Only that Einstein posited that his own form of gravitation was a fictitious force. Whether you decided to argue in ignorance or just to disagree, I do not care.

Your understanding of the use of the term fictitious is flawed. It's not gravity, or it's affects, that are being called fictitious, but it's manifestation as a force.  In curved space/time, something can appear to be affected by a force when it isn't. 

Regarding the so called disproof of gravity, it is not gravity that has been disproved, but the theory of how gravity works ie: in light of discoveries in quantum mechanics, the previous theory of gravity has been shown to be incomplete.  This is no different essentially to how Einstein's Theory of Relativity modified Newtonian Gravity. 

The Theory of Gravity as elucidated by Relativity was not 'disproved' until 2004.  This was long after Einstein's death and his statement about fictitious forces was not meant to imply Gravity didn't exist.  His Theory of Gravity was compatible with the idea of fictitious forces infact it was the idea that Gravity might be fictitious (inertial) that led him on to develop a theory of gravity.  The idea also forms the basis for General Relativity.

Neither Einstein's Theory of Gravity nor his Theory of General Relativity are disproved by quantum field discoveries; rather they have been found to be incomplete and in need of modification to work at a quantum level.

The other three base forces of nature have been reconciled with quantum mechanics, the fact that gravity has not yet been reconciled means nothing.

We can argue about it all day, but the fact remains you cannot claim that Einstein's work somehow supports the proposition that the Earth rushes up to meet you when you step off a chair. 

I'm not sure if you're being deliberately obtuse or if your desire to argue is overcoming your reading comprehension.

Ok,  explain this.  If gravity really is the earth moving upwards,   why is it that Canada has a section that has less gravity than the rest of the world.  Is that part accelerating slower?   

And what about the earths magnetic field?  Is magnetic north just a figment of our imagination or was it somehow put there by the "conspiracy?"

I'm not sure if you're being deliberately obtuse or if your desire to argue is overcoming your reading comprehension.

If you can't understand what I'm saying just say so don't accuse me of being obtuse...

If you are claiming that Einstein refuted gravity then we have something to continue to argue about, if not, then I must have misunderstand where you are coming from.

If it's the former, and you can't grasp the fact that "fictitious" as used by Einstein does not mean "the affect doesn't exist" then you need to read a little more yourself.  The centrifugal force is also "fictitious" yet you can't deny it's affect any time you go around a corner in a car.  The affect is real, and it's due to inertia, not due to a force, hence it can't be measured in the classical way that a force would be measured.

Quote from: Ski on October 25, 2011, 11:41:32 AM

I'm not sure if you're being deliberately obtuse or if your desire to argue is overcoming your reading comprehension.

If you are claiming that Einstein refuted gravity then we have something to continue to argue about, if not, then I must have misunderstand where you are coming from.

Then you have misunderstood. Einstein is refuting gravity, but obviously not gravitation.

Quote from: pitdroidtech on October 28, 2011, 06:28:48 AM

Quote from: Ski on October 25, 2011, 11:41:32 AM

I'm not sure if you're being deliberately obtuse or if your desire to argue is overcoming your reading comprehension.

If you are claiming that Einstein refuted gravity then we have something to continue to argue about, if not, then I must have misunderstand where you are coming from.

Then you have misunderstood. Einstein is refuting gravity, but obviously not gravitation.

grav·i·ty
noun, often attributive \ˈgra-və-tē\
plural grav·i·ties
Definition of GRAVITY
1
a : dignity or sobriety of bearing b : importance, significance; especially : seriousness c : a serious situation or problem
2
: weight
3
a (1) : the gravitational attraction of the mass of the earth, the moon, or a planet for bodies at or near its surface (2) : a fundamental physical force that is responsible for interactions which occur because of mass between particles, between aggregations of matter (as stars and planets), and between particles (as photons) and aggregations of matter, that is 10-39 times the strength of the strong force, and that extends over infinite distances but is dominant over macroscopic distances especially between aggregations of matter —called also gravitation, gravitational force — compare electromagnetism 2a, strong force, weak force b : acceleration of gravity c : specific gravity

http://www.merriam-webster.com/dictionary/gravity

Quote from: Ski on October 28, 2011, 08:18:22 AM

Quote from: pitdroidtech on October 28, 2011, 06:28:48 AM

Quote from: Ski on October 25, 2011, 11:41:32 AM

I'm not sure if you're being deliberately obtuse or if your desire to argue is overcoming your reading comprehension.

If you are claiming that Einstein refuted gravity then we have something to continue to argue about, if not, then I must have misunderstand where you are coming from.

Then you have misunderstood. Einstein is refuting gravity, but obviously not gravitation.

grav·i·ty
noun, often attributive \ˈgra-və-tē\
plural grav·i·ties
Definition of GRAVITY
1
a : dignity or sobriety of bearing b : importance, significance; especially : seriousness c : a serious situation or problem
2
: weight
3
a (1) : the gravitational attraction of the mass of the earth, the moon, or a planet for bodies at or near its surface (2) : a fundamental physical force that is responsible for interactions which occur because of mass between particles, between aggregations of matter (as stars and planets), and between particles (as photons) and aggregations of matter, that is 10-39 times the strength of the strong force, and that extends over infinite distances but is dominant over macroscopic distances especially between aggregations of matter —called also gravitation, gravitational force — compare electromagnetism 2a, strong force, weak force b : acceleration of gravity c : specific gravity

http://www.merriam-webster.com/dictionary/gravity

They aren't the same except in common speech.  Merriam webster isn't an appropriate source for this.

From what little I've read of this thread, ski is correct.

Gravity is a pseudoforce.  Objects travel their inertial paths.   When something falls, it goes in a straight line.

When something falls, it goes in a straight line.

Or a parabola.

Quote from: John Davis on October 28, 2011, 09:55:13 AM

When something falls, it goes in a straight line.

Or a parabola.

Nope, always a straight line unless acted upon by a real force.

Quote from: Nolhekh on October 28, 2011, 01:11:39 PM

Quote from: John Davis on October 28, 2011, 09:55:13 AM

When something falls, it goes in a straight line.

Or a parabola.

Nope, always a straight line unless acted upon by a real force.

If that is true and gravity doesn't count as a "real" force, then it must be concluded that the only way that objects can travel in "straight lines" that matches everyday experience, it must be concluded that space must be warping.

Quote from: John Davis on October 28, 2011, 01:54:31 PM

Quote from: Nolhekh on October 28, 2011, 01:11:39 PM

Quote from: John Davis on October 28, 2011, 09:55:13 AM

When something falls, it goes in a straight line.

Or a parabola.

Nope, always a straight line unless acted upon by a real force.

If that is true and gravity doesn't count as a "real" force, then it must be concluded that the only way that objects can travel in "straight lines" that matches everyday experience, it must be concluded that space must be warping.

Correct.

Gravity isn't a real force in relativity.  That has been the whole point of the last page of posts.  Its a pseudoforce or ficticious force.    And yes "space is warping" so to speak.  Things travel their inertial path (a straight line).

Quote from: Nolhekh on October 28, 2011, 01:11:39 PM

Quote from: John Davis on October 28, 2011, 09:55:13 AM

When something falls, it goes in a straight line.

Or a parabola.

Nope, always a straight line unless acted upon by a real force.

Think about projectile motion.  A rock thrown by a trebuchet, once released, has no forces acting on it except air resistance, which is minimal.  The rock follows a parabolic arc, as it's both accelerating towards the ground, and moving at a constant horizontal speed.

Quote from: John Davis on October 28, 2011, 01:54:31 PM

Quote from: Nolhekh on October 28, 2011, 01:11:39 PM

Quote from: John Davis on October 28, 2011, 09:55:13 AM

When something falls, it goes in a straight line.

Or a parabola.

Nope, always a straight line unless acted upon by a real force.

Think about projectile motion.  A rock thrown by a trebuchet, once released, has no forces acting on it except air resistance, which is minimal.  The rock follows a parabolic arc, as it's both accelerating towards the ground, and moving at a constant horizontal speed.

I'm sorry, but it only follows a parabolic arc from an inertial frame of reference.  From a non-inertial stand-point it travels in a straight line.

I'm sorry, but it only follows a parabolic arc from an inertial frame of reference.  From a non-inertial stand-point it travels in a straight line.

I think I know what you're trying to say, but I understand it to be the other way around.  Taking an accelerating earth, for example, the earth itself is a non-inertial frame as it is accelerating.  From this non-inertial frame, the rock follows the parabola.  From an inertial frame, say, another rock thrown straight up, the original rock appears to move straight horizontally.  Also, from the original rock's inertial frame of reference, the earth is following a parabolic trajectory.

Quote from: John Davis on October 28, 2011, 04:43:28 PM

I'm sorry, but it only follows a parabolic arc from an inertial frame of reference.  From a non-inertial stand-point it travels in a straight line.

I think I know what you're trying to say, but I understand it to be the other way around.  Taking an accelerating earth, for example, the earth itself is a non-inertial frame as it is accelerating.  From this non-inertial frame, the rock follows the parabola.  From an inertial frame, say, another rock thrown straight up, the original rock appears to move straight horizontally.  Also, from the original rock's inertial frame of reference, the earth is following a parabolic trajectory.

A non-intertial FoR is a FoR that is accelerating.  The earth is not following a parabolic trajectory, its just that parallel lines can intersect.

The earth is not following a parabolic trajectory, its just that parallel lines can intersect.

If I jump down a couple steps off a porch, the earth appears to follow a parabolic arc, relative to my inertial frame of reference.  To the non inertial FOR of the earth, I am the one following the parabola.  Not sure where parallel lines are relevant.  Also, if two lines intersect, they are by definition not parallel.  Why would you suggest otherwise?

Not sure where parallel lines are relevant.  Also, if two lines intersect, they are by definition not parallel.  Why would you suggest otherwise?

Because space is non Euclidean.  I think thats the piece of the puzzle you are missing and its key to understanding this.  I'm about to go offline for a bit, but I'll talk about this more with you at a later time, if you'd like.

I think that limes are yellow because of a strange kind of sound that is produced only by the inverse kinematics of a former yesterday.  As this with my logic, when scissors shut they are only purposed to cut whatever lay ahead and not any light or Tupperware.  And it is for this reason that is a trademark of Google, Inc.  Anyone who has any comment on my basic theory of spider webs please insert ticket here.

Quote from: jraffield1 on October 28, 2011, 02:41:24 PM

Quote from: John Davis on October 28, 2011, 01:54:31 PM

Quote from: Nolhekh on October 28, 2011, 01:11:39 PM

Quote from: John Davis on October 28, 2011, 09:55:13 AM

When something falls, it goes in a straight line.

Or a parabola.

Nope, always a straight line unless acted upon by a real force.

If that is true and gravity doesn't count as a "real" force, then it must be concluded that the only way that objects can travel in "straight lines" that matches everyday experience, it must be concluded that space must be warping.

Correct.

Gravity isn't a real force in relativity.  That has been the whole point of the last page of posts.  Its a pseudoforce or ficticious force.    And yes "space is warping" so to speak.  Things travel their inertial path (a straight line).

I'm well aware of the difference between gravity and gravitation, but the fact remains, Einstein WAS NOT proposing that gravity doesn't exist, he was proposing that it is not a force.

This was Ski's quote that started this little sub-debate:

On a round earth the person falling is still being pulled down by the mythical force of gravity. This would not account for the "normal" sensation.

In fact, Ski was trying to refute Markjo's invocation of the equivalence principle.  As Ski himself says, a falling body is not subject to any forces; therefore the feeling of weightlessness that one feels while falling (after having reached terminal velocity) is not evidence of the earth rushing up to meet the "falling" person.  The falling scenario is as Markjo stated, subject to the equivalence principle.

No. Markjo completely misapplied the equivalence principle to explain the scenario. The "falling sensation" has to do with contact force. It matters not whether the earth is round or flat in this scenario. The earth is accelerating upward, as is easily measured by an accelerometer. No measurable force is being applied to a falling-body. In either scenario it is more proper to say the earth is accelerating upward (or in a globe's case "outward"). In fact, it would best be described by saying that matter constantly expands and that local time is not linear but slows at a proportional rate.
 
Further, the idea of gravity pulling you down (his idea and words, not mine) is not relativistic gravitation nor universal acceleration, but Newtonian Gravity and the equivalence principle becomes meaningless. If being pulled down by Newtonian Gravity was "normal" as he stated, the sky diver would never notice a "falling sensation" because he would undergo continuous acceleration (which we know is not true, b/c we can measure it's absence with an accelerometer-- or in this case one's bowels).

No. Markjo completely misapplied the equivalence principle to explain the scenario. The "falling sensation" has to do with contact force. It matters not whether the earth is round or flat in this scenario. The earth is accelerating upward, as is easily measured by an accelerometer. No measurable force is being applied to a falling-body. In either scenario it is more proper to say the earth is accelerating upward (or in a globe's case "outward"). In fact, it would best be described by saying that matter constantly expands and that local time is not linear but slows at a proportional rate.
 
Further, the idea of gravity pulling you down (his idea and words, not mine) is not relativistic gravitation nor universal acceleration, but Newtonian Gravity and the equivalence principle becomes meaningless. If being pulled down by Newtonian Gravity was "normal" as he stated, the sky diver would never notice a "falling sensation" because he would undergo continuous acceleration (which we know is not true, b/c we can measure it's absence with an accelerometer-- or in this case one's bowels).

Relativistic Gravitation refers to the attraction of two bodies to eachother.  Indeed the earth IS being pulled towards the jumper, but at a far less rate than the jumper is being pulled towards the earth.  Now whether you call it 'pulled' or 'attracted' is purely semantics.  Whether you call it up or down is purely semantics.  Newtonian Gravity isn't anything different to relativistic gravitation; it is simply a less complete explanation of gravitation.  Similiarly Relativistic Gravitation will be found to be a less complete explanation of gravitation when the Quantum model is completed.

Let's put it this way.  If you were in a rocketship accelerating at say 9.8m/s/s, standing on a chair placed on a floor perpendicular to the travel of the rocket, you would feel a force equivalent to gravity, though it would infact be a fictitious force (as is gravity).  If the chair was to be suddenly removed you would "gravitate" towards the floor of the rocketship and in the process, you would have a temporary feeling of weightlessness (akin to when a lift drops from under you).  This is because for that moment, no force is acting upon you.  You have ceased accelerating and any residual forward motion is due to your inertia and is at a constant (not accelerating) volocity.  Eventually the ship catches up with you and you start accelerating again.

Now if you don't agree with this please explain where I am wrong?

I think that limes are yellow ...

Limes are green.

Quote from: John Davis on October 28, 2011, 03:25:21 PM

Quote from: jraffield1 on October 28, 2011, 02:41:24 PM

Quote from: John Davis on October 28, 2011, 01:54:31 PM

Quote from: Nolhekh on October 28, 2011, 01:11:39 PM

Quote from: John Davis on October 28, 2011, 09:55:13 AM

When something falls, it goes in a straight line.

Or a parabola.

Nope, always a straight line unless acted upon by a real force.

If that is true and gravity doesn't count as a "real" force, then it must be concluded that the only way that objects can travel in "straight lines" that matches everyday experience, it must be concluded that space must be warping.

Correct.

Gravity isn't a real force in relativity.  That has been the whole point of the last page of posts.  Its a pseudoforce or ficticious force.    And yes "space is warping" so to speak.  Things travel their inertial path (a straight line).

I'm well aware of the difference between gravity and gravitation, but the fact remains, Einstein WAS NOT proposing that gravity doesn't exist, he was proposing that it is not a force.

Yes, which would make it a ficticious or pseudoforce.  It only exists from taking a noninertial FoR as a inertial  FoR

This was Ski's quote that started this little sub-debate:

Quote

On a round earth the person falling is still being pulled down by the mythical force of gravity. This would not account for the "normal" sensation.

I see nothing wrong with that statement.  The word mythical is accurate.  The force itself is non-existent within relativity.  Its a pseudoforce or ficticious force.  This is opposed to an actual force.

In fact, Ski was trying to refute Markjo's invocation of the equivalence principle.  As Ski himself says, a falling body is not subject to any forces; therefore the feeling of weightlessness that one feels while falling (after having reached terminal velocity) is not evidence of the earth rushing up to meet the "falling" person.  The falling scenario is as Markjo stated, subject to the equivalence principle.

Yes, ski is also correct here. 

eta:

Quote from: markjo on October 22, 2011, 06:13:05 PM

Quote from: Ski on October 22, 2011, 04:25:58 PM

The feeling of being accelerated upwards is "normal". The absence of this acceleration is the feeling you describe.

Thanks to the equivalence principle, we can just as readily say that the feeling of being pulled down by gravity is "normal".

No, markjo. Thanks to the equivalence principle, we can just as readily say that the earth is accelerating us upwards on either a flat or round earth.

On a round earth the person falling is still being pulled down by the mythical force of gravity. This would not account for the "normal" sensation.

At first glance this seems fine.  He has said that a re or a flat earth would have the same experience in this case due to the e.p.

Quote from: Ski on October 29, 2011, 01:57:18 AM

No. Markjo completely misapplied the equivalence principle to explain the scenario. The "falling sensation" has to do with contact force. It matters not whether the earth is round or flat in this scenario. The earth is accelerating upward, as is easily measured by an accelerometer. No measurable force is being applied to a falling-body. In either scenario it is more proper to say the earth is accelerating upward (or in a globe's case "outward"). In fact, it would best be described by saying that matter constantly expands and that local time is not linear but slows at a proportional rate.
 
Further, the idea of gravity pulling you down (his idea and words, not mine) is not relativistic gravitation nor universal acceleration, but Newtonian Gravity and the equivalence principle becomes meaningless. If being pulled down by Newtonian Gravity was "normal" as he stated, the sky diver would never notice a "falling sensation" because he would undergo continuous acceleration (which we know is not true, b/c we can measure it's absence with an accelerometer-- or in this case one's bowels).

Relativistic Gravitation refers to the attraction of two bodies to eachother.

Relativistic gravition has nothing to do with the attraction of two bodies.  It has to do with two bodies travelling straight lines.

If he is saying that on the flat earth you would have the "normal" feeling but on the RE you would not he is incorrect.  He does not seem to be saying this however.

The earth accelerating you upwards is what you feel on ground.  Think of the elevator thought experiment.  On the elevator you feel a pull downwards while accelerated upwards.  When in the air, this feeling is gone as you are no longer being accelerated upwards but in an inertial FoR.   The pull downwards is the normal feeling caused by being accelerated upwards.

I think that limes are yellow because of a strange kind of sound that is produced only by the inverse kinematics of a former yesterday.  As this with my logic, when scissors shut they are only purposed to cut whatever lay ahead and not any light or Tupperware.  And it is for this reason that is a trademark of Google, Inc.  Anyone who has any comment on my basic theory of spider webs please insert ticket here.

Stop it you guys.

No. Markjo completely misapplied the equivalence principle to explain the scenario. The "falling sensation" has to do with contact force. It matters not whether the earth is round or flat in this scenario.

  When did I say anything about the shape of the earth.  Remember that the Davis FE model does use gravity.  All I said is that the EP (when properly applied) makes it impossible to feel the difference between gravity and acceleration.  Therefore, free fall will feel exactly the same regardless of whether the FE earth is rushing up to meet you or if the gravity of the FE is pulling you down.

I had a feeling you two were agreeing and everyone else was just trying to make a stink of it through misunderstanding heh.

If he is saying that on the flat earth you would have the "normal" feeling but on the RE you would not he is incorrect.  He does not seem to be saying this however.

He attempted to use this point to discredit Markjo's invocation of the equivalence principle.

Because Markjo was attempting Newtonian force of gravity with equivalence. It cannot work that way.

When did I invoke Newton?