# Gravity Mysteries

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If gravity didn't exist, then nor would the normal force exist (upward force from ground). So to reconcile gravity as a contact force as opposed to an action at a distance would require an altered viewpoint on multiple forces. I once gave an example in the philosophical antirealism thread about the irregular rotation of the Earth somehow creating a downward Euler force to mimic gravity. In my lucid dreaming thread (profile blog) I recalled an experience of going up in an elevator and having the backpack increase in weight relative to the horizon. So I wasn't throwing the backpack upwards and rather I was going upwards in sync with the elevator floor. I don't know much about the maths or physics of Euler forces. So does anyone know any symbolic way to elaborate on fictitious forces like the Euler force so as to mimic gravity? For example you could think about a closed system like a rotating asteroid. What if you were going upwards in a lift on top of an asteroid?!

"The Euler force is one of three fictitious forces found in rotating frames of reference, the others being the centrifugal and Coriolis forces. It depends on the angular acceleration of the rotating reference frame and the position of a particle in that frame." (conservapedia)

(Use the search box and type "Euler" to see relevant posts.)

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1 hour ago, Michael McMahon said:

So does anyone know any symbolic way to elaborate on fictitious forces like the Euler force so as to mimic gravity?

Newton's Bucket ?

By the way that's a crap picture you posted, quite unrepresentative of even the simplest classical mechanics taught in junior high school.

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I might be wrong on this but if relativity is explained by the Earth's surface moving upwards to catch up with a thrown object, then it'd be like the normal force from the ground actually exceeds the conventional downwards force of Newtonian gravity.

Edited by Michael McMahon
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1 hour ago, Michael McMahon said:

So to reconcile gravity as a contact force as opposed to an action at a distance would require an altered viewpoint on multiple forces.

What makes you think gravity is a force?

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50 minutes ago, dimreepr said:

What makes you think gravity is a force?

Because it describes the interaction between two masses. But gravity isn't just a force, it's also an effect of space and time, sort of built in to the universal system.

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6 minutes ago, Phi for All said:

Because it describes the interaction between two masses. But gravity isn't just a force, it's also an effect of space and time, sort of built in to the universal system.

Indeed, it's a path that we're forced to follow, apparently.

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Sometimes you can look at the same fact from different perspectives...

Example:

In order to find its path from A, a particle follows the clue of velocity and force

or,

In order to go from A to B, a particle tries to minimise its action

Both are mathematically equivalent.

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• 2 weeks later...

Even if a Euler hypothesis on gravity is flawed or unprovable it might still be an interesting area of study simply to explore the mathematics and poetry of it.

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8 hours ago, Michael McMahon said:

Even if a Euler hypothesis on gravity is flawed or unprovable it might still be an interesting area of study simply to explore the mathematics and poetry of it.

If you were more specific our answers could also be more specific and this discussion might then progress.

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On 10/27/2022 at 2:25 PM, Phi for All said:

Because it describes the interaction between two masses. But gravity isn't just a force, it's also an effect of space and time, sort of built in to the universal system.

I like to think of gravity in just of "interaction" terms. When a imagine the force of gravity I imagine it in the classical sense of a force and then struggle to consolidate this with the GR model of gravity.

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25 minutes ago, Intoscience said:

I like to think of gravity in just of "interaction" terms. When a imagine the force of gravity I imagine it in the classical sense of a force and then struggle to consolidate this with the GR model of gravity.

Think of a gyroscope, in the 80's it was proposed that 2 opposing gyroscope's could be used as propulsion, but it's only an apparent force because it just follows the path it's forced to travel.

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There are different models for gravity.
All have specific areas of applicability.

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14 hours ago, MigL said:

There are different models for gravity.
All have specific areas of applicability.

This is something that bugs me. I can't get my head around why there should be different models. I appreciate that they may be used for different applications, much like you may use different tools in engineering to achieve the same goal. But in my mind there will be just one that is the correct one, so all the others are useful approximations.

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44 minutes ago, Intoscience said:

This is something that bugs me. I can't get my head around why there should be different models. I appreciate that they may be used for different applications, much like you may use different tools in engineering to achieve the same goal. But in my mind there will be just one that is the correct one, so all the others are useful approximations.

Newtonian gravity is descibed as a force. GR is curved spacetime and Quantum Gravity has it mediated by graviton particles. GR comes up short below Planck level and QG comes up short at the macro level, so which level you look at determines which you use. This is the 'domain of applicability'.

Edited by StringJunky
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10 minutes ago, StringJunky said:

Newtonian gravity is descibed as a force. GR is curved spacetime and Quantum Gravity has it mediated by graviton particles. GR comes up short below Planck level and QG comes up short at the macro level, so which level you look at determines which you use. This is the 'domain of applicability'.

Yes, I agree and familiar with each model. I just can't get my head around which model actually describes gravity in its "true" form. All the models make accurate predictions even, Newtonian that has been succeeded by GR still is accurate enough for most applications. But if all fail at some level then in my feeble mind all are just approximations and don't describe gravity at the most fundamental level.

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1 hour ago, Intoscience said:

Yes, I agree and familiar with each model. I just can't get my head around which model actually describes gravity in its "true" form. All the models make accurate predictions even, Newtonian that has been succeeded by GR still is accurate enough for most applications. But if all fail at some level then in my feeble mind all are just approximations and don't describe gravity at the most fundamental level.

Every model fails at some point eventually when new data comes in that doesn't fit.

Edited by StringJunky
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3 hours ago, Intoscience said:

Yes, I agree and familiar with each model. I just can't get my head around which model actually describes gravity in its "true" form. All the models make accurate predictions even, Newtonian that has been succeeded by GR still is accurate enough for most applications. But if all fail at some level then in my feeble mind all are just approximations and don't describe gravity at the most fundamental level.

Are you really familiar with Newton ?

I described the opening post as

On 10/27/2022 at 1:02 PM, studiot said:

By the way that's a crap picture you posted, quite unrepresentative of even the simplest classical mechanics taught in junior high school.

Do you know what was wrong with it ?

And yes I realise you are not Michael McMahon and this is not a criticism but an offer to dispel some common misconceptions you may have picked up since you have always struck me as a level headed member.

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4 hours ago, Intoscience said:

Yes, I agree and familiar with each model. I just can't get my head around which model actually describes gravity in its "true" form.

None of the models describe the "true" form of gravity.  The models are useful approximations of what is "really" happening.

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3 hours ago, studiot said:

Are you really familiar with Newton ?

I described the opening post as

Do you know what was wrong with it ?

And yes I realise you are not Michael McMahon and this is not a criticism but an offer to dispel some common misconceptions you may have picked up since you have always struck me as a level headed member.

I'm not taking it as criticism, I appreciate your offer and would be interested in gaining a better understanding. I'm sure I have many misconceptions, which is probably why I struggle to get my head around the models, their relationship and how they fit into the big picture (or small picture).

2 hours ago, Bufofrog said:

None of the models describe the "true" form of gravity.  The models are useful approximations of what is "really" happening.

Yes, and this is my question really. Can any model describe to a fundamental level which describes the underlining mechanics?

I was listening to a TED talk where a scientist (can't recall the name) mentioned that some well know physicists are exploring theories that go beyond what we may currently consider as fundamental such as space & time. That such things like space & time maybe projections from a deeper more fundamental reality.

5 hours ago, StringJunky said:

Every model fails at some point eventually when new data comes in that doesn't fit.

Yes, I appreciate this and it maybe the case that the deeper we delve the more models arise and then fail as we go deeper still.

My question is as per my reply to Bufofrog

Edited by Intoscience
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16 minutes ago, Intoscience said:

Yes, and this is my question really. Can any model describe to a fundamental level which describes the underlining mechanics?

If I understand your question correctly...

No, a model cannot describe anything to a fundamental level. A model is a representation of a system that describes the workings of that system in terms we can understand. It is not meant to represent "reality".

Gravity is a force when talking Newtonian gravity, but not a force when talking about Relativity. Neither is "right" or "wrong" except in context of the model you are discussing at the time.

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2 hours ago, Intoscience said:

Yes, and this is my question really. Can any model describe to a fundamental level which describes the underlining mechanics?

Models describe behavior, and can only be tested by comparing with observed behavior.

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10 hours ago, Intoscience said:

I just can't get my head around which model actually describes gravity in its "true" form

No model describes anything in its true form.

To make it really simple ...  Studiot and Bufofrog each give me an apple.
I decide to mathematically model the interaction with the relation

1 + 1 = 2

Yet I can't eat any part of the model.

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15 hours ago, zapatos said:

If I understand your question correctly...

No, a model cannot describe anything to a fundamental level. A model is a representation of a system that describes the workings of that system in terms we can understand. It is not meant to represent "reality".

Gravity is a force when talking Newtonian gravity, but not a force when talking about Relativity. Neither is "right" or "wrong" except in context of the model you are discussing at the time.

Ok thanks,

I guess then what I'm really asking is why the models (lets just keep it to QM & GR for arguments sake) are conflicting. In that one describes gravity as a force (particle exchange) and the other as geodesics. This then in my mind sort of emulates the wave particle duality we see with particles. Where similarly gravity can be one or the other depending on the context of the observation/experiment.

12 hours ago, MigL said:

No model describes anything in its true form.

To make it really simple ...  Studiot and Bufofrog each give me an apple.
I decide to mathematically model the interaction with the relation

1 + 1 = 2

Yet I can't eat any part of the model.

Ok, I get this thanks,

what I'm really asking then is, what is gravity at its most fundamental level a geodesic due to the interaction between mass and space or a force due to the interaction between 2 or more massive objects? Or neither, as these are just different models representing the same effect?

13 hours ago, swansont said:

Models describe behavior, and can only be tested by comparing with observed behavior.

Ok, maybe I'm confusing models with description.

Thanks

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6 hours ago, Intoscience said:

Ok, maybe I'm confusing models with description.

Not sure how that changes things.

Newtonian gravity doesn’t have a mechanism. GR has warped spacetime. Quantum gravity would have an exchange of virtual gravitons. How do you test which one is the “true” form? How do we know it’s not invisible pink fairies?

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6 hours ago, Intoscience said:

I guess then what I'm really asking is why the models (lets just keep it to QM & GR for arguments sake) are conflicting. In that one describes gravity as a force (particle exchange) and the other as geodesics.

Just to reiterate, remember that none of the models are saying that in "reality" gravity is a force, and none of the models are saying that gravity is in "reality" the result of geodesics. What they are saying is "If you look at it this way, it will explain why we get the results we do...".

There are multiple theories on what motivates people. Maslow says people are motivated to meet needs. Skinner says people are motivated by reinforcement. Those are two conflicting  ways to look at human motivation. The two models of human motivation conflict because two different people worked out a model of human motivation that successfully predicted behavior.

Similarly in the future a person may come up with another model whose description of gravity conflicts with QM and GR. If it turns out that this new model makes better predictions, is easier to use, or is in some other way superior to the existing two, we will then have a third way to describe gravity.

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