Abstract maths does not mean anything. Your cat does not occupy its own 'space-time' with its own 'clock'. Nor, when it swats a mouse, is there an 'equal and opposite reaction' from the mouse.
There is a physical reality to the third law. The arrow that hits something can get splintered, the bullet deformed, the hammer bounces back off a wall, if you punch someone you can break your hand etc etc.
These engineers are disagreeing with you because they use this law when they do free body diagrams -- if you don't put in the reaction forces, it won't match reality. This is how buildings, structures, mechanical systems etc are designed, it is definitely real.
I honestly think you should delete that part, because my takeaway is, if I can't trust his reasoning on the stuff I understand such as Newton's laws, then why should I trust him on the things which I don't understand, such as relativity? I don't want to be mean, this is just how it comes across to me. I think alternative physics theories are great because clearly there are issues with the current theories, keep doing what you're doing :)
Yes Einstein the stage performer. He pulled more than just rabbits from his hat. He conjured up complete fantasy worlds, all proven by his maths :) None of these fantasies are falsifiable. I wonder why Popper never applied his axiom to the Einstotle cult.
I applaud your scholarly evisceration of Einsteinian “space-time” nonsense, but your hubris in impugning Newton’s 3rd law astonishes me. As an engineer, I can assure you Newton’s 3rd law will be working in the cases you describe, despite your inability to ‘model’ the penetration, deformation and damage done to the various ‘targets’ (face, body, wall, target) by the ‘missiles’ (fist, arrow, hammer, bullet) you threw at them.
• Your difficulty lies in not being able to model the rapid changes in the motions, dynamic distortions, changing contact areas, and structural damage of each object in real time.
Given sufficient time and money, each impact could be modelled in a supercomputer. With a Finite Element Model (FEM) of your various missiles and targets, a Finite Element Analysis (FEA) program would handle the dynamic changes in the anisotropic properties of each body as it moves, deforms, or fractures during the brief interaction period. That FEA would apply Newton’s 3rd law as a ‘boundary condition’ where the Elements of each FEM were in contact and ensure equal and opposite Force Elements act perpendicular to Contact Elements and allow equal and opposite friction effects to act on (and parallel to) those Contact Elements, as they slide.
• Your sense of the word “reaction” seems to refer to the huge difference between the EFFECTS an impact has on your selected ‘stationary’ objects, and the EFFECTS of the same impact on your selected ‘moving’ objects. That huge difference seems to have distracted you from the mutual contact FORCE itself, which occurred before (and caused) all those subsequent EFFECTS. But that difference relates to the huge differences between the colliding bodies, not to a flaw in the 3rd law.
Newtonian ‘actions’ and ‘reactions’ are ‘mirror images’ of each other and are as inextricably linked as you and your image in a mirror are linked. One may seem to be ‘causal’ and the other its ‘effect’, due solely to our human awareness of sequential time. But inanimate objects have no perception of time; each simply ‘reacts’ to the other, and that common ‘reaction’ force acts equally in both directions at the same instant. Whether its EFFECT is insignificant or devastating depends solely on the NATURE of each object.
From my amateur observer point of view this does not ring true. When I swing hammer and hit the window it gets shattered so it can hardly hit back or resist with equal force. If it did it should stop the hammer. Whatever effect the glass has on the hammer (scratching, slowing down) is done by forces present within the structure of the glass itself making up it's properties I guess. But I am not an engineer.
Of course you are right. You punch someone in the face, their face does not give an equal and opposite reaction. Newton may have been musing about corpuscles or particles. In reality energy and force do not operate as his ‘law’ states. Like Descartes, Newton continues the use of abstract maths to explain inferential generalisations which are simply invalid in many use cases.
I understand Pat's explanation as that momentum becomes force when the object hits the surface of another object. Now this force is only as big as needed to break the window for example. Usually little force is needed to break a window so the window's resistance does not reduce hammer's momentum very much. In comparison, a face usually stops the fist or, at least, slows it down significantly. This resistance occurs only when the hit lands and it must be exactly the same size as the force that landed, only in the opposite direction. Apparently, Newton called this resistance a reaction. In a sense, this is an actual force while the momentum (and other properties) of an object in rest or in motion is a potential force because it has not yet landed. This hinges on making a distinction between momentum and force. Certainly, force depends on momentum (force cannot be bigger) but it really seems distinct from it. That's how I wrapped my head around it but I am open to be corrected.
The 3rd law does not mention "energy". That is your departure point from Newton.
Newton's "reaction" is specifically and only the mutual contact "force"; you are exploring the EFFECTS of those two equal forces" on "unequal objects".
Your intuitive feeling that the "weakness" of the glass should prevent it from generating the sort of "force" you imagine the hammer is putting on the glass is not unusual, and is obviously shared by the authour of the above article. But what you and Dr Ferdinand Santos III imagine to be the much larger "force" of the hammer on the glass is not a "force" but its momentum (mass x velocity).
The hammer will experience a very weak "glass-force", and the EFFECT on the hammer, though small, will be measurable. That “glass-force” on the hammer will be equal to the “hammer-force” on the glass, because each force is caused by the other's reaction to it.
Your intuition about the inequality of the “hammer action-force on the glass” and the “glass reaction-force on the hammer” is explained by the huge inequality between the relative “strength” of the hammer (to resist *compression*) and the relative “weakness” of the glass (to resist *bending*).
The two contact forces do have the same magnitude, and are opposite in direction, but can still have different EFFECTS because of the different STRENGTHS of the glass and hammer.
A Doctor of Philosophy in Physics who cannot distinguish an initiating cause from its subsequent effects cannot criticise Newton’s 3rd law, which is not trying to prove anything, but describing a repeatedly observed and measurable relationship between very carefully described physical processes: specifically, the PAIR OF EQUAL AND OPPOSITE FORCES which mutually generate each other during an impact (not their DIFFERENT EFFECTS on colliding bodies with DIFFERENT masses, strengths, shapes, velocities, etc.).
Introducing so many different UNEQUAL COLLISION EXAMPLES into the discussion demonstrates your fixation on those DIFFERENCES and confirms your inability to distinguish the pair of EQUAL and opposite (i.e. reaction) FORCES from their UNEQUAL EFFECTS on UNEQUAL COLLIDING BODIES.
Since you admit that “the 3rd law is a statement about the nature of FORCES themselves, not about the observable [EFFECTS] of those FORCES”, this article should be rewritten to remove the claim that you have disproved (or even cast any reasonable doubt on) Newton’s 3rd law simply because you have seen the UNEQUAL EFFECTS of Newton’s observed EQUAL FORCES on UNEQUAL colliding bodies. It really is time to back off, as Newton settled that argument centuries ago.
There is a physical reality to the third law. The arrow that hits something can get splintered, the bullet deformed, the hammer bounces back off a wall, if you punch someone you can break your hand etc etc.
These engineers are disagreeing with you because they use this law when they do free body diagrams -- if you don't put in the reaction forces, it won't match reality. This is how buildings, structures, mechanical systems etc are designed, it is definitely real.
I honestly think you should delete that part, because my takeaway is, if I can't trust his reasoning on the stuff I understand such as Newton's laws, then why should I trust him on the things which I don't understand, such as relativity? I don't want to be mean, this is just how it comes across to me. I think alternative physics theories are great because clearly there are issues with the current theories, keep doing what you're doing :)
Thanks - there is a difference between kinematic energy exchange and a reaction :)
It’s all Scientism. I’m waiting for Einstein to pull a rabbit from his hat.
Yes Einstein the stage performer. He pulled more than just rabbits from his hat. He conjured up complete fantasy worlds, all proven by his maths :) None of these fantasies are falsifiable. I wonder why Popper never applied his axiom to the Einstotle cult.
I applaud your scholarly evisceration of Einsteinian “space-time” nonsense, but your hubris in impugning Newton’s 3rd law astonishes me. As an engineer, I can assure you Newton’s 3rd law will be working in the cases you describe, despite your inability to ‘model’ the penetration, deformation and damage done to the various ‘targets’ (face, body, wall, target) by the ‘missiles’ (fist, arrow, hammer, bullet) you threw at them.
• Your difficulty lies in not being able to model the rapid changes in the motions, dynamic distortions, changing contact areas, and structural damage of each object in real time.
Given sufficient time and money, each impact could be modelled in a supercomputer. With a Finite Element Model (FEM) of your various missiles and targets, a Finite Element Analysis (FEA) program would handle the dynamic changes in the anisotropic properties of each body as it moves, deforms, or fractures during the brief interaction period. That FEA would apply Newton’s 3rd law as a ‘boundary condition’ where the Elements of each FEM were in contact and ensure equal and opposite Force Elements act perpendicular to Contact Elements and allow equal and opposite friction effects to act on (and parallel to) those Contact Elements, as they slide.
• Your sense of the word “reaction” seems to refer to the huge difference between the EFFECTS an impact has on your selected ‘stationary’ objects, and the EFFECTS of the same impact on your selected ‘moving’ objects. That huge difference seems to have distracted you from the mutual contact FORCE itself, which occurred before (and caused) all those subsequent EFFECTS. But that difference relates to the huge differences between the colliding bodies, not to a flaw in the 3rd law.
Newtonian ‘actions’ and ‘reactions’ are ‘mirror images’ of each other and are as inextricably linked as you and your image in a mirror are linked. One may seem to be ‘causal’ and the other its ‘effect’, due solely to our human awareness of sequential time. But inanimate objects have no perception of time; each simply ‘reacts’ to the other, and that common ‘reaction’ force acts equally in both directions at the same instant. Whether its EFFECT is insignificant or devastating depends solely on the NATURE of each object.
From my amateur observer point of view this does not ring true. When I swing hammer and hit the window it gets shattered so it can hardly hit back or resist with equal force. If it did it should stop the hammer. Whatever effect the glass has on the hammer (scratching, slowing down) is done by forces present within the structure of the glass itself making up it's properties I guess. But I am not an engineer.
Of course you are right. You punch someone in the face, their face does not give an equal and opposite reaction. Newton may have been musing about corpuscles or particles. In reality energy and force do not operate as his ‘law’ states. Like Descartes, Newton continues the use of abstract maths to explain inferential generalisations which are simply invalid in many use cases.
I understand Pat's explanation as that momentum becomes force when the object hits the surface of another object. Now this force is only as big as needed to break the window for example. Usually little force is needed to break a window so the window's resistance does not reduce hammer's momentum very much. In comparison, a face usually stops the fist or, at least, slows it down significantly. This resistance occurs only when the hit lands and it must be exactly the same size as the force that landed, only in the opposite direction. Apparently, Newton called this resistance a reaction. In a sense, this is an actual force while the momentum (and other properties) of an object in rest or in motion is a potential force because it has not yet landed. This hinges on making a distinction between momentum and force. Certainly, force depends on momentum (force cannot be bigger) but it really seems distinct from it. That's how I wrapped my head around it but I am open to be corrected.
The 3rd law does not mention "energy". That is your departure point from Newton.
Newton's "reaction" is specifically and only the mutual contact "force"; you are exploring the EFFECTS of those two equal forces" on "unequal objects".
Your intuitive feeling that the "weakness" of the glass should prevent it from generating the sort of "force" you imagine the hammer is putting on the glass is not unusual, and is obviously shared by the authour of the above article. But what you and Dr Ferdinand Santos III imagine to be the much larger "force" of the hammer on the glass is not a "force" but its momentum (mass x velocity).
The hammer will experience a very weak "glass-force", and the EFFECT on the hammer, though small, will be measurable. That “glass-force” on the hammer will be equal to the “hammer-force” on the glass, because each force is caused by the other's reaction to it.
Your intuition about the inequality of the “hammer action-force on the glass” and the “glass reaction-force on the hammer” is explained by the huge inequality between the relative “strength” of the hammer (to resist *compression*) and the relative “weakness” of the glass (to resist *bending*).
The two contact forces do have the same magnitude, and are opposite in direction, but can still have different EFFECTS because of the different STRENGTHS of the glass and hammer.
A Doctor of Philosophy in Physics who cannot distinguish an initiating cause from its subsequent effects cannot criticise Newton’s 3rd law, which is not trying to prove anything, but describing a repeatedly observed and measurable relationship between very carefully described physical processes: specifically, the PAIR OF EQUAL AND OPPOSITE FORCES which mutually generate each other during an impact (not their DIFFERENT EFFECTS on colliding bodies with DIFFERENT masses, strengths, shapes, velocities, etc.).
Introducing so many different UNEQUAL COLLISION EXAMPLES into the discussion demonstrates your fixation on those DIFFERENCES and confirms your inability to distinguish the pair of EQUAL and opposite (i.e. reaction) FORCES from their UNEQUAL EFFECTS on UNEQUAL COLLIDING BODIES.
Since you admit that “the 3rd law is a statement about the nature of FORCES themselves, not about the observable [EFFECTS] of those FORCES”, this article should be rewritten to remove the claim that you have disproved (or even cast any reasonable doubt on) Newton’s 3rd law simply because you have seen the UNEQUAL EFFECTS of Newton’s observed EQUAL FORCES on UNEQUAL colliding bodies. It really is time to back off, as Newton settled that argument centuries ago.
Kinetic energy is different than Newton's idea of a reaction.