Hi everyone...
Now, years after high-school and college (non physics-related), I realise
that I don't really understand the "nature" of inertia (or inertial mass as
we call it now).
So I turned to Galileo's bouncing balls reasoning, were a downward-rolling
ball reaches ground and climbs up an upward incline even against gravity
(due to inertia).
But after some time I discovered that I don't understand how can the ball
keep moving on itself, even against the pulling gravity.
Let me see: Galileo discovered that "An object keeps it's state of motion
(speed and direction)"; later Newton formalized it and added that a "force"
doesn't "cause" motion.. rather, it changes it.
OK, but how is that possible? I mean, **why** does an object keep moving
with the "last" speed and direction if left unpertubed?
Furthermore, my mental picture gets even more confused when I think of an
"object" as a bunch of atoms (well quarks... well fermions and bosons). how
do they "all" keep moving the same way?
What puzzles me is that I can somehow picture "interaction" as the source of
change.... but motion sustains itself without no interaction? How is that
possible!? If everything in the universe, except *only one* single
fundamental particle with mass (a fermion) would instantly disappear, the
particle would "move" forever?.... but what keeps this motion? and what is
it anyway (how can be motion of a single entity, that is, without
reference?)
Well, I hope this confusion is simply the result of ignorance about more
advanced physics...
TIA
Fernando Cacciola
Not to add to the confusion, but I have a fascination with perpetual motion, and have a particular design where it appears inertia would NOT be sufficient to stop it, unless the geometry itself is sufficient.
In one particular configuration (Motive Mass Iteration 2) it appears that the weight of a rolling mass, once it has reached one end of a delta-shaped track mounted over a see-saw, would have sufficient downward force to pull another equal weight by pulley up a similar inclined track. When the second weight rolls to the end of its track, it seems that its weight could be used in the same way. In a simplified way, they might be used to create a loop of three see-saws that continue to toggle one another (which actually requires two cycles).
It seems to me that IF the weight is sufficient to move the next weight to the point where it would roll to the end of the see-saw, the next weight would have the same amount of force on the end, becuase none of the force derived is from the motion of the weight. The motion contributes to the speed of the machine, but not for the most part to the force exherted on the next weight.
In that way I am reluctant to believe that inertia is a significant factor, but rather geometry and perhaps the absence of sufficient momentum in the first place.
HOWEVER, MY DESIGN APPEARS TO SOLVE MOST OF THE GEOMETRIC PROBLEMS ASCRIBED TO MANY PERPETUAL MOTION DESIGNS...
My website may be found at NATHANCOPPEDGE.COM
In one particular configuration (Motive Mass Iteration 2) it appears that the weight of a rolling mass, once it has reached one end of a delta-shaped track mounted over a see-saw, would have sufficient downward force to pull another equal weight by pulley up a similar inclined track. When the second weight rolls to the end of its track, it seems that its weight could be used in the same way. In a simplified way, they might be used to create a loop of three see-saws that continue to toggle one another (which actually requires two cycles).
It seems to me that IF the weight is sufficient to move the next weight to the point where it would roll to the end of the see-saw, the next weight would have the same amount of force on the end, becuase none of the force derived is from the motion of the weight. The motion contributes to the speed of the machine, but not for the most part to the force exherted on the next weight.
In that way I am reluctant to believe that inertia is a significant factor, but rather geometry and perhaps the absence of sufficient momentum in the first place.
HOWEVER, MY DESIGN APPEARS TO SOLVE MOST OF THE GEOMETRIC PROBLEMS ASCRIBED TO MANY PERPETUAL MOTION DESIGNS...
My website may be found at NATHANCOPPEDGE.COM
QUOTE
So I turned to Galileo's bouncing balls reasoning, were a downward-rolling
ball reaches ground and climbs up an upward incline even against gravity
(due to inertia).
ball reaches ground and climbs up an upward incline even against gravity
(due to inertia).
I always believed that inertia is a mass's resistance to move and it is momentum that keeps mass in motion once put in motion. So say you are floating in outer space and next to you is a space shuttle. You try to push the shuttle away but you move instead. If you and the shuttle are both weightless why does this happen? Because the shuttle has much more mass and therefore much more inertia than you. Now that you are moving through space you will continue to do so until a force acts upon you to slow you down. The reason you continue to drift is due to momentum.
Hi Fernando Cacciola,
I think this is a much deeper question than many people might realize. I will give my point of view on it, although my final conclusion may make your head hurt, and may be more puzzling than your original question! (Fair warning.)
First, from Galileo's and Newton's point of view, the idea that motion could be sustained without outside force was a big breakthrough. This overturned the old philosophical physics of Aristotle and other classical thinkers, and led to a workable theory of mechanics for the first time.
It also raised just the conundrum you have mentioned. This is in fact why Newton chose to state it boldly as his first law. In the days when Newton wrote, much scientific writing was still modeled after philosophy, specifically Scholastic Philosophy, and one of the standard methods of exposition was the "scholium." The rhetorical purpose of a scholium was to prevent a later reviewer from picking on some aspect of the paper as a "flaw" and using it to dismiss the writer's conclusion. By thinking ahead about the objections that readers might raise to the new theory, and then stating the potentially objectionable ideas in scholia, the author in effect was saying, "yes, I really meant this, no this is not an unnoticed flaw in my reasoning or an unintended consequence of my theory." The scholium served to highlight these challenging ideas and allow the author to head off objections to them.
Newton's First Law is precisely such a scholium, because mathematically it is a consequence of the Second Law (just set acceleration to zero), and so would not need to be stated separately for purposes of the theory. This shows that Newton was keenly aware of the objections that prevailing opinion would raise to his theory. Motion was (and usually still is) thought of as a form of change which was tied to the question of whether the world was perfect and unchanging or imperfect and changing. Change was (and usually still is) thought of as requiring a cause, and the persistence of motion (thought of as change in position) with no active cause, went squarely against the philosophical ideas of Newton's Day.
Newton's answer was to state boldly and simply that this is the way things are, like it or not, and the theory that grows from these postulates justifies them by agreeing with experimental evidence. Newton went a bit further than this also: he referred to objects as being in a "state of rest" or a "state of motion." Modern readers might go right past this phrase without noticing it, but "state of motion" is a RADICAL departure from the pre-Newtonian world view. It is in fact still radical today, because it still has not filtered into the culture as a whole that motion is a "state" not an "activity." By referring to motion as a state, Newton was choosing his terminology in a way that encouraged people to see things his way, and to regard motion as something that DOES NOT NEED a continuing active cause.
The concept of motion as a state rather than an action is central to Galileo's principle of relativity, which says that experiments conducted in a smoothly moving closed room (his example was a ship on a calm sea) would yield results identical to those conducted in a stationary room. If motion required a continuing active cause, then objects that appeared to be at rest in the moving room would need something to keep them moving, and experiments performed on them should detect this force, contradicting Galilean relativity. This means that Galilean relativity amounts to the assumption that the laws of physics are the same inside a moving room, and that the state of rest or motion makes no difference to them.
While Galileo and Newton treated states of motion and of rest equally in their theories, they still did distinguish them. It was not until Einstein that the distinction between them was completely erased. By formulating the special theory of relativity around the assumption that there was NO such thing as absolute rest, Einstein eliminated the state of rest from physics entirely. Rest is merely what the state of the object looks like when you are staying alongside it, and motion is merely what the state looks like if you are not.
From this point of view, the question of what maintains motion becomes completely unnecessary. If I roll a heavy ball forward and ask what keeps it going after it leaves my hand, my question is really no different from asking what keeps my house moving away from me when I drive to work. It is a matter of point of view ONLY, that the house is moving or not moving, and so no physical explanation is required. To me, this is a very interesting way of answering the question. It seems that sometimes the deepest answer to a question is to reformulate our understanding in such a way that the question ceases to mean anything, and that is the case here.
But there is more to this still! Merely saying that motion is a state and that all motion is relative removes the original question, but then a new question arises: WHY is motion a state when it looks so much like change, and when in fact velocity is DEFINED to be rate of change of position? There is a quantum mechanical answer to this question, and it is here that things begin to get rather strange.
From a quantum point of view, any object will have both a particle nature and a wave nature. The waves are usually interpreted as relating to the probability of finding the object at a specific location. For large everyday objects, the wavelength is so very small that it is completely undetectable, but it is nevertheless present. Position and momentum are completely separate variables in quantum mechanics, so momentum is NOT defined as mass*velocity, and velocity is NOT defined as rate of change of position.
Now suppose an object is given some momentum. This places it into a certain quantum state (note that word "state" again). The uncertainty principle says that as long as the object is in a relatively well-defined location, it cannot have just ONE momentum, but actually has a mixture of several momenta, averaging out to the momentum from classical physics. The momenta control the wavelength and phase of the probability waves, which in turn controls how they interfere with each other. Where they interfere constructively, there is a high probability of finding the object there.
A state with NO momentum has a certain spectrum of probability waves, which interfere in such a way that there is an almost certain probability of finding the object in the same location at all times. A state WITH momentum has an altered spectrum of probability waves, which interfere differently, so that the location of constructive interference moves as time goes on. Therefore, you are likely to find the object at a different place at a later time.
In other words, when a force gives an object some momentum, it causes a change in its spectrum, and after the force ceases, the new spectrum is constant just like the original spectrum was. So this truly is a "state" because it persists unchanged. Motion through space is just a SIDE-EFFECT of how interference among the probability waves of the object's momentum spectrum.
It is interesting also to consider how this meshes with relativity. Suppose I have an object and observer moving together, and another observer at rest watching them both. The observer at rest will see the object as having a momentum spectrum that moves its probable location forward as time passes. The observer moving alongside the object will see it at rest, so he must perceive a spectrum that does not move the object forward. How can this be? The answer is that since the probable position is controlled by waves, it is subject to the Doppler shift when there is a moving observer. The Doppler shift of the momentum spectrum makes it look exactly like the momentum spectrum of a stationary object as seen by the observer moving alongside it. Therefore the ideas or relativity still work, and the laws of quantum physics are again the same for observations made from within stationary or moving rooms.
This is probably a lot more than you wanted to read, I hope it helps you with your question!
--Stuart Anderson
I think this is a much deeper question than many people might realize. I will give my point of view on it, although my final conclusion may make your head hurt, and may be more puzzling than your original question! (Fair warning.)
First, from Galileo's and Newton's point of view, the idea that motion could be sustained without outside force was a big breakthrough. This overturned the old philosophical physics of Aristotle and other classical thinkers, and led to a workable theory of mechanics for the first time.
It also raised just the conundrum you have mentioned. This is in fact why Newton chose to state it boldly as his first law. In the days when Newton wrote, much scientific writing was still modeled after philosophy, specifically Scholastic Philosophy, and one of the standard methods of exposition was the "scholium." The rhetorical purpose of a scholium was to prevent a later reviewer from picking on some aspect of the paper as a "flaw" and using it to dismiss the writer's conclusion. By thinking ahead about the objections that readers might raise to the new theory, and then stating the potentially objectionable ideas in scholia, the author in effect was saying, "yes, I really meant this, no this is not an unnoticed flaw in my reasoning or an unintended consequence of my theory." The scholium served to highlight these challenging ideas and allow the author to head off objections to them.
Newton's First Law is precisely such a scholium, because mathematically it is a consequence of the Second Law (just set acceleration to zero), and so would not need to be stated separately for purposes of the theory. This shows that Newton was keenly aware of the objections that prevailing opinion would raise to his theory. Motion was (and usually still is) thought of as a form of change which was tied to the question of whether the world was perfect and unchanging or imperfect and changing. Change was (and usually still is) thought of as requiring a cause, and the persistence of motion (thought of as change in position) with no active cause, went squarely against the philosophical ideas of Newton's Day.
Newton's answer was to state boldly and simply that this is the way things are, like it or not, and the theory that grows from these postulates justifies them by agreeing with experimental evidence. Newton went a bit further than this also: he referred to objects as being in a "state of rest" or a "state of motion." Modern readers might go right past this phrase without noticing it, but "state of motion" is a RADICAL departure from the pre-Newtonian world view. It is in fact still radical today, because it still has not filtered into the culture as a whole that motion is a "state" not an "activity." By referring to motion as a state, Newton was choosing his terminology in a way that encouraged people to see things his way, and to regard motion as something that DOES NOT NEED a continuing active cause.
The concept of motion as a state rather than an action is central to Galileo's principle of relativity, which says that experiments conducted in a smoothly moving closed room (his example was a ship on a calm sea) would yield results identical to those conducted in a stationary room. If motion required a continuing active cause, then objects that appeared to be at rest in the moving room would need something to keep them moving, and experiments performed on them should detect this force, contradicting Galilean relativity. This means that Galilean relativity amounts to the assumption that the laws of physics are the same inside a moving room, and that the state of rest or motion makes no difference to them.
While Galileo and Newton treated states of motion and of rest equally in their theories, they still did distinguish them. It was not until Einstein that the distinction between them was completely erased. By formulating the special theory of relativity around the assumption that there was NO such thing as absolute rest, Einstein eliminated the state of rest from physics entirely. Rest is merely what the state of the object looks like when you are staying alongside it, and motion is merely what the state looks like if you are not.
From this point of view, the question of what maintains motion becomes completely unnecessary. If I roll a heavy ball forward and ask what keeps it going after it leaves my hand, my question is really no different from asking what keeps my house moving away from me when I drive to work. It is a matter of point of view ONLY, that the house is moving or not moving, and so no physical explanation is required. To me, this is a very interesting way of answering the question. It seems that sometimes the deepest answer to a question is to reformulate our understanding in such a way that the question ceases to mean anything, and that is the case here.
But there is more to this still! Merely saying that motion is a state and that all motion is relative removes the original question, but then a new question arises: WHY is motion a state when it looks so much like change, and when in fact velocity is DEFINED to be rate of change of position? There is a quantum mechanical answer to this question, and it is here that things begin to get rather strange.
From a quantum point of view, any object will have both a particle nature and a wave nature. The waves are usually interpreted as relating to the probability of finding the object at a specific location. For large everyday objects, the wavelength is so very small that it is completely undetectable, but it is nevertheless present. Position and momentum are completely separate variables in quantum mechanics, so momentum is NOT defined as mass*velocity, and velocity is NOT defined as rate of change of position.
Now suppose an object is given some momentum. This places it into a certain quantum state (note that word "state" again). The uncertainty principle says that as long as the object is in a relatively well-defined location, it cannot have just ONE momentum, but actually has a mixture of several momenta, averaging out to the momentum from classical physics. The momenta control the wavelength and phase of the probability waves, which in turn controls how they interfere with each other. Where they interfere constructively, there is a high probability of finding the object there.
A state with NO momentum has a certain spectrum of probability waves, which interfere in such a way that there is an almost certain probability of finding the object in the same location at all times. A state WITH momentum has an altered spectrum of probability waves, which interfere differently, so that the location of constructive interference moves as time goes on. Therefore, you are likely to find the object at a different place at a later time.
In other words, when a force gives an object some momentum, it causes a change in its spectrum, and after the force ceases, the new spectrum is constant just like the original spectrum was. So this truly is a "state" because it persists unchanged. Motion through space is just a SIDE-EFFECT of how interference among the probability waves of the object's momentum spectrum.
It is interesting also to consider how this meshes with relativity. Suppose I have an object and observer moving together, and another observer at rest watching them both. The observer at rest will see the object as having a momentum spectrum that moves its probable location forward as time passes. The observer moving alongside the object will see it at rest, so he must perceive a spectrum that does not move the object forward. How can this be? The answer is that since the probable position is controlled by waves, it is subject to the Doppler shift when there is a moving observer. The Doppler shift of the momentum spectrum makes it look exactly like the momentum spectrum of a stationary object as seen by the observer moving alongside it. Therefore the ideas or relativity still work, and the laws of quantum physics are again the same for observations made from within stationary or moving rooms.
This is probably a lot more than you wanted to read, I hope it helps you with your question!
--Stuart Anderson
QUOTE (Fernando Cacciola+Jul 5 2004, 11:18 PM)
OK, but how is that possible? I mean, **why** does an object keep moving with the "last" speed and direction if left unperturbed?
By AWT every object motion is just temporal, because it should be qualified as the leveling of Aether mass density concentration in different dimensions - the causality just flows from one space time into another, while the total causality density remains huge and as such unchanged. The total inertia of Universe is limited just by our capability to comprehend it and understand it. Indeed, from limited space/time perspective the motion can be described by Newton inertia law: the matter is the standing wave packet, so it moves/propagates like soliton wave through Aether foam. But the true origin of inertia is unclear even from AWT perspective. The AWT just assumes, the Universe is full of inertial matter in chaotic motion. The randomness of motion gives such environment the appearance of emptiness, because its inertial effects of this motion are compensating at short distances. By such way, the observable inertia is always connected with the violation of chaos, i.e. the less or more causal mass/energy density gradients. The most causal is the harmonic motion, because it's recursively driven by gradients.
The local mechanism of inertia is connected with the formation of deBroglie wave, which creates an additional increasing of vacuum density in the neighborhood of each moving particle by the same way, like the standing wave, which is forming above the fish swimming beneath the water surface. This area of dense vacuum acts as the source of inertial energy and so called relativistic mass at the same time. The deBroglie wave makes the Aether more causal by introducing of local density gradients, so it can manifests its incredible energy density. By such way, the explanation of inertia by AWT is infinitely recursive, because whole the AWT just depends on the Newton inertia laws. Whole the question about origin of some phenomena is infinitely recursive, because you can always ask about origin of such origin. Because the recursive question can only supply the recursive answer, you are simply required to put the better questions, if you're really interested about true origin of the Universe inertia. The inter-subjective understanding of causality concept by Popper methodology gives not the suitable framework for answering of final questions, because of its inherent recursively: every reason can have another reasons, therefore every reasoning is just local and temporary. From this point of view, every self-referencing recursive tautology can be considered as the final answer in context of Popper's causality methodology.
By AWT every object motion is just temporal, because it should be qualified as the leveling of Aether mass density concentration in different dimensions - the causality just flows from one space time into another, while the total causality density remains huge and as such unchanged. The total inertia of Universe is limited just by our capability to comprehend it and understand it. Indeed, from limited space/time perspective the motion can be described by Newton inertia law: the matter is the standing wave packet, so it moves/propagates like soliton wave through Aether foam. But the true origin of inertia is unclear even from AWT perspective. The AWT just assumes, the Universe is full of inertial matter in chaotic motion. The randomness of motion gives such environment the appearance of emptiness, because its inertial effects of this motion are compensating at short distances. By such way, the observable inertia is always connected with the violation of chaos, i.e. the less or more causal mass/energy density gradients. The most causal is the harmonic motion, because it's recursively driven by gradients.
The local mechanism of inertia is connected with the formation of deBroglie wave, which creates an additional increasing of vacuum density in the neighborhood of each moving particle by the same way, like the standing wave, which is forming above the fish swimming beneath the water surface. This area of dense vacuum acts as the source of inertial energy and so called relativistic mass at the same time. The deBroglie wave makes the Aether more causal by introducing of local density gradients, so it can manifests its incredible energy density. By such way, the explanation of inertia by AWT is infinitely recursive, because whole the AWT just depends on the Newton inertia laws. Whole the question about origin of some phenomena is infinitely recursive, because you can always ask about origin of such origin. Because the recursive question can only supply the recursive answer, you are simply required to put the better questions, if you're really interested about true origin of the Universe inertia. The inter-subjective understanding of causality concept by Popper methodology gives not the suitable framework for answering of final questions, because of its inherent recursively: every reason can have another reasons, therefore every reasoning is just local and temporary. From this point of view, every self-referencing recursive tautology can be considered as the final answer in context of Popper's causality methodology.
The persitence of motion is a gravitational effect. Newton's Universal Gravitation and 1st Law are 2 features of the same principle, a principle that dictate how mass behaves. (Do you accept Newton's Universal Gravitation?) Both features require the presence of another mass, but the requirement for inertia is more subtle/philosophical, and I suppose Newton may disagree with me and propose the existence of absolute space. However, Newton may just appeal to "the fixed stars", which would provide a very real and immense other massive object.
Frome here:-
http://www.physforum.com/index.php?showtop...ndpost&p=184048
Now suppose an object is given some momentum. This places it into a certain quantum state (note that word "state" again). The uncertainty principle says that as long as the object is in a relatively well-defined location, it cannot have just ONE momentum, but actually has a mixture of several momenta, averaging out to the momentum from classical physics. The momenta control the wavelength and phase of the probability waves, which in turn controls how they interfere with each other. Where they interfere constructively, there is a high probability of finding the object there.
I may be taking this further than intended and making an incorrect guess .. however..
If an electron is in an accelerated state then there is no way the probability waves can truly interfere to a single position without something extra happening .. the guess is that the 'extra' is the emission of photons which fill in the probability wave of the electron's momentum/position/charge.
Comments/thoughts most welcome.
-C2.
http://www.physforum.com/index.php?showtop...ndpost&p=184048
QUOTE (Mr Homm+)
Now suppose an object is given some momentum. This places it into a certain quantum state (note that word "state" again). The uncertainty principle says that as long as the object is in a relatively well-defined location, it cannot have just ONE momentum, but actually has a mixture of several momenta, averaging out to the momentum from classical physics. The momenta control the wavelength and phase of the probability waves, which in turn controls how they interfere with each other. Where they interfere constructively, there is a high probability of finding the object there.
I may be taking this further than intended and making an incorrect guess .. however..
If an electron is in an accelerated state then there is no way the probability waves can truly interfere to a single position without something extra happening .. the guess is that the 'extra' is the emission of photons which fill in the probability wave of the electron's momentum/position/charge.
Comments/thoughts most welcome.
-C2.
QUOTE (mr_homm+Mar 2 2007, 09:52 PM)
Hi Fernando Cacciola,
I think this is a much deeper question than many people might realize. I will give my point of view on it, although my final conclusion may make your head hurt, and may be more puzzling than your original question! (Fair warning.)
First, from Galileo's and Newton's point of view, the idea that motion could be sustained without outside force was a big breakthrough. This overturned the old philosophical physics of Aristotle and other classical thinkers, and led to a workable theory of mechanics for the first time.
It also raised just the conundrum you have mentioned. This is in fact why Newton chose to state it boldly as his first law. In the days when Newton wrote, much scientific writing was still modeled after philosophy, specifically Scholastic Philosophy, and one of the standard methods of exposition was the "scholium." The rhetorical purpose of a scholium was to prevent a later reviewer from picking on some aspect of the paper as a "flaw" and using it to dismiss the writer's conclusion. By thinking ahead about the objections that readers might raise to the new theory, and then stating the potentially objectionable ideas in scholia, the author in effect was saying, "yes, I really meant this, no this is not an unnoticed flaw in my reasoning or an unintended consequence of my theory." The scholium served to highlight these challenging ideas and allow the author to head off objections to them.
Newton's First Law is precisely such a scholium, because mathematically it is a consequence of the Second Law (just set acceleration to zero), and so would not need to be stated separately for purposes of the theory. This shows that Newton was keenly aware of the objections that prevailing opinion would raise to his theory. Motion was (and usually still is) thought of as a form of change which was tied to the question of whether the world was perfect and unchanging or imperfect and changing. Change was (and usually still is) thought of as requiring a cause, and the persistence of motion (thought of as change in position) with no active cause, went squarely against the philosophical ideas of Newton's Day.
Newton's answer was to state boldly and simply that this is the way things are, like it or not, and the theory that grows from these postulates justifies them by agreeing with experimental evidence. Newton went a bit further than this also: he referred to objects as being in a "state of rest" or a "state of motion." Modern readers might go right past this phrase without noticing it, but "state of motion" is a RADICAL departure from the pre-Newtonian world view. It is in fact still radical today, because it still has not filtered into the culture as a whole that motion is a "state" not an "activity." By referring to motion as a state, Newton was choosing his terminology in a way that encouraged people to see things his way, and to regard motion as something that DOES NOT NEED a continuing active cause.
The concept of motion as a state rather than an action is central to Galileo's principle of relativity, which says that experiments conducted in a smoothly moving closed room (his example was a ship on a calm sea) would yield results identical to those conducted in a stationary room. If motion required a continuing active cause, then objects that appeared to be at rest in the moving room would need something to keep them moving, and experiments performed on them should detect this force, contradicting Galilean relativity. This means that Galilean relativity amounts to the assumption that the laws of physics are the same inside a moving room, and that the state of rest or motion makes no difference to them.
While Galileo and Newton treated states of motion and of rest equally in their theories, they still did distinguish them. It was not until Einstein that the distinction between them was completely erased. By formulating the special theory of relativity around the assumption that there was NO such thing as absolute rest, Einstein eliminated the state of rest from physics entirely. Rest is merely what the state of the object looks like when you are staying alongside it, and motion is merely what the state looks like if you are not.
From this point of view, the question of what maintains motion becomes completely unnecessary. If I roll a heavy ball forward and ask what keeps it going after it leaves my hand, my question is really no different from asking what keeps my house moving away from me when I drive to work. It is a matter of point of view ONLY, that the house is moving or not moving, and so no physical explanation is required. To me, this is a very interesting way of answering the question. It seems that sometimes the deepest answer to a question is to reformulate our understanding in such a way that the question ceases to mean anything, and that is the case here.
But there is more to this still! Merely saying that motion is a state and that all motion is relative removes the original question, but then a new question arises: WHY is motion a state when it looks so much like change, and when in fact velocity is DEFINED to be rate of change of position? There is a quantum mechanical answer to this question, and it is here that things begin to get rather strange.
From a quantum point of view, any object will have both a particle nature and a wave nature. The waves are usually interpreted as relating to the probability of finding the object at a specific location. For large everyday objects, the wavelength is so very small that it is completely undetectable, but it is nevertheless present. Position and momentum are completely separate variables in quantum mechanics, so momentum is NOT defined as mass*velocity, and velocity is NOT defined as rate of change of position.
Now suppose an object is given some momentum. This places it into a certain quantum state (note that word "state" again). The uncertainty principle says that as long as the object is in a relatively well-defined location, it cannot have just ONE momentum, but actually has a mixture of several momenta, averaging out to the momentum from classical physics. The momenta control the wavelength and phase of the probability waves, which in turn controls how they interfere with each other. Where they interfere constructively, there is a high probability of finding the object there.
A state with NO momentum has a certain spectrum of probability waves, which interfere in such a way that there is an almost certain probability of finding the object in the same location at all times. A state WITH momentum has an altered spectrum of probability waves, which interfere differently, so that the location of constructive interference moves as time goes on. Therefore, you are likely to find the object at a different place at a later time.
In other words, when a force gives an object some momentum, it causes a change in its spectrum, and after the force ceases, the new spectrum is constant just like the original spectrum was. So this truly is a "state" because it persists unchanged. Motion through space is just a SIDE-EFFECT of how interference among the probability waves of the object's momentum spectrum.
It is interesting also to consider how this meshes with relativity. Suppose I have an object and observer moving together, and another observer at rest watching them both. The observer at rest will see the object as having a momentum spectrum that moves its probable location forward as time passes. The observer moving alongside the object will see it at rest, so he must perceive a spectrum that does not move the object forward. How can this be? The answer is that since the probable position is controlled by waves, it is subject to the Doppler shift when there is a moving observer. The Doppler shift of the momentum spectrum makes it look exactly like the momentum spectrum of a stationary object as seen by the observer moving alongside it. Therefore the ideas or relativity still work, and the laws of quantum physics are again the same for observations made from within stationary or moving rooms.
This is probably a lot more than you wanted to read, I hope it helps you with your question!
--Stuart Anderson
Excellent post Stuart....something not found often on these sites.
You may want to address "Confused2"s post as to what happens in an accelerated frame.
JW
I think this is a much deeper question than many people might realize. I will give my point of view on it, although my final conclusion may make your head hurt, and may be more puzzling than your original question! (Fair warning.)
First, from Galileo's and Newton's point of view, the idea that motion could be sustained without outside force was a big breakthrough. This overturned the old philosophical physics of Aristotle and other classical thinkers, and led to a workable theory of mechanics for the first time.
It also raised just the conundrum you have mentioned. This is in fact why Newton chose to state it boldly as his first law. In the days when Newton wrote, much scientific writing was still modeled after philosophy, specifically Scholastic Philosophy, and one of the standard methods of exposition was the "scholium." The rhetorical purpose of a scholium was to prevent a later reviewer from picking on some aspect of the paper as a "flaw" and using it to dismiss the writer's conclusion. By thinking ahead about the objections that readers might raise to the new theory, and then stating the potentially objectionable ideas in scholia, the author in effect was saying, "yes, I really meant this, no this is not an unnoticed flaw in my reasoning or an unintended consequence of my theory." The scholium served to highlight these challenging ideas and allow the author to head off objections to them.
Newton's First Law is precisely such a scholium, because mathematically it is a consequence of the Second Law (just set acceleration to zero), and so would not need to be stated separately for purposes of the theory. This shows that Newton was keenly aware of the objections that prevailing opinion would raise to his theory. Motion was (and usually still is) thought of as a form of change which was tied to the question of whether the world was perfect and unchanging or imperfect and changing. Change was (and usually still is) thought of as requiring a cause, and the persistence of motion (thought of as change in position) with no active cause, went squarely against the philosophical ideas of Newton's Day.
Newton's answer was to state boldly and simply that this is the way things are, like it or not, and the theory that grows from these postulates justifies them by agreeing with experimental evidence. Newton went a bit further than this also: he referred to objects as being in a "state of rest" or a "state of motion." Modern readers might go right past this phrase without noticing it, but "state of motion" is a RADICAL departure from the pre-Newtonian world view. It is in fact still radical today, because it still has not filtered into the culture as a whole that motion is a "state" not an "activity." By referring to motion as a state, Newton was choosing his terminology in a way that encouraged people to see things his way, and to regard motion as something that DOES NOT NEED a continuing active cause.
The concept of motion as a state rather than an action is central to Galileo's principle of relativity, which says that experiments conducted in a smoothly moving closed room (his example was a ship on a calm sea) would yield results identical to those conducted in a stationary room. If motion required a continuing active cause, then objects that appeared to be at rest in the moving room would need something to keep them moving, and experiments performed on them should detect this force, contradicting Galilean relativity. This means that Galilean relativity amounts to the assumption that the laws of physics are the same inside a moving room, and that the state of rest or motion makes no difference to them.
While Galileo and Newton treated states of motion and of rest equally in their theories, they still did distinguish them. It was not until Einstein that the distinction between them was completely erased. By formulating the special theory of relativity around the assumption that there was NO such thing as absolute rest, Einstein eliminated the state of rest from physics entirely. Rest is merely what the state of the object looks like when you are staying alongside it, and motion is merely what the state looks like if you are not.
From this point of view, the question of what maintains motion becomes completely unnecessary. If I roll a heavy ball forward and ask what keeps it going after it leaves my hand, my question is really no different from asking what keeps my house moving away from me when I drive to work. It is a matter of point of view ONLY, that the house is moving or not moving, and so no physical explanation is required. To me, this is a very interesting way of answering the question. It seems that sometimes the deepest answer to a question is to reformulate our understanding in such a way that the question ceases to mean anything, and that is the case here.
But there is more to this still! Merely saying that motion is a state and that all motion is relative removes the original question, but then a new question arises: WHY is motion a state when it looks so much like change, and when in fact velocity is DEFINED to be rate of change of position? There is a quantum mechanical answer to this question, and it is here that things begin to get rather strange.
From a quantum point of view, any object will have both a particle nature and a wave nature. The waves are usually interpreted as relating to the probability of finding the object at a specific location. For large everyday objects, the wavelength is so very small that it is completely undetectable, but it is nevertheless present. Position and momentum are completely separate variables in quantum mechanics, so momentum is NOT defined as mass*velocity, and velocity is NOT defined as rate of change of position.
Now suppose an object is given some momentum. This places it into a certain quantum state (note that word "state" again). The uncertainty principle says that as long as the object is in a relatively well-defined location, it cannot have just ONE momentum, but actually has a mixture of several momenta, averaging out to the momentum from classical physics. The momenta control the wavelength and phase of the probability waves, which in turn controls how they interfere with each other. Where they interfere constructively, there is a high probability of finding the object there.
A state with NO momentum has a certain spectrum of probability waves, which interfere in such a way that there is an almost certain probability of finding the object in the same location at all times. A state WITH momentum has an altered spectrum of probability waves, which interfere differently, so that the location of constructive interference moves as time goes on. Therefore, you are likely to find the object at a different place at a later time.
In other words, when a force gives an object some momentum, it causes a change in its spectrum, and after the force ceases, the new spectrum is constant just like the original spectrum was. So this truly is a "state" because it persists unchanged. Motion through space is just a SIDE-EFFECT of how interference among the probability waves of the object's momentum spectrum.
It is interesting also to consider how this meshes with relativity. Suppose I have an object and observer moving together, and another observer at rest watching them both. The observer at rest will see the object as having a momentum spectrum that moves its probable location forward as time passes. The observer moving alongside the object will see it at rest, so he must perceive a spectrum that does not move the object forward. How can this be? The answer is that since the probable position is controlled by waves, it is subject to the Doppler shift when there is a moving observer. The Doppler shift of the momentum spectrum makes it look exactly like the momentum spectrum of a stationary object as seen by the observer moving alongside it. Therefore the ideas or relativity still work, and the laws of quantum physics are again the same for observations made from within stationary or moving rooms.
This is probably a lot more than you wanted to read, I hope it helps you with your question!
--Stuart Anderson
Excellent post Stuart....something not found often on these sites.
You may want to address "Confused2"s post as to what happens in an accelerated frame.
JW
============.
From an article:
“An old professor of mine used to say
that anyone who can answer that question
what inertia is , would win a Nobel Prize. “
===============.
From an article:
“An old professor of mine used to say
that anyone who can answer that question
what inertia is , would win a Nobel Prize. “
===============.
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