Newton's Laws

This is to continue the discussion started in "What is a creationist"

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Common sense isn't

Eventually you get to a point where you're proposing new energies to explain unique circumstances. Magnetism is a general phenomenon that explains several things besides these apparent contraditions of Newton's Laws.Tidhare: Magnetism explains the APPERENT contradictions in Newton’s laws? It was these REAL contradictions which lead to the theory of relativity.On the chance that you do know what you are talking about can you explain how the contradictions caused by magnetism lead to relativity. It was real contradictions but not magnetism.As noted elsewhere you have confounded the laws of motion with Newton's theory of gravity.

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Common sense isn't

Sorry, I am trying to switch treads but I am unsure of how to post without simply replying. If you could please inform the person that I am having this discussion with that I have moved here, I would be grateful. Only by stating that the electromagnetic field carries momentum and energy, which is ad hoc to save Newton’s laws. I only mentioned Newton’s law of gravitation previously because it was the only fundamental force known to Newton himself. Other forces were later added, ad hoc, to preserve Newton’s laws. Which once again brings up the question, how exactly would you test or verify Newton’s laws? So when exactly was electromagnetism recognized as a force? How exactly was electromagnetism recognized as a force? I hope you do not misunderstand me. I do not think Newton was either right or wrong. He put forth a way of looking at the world. You say it is simply a matter of not getting all his basic assumptions correct. How exactly would you prove his basic assumptions are wrong?

Sure. It was the contradiction between Newton’s laws which specified no preferred frame of reference and the laws of electromagnetism which specified the preferred frame where the velocity of electromagnetic propagation was c (speed of light in vaccum). Could you please point out where I have done so.

Could you explain more? All that the field has to do is exert a force. Objects subject to that force obey Newton's laws very precisely. Do you want the history in detail? I'd have to look it up. Basically it was early 19th century and by seeing that it had an affect on objects. Why? I don't see the definition of "ad hoc" being applicable here. Ad hoc, to me, means constructed and used to solve one specific problem with disregard for other issues. The other forces fit in very well in many places, do not conflict with any other observations. I don't see how this is "ad hoc". As noted, is the Rover on Mars? Will the next eclipse occur on time? Can a missle be fired form California to the mid pacific and be where it is predicted to be? By observation, and his basic assumptions where wrong! F does not equal ma at relativisitic speeds.

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Common sense isn't

What is a field? How does a field exert a force? These things were invented just so Objects subject to that force obey Newton's laws very precisely. Ok, I withdraw the when question. HOW exactly was electromagnetism recognized as a force? What effect did it have on objects? HOW WOULD YOU TEST OR VERIFY THAT NEWTON’S LAWS ARE CORRECT? There was an acceleration with no KNOWN force, so they made one upad hoc. Did I not say that the verifiability of science was in its USEFULNESS? I don’t believe Newton said F=ma. He said force is equal to the time rate of change of momentum (d/dt(mv)). Are you saying this isn’t true relativisitically?

It depends on how picky you are being with Newton. He did assume that the mass was constant and didn't separate the idea of rest mass out. He calculated speeds based on the accelerations and they are wrong. It takes relativistic speeds or enormous precision to be able to observe the error though.Fields are a conceptual idea, invented as you say. However, they are perfectly useful concepts. Now we understand that an exchange of photons is what we see as the EM field. Any more detail than that and you're going to have to talk to a real physicist. And, again, which you have avoided getting to. So what?The development of EM theory has been very successful in predicting observations. It combined with Newton's laws of motion stand up very well. What's wrong witht that?You seem to think there is some problem with adding new concepts as new observations make it necessary. Why? I'm not at all sure what you are looking for? I'd measure them. I think you'll find that the whole thing eventually gets down to things like conservation of mass/energy. Yea, sorta. But you have to ignore a lot of what has really transpired to make such an oversimplied, and therefore in this case, wrong, statement. Actually, we have a case where Newton's laws have done very well. Then we get an acceleration without an apparent force. Two choices are available. Toss Newton's laws which are very useful or postulate an additional force.Ok, if there is an additional force then what? Well lots of things. And guess what! Those lots of things are observable. That suggests that the additional force was the right thing to postualate. The additional force leads to lots of other useful predictions. It ties in nicely with everything else. It is not "ad hoc" as I was defining it. "Ad hoc" does not mean "new" it means something like "to this special case". So? You agree these are 'useful' tests of Newton's laws? And would they have been less meaningful if the results had been not useful in some way but simply tests. For example, flying atomic clocks in airliners?

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What goes? The Nose Knows!

The truth depends on how picky I am? He would have had no idea what rest mass even means. I see no calculations of speed in Newton’s three laws. Einstein seemed to notice. They have momentum and energy. How many conceptual things do you know of that have momentum and energy? As I said, the verifability of science is in its usefulness. So what? Someone said Newton’s laws were created testable and verifiable. I asked how are they testable and verifiable. Electromagnetic theory conflicts with Newton’s laws, hence relativity. No. I had a problem with someone saying Newton’s laws were only science because they were testable and verifiable. You would measure Newton’s laws? What does this mean? Classically, energy is not a fundamental quantity. It was made up. How is it yea sorta and wrong at the same time? I never said they weren’t USEFUL. Right. So once again, how do you verify Newton’s laws? What in the world is observable about gravity but its effect? I never said that Newton’s laws weren’t useful I wonder why. So you make up a force because you need one to fit your theory and you say it is not ad hoc? What tests? If a body does not act in the way predicted by Newton’s laws you simply make up a force to account for it. You can’t be wrong. You have tested nothing.Sincerely
Tidhare

No, of course not. However, if F=ma at relativistic speeds (and I'm not sure it does) you get a choice of whether you choose to consider Newton wrong or not. His F=ma may be correct but, as you note, he was, underlying that assuming that m was constant, that a could be any size you wanted and it's integral could be any magniture. Since we know those assumptions are wrong we could consider Newton wrong even if his laws do hold (if they do). Exactly, so he was "wrong". And what is the integral of a? No he didn't. Einstein was a theoretician and didn't make observations. Do they? Particularly momentum, I didn't know that. Besides if they are only conceptual in that the force is actually the result of an exchange of photons then we are only using the properties of the EM field as a useful tool in conceptualizing and calculations. As I understand it someone who takes the view that what works is good enough and doesn't care what is "really" under there is a "positivist". So you , it seems are a positivist. So they aren't "really" (whatever that means) there. I think someone already pointed out that this isn't the case. Can you explain how your "hence" works there? If I apply a force to a mass for a period of time I measure it's speed and derive it's acceleration. You have a problem with that?The laws are an explanation of ratios between some values. Do they hold or not? So is force, acceleration and so on. What does that matter. They are humans generalizations of observations in nature. What do you mean by "classically". This is a new term to me. Have you missed that fact that Newton's laws have not only been tested but falsified? They are, afterall, wrong. They are right enough to be very useful still but they are it turns out not precisely right. So they have been "verified" or rather tested since "verified" isn't the right word here. That is dangerously close to "proven". Yes, because it fits in with other observations and a unified explanation. It's usefulness is not restricted to this special case.I made an attempt to supply my idea of what "ad hoc" is. Perhaps you need to do that now. Uh, Tidhare, what is observable about anything but it's effects? Gee, you missed the little point that Newton's laws are, in fact, wrong. So much for that.

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Common sense isn't

I found it, but like I said before I'm no phsyicist so I think we're already beyond my ability to make cogent points. I'm bowing out - with one last comment:If you're trying to argue that Newton's Laws of motion are unfalsifiable simply because they can lead to the assumption of new forces, well, I don't see that as ad-hoc reasoning but simply modification of theory by new data. And furthermore you're going to have a hard time arguing that Newton's laws are unfalsifiable given that the theory of realtivity totally falsified them.[This message has been edited by crashfrog, 01-21-2004]

qs No, of course not. However, if F=ma at relativistic speeds (and I'm not sure it does) you get a choice of whether you choose to consider Newton wrong or not. His F=ma may be correct but, as you note, he was, underlying that assuming that m was constant, that a could be any size you wanted and it's integral could be any magniture. Since we know those assumptions are wrong we could consider Newton wrong even if his laws do hold (if they do).[/qs] Newton’s second law states that force is equal to the time rate of change of momentum. This is true relativistically. It is the classical conventions for momentum which must be altered to retain conservation of momentum in special relativity. You keep saying Newton was wrong. Could you please state specifically which of his three laws were proven wrong? Please state specifically which of Newton’s three laws was proven wrong. There is no a in Newton’s three laws. Einstein saw the need for special relativity and he didn’t need observations of relativistic speeds or enormous precision Photons are quantized fluctuations of the electromagnetic field. Fluctuations of the electromagnetic field carry both energy and momentum. Are you saying I should ask WHY physics behaves the way it does? Seems more like a metaphysical question to me. What’s not really there? Photons? If it is not there why would we pretend it is?
. [qs] I think someone already pointed out that this isn't the case. Can you explain how your "hence" works there? [qs] Newton’s first law states that the laws of physics are valid in any non-accelerating reference frame. That is if the laws of physics are valid in a given reference frame then the laws of physics are also valid in any frame which has a uniform velocity to the given frame. Therefore, no specific inertial reference frame is preferred for the laws of physics. Maxwell’s equations, however, state that they are valid only for the frame where the propagation of electromagnetic waves is a speed c. This is a conflict. I don’t see how this is measuring Newton’s laws. Yes the laws hold. Because if they don’t you make up a force which causes them to hold. Force is a fundamental quantity in classical physics. Energies are merely quantities derived from Newton’s laws. This is not the case however in quantum mechanics, where the energies are the fundamental quantities. Classical physics simply means pre-quantum theory physics. I wish you would please specify which of Newton’s three laws was proven wrong. And I take it these observations are you have accelerations and you need a force. That is circular reasoning. My definition of ad hoc is you postulate something after observation to make the observation fit your theory. So where are the lots of things. And guess what! Those lots of things are observable When I put up my first post I actually had a point Newton’s laws are based on circular reasoning. Newton simply said an object at rest stays that way unless acted upon by a force. He then defines a force as a mass times its acceleration. There is no way to verify if this is true or not. Suppose you have a situation and you apply Newton’s laws to determine the motion of an object. Suppose the motion you derive doesn’t match the motion you observe. Do you say well then Newton’s laws must be wrong or do you say there must be forces I didn’t consider? You do realize that people apply Newton’s laws to non-inertial reference frames and make up fictitious forces just so the laws will be correct.

I'll come back to more later as I don't have time right now but: How is this circular reasoning?What he is saying is that an object stays at rest or in motion unless acted upon by a force. He doesn't define force that I am aware of. He then says that there is a particular ration between the force applied and the resulting change in motion. It is an elaboration on the first statement. [qs]Suppose you have a situation and you apply Newton’s laws to determine the motion of an object. Suppose the motion you derive doesn’t match the motion you observe. Do you say well then Newton’s laws must be wrong or do you say there must be forces I didn’t consider? /qsBoth as has been noted. First, we have many cases of Newton's laws being thoroughly useful. Then we have cases where there does seem to be something else going on (eg the discovery of Uranus). Then we have the case where it turns out Newton is wrong. If it can't be tested how did we get to that point.Now when additional forces are postulated is that the end of it? No! These additional forces need a source, need to behave in some reasonable way, need to be subject to further testing etc. etc. Only if they pass through this rigor do we decide that Newton's laws have survived for the time being. I suspect you are talking about the so-called "centrifical force". That is not why that concept is used. In fact it has nothing to do with making Newton's laws correct. If you are talking about something else you will have to explain.

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Common sense isn't

Force is defined as the time rate of change of momentum. He says that an object at rest stays at rest unless acted upon by a force. I say prove it. Furthermore, what if I told you I saw an object accelerate with no force acting on it. What would you say? We got to this point because his theory conflicted with another theory. Because of this his definition of momentum had to be modified. Regardless, the law still states that an object at rest will remain that way unless acted upon by a force. I say prove it. What is the source for the electric force? Now don’t just make something up and call it for instance charge. What does this source look like? How much does it weigh? This is ridiculous. Why would a force need to behave in some reasonable way? If you have an unexplained acceleration Newton’s law says you have a force you’re not considering. Why would you need further testing to figure this out? The rigors of what? Making up forces for accelerations you can’t explain? Why when you roll a ball on the ground does it come to rest? Doesn’t Newton’s law say it should keep rolling? Shucks, must be some force causing the ball to slow down. I know Newton can’t be wrong. That would be one, Coriolis is another. Why in the world would we make up a force if not to correctly describe the motion of an object? That is what Newton’s laws do right?

Because we don't make up such a force. That is why. I'd say let's replicate your work. Then I'd look very carefully. In fact everything that I can reasonably think of doing has been done. See the next bit.What would be done is exactly what has been done. The possibility of addition forces has been considered and the possibility of Newton's laws breaking down.

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Astronomers studied the Doppler shift of the radio signals to help calculate the distances of the probes. After extensive analysis, they dismissed instrumentation error, propellant leaks and minor heat emissions as causes of the negative thrust. "Perhaps the spacecraft inadvertently produced an unknown force that is not yet understood. Perhaps scientists will have to reconsider basic assumptions about the laws of physics. No one has come up with a conventional explanation. One possible reason is that it is a modification of gravity."

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from:http://www.geocities.com/solarstormmonitor/Pioneer.htmlNow if over centuries the postualtion of a force when descrepancies were noted had always produced new interesting science and real discoveries, that is it was a useful thing to do, what would you think would be a good bet when the situation arose again. Right, postulate a force!However, as you can see above, when the observations require change it is considered. And here they are considering pretty fundamental change.However, would you through something out at the first moment of a discrepancy? Not until you have lots of good information. Science is conservative when it comes to well tested ideas.Now, I think we've reached a point where you can see that Newton's laws can be tested. They aave actually been falsified in the case of relativity. (I'll get to that when I catch up with the rest of a previous post) The possibility of significant change beyond postualting a new force has also been considered. Is there anything else that one could reasonably consider doing? For a wide variety of conditions it has been tested and "proved". The coreolis and centrifigal forces are frequently called "fictitious forces". They are convenient in allow an intuitive understanding of what goes on. They are completely unnecessary if you want to do detailed classical mechanical calculations directly using Newton's laws. Your problem with this hints that you aren't all that familiar with the physics. Sorry, figure of speech. Any postulated additional force (or other effect) needs to be fitted into what is already known. It can not contradict well founded observations already made under other conditions.Thus, if the pioneer problem requires a modification to gravity then apples must still be predicted to fall. Obviously, one possibility is always experimental error. With something as well established as the laws of motion a single anomaly wouldn't result in an instant chucking of the whole thing. Once error and other things have been ruled out then it gets very interesting. As an example see the Pioneer anomaly. Guess what, the images you are seeing on the screen are a result of those sources. Discovered well after the idea of charge was needed. You don't know the history of this very well do you? And gee, amazing isn't it? When the additional force is postulated, mechanisms for it are found, it is measured and observed directly and when tests are done minimizing or removing it altogether then Newton's laws hold. This is obviously why only an idiot would object to trying the same trick the next time some discrepancy shows up. It has worked spectacularly well in the past. As you say, "Is it useful?"Even with that spectacular success there is the possibliity of considering other things as noted above.

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Common sense isn't

When F=ma is integrated it produces a speed. Newton assumed a constant mass. This was wrong. The speed calculated by Newton's laws is incorrect under some conditions. If you assume, as Newton did, that m is constant then the derivative of momentum is an acceleration. We were discussing observations (as in "saw") and tests when this came up. Einstein "saw", (experimentally observed) no such thing. His work was not based on any discrepancy in Newton's laws at all. They discrepancies came out of his work. The offered a testable prediction. Until tests were done his work was very interesting but not accepted as it is now. Are they? Could you explain please? I'm not an expert, but yes, I think positivism is a metaphysical position. I do know that many physicists avoid asking "why" quantum mechanics behaves as it does. It works too well.However, there are those who do grapple with the hard question of what underlies it all. Why is the question we would like to answer. This is a century when that may actually have an answer. Meanwhile most are content to know how things behave first. I still don't get it. Could you explain the conflict in more detail and how Einstein used it to get to special relativity? Do the formulae of the laws hold? How is this not testing the laws? And you would do something else when this has worked so very well before? And as noted in another post this is not always done. You are making assertions which are contradicted by what has actually gone on. You also seem to think it makes sense to ignore very successful approachs that have lead to very useful results over and over again. I am being a bit more restrictive than that.

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The Latin phrase ad hoc means "for this [special purpose]." Almost any explanation could be considered "ad hoc" if we define the concept broadly because every hypothesis is designed to account for some observed event. However, the term is normally used more narrowly to refer to some explanation which is exists for no other reason but to save a favored hypothesis.

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Here is a wording I've borrowed. In the case we are discussing the clinging to an additional mysterious "force" just to solve a specific problem would be ad hoc. When a theory has worked as well as Newton's laws a techncially "ad hoc" explanation is jumped to when a discrepancy shows up. If it was held on to for just that specific reason then it would indeed be "ad hoc". However, in the cases of friction and EM forces (for example) the originally "ad hoc" explanation has proved to be very useful far beyond the specific case and has been independently tested. I don't call them ad hoc any more. You may choose to do so but then almost any explanation is "ad hoc" to you. As noted elsewhere you fictitious forces comment is wrong.Also as noted elsewhere, for very good reasons, new forces are considered. And as noted other possibilities including errors in the laws are considered. What else whould you do?Would you say, on one test that something that has proved very useful is wrong? Just one? Or would you think about it and be very, very careful in further testing and thinking all the while remaining open to the possibility of other explanations. Exactly as has been done.

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Common sense isn't