ewv

The Logical Leap and criticism

529 posts in this topic

This thread is a branch continuing discussion of one of the subjects in the thread "John McCaskey resigns from ARI Board" regarding the dispute over Dave Harriman's book The Logical Leap listed and discussed here at amazon.

Specifically, this thread is intended to deal with the scientific and philosophical content of the book and articles about it, such John McCaskey's post at amazon, not the character, behavior or motives of those invoved in the dispute over John McCaskey's resignation from the ARI Board of Directors.

The most relevant posts in the original thread are: 2 Paul's Here, 6 inventor, 8 Paul's Here, 11 ewv, 12 inventor, 13 inventor.

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An error appears to exist in McCaskey's article, and if that is so Harriman is correct...
... Galileo did not discover or prove the conclusion by means of deduction. The principle could only be known by means of induction.

I find that Harriman agrees with Galileo. McCaskey appears to be wrong in his understanding of both Harriman and Galileo.

McCaskey describes how Galileo's own account differs from Harriman's description of it.

Harriman was speaking of induction and that Galileo used induction in identifying principles that he then demonstrated. One could quibble whether Galileo used the correct scientific method in every way or that he dotted every i for his description, however, Galileo did identify the principles of gravity correctly. He used induction correctly. Galileo's explanations were abbreviated, and he left a lot of the descriptions to be filled in by the reader. Harriman, similarly, could have explained his points regarding the example of Galileo's induction and the related demonstgration in a little greater detail for the sake of clarity. Harriman left some grammatical space for doubt, however, it is safe to say in overview that if Galileo was right, and if Harriman agreed with Galileo, then Harriman was right. McCaskey was not correctly seeing the whole picture of the gravity principles identified by Galileo in a relationship to the intellectual method used by, and indicated by, Galileo. Harriman correctly pointed out with minimal explanations the existence of the inductive method.

He [Harriman][No, not Harriman, McCaskey] did not say it was a distinction between induction and deduction.

Galileo did imply that it was induction that was operative in the discovery and identification of the specified principles of gravity, and he did not spell out syllogistic steps to explain the discovery, which, at any rate, would have been impossible. Harriman correctly identified that induction was what Galileo used, and in the parts that I read of Harriman, Harriman did not speak of deduction, which was unnecessary for the discussion of induction.

Inventor continues to misunderstand the point on Galileo in several ways. Inventor said he found an error in John McCaskey's amazon article but did not say what it was, he has misrepresented what McCaskey argued, and then inexplicably wrote in his own later post 13 that "Harriman is wrong in that particular conclusion, and that McCaskey is right", without acknowledging his previous posts contradicting it or the responses to them.

McCaskey did not say anything about deduction versus induction and neither has anyone else besides Inventor. Distinctions between deduction and induction are irrelevent to the McCaskey's critique of the Harriman account of Galileo's free fall experiments.

And it is not "safe to say in overview that if Galileo was right, and if Harriman agreed with Galileo, then Harriman was right." That is a non-sequitur and has nothing to do with McCaskey's criticism. McCaskey said that Harriman's description of the experiments and reasoning process contradicted Galileo's own description of his own work.

In one aspect of this, Dave Harriman wrote that if Galileo based his results on objects falling in air and had he done his experiments on a fluid like water instead of air, they would not have yielded anything of importance. According to McCaskey (and Galileo), this contradicts what Galileo himself did and wrote. McCaskey points out that Galileo did in fact consider the resistance of water in addition to air and "presents [in his Discorsi] the difference between dropping balls through air and dropping them through water as the very heart of his discovery. (Day One, 8:110-116)."

Galileo himself wrote:

Our problem is to find out what happens to bodies of different weight moving in a medium of resistance, so that the only difference in speed is that which arises from inequality of weight. Since no medium except one entirely free from air and other bodies, be it ever so tenuous and yielding, can furnish our senses with the evidence we are looking for, and since such a medium is not available, we shall observe what happens in the rarest and least resistant media as compared [emphasis added] with what happens in denser and more resistant media. Because if we findas a fact that the variation of speed among bodies of different specific gravities is less and less according as the medium becomes more and more yielding, and if finally in a medium of extreme tenuity, though not a perfect vacuum, we find that, in spite of great diversity of specific gravity [peso], the difference in speed is very small and almost inappreciable, then we are justified in believing it highly probable that in a vacuum all bodies would fall iwth the same speed. -- Galileo Galilei, Dialogues Concerning Two New Sciences (Discorsi), translated by Henry Crew and Alfonso de Salvio, Dover, 1954, p. 72.

McCaskey summed this up in his amazon article:

He begins by recounting a report of the tower experiment but does not consider it sufficient to establish the law. He instead explains that we must consider air as a medium and compare what happens in other mediums, such as water and mercury. He notes that heavier things (ones heavy enough not to float) do land at different times and the difference is bigger the higher the resistance of the medium. In water the difference is higher than in air; in mercury, the difference even higher. Galileo extrapolates and concludes that in a medium that offered no resistance, there would be no difference in speed of fall and all objects would hit at the same time. Galileo claimed that comparing the dropping of objects in air, in water, and in mercury is exactly what justifies his discovery, contra Harriman's claim.

Historian of science Gerald Holton notes "Galileo's frequently invoked method of the limiting case, which has ever since been one of the standard tools of scientific thought" (Holton, Introduction to Concepts and Theories in Physical Science, Addison-Wesley, 1952, p.33).

Before assessing Galileo's reasoning about what he did and explaining in "essentials" what the proper reasoning is, one must first establish and accurately describe what Galileo in fact did and said about what he did. After that, one can argue what may have been right or wrong about it, and what is "essential", but not without first acknowledging, without contradiction, what he in fact did and said about it. Contrary to Inventor's conclusion, there is no evidence that McCaskey's amazon article does not understand what either Galileo or Harriman wrote.

Dave Harriman's pre-publication of the chapter containing the discussion of Galileo is in his article "Induction and Experimental Method" in The Objective Standard, Spring 2007, available here for those with online subscription access or willing to pay for a pdf download of the article. That article is consistent with what John McCaskey said about it.

Dave Harriman bases his analysis only on Galileo's experiments dropping objects through air, and he rejects what he refers to only as "imagined" experiments using water as irrelevant and potentially misleading (TOS article, p. 79). Perhaps Dave Harriman had in mind using only water instead of air, but in fact Galileo used multiple mediums in both his experiments and in his reasoning, and explicitly compared the effects of multiple media in drawing his conclusions.

The "method of the limiting case" employed by Galileo is not the whole epistemological story and is not a substitute for the fundamental idea of inductive generalization, but it was an essential part of Galileo's reasoning that cannot be ignored or treated in the epistemological analysis as if it did not exist. Dave Harriman may regard it as non essential in an effort to simplify the account, but the omission is misleading to the description of what Galileo actually did as well as to the reasoning he employed. If someone believes that this was not essential to the reasoning (which would in this case be incorrect), it is still not appropriate to base an analysis of a reasoning process on an historical account without including the relevant historical account of what actually happened.

This is an illustration of why I previously wrote here on the Forum:

David Harriman's articles have been inspiring and well-written, in an area no one else is publishing in, but he is intentionally writing this for a non-physicist, general audience, so you should recognize the level of simplification. For every topic he covers you should look up more technical accounts of both the history and the principles so you can see for yourself what it actually means and decide the validity. His writing will save you a lot of time in tying things together by essentials and explaining conceptual issues that you might not otherwise encounter or think of yourself.

You should also read biographies of famous scientists to better understand how they approached the subject and what it was like.

I am not an expert in the history of science, but in his description of a couple of other technical subjects that Dave Harriman pre-published in TOS I noticed some technical over-simplification that was misleading, yet which with fuller elaboration would actually further support Dave's thesis about them. John McCaskey, a professional historian of science, has now raised the question that in some of the accounts in areas in which he is personally knowledgeable the opposite may be the case, suggesting that the actual historical evidence may not be compatible with the epistemological analysis in its current state.

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I observe separately from the above discussion that Galileo was framing his descriptions of the gravity demonstrations in terms of the concepts of the implied 'nature" of the weight-sizes oak and lead materials of the dropped items, and of the implied 'powers of functioning' of the air, water, and mercury fluid materials, that when functiong in the context of the demonstrations, produced the results of the resistive forces upon the falling objects. Also note that Gallileo omitted the use of measurement numbers, and that he presented the concepts in the form of principles. In science specific numbers would have been used in more detailed demonstrations, which could then have been followed with deductive proofs. Galileo must have been reading Aristotle.

Galileo compared the resistive effect of different media for the same objects moving within them. He measured distances and times and referred to numerical values, though he did not report tables of numbers in his Diaglogues. In his purposeful experiments and reasoning about them he employed "non-contradictory" identifications that was actively reality centered and he employed a quantitative approach, all in contrast to the rationalistic medieval scholastic tradition tied to Aristotle and which was being overthrown by the scientific revolution.

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McCaskey concludes, from the above, "Galileo claimed that comparing the dropping of objects in air, in water, and in mercury is exactly what justifies his discovery, contra Harriman's claim." I think that Harriman is wrong in that particular conclusion, and that McCaskey is right. The reason is that the resistive forces (that Galileo for simplicity's sake calls "friction") of the air, water, and mercury are different in amount relative to the density-sizes of the falling objects, and Galileo also identifies that principle correctly.

Galileo did not use the concept or word "friction" in his reasoning, which he apparently could not isolate or distinguish from buoyancy. His use of different fluid media in experiments were his means of isolating and eliminating the role of resistive forces, regardless of their nature or cause, so he could focus on the essential factors in formulating a law of falling bodies for contexts in which resistance can be neglected to some degree of precision. That was done by observing a trend as he compared the effects of air, water and mercury, and concluding that air was the best medium to use for the final measurements in which height of drop and the types of objects were varied.

As I wrote previously, the "method of the limiting case" which Galileo employed in this process is not a substitute for the more fundamental process of induction in which generalization is made from observing what is relevant and irrelevant. The "limiting case" approach was essential to Galileo in eliminating one factor as part of his overall inductive reasoning process for the general law, but the more fundamental process of induction as such was left implicit by Galileo's description. His description emphasized the crucial idea of how he eliminated the factor of resistance due to the medium, and he did describe how he isolated other factors as relevant or irrelevant, but he did not integrate it all into an explicit description of the inductive process as such.

David Harriman recognized and emphasized that what he loosely called "friction" was carefully analyzed by Galileo, though he did not describe what Galileo did or how he did it, and he confused his discussion by implying (perhaps by poor choice of wording) that experiments with water were not performed and would not have been important. Unfortunately, in his simplified description Harriman did not provide a sufficiently detailed analysis of these particular experiments by Galileo on free fall and his reasoning processes to make it clear what he, Harriman, believes the full reasoning process was or should be in this particular case.

Consequently, as far as I can tell, McCaskey is right in that Harriman's description is over simplified and conflicts with Galileo's own description. It does not mean that Harriman was wrong because "the resistive forces ... of the air, water, and mercury are different in amount relative to the density-sizes of the falling objects, and Galileo also identifies that principle correctly " that Inventor claimed as the reason. (And it does not mean that the crucial method of the limiting case employed by Galileo was the most fundamental aspect of his reasoning.)

... we wish that he [Galileo] would have taken that line of thought further possibly to discover and found the science of aerodynamics.

That line of thought could not have led Galileo to the science of aerodynamics. Aerodynamics, i.e., fluid dynamics, is not based on a line of thought relating resistive forces to density-sizes of [solid] objects" moving relative to a fluid.

Aerodynamics is based on Newton's laws applied to a continuum subject to relative motion, in which shearing forces cannot be sustained in equilibrium. The founder of fluid dynamics was Euler, who about a centuriy after Galileo in the 1700s formulated his famous equations by applying Newton's second law, with additional concepts, and relating his formulation of the convective acceleration to pressure gradients and other forces within the field of the fluid. This was later expanded with additional terms including the effect of viscosity -- i.e., internal fluid friction -- with the Navier Stokes equations in the 19th century. The nature and cause of viscosity of air and other gases was explained by Maxwell later in the 19th century in terms of the kinetic theory of gases. A comprehensive theory of lift and drag for objects like airplane wings was not developed until the work of Prandtl and others applying principles of flow circulation and separation in the early 20th century. None of this is based on relating "resistive forces to density-sizes of objects" or the work of Galileo on objects in free fall.

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[...]

A request has been made by my friend that I should not engage in what I term a mix of arguments. It's simnply too confusing to me and to the reader.

I did write a really nice piece that I was about to post, and my writing disappeared possibly within minutes of the thread being closed. I'm sorry that my remarks have not been forthcoming. I have nothing more to say than I have already said.

Inventor.

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[...]

A request has been made by my friend that I should not engage in what I term a mix of arguments. It's simnply too confusing to me and to the reader.

I did write a really nice piece that I was about to post, and my writing disappeared possibly within minutes of the thread being closed. I'm sorry that my remarks have not been forthcoming. I have nothing more to say than I have already said.

This thread is not closed, but it is about the facts of the science and philosophy in Dave Harriman's book and so isn't the place to discuss unrelated topics about another thread. If a post of yours that you were still editing for the thread on John McCaskey leaving the ARI board disappeared because the thread was locked, it wasn't relevant to this thread, which started several hours later. If you appear to loose your writing because a thread closes, you can return your browser to the previous page to retrieve your editing and save it locally. That happened to me, which is why I later started this thread on a narrower topic, but I don't want to discuss the process further here because it is off topic.

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Instead of the type of resistance that Galileo called "friction", and that was referred to by Harriman, I think that the concept that is common to all the media and applications that Galileo referred to is what we would call, 'viscosity'. That concept is equally applicable in hydrodynamics and aerodynamics.

Galileo did not call out 'bouyancy', now that I think of it, and bouyancy while offering resistance to the falling objects, or simple support for a static object, operates according to a different principle than "friction". Bouyancy may work for less dense objects, and it is nonetheless a different type of functioning. The concept of friction means resistance to the rectilinear motion [Aris.] of objects that are sliding next to one another.

Viscosity works for the theory of the resisting forces, and, in the one type of instance demonstrated multiple times, that means that viscosity is the property of rapid or slow flow of a fluid usually from out of the way of an object moving through the fluid.

Ordinary friction also functions in addition to the primary resisting force of viscosity.

I suspect that Galileo referred to mercury in order that the observer would do some additional thinking. One idea that comes to mind is that an object that is more dense than mercury, e.g., lead, could make the lead object and the mercury fluid cardidates for the demonstration of the induction. Also, the oak would not work in a practical sense in the demonstration for bouyancy in all three fluids mentioned, even though it has been subsequently discovered that for objects in a fluid in a gravitational field, the principle of bouyancy always functions. Thus bouyancy is out of the question for all evaluations in Galileo's gravity demonstrations. "Friction", or, better, "resistance to motion" of falling or moving objects in a specifically fluid medium is what Galileo probably meant. That gives us the permission to say that the concept that Galileo probably had in mind was "viscosity", and that it is merely for convenience sake that he termed the resistance to falling, "friction".

Inventor

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Instead of the type of resistance that Galileo called "friction", and that was referred to by Harriman, I think that the concept that is common to all the media and applications that Galileo referred to is what we would call, 'viscosity'. That concept is equally applicable in hydrodynamics and aerodynamics.

Galileo did not call out 'bouyancy', now that I think of it, and bouyancy while offering resistance to the falling objects, or simple support for a static object, operates according to a different principle than "friction". Bouyancy may work for less dense objects, and it is nonetheless a different type of functioning. The concept of friction means resistance to the rectilinear motion [Aris.] of objects that are sliding next to one another.

Viscosity works for the theory of the resisting forces, and, in the one type of instance demonstrated multiple times, that means that viscosity is the property of rapid or slow flow of a fluid usually from out of the way of an object moving through the fluid.

Ordinary friction also functions in addition to the primary resisting force of viscosity.

I suspect that Galileo referred to mercury in order that the observer would do some additional thinking. One idea that comes to mind is that an object that is more dense than mercury, e.g., lead, could make the lead object and the mercury fluid cardidates for the demonstration of the induction. Also, the oak would not work in a practical sense in the demonstration for bouyancy in all three fluids mentioned, even though it has been subsequently discovered that for objects in a fluid in a gravitational field, the principle of bouyancy always functions. Thus bouyancy is out of the question for all evaluations in Galileo's gravity demonstrations. "Friction", or, better, "resistance to motion" of falling or moving objects in a specifically fluid medium is what Galileo probably meant. That gives us the permission to say that the concept that Galileo probably had in mind was "viscosity", and that it is merely for convenience sake that he termed the resistance to falling, "friction".

Inventor

Viscosity is more of a measure of internal fluid flow resistance and not necessarily the resistance to movement of another object through it. A lead ball falling in water would have a certain resistance; a glass ball falling in water would have a different resistance. The viscosity of water in either experiment would not change. In other words, a fluid that has a relatively high viscosity offers more resistance to movement of objects because it requires more force for the fluid to move out of the way of the object that is displacing the volume of fluid.

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I just purchased The Logical Leap, and hope go get into it soon.

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... Galileo did not call out 'bouyancy', now that I think of it, and bouyancy while offering resistance to the falling objects, or simple support for a static object, operates according to a different principle than "friction". Bouyancy may work for less dense objects, and it is nonetheless a different type of functioning. The concept of friction means resistance to the rectilinear motion [Aris.] of objects that are sliding next to one another.

No, the only retarding force to motion that Galileo referred to or described throughout this whole discussion was buoyancy. He did not use the term but defined the force he was talking about as "the effect of the medium is to diminish the weight of the body by the weight of the of the medium displaced" [119] and he described the results of this several times. That was always in the context of how fast (or whether) a submerged object rises or falls in comparison with other objects and different fluid media.

It is true that buoyancy is not the same kind of force as drag on a moving object, but all indications in what Galileo wrote are that he did not realize that. He had no concept of either fluid friction or of drag on a moving object as we understand them today, let alone what causes them. Furthermore, drag and fluid friction are not the same thing, in addition to neither being buoyancy, see below.

Galileo realized that there was a drag force and even noticed the phenomenon of terminal velocity [119], but his understanding of the nature of the resistance was very limited, and in measuring buoyancy he didn't measure what he thought he was in his analysis.

He used his comparative analysis of degrees of buoyancy as a measure of comparing 'resistances' in order to show that air was the proper medium to use for his free fall experiment that ultimately showed that the time of fall is independent of weight to the extent that resistance of any kind is negligible (approaching the "limiting case"). But the buoyancy measurements were not a properly complete analysis of either "friction" or drag. He correctly saw that the 'resistance' of air was the least for the different media in his comparative analysis, but he had the wrong explanation of the cause of the resistance, not realizing that in addition to the force of buoyancy, the drag he must have felt pushing an object through water was not buoyancy, and he confused his measurements of the effects of buoyancy with direct measurements of relative drag.

Because he got the right medium (air) as the least resistive, his induction about the law of free fall being independent of weight when there is no resistance turned out to be correct. But this was because his law was kinematics, not dynamics, i.e., it was about motion, without regard to the role of forces -- it did not include either a gravitational force or a resistance force, only the results of gravitational acceleration with no resistance. His induction process did not depend on the nature of the resistance or what kind of force it was, only that it be negligible whatever its nature.

This was a second point John McCaskey made about Dave Harriman's discussion of the free fall experiment. Dave Harriman wrote that Galileo made a careful analysis of "friction" which was necessary for his reasoning, but in not discussing the nature of that analysis he of course did not discuss how Galileo measured the wrong force and yet still managed to get the right result despite his bad concepts for resistance. (See below for why it worked.)

I suspect that Galileo referred to mercury in order that the observer would do some additional thinking.

No, it was more explicit than just expecting others to do more thinking. He explicitly included mercury ("quicksilver") to show a range of media resistance [116]. Mercury was at the opposite extreme from air.

One idea that comes to mind is that an object that is more dense than mercury, e.g., lead, could make the lead object and the mercury fluid cardidates for the demonstration of the induction. Also, the oak would not work in a practical sense in the demonstration for bouyancy in all three fluids mentioned, even though it has been subsequently discovered that for objects in a fluid in a gravitational field, the principle of bouyancy always functions. Thus bouyancy is out of the question for all evaluations in Galileo's gravity demonstrations.

He did discuss objects of different specific gravity in mercury and found that most elements he tried did not sink in it at all. He used that as part of his argument that mercury has more 'resistance' than either air or water -- but making the same mistake of implicitly equating drag with with buoyancy.

"Friction", or, better, "resistance to motion" of falling or moving objects in a specifically fluid medium is what Galileo probably meant.

Friction and the drag on an object are two different concepts, neither of which he held clearly enough to distinguish them from buoyancy. You can't say that he probably meant either one as opposed to buoyancy because he didn't understand that they are different from buoyancy. The best you can say for it is that he had a general idea of resistance to motion through a fluid, i.e., what we know as the drag force, including the idea of terminal velocity, but confused measuring drag with measuring buoyancy (which as a constant, velocity independent force is unrelated to terminal velocity).

[out of order]Instead of the type of resistance that Galileo called "friction", and that was referred to by Harriman, I think that the concept that is common to all the media and applications that Galileo referred to is what we would call, 'viscosity'. That concept is equally applicable in hydrodynamics and aerodynamics.
[Out of order] Viscosity works for the theory of the resisting forces, and, in the one type of instance demonstrated multiple times, that means that viscosity is the property of rapid or slow flow of a fluid usually from out of the way of an object moving through the fluid.
That gives us the permission to say that the concept that Galileo probably had in mind was "viscosity", and that it is merely for convenience sake that he termed the resistance to falling, "friction".

No, viscosity and drag are two different concepts. Nor did Galileo use the term "friction" -- Dave Harriman called it that.

"Viscosity" is the internal friction within a fluid and is a property of the fluid alone. It manifests itself as a shearing (tangential) stress due to a gradient in velocity across the plane of the shear. It is regarded as "friction" because it is a nonconservative force that dissipates energy from the fluid.

The drag on an object, which is what Galileo was trying to take into account even though he didn't understand how it works and measured buoyancy instead, is a net force directly on the moving object due to tangential and normal stresses in the fluid on the surface of the object. There is no "sliding" of the fluid against the surface of the solid object: both the normal and tangential velocities of the fluid relative to the surface of the solid are always zero (called the "no slip condition" for the zero tangential velocity, due apparently to molecular forces). The fluid flows past the object at a distance and the drag is analyzed in terms of the stresses transmitted through the fluid in a complex mathematical analysis. You have to know what the flow field pattern is to compute lift and draft on an object by computing stresses in the fluid acting across the surface of the solid object.

Drag on an object may or may not be related to the degree of viscosity. the drag is a complicated function of geometry, fluid density, viscosity and velocity. For the same object moving through the same fluid, at extreme cases of a low and high velocities drag is proportional to:

  • speed, size and fluid viscosity, for low velocities
  • approximately speed squared, size squared and fluid density, for high velocities.

Buoyancy, in contrast, is a "body" force, not a surface force, that ordinarily can be removed from the equations of motion in the form of a modified pressure.

[Out of order] Ordinary friction also functions in addition to the primary resisting force of viscosity.

There is no "ordinary friction" in addition to the internal fluid friction due to viscosity.

What Dave called "friction" is justified as a different, looser, use of the term: the falling object causes a flow field around it, which imparts a drag on it, and there is some dissipation of energy to the extent there are viscous forces within the fluid near the object which dissipate energy. But that "frictional" force on the object is distinct from the viscous forces that are the internal friction in the fluid.

The complexity of a basic analysis of the nature of drag and "friction", and the facts that Galileo had a very limited understanding and measured the wrong effect (buoyancy), is what John McCaskey was referring to when he said that Galileo's induction was performed with imperfect concepts.

It worked because

  • The differences in buoyancy were due to differences in fluid density -- mercury is denser than water which is denser than air -- so he was indirectly doing comparative measurements of density even though he didn't realize it or why that was relevant;
  • The differences in density also caused the corresponding differences in drag for high enough velocities and/or the absolute viscosities of the three substances are also in the right order for drag at low velocities;
  • Galileo had an approximate sense of the differences in drag through the three fluids even though he didn't understand the difference between that and buoyancy or why what he did with his buoyancy measurements was relevant -- he didn't have all the right concepts but he was on the right track; and
  • He didn't need precise numerical measurements of buoyancy to realize that air easily had the least resistance and was therefore by far the most suitable for free fall with negligible resistance; his law was kinematics, not dynamics, and depends on being able to neglect resistance, not the nature of the force.

In this sense Dave Harriman was right to say that Galileo did a necessary analysis of "friction" (even though the analysis was confused) and to suggest that if Galileo had relied [solely] on free falls through water or mercury his experiment probably would not have succeeded in giving the the law he sought. But John McCaskey is right to point out that Galileo's reasoning process had not been properly described because of important historical omissions and that more is required to validate the induction as it pertains to concepts held by Galileo, which is not so simple as one would be lead to believe by Dave Harriman's account.

Thanks to Inventor for raising the questions he did, even though they contained several misconceptions, leading to more detailed discussion of these issues.

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Viscosity is more of a measure of internal fluid flow resistance and not necessarily the resistance to movement of another object through it. A lead ball falling in water would have a certain resistance; a glass ball falling in water would have a different resistance. The viscosity of water in either experiment would not change. In other words, a fluid that has a relatively high viscosity offers more resistance to movement of objects because it requires more force for the fluid to move out of the way of the object that is displacing the volume of fluid.

Viscosity is a material property of a fluid and the drag pertains to an object with a particular flow around it, but the drag is not necessarily dependent on the viscosity; drag is dominated by density for higher velocities. See the preceding post. Normally the viscosity throughout the fluid is irrelevant and only plays a role where there is a sharp velocity gradient in the boundary layer at the surface of the object. For high enough velocities other factors dominate the creation of tangential and normal stresses on the surface.

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Viscosity is more of a measure of internal fluid flow resistance and not necessarily the resistance to movement of another object through it. A lead ball falling in water would have a certain resistance; a glass ball falling in water would have a different resistance. The viscosity of water in either experiment would not change. In other words, a fluid that has a relatively high viscosity offers more resistance to movement of objects because it requires more force for the fluid to move out of the way of the object that is displacing the volume of fluid.

"Viscosity is a measure of shear force / rate of shear." [Norcross Corporation defn.] Shear is the process that occurs within a fluid when adjacent parts of the fluid move relative to one another, for example in laminar or turbulent flows in pipes or around aircrfaft wings. The internal cohesion of the parts of adjecent parts of the fluid requires a force in order to impart the motion and to slide the parts past one another.

You say in the above remark that, "The viscosity of water in either experiment would not change." True. That is a natural property of the liquid.

Prior to that you say, "Viscosity is more of a measure of internal fluid flow resistance and not necessarily the resistance to movement of another object through it." The first part of what you say is true also. The second part, however, requires a requalification because the "resistance to movement of another object through it" is a result of the first part, the "internal fluid flow resistance".

Shearing within the liquid requires a force, and by the principle of equal and opposite forces, the falling object that is pulled downwards by the force of the acceleration of gravity, has a resisting viscous shear force imparted upon it, thus slowing it.

Objects of the same size, shape, and different mass, and [importantly] that have the same velocity will have the same decelleration force applied to them by the same viscosity fluid. If the viscosity of the fluid value is zero, the resisting force is zero. In that case all objects will fall at the same rate independent of their mass, shape, size, or surface characteristics, and as Galileo explained, they would fall all the same rate in a vacuum.

That's why I disagree with your statement that, "Viscosity is [...] not necessarily the resistance to movement of another object through it."

In a sense, viscosity is a type of internal friction. Forces causing viscous flow or motion result in heat [although that is not what we are discussing]. The part of the viscous fluid that is in direct contact with the surface of the falling object shears against the surface of the object. That also causes friction forces that result in heat. A force is required to cause the relative motions of the object and fluid, and the falling object is accordingly slowed in its fall. Galileo was right about the "friction", and possibly even right about the internal viscous friction.

Galileo's main point was that the different rates or times of fall were a result of the resistances to movement of the falling objects falling through different frictional fluids, or that in the same fluid, that the different rates of fall of similar objects in the similar fluids were due to the different total weights [of oak and lead] [due to mass differences] in the otherwise similar objects, and that the greater weight objects would provide a greater force to overcome the resistance.

Inventor

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Viscosity is more of a measure of internal fluid flow resistance and not necessarily the resistance to movement of another object through it. A lead ball falling in water would have a certain resistance; a glass ball falling in water would have a different resistance. The viscosity of water in either experiment would not change. In other words, a fluid that has a relatively high viscosity offers more resistance to movement of objects because it requires more force for the fluid to move out of the way of the object that is displacing the volume of fluid.

"Viscosity is a measure of shear force / rate of shear." [Norcross Corporation defn.] Shear is the process that occurs within a fluid when adjacent parts of the fluid move relative to one another, for example in laminar or turbulent flows in pipes or around aircrfaft wings. The internal cohesion of the parts of adjecent parts of the fluid requires a force in order to impart the motion and to slide the parts past one another.

Viscosity of a fluid is not a "measure of shear force / rate of shear". "Measure of the shear-force" is a sloppy description of a well-defined concept in fluid dynamics. Viscosity as "rate of shear" is incorrect. (And viscosity of gases like air is explained by patterns in momentum transport in the kinetic theory of gases, not "cohesion of the parts of adjecent parts of the fluid").

Viscosity is a property of the fluid that creates a shear force within the fluid when adjacent portions move relative to each other tangentially. The shear stress due to viscosity is proportional to the gradient of the tangential fluid velocity, normal to the plane of the shear stress (so the stress, not the viscosity, is proportional to the rate of shear). The viscosity ν is the proportionality coefficient: τ = ν ∂u/∂n. The stress τ is required to maintain the rate of shearing ∂u/∂n in accordance with the value of the viscosity ν. For fluids like air, water and mercury, the viscosity is a constant of the fluid at a specified temperature, independent of velocity. Viscosity is not defined in terms of flows around or in solid objects like pipes or airfoils. The definition and meaning of the concept of viscosity and its implications and methods of measurement can be found in any reputable introductory fluid dynamics text.

You say in the above remark that, "The viscosity of water in either experiment would not change." True. That is a natural property of the liquid.

Prior to that you say, "Viscosity is more of a measure of internal fluid flow resistance and not necessarily the resistance to movement of another object through it." The first part of what you say is true also. The second part, however, requires a requalification because the "resistance to movement of another object through it" is a result of the first part, the "internal fluid flow resistance".

That viscous forces are "not necessarily the resistance to movement of another object throught it" requires no such qualification. Viscosity is not defined in terms of forces that may or may not result from it and is not characterized by forces that may not result from degree of viscosity at all.

As explained previously in this thread, viscous forces are not the only forces in a fluid and are not the only source of resistance to moving objects. Experiments and instruments used to measure viscosity by forces on an object immersed in the fluid must be carefully designed and controlled to eliminate forces on the object not due to viscosity, under conditions in which the drag force on the solid object does depend on the amount of viscosity.

Shearing within the liquid requires a force, and by the principle of equal and opposite forces, the falling object that is pulled downwards by the force of the acceleration of gravity, has a resisting viscous shear force imparted upon it, thus slowing it.

That is a non-sequitur. You have ignored the mechanism by which stresses in a fluid are transmitted to an object moving within it, and ignored what all the relevant forces in the fluid are. The forces in a fluid are characterized and quantified by a tensor field of normal and shear stresses, including obviously pressure, not a single viscous force. For fast enough velocities the drag on a moving object is independent of the value of the viscosity in the fluid, as explained previously in this thread.

Objects of the same size, shape, and different mass, and [importantly] that have the same velocity will have the same decelleration force applied to them by the same viscosity fluid. If the viscosity of the fluid value is zero, the resisting force is zero. In that case all objects will fall at the same rate independent of their mass, shape, size, or surface characteristics, and as Galileo explained, they would fall all the same rate in a vacuum.

No, you are ignoring the density of the fluid and forces not due to viscosity.

That's why I disagree with your statement that, "Viscosity is [...] not necessarily the resistance to movement of another object through it."

Your disagreement is contrary to the science of fluid dynamics and its empirical basis.

In a sense, viscosity is a type of internal friction. Forces causing viscous flow or motion result in heat [although that is not what we are discussing]. The part of the viscous fluid that is in direct contact with the surface of the falling object shears against the surface of the object. That also causes friction forces that result in heat.

As explained previously in this thread that is not correct. The fluid immediately adjacent to the surface of a solid moves with the solid. It does not "shear against the object" in the sense of sliding along the surface of the solid. The shear (and normal) stresses are transmitted through the nearby fluid. The velocity of the fluid varies across the flow field, matching the velocity of the solid object at its surface, and may have a sharp gradient within a thin boundary layer along the object. There is no additional "friction" between the solid and the fluid allegedly sliding along the surface of the solid. Your assertions contradict the science of fluid dynamics and observation.

A force is required to cause the relative motions of the object and fluid, and the falling object is accordingly slowed in its fall. Galileo was right about the "friction", and possibly even right about the internal viscous friction.

Galileo said nothing about a "friction" that does not exist or the internal fluid friction due to viscosity. He could not have been right about things he did not say and knew nothing about.

Galileo's main point was that the different rates or times of fall were a result of the resistances to movement of the falling objects falling through different frictional fluids, or that in the same fluid, that the different rates of fall of similar objects in the similar fluids were due to the different total weights [of oak and lead] [due to mass differences] in the otherwise similar objects, and that the greater weight objects would provide a greater force to overcome the resistance.

That is not what he said. He said that to the exent that resistance can be neglected all objects fall with the same acceleration.

More fundamentally, Galileo's main point was that scientific principles are discovered by actively looking at reality through experiments and measurement, and that inducing principles for the laws of nature is based on that instead of the rationalism of medieval scholasticism that had dominated prior to the scientific revolution. The same is true today and Objectivists should not rationalize about science in the manner of the scholastics, imagining what "must" be the case in ignorance of and without regard to established science developed for centuries, or rationalize what earlier scientists did and thought without regard to what they actually wrote.

Ayn Rand was very careful to base her philosophy on facts that can be known to anyone, which distinguishes general philosophy from a philosophy of a special science. She did not speculate about what "must be", in rationalistic attempts to deduce reality from philosophy, including in the name of "applying" philosophy. She knew she had little knowledge in the special sciences like physics and was careful to appropriately limit her statements about them. Objectivists who want to understand or make statements about science should learn the science and not speculate. That is not what Ayn Rand's philosophy is or could ever be. Valuing Ayn Rand's or Aristotle's philosophies is not license to return to the rationalism of medieval scholasticism in the name of science.

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EWV: I was about to answer Inventor with a simple "I disagree with you." But your analysis is much more elegant.

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[...]
That's why I disagree with your statement that, "Viscosity is [...] not necessarily the resistance to movement of another object through it."

Your disagreement is contrary to the science of fluid dynamics and its empirical basis. [...]

Check your work.

See Wikipedia at:

http://en.wikipedia.org/wiki/Inviscid_flow

"

Inviscid flow

[...]

In fluid dynamics there are problems that are easily solved by using the simplifying assumption of an ideal fluid that has no viscosity. The flow of a fluid that is assumed to have no viscosity is called inviscid flow.[1]

The flow of fluids with low values of viscosity agree closely with inviscid flow everywhere except close to the fluid boundary where the boundary layer plays a significant role.[2]

Reynolds number

The assumption of inviscid flow is generally valid where viscous forces are small in comparison to inertial forces. Such flow situations can be identified as flows with a Reynolds number much greater than one. The assumption that viscous forces are negligible can be used to simplify the Navier-Stokes solution to the

Euler equations.

In the case of incompressible flow, the Euler equations governing inviscid flow are:

[ math equations omitted ... ]

which, in the steady-state case, can be solved using potential flow theory. More generally, Bernoulli's principle can be used to analyse certain time-dependent compressible and incompressible flows.

Problems with the inviscid-flow model

While throughout much of a flow-field the effect of viscosity may be very small, a number of factors make the assumption of negligible viscosity invalid in many cases. Viscosity cannot be neglected near fluid boundaries because of the presence of a boundary layer which enhances the effect of even a small amount of viscosity. Turbulence is also observed in some high-Reynolds-number flows, and is a process through which energy is transferred to increasingly small scales of motion until it is dissipated by viscosity. "

Inventor

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I think we're getting away from EWV's original request as to what we should be discussing, so I will attempt to put us back on track.

------------------------------------------------------------------------------------

Now that I’ve read the relevant chapters of the book, I want to state that I do not think that McCaskey accurately addresses the issues that Harriman is presenting.

These are the points I want to address:

McCaskey states in his resignation letter:

The historical accounts as presented are often inaccurate, and more accurate accounts would be difficult to reconcile with the philosophical point the author is claiming to make.

McCaskey states in his Amazon review:

Harriman, for example, recounts how Galileo determined that "the rate at which a body falls is independent of its weight."

McCaskey’s criticisms, even if historically accurate as seems to be the case based upon the quotes provided by EWV above, is a criticism that is out of context from the purpose of the book as well as the function of the examples Harriman provides.

(Henceforth, DH = Harriman; JM = McCaskey)

In the preface, DH says, “any errors in the science and its history are entirely my responsibility.” So, is JM’s claim of an error on DH’s part correct? In order to judge if a factual statement is an error, one must know the context. After all, both DH and JM agree that Galileo did the experiment and used the results to draw the conclusion that "the rate at which a body falls is independent of its weight." JM holds that Galileo did additional experiments that were important to the conclusion that DH drew. JM acknowledges that those experiments would not have demonstrated the generalization. So what is the context of DH’s statement and is it an error in that context?

DH states in Chap 1 that “the problem is to identify the method of induction.” “It is futile to ponder the validity of a generalization unless we know how we arrived at it…” This sets the focus of what the book is about. Later, quoting Dr. Peikoff on the meaning of reduction, “since there are options in the detail of a learning process, one need not always retrace the steps one initially happened to take. What one must retrace is the essential logical structure.” DH later brings up the point that “the knowledge possessed by a rational inducer is always limited, but it is nevertheless real. Because it is limited, it is open to future qualifications. Because it is real, however, the qualifications have no negative significance.” (my bold)

In Chap. 2, DH briefly presents the problems that the Greeks had because of the Platonic element in their thinking, and he then brings in the issue of the distinctive method of modern science: experimentation by controlling variables. When we get to “Galileo’s Kinematics”, it is clear that we are not engaged in a detailed history of scientific thought but a demonstration of how scientists arrive at a generalization. After demonstrating how Galileo began his scientific investigation into the motion of pendulums, DH goes into Galileo’s attempt to answer the question “how does the weight of a body affect the rate at which it falls?” Then, “Galileo demonstrated the answer with his characteristic dramatic flair.” Followed by the rest of the quote provided by JM.

What is DH doing with this example and why not mention the experiments with other fluids? If one was paying attention to the “solution to the problem of induction” in Chap. 1, one would have grasped that all generalizations must be reducible to perceptual level, “first-level generalizations.” In other words, DH is demonstrating that Galileo used a first-level generalization (if I let an object go, it falls) to ground his abstract generalization upon (when I let two objects with different weights fall, they fall at the same rate). Why is it necessary for a demonstration in other media to illustrate that point? It is irrelevant!!

Galileo’s use of different media to induce that resistance goes to zero is a very broad generalization that would only require further examples and explanation. Not relevant to what DH is trying to demonstrate here. Clearly Galileo was aware of air resistance, or “friction” which is sometimes used in quotes which may indicate that DH is aware that Galileo did not have that concept fully developed. It may just indicate that DH is using the common scientific term for what air resistance is so as to make it clear to a modern audience. This is hardly an error on DH’s part. (For example, on p57: “In addition to the concept of “friction,” this discovery depended upon Galileo’s prior development of two key concepts of motion.”) Introducing concepts such as “Archimedean buoyancy” would hardly clarify the issue pertaining to induction and the epistemological base of Galileo’s induction.

In conclusion, JM does not demonstrate that DH’s account is different than the historical account of others for that is not what DH was offering up for consideration. DH demonstrates that Galileo used experimentation to inductively ground his conclusion on first-level generalizations. DM’s conclusion about DH’s theory, “if it is to be widely adopted, it will need to be better reconciled with the historical record as the theory gets fleshed out and refined,” is without merit. The charge that the theory is “inchoate” is baseless. Chapter 1, which provided the justification for induction in terms of Objectivist epistemology, provides an excellent justification for inductive generalizations. It is interesting to note that JM’s “review” of a book on induction does not evaluate the theory presented in the book other than a charge of “inchoate.” After getting the facts by reading the book, it is my opinion that JM’s review is incoherent.

If "accurate accounts would be difficult to reconcile with the philosophical point the author is claiming to make" then where's the demonstration? Where in the review is JM's demonstration that he understands DH's ideas?

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[...]
That's why I disagree with your statement that, "Viscosity is [...] not necessarily the resistance to movement of another object through it."

Your disagreement is contrary to the science of fluid dynamics and its empirical basis. [...]

Check your work.

See Wikipedia at:

http://en.wikipedia.org/wiki/Inviscid_flow

"

Inviscid flow

[...]

In fluid dynamics there are problems that are easily solved by using the simplifying assumption of an ideal fluid that has no viscosity. The flow of a fluid that is assumed to have no viscosity is called inviscid flow.[1]

The flow of fluids with low values of viscosity agree closely with inviscid flow everywhere except close to the fluid boundary where the boundary layer plays a significant role.[2]

Reynolds number

The assumption of inviscid flow is generally valid where viscous forces are small in comparison to inertial forces. Such flow situations can be identified as flows with a Reynolds number much greater than one. The assumption that viscous forces are negligible can be used to simplify the Navier-Stokes solution to the

Euler equations.

In the case of incompressible flow, the Euler equations governing inviscid flow are:

[ math equations omitted ... ]

which, in the steady-state case, can be solved using potential flow theory. More generally, Bernoulli's principle can be used to analyse certain time-dependent compressible and incompressible flows.

Problems with the inviscid-flow model

While throughout much of a flow-field the effect of viscosity may be very small, a number of factors make the assumption of negligible viscosity invalid in many cases. Viscosity cannot be neglected near fluid boundaries because of the presence of a boundary layer which enhances the effect of even a small amount of viscosity. Turbulence is also observed in some high-Reynolds-number flows, and is a process through which energy is transferred to increasingly small scales of motion until it is dissipated by viscosity. "

Inventor's appeal to out of context snippets from Wikipedia do not address what I wrote and neither does he, nor does any of it support his assertions, which are simply wrong. Proper accounts are in reputable texts on fluid dynamics. This is not controversial among those who understand the subject, and is not refuted by the rationalism of what someone imagines "must" be the case, followed by an incomprehensible appeal to "Wikipedia" as authority, with no explanation of how it is expected to support anything.

The Wikipedia article has nothing to do with Galileo's experiment. It attempts to very briefly address the fact that portions of flow fields can often be analyzed without regard to viscosity because the viscosity is not relevant in those regions, but that viscosity cannot always be ignored. A standard method of analysis in steady state airfoil theory is to piece together a solution by first analyzing the flow as if it were (an inviscid) potential flow and to then use the results of that for a local "boundary layer analysis" of the flow near the surface of the solid object, where the role of viscosity is essential. None of this method is a "problem" in a so-called "inviscid flow model" for those who know what they are doing and why, thinking in terms of concepts of reality and objective method taking into account what matters where, not free-floating "models".

The near impossibility of a fluid with no viscosity at all does not mean that fluid viscosity is the drag force or the only cause of the drag force, or that the drag force must in all circumstances depend on the degree of viscosity as opposed to other factors, which claims are all false. To obtain the drag force one must integrate the stresses in the fluid around the surface of the object. This includes pressure. Viscous stresses are not the only stresses in the fluid.

Depending on the conditions, the drag may or may not depend on the numerical degree of viscosity, as previously explained in this thread, even though viscosity is always present and is necessary to explain the patterns of circulation, separation of the flow behind an object, and the production of eddies and wakes that dissipate energy and which can create a pressure differential directly retarding motion of the object. Airfoil theory depends on understanding those mechanisms. It does not mean that drag is viscosity.

These details are not required to understand or justify Galileo's experiment, which was about comparative rates of free fall when resistance is negligible, regardless of its nature and cause, and they do not support the bizarre assertions made about either fluid dynamics or Galileo in insistent rationalism employed by those who don't understand what they are talking about and don't realize it.

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I'm sincerely sorry that I replied to the post on the instant topic.

Constructive discussions and criticism are of interest to me, and I didn't find that. What I find in the replies to my posts are writings that seem to have the purpose of confounding the reader. For example, paraphrasings of scientific concepts, e.g., that Galileo used the term, "friction", when apparently he did not, and that Harriman did. Or that rebuttals to what I have said are are cast in terms that simply deny what I said, e.g., that in fluid flow thare is no friction between the object and fluid, which is not true.

I'll try to stay away from these discussions.

Now if you want to discuss induction .......

Inventor

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-------------------

Now if you want to discuss induction .......

Inventor

So, discuss my post if you want to discuss that subject.

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I'm sincerely sorry that I replied to the post on the instant topic.

Constructive discussions and criticism are of interest to me, and I didn't find that. What I find in the replies to my posts are writings that seem to have the purpose of confounding the reader. For example, paraphrasings of scientific concepts, ...

I don't know what an "instant topic" is or which of his replies he is referring to (the one removed?), but his assertion that my explanations of the physics are written for "the purpose of confounding the reader" is pure psychologizing and is false and baseless. His own statements have been quoted in full, not "paraphrased", and have in fact been answered with "constructive criticism" explaining the physics. If inventor is "confounded" it is because, as his posts indicate, he does not understand the subject matter and the terminology. These matters must be understood in terms of legitimate science, not mental pictures based on speculation.

..., e.g., that Galileo used the term, "friction", when apparently he did not, and that Harriman did. Or that rebuttals to what I have said are are cast in terms that simply deny what I said, e.g., that in fluid flow thare is no friction between the object and fluid, which is not true.

Inventor's posts misrepresented the resistance to the object in free fall as "viscosity" and misquoted Galileo. It is important to understand that:

  • Viscosity is a property of the fluid (like air) alone, not a force on a solid object moving through it.
  • Viscosity is not the sole source of the resistance to the moving object. Pressure drag is not friction drag. Drag depends on density of the fluid and other factors except at very low speeds of small objects in a fluid with relatively high viscosity. Think of the difference between the extreme cases of a small speck of dust moving slowly through the air (or higher viscosity fluid) versus a canon ball falling rapidly through air (not mercury). In the first case, viscosity dominates the source of the resistance, in the second the density of the fluid dominates the resistance in comparison with viscosity. In both cases, energy is dissipated, but by different mechanisms.
  • There is no "additional friction" force, beyond the internal viscous friction within the air. A solid object does not slide against the air with additional friction, as incorrectly asserted. A layer of air 'sticks' to the object and moves with it. The viscous shear force is entirely within the air and is the source and meaning of "skin friction".

This has been explained in more detail previously, in the context of assertions to the contrary which mislead those not familiar with the science. My explanations have not been "cast in terms that simply deny what [inventor] said". His speculations have no basis and contradict well known basic knowledge in the science of fluid dynamics, which can be verified by consulting any reputable introductory text on the subject.

Understanding the nature of resistance in Galileo's inductive process is important because it was central to Galileo's own argument. He analyzed what he thought was the resistance, which he did not call friction, with a comparison of resistance due to different fluids: air, water and mercury. He did this to identify, through quantitative measurement, the least resistive medium, air. He did not simply repeat the experiment in different media and pick the least resistive for his results: He sought to establish a trend because he established a law pertaining to what happens when resistance is not a factor at all, as what is now called a "limiting case". He knew (and said) that objects do not fall at the same rate in air, but that the differences are smaller and that his law pertains to what would happen in a complete absence of resistance.

There are several epistemological assumptions and aspects to this procedure that could be discussed (in addition to the role of what we know today versus what was possible for Galileo to know), but the glaring problem in Galileo's inductive process, which John McCaskey pointed out, was that Galileo's comparative analysis did not measure what he thought he was measuring because he conflated buoyancy with resistance to a falling body. He did not carefully analyze friction, as has been claimed, or the actual resistive forces at all. The kind of "resistance" he measured and discussed was the upward force of buoyancy, which is a different and irrelevant kind of "resistance". It does not have the same effect as aerodynamic resistance that is due to motion (regardless of the role of viscosity). The buoyancy reduces the effective density -- or effective weight -- of the falling object, which is irrelevant to its rate of fall because all objects experience the same gravitational acceleration regardless of their density. Galileo's comparative analysis based on buoyancy indirectly measured comparative density of the fluids, which is relevant to resistance, but he didn't know that.

Galileo got the right answer for partially the wrong reasons, which ought to be pertinent to any analysis of his inductive process, especially when trying to use historical accounts to illustrate the validity of induction. The context of Galileo's knowledge was not just "limited", as it had to be. An essential part of his knowledge was wrong -- the concept of resistance Galileo employed and tried to use in measurements was (as he described it) at least partially incorrect -- in addition to his necessarily employing more primitively defined concepts than the scope and depth of understanding we have today. This cannot be glossed over in a theory that grounds inductive generalization on concepts, and it cannot be discussed at all using replacements misrepresenting Galileo's work with rationalistic speculation in place of legitimate science -- along with bogus excuses claiming that explanations of the science are really written for "the purpose of confounding the reader". Careful understanding of the science may be inconvenient for some, but it is essential that it be correct, even if limited. The importance of valid, first-hand understanding of science through proper means based on fact, not rationalization or authority, is one of Dave Harriman's central themes.

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ewv.

I consistently find your posts illuminating. I do not know if you have any particular expertise in the field, but I find your explanations of fluid dynamics very helpful.

Inventor, you will have to offer a better argument for your viewpoint than the cutting and pasting of a wikipedia article. ewv is offers a far more persuasive argument, one that meshes with my understanding of fluid dynamics.

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I think we're getting away from EWV's original request as to what we should be discussing, so I will attempt to put us back on track.

------------------------------------------------------------------------------------

Now that I’ve read the relevant chapters of the book, I want to state that I do not think that McCaskey accurately addresses the issues that Harriman is presenting.

These are the points I want to address:

McCaskey states in his resignation letter:

The historical accounts as presented are often inaccurate, and more accurate accounts would be difficult to reconcile with the philosophical point the author is claiming to make.

McCaskey states in his Amazon review:

Harriman, for example, recounts how Galileo determined that "the rate at which a body falls is independent of its weight."

McCaskey’s criticisms, even if historically accurate as seems to be the case based upon the quotes provided by EWV above, is a criticism that is out of context from the purpose of the book as well as the function of the examples Harriman provides.

(Henceforth, DH = Harriman; JM = McCaskey)

In the preface, DH says, “any errors in the science and its history are entirely my responsibility.” So, is JM’s claim of an error on DH’s part correct? In order to judge if a factual statement is an error, one must know the context. After all, both DH and JM agree that Galileo did the experiment and used the results to draw the conclusion that "the rate at which a body falls is independent of its weight." JM holds that Galileo did additional experiments that were important to the conclusion that DH drew. JM acknowledges that those experiments would not have demonstrated the generalization. So what is the context of DH’s statement and is it an error in that context?

DH states in Chap 1 that “the problem is to identify the method of induction.” “It is futile to ponder the validity of a generalization unless we know how we arrived at it…” This sets the focus of what the book is about. Later, quoting Dr. Peikoff on the meaning of reduction, “since there are options in the detail of a learning process, one need not always retrace the steps one initially happened to take. What one must retrace is the essential logical structure.” DH later brings up the point that “the knowledge possessed by a rational inducer is always limited, but it is nevertheless real. Because it is limited, it is open to future qualifications. Because it is real, however, the qualifications have no negative significance.” (my bold)

In Chap. 2, DH briefly presents the problems that the Greeks had because of the Platonic element in their thinking, and he then brings in the issue of the distinctive method of modern science: experimentation by controlling variables. When we get to “Galileo’s Kinematics”, it is clear that we are not engaged in a detailed history of scientific thought but a demonstration of how scientists arrive at a generalization. After demonstrating how Galileo began his scientific investigation into the motion of pendulums, DH goes into Galileo’s attempt to answer the question “how does the weight of a body affect the rate at which it falls?” Then, “Galileo demonstrated the answer with his characteristic dramatic flair.” Followed by the rest of the quote provided by JM.

What is DH doing with this example and why not mention the experiments with other fluids? If one was paying attention to the “solution to the problem of induction” in Chap. 1, one would have grasped that all generalizations must be reducible to perceptual level, “first-level generalizations.” In other words, DH is demonstrating that Galileo used a first-level generalization (if I let an object go, it falls) to ground his abstract generalization upon (when I let two objects with different weights fall, they fall at the same rate). Why is it necessary for a demonstration in other media to illustrate that point? It is irrelevant!!

Galileo’s use of different media to induce that resistance goes to zero is a very broad generalization that would only require further examples and explanation. Not relevant to what DH is trying to demonstrate here. Clearly Galileo was aware of air resistance, or “friction” which is sometimes used in quotes which may indicate that DH is aware that Galileo did not have that concept fully developed. It may just indicate that DH is using the common scientific term for what air resistance is so as to make it clear to a modern audience. This is hardly an error on DH’s part. (For example, on p57: “In addition to the concept of “friction,” this discovery depended upon Galileo’s prior development of two key concepts of motion.”) Introducing concepts such as “Archimedean buoyancy” would hardly clarify the issue pertaining to induction and the epistemological base of Galileo’s induction.

In conclusion, JM does not demonstrate that DH’s account is different than the historical account of others for that is not what DH was offering up for consideration. DH demonstrates that Galileo used experimentation to inductively ground his conclusion on first-level generalizations. DM’s conclusion about DH’s theory, “if it is to be widely adopted, it will need to be better reconciled with the historical record as the theory gets fleshed out and refined,” is without merit. The charge that the theory is “inchoate” is baseless. Chapter 1, which provided the justification for induction in terms of Objectivist epistemology, provides an excellent justification for inductive generalizations. It is interesting to note that JM’s “review” of a book on induction does not evaluate the theory presented in the book other than a charge of “inchoate.” After getting the facts by reading the book, it is my opinion that JM’s review is incoherent.

If "accurate accounts would be difficult to reconcile with the philosophical point the author is claiming to make" then where's the demonstration? Where in the review is JM's demonstration that he understands DH's ideas?

Paul, when you are finished with the book, you should post this as a response to JM's review on Amazon.

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[...]

Inventor, you will have to offer a better argument for your viewpoint than the cutting and pasting of a wikipedia article. [...]

The purpose of the article was to offer information regarding the definitions of the terms being discussed. The purpose for the action was, e.g., to add clarity and delimited understanding rather than to promote additional confusion.

Note that on the instant thread there is a paucity of definitions.

Why are definitions important? Definitions, while they are arrived at by means of induction and demonstrated and proved by means of deductive logic, are the essential building blocks of science, that is, to the inductive formulation of new higher level concepts. Or, to the re-validation and proof of existing concepts. They are the standard of proof where experiments are designed to test hypotheses relative to the facts, identities, properties, and relationships of the existents of the universe, especially where a hierarchy of concepts is required. Definitions provide the hierarchical structure of all knowledge by means of setting forth the classifications, sub-classifications, and essential defining characteristics of the concepts being iterated with respect to factual physical existents and all conceptual existents.

All scientific papers that have any merit state at the top of the texts the pertinent definitions that are used in the arguments and conclusions being discussed. Without a hierarchy of definitions any argument is a mish-mash of suppositions, assertions, circularity, dedundant reiterations, and guesswork.

[Note the use of the last comma. That usage of the comma separator is often superfluous in literature, however, in technical scientific statements that have many symbols and terms that have their own immiscible definitions, the comma adds clarity.]

I suggest that the way out of the horrible mixups of discussion that have occurred on this thread is to define all concepts. State the definitions and proceed clearly from there.

For example, one example of a definition that I wrote is that for the universe: "The universe is a continuing plurality of physical existents." What happens in some discussions is, for example, that some proponents of creationism, or the "Big Bang Theory", claim that there is one thing from which the universe was caused or that the universe is one thing. They are wrong. The facts of reality are quite the opposite, however, for it is demonstrable and provable every which way that the existents comprising the universe are several, and that they are continuing. That's the short form of the definition, and in other contexts, I would break the definition down into two definitions, e.g., "The universe is a plurality of physical existents," and, "The universe is the continuity of all physical existents", and the latter definition is a corollary for the first definition. Actually, while I'm at it, it could be said that the first definition is in the context of the primary properties of substance, that several or a number of things exist, and that the second definition is stated in the context of the property of the continuity of functioning [being] of the existents. That substantial things have two primary identities plurality and continuity. [Aris. theory, my definitions.].

Inventor

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[...]

Inventor, you will have to offer a better argument for your viewpoint than the cutting and pasting of a wikipedia article. [...]

The purpose of the article was to offer information regarding the definitions of the terms being discussed. The purpose for the action was, e.g., to add clarity and delimited understanding rather than to promote additional confusion.

That was not Inventor's stated purpose. He explicitly stated in his post only "do your homework" and nothing else, followed by a cut and paste Wikipedia snippet that did not address what I said, contained only one definition that was irrelevant to the discussion ("inviscid flow"), and did not support inventor's previous incorrect assertions.

Note that on the instant thread there is a paucity of definitions.

I have explained the important concepts I used. As previously discussed, Inventor misused well known scientific concepts, did not define his own use except for one incorrect definition of viscosity, and asserted several falsehoods, e.g. with regard to the resistant force on a moving object: "Ordinary friction also functions in addition to the primary resisting force of viscosity", which is false in several ways.

I suggest that the way out of the horrible mixups of discussion that have occurred on this thread is to define all concepts. State the definitions and proceed clearly from there.

The only "horrible mixups" have been in inventor's own posts, which misrepresent numerous aspects of fluid dynamics and Galileo's free fall experiment, which he has been unable to defend, in addition to rambling irrelevancy.

Why are definitions important? Definitions, while they are arrived at ...[long rambling]... All scientific papers that have any merit state at the top of the texts the pertinent definitions that are used in the arguments and conclusions being discussed... Note the use of the last comma. That usage of the comma separator is ...

"All scientific papers that have any merit" do not begin with "definitions". None of this rambling, stilted pontification purporting to be about definitions, the use of commas, the "universe" at large and the "Big Bang" has anything to do with the subject of the thread, nor does it justify the previous incorrect assertions about fluid dynamics and Galileo. If posts like this are permitted in a serious thread, then it must be presumed that its author is to be regarded as possessing the sanity and self-control to decide what to write here, and explicitly held responsible for the distraction. This is not the first thread on which he has done this.

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No reply is necessary. If there is a single sentence, point of fact, grammatical error, or fault of logic, however, I'll be happy to correct what has been said and to reply.

Inventor

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