Forces of nature and such

[Radagast]

That does not mean that the attraction of the objects necessarily creates said force

"Attraction" just means an inwards force (☐ → ← ☐), that's all it means. Neither Newton nor Cavendish provide a reason for the force.

and by stating it satisfies the equation, you are applying Newton's laws

You're really not getting this, are you? The equation F = G M m / r^2 can be obtained from the Cavendish experiment itself, by varying M, m, and r, and measuring F. It's not assumed in any way. In fact, one reason for running Cavendish-type experiments is to check whether the power really is 2.

and requires computation and application of relations in addition to simple measurement with a device.

Clearly you don't understand measurement instruments either. I've already pointed out that the principle Cavendish used is the same one as in a torsion galvanometer.

 

[Quid est Veritas?]

You're really not getting this, are you? The equation F = G M m / r^2 can be obtained from the Cavendish experiment itself, by varying M, m, and r, and measuring F. It's not assumed in any way. In fact, one reason for running Cavendish-type experiments is to check whether the power really is 2.

Yes? What is this supposed to prove? If I gave this apparatus to Aristotle, would he derive said equation? You have to equate the force from the torque to a force that you ascribe to the product of masses divided by the square of distance between them. You have to apply Newton's Law of universal gravitation. So yes, you can derive it, but it was created with that in mind. It is a mutually dependant experiment and theory. How on earth does this equate to a direct observation thereof?

Clearly you don't understand measurement instruments either. I've already pointed out that the principle Cavendish used is the same one as in a torsion galvanometer.

Which is an instrument using indirect observation. We aren't directly observing current, but observing change in position due to a magnetic field as a response to it. Humans cannot directly perceive current except in secondary causes like heat produced or deflection of a needle. Again, what on earth is your point?


We are getting nowhere. I am going to stop this discussion in all probability. I thank you for your time.

 

[Radagast]

If I gave this apparatus to Aristotle, would he derive said equation?

Don't know about Aristotle, but I'm confident that Archimedes would.

You have to equate the force from the torque to a force that you ascribe to the product of masses

You don't ascribe it to the product of masses, you notice that it's proportional to m and proportional to M.

divided by the square of distance between them

And you notice that it's inversely proportional to the square of r.

You have to apply Newton's Law of universal gravitation

No, I could give the equipment to Archimedes, and he would derive F ∝ M m / r^2. Of course, he would interpret this as the ratio of the area of the rectangle Mm to the area of the square r^2.

We aren't directly observing current, but observing change in position due to a magnetic field as a response to it. Humans cannot directly perceive current except in secondary causes like heat produced or deflection of a needle.

In that case we can't observe anything "directly," so we can't do science at all. Never mind, you can leave, and the rest of us will keep on doing science.

 

[J_B_]

I am still awaiting this example of a directly measured F, though. Cavendish is measuring a deflection, and inferring therefore a force applied. This is not directly observed. This is similar to saying Gravity is observed because apples fall from trees.

We are going around in circles though, over merely an illustration of my main point, so I have said my peace for now.

I agree with your position and have had similar difficulties showing people the paradigm to which they adhere.

 

[FrumiousBandersnatch]

Of course if you go the ad absurdam route, you can always say there must be light bouncing off and then perceived by the eye, pruned by the sensory neurons and then interpreted, etc. So any perception requires participation in a sense between observer and observed. But that is certainly not what I mean.

Certain things can be directly observed. I can pick up an object and feel its weight, its mass, its temperature and heat. I can visually perceive speed and acceleration, length and luminosity. Of course, for precision and intersubjectivity, we create scales and surrogate measuring apparatus to make sure we are all on the same page, that had been calibrated via direct human perception thereof at some point. So although often not directly observed today, they are ultimately directly observable phenomena. Other things are second order, in that they are determined via these, such as F=ma, or derived.

Anyway, as far as I know, physics defines direct observation as observation via your senses (or more generally, when I have an instrument derivitive from that sensory effect for that quality); and indirect observation, as that made by measuring something and using that to determine something else, via relation or computation. Apologies for the rough definitions, but I am not completely sure where to find my old physical measurements textbook.

Anyway, so Cavendish directly measured the angle of deflection and the length of the wire, then indirectly computed a force of torque (which is indirectly derived via measuring length ultimately) and then assuming Newton's laws, declares it equal to the force that opposes it when the system is in equilibrium, and ascribing that to the attraction between the objects. Little of that is a direct observation, and the whole only means something if you are already assuming Newton valid from the get go. It is a good experiment, but philosophically and logically, it is a circular argument as an observation of Newton's laws or gravity.

Science is explicitly making the same kinds of inferences that your brain makes implicitly - except that science also has explicit validations and verifications.

 

[Quid est Veritas?]

Don't know about Aristotle, but I'm confident that Archimedes would

No, I could give the equipment to Archimedes, and he would derive F ∝ M m / r^2. Of course, he would interpret this as the ratio of the area of the rectangle Mm to the area of the square r^2.

I disagree he would. You are assuming a post-Newtonian mindset. Prior to this, the assumption was not that a force was required to counteract another force, but that objects naturally tried to return to a state of rest. Things only moved if something moved them, and came to rest afterward. So noting the movement on the apparatus, he would in all likelihood, believe it came to rest due this natural tendency along with the torque of the wire counteracting it. The movement would also not be seen as attraction between the objects, but probably related to the Movement of the Spheres, or to their elemental constituents attempting to return to their appropriate level - as air and fire rises, and water and earth falls. Certainly he would not derive the formula.

I am not even sure someone as late as Galileo would have.

You don't ascribe it to the product of masses, you notice that it's proportional to m and proportional to M.

Doesn't change my point in the least.

In that case we can't observe anything "directly," so we can't do science at all.

Untrue. We can observe blood pressure both directly, via an invasive BP monitor with a column of water, and indirectly, via a cuff BP monitor and either oscillometry or listening for Korotkoff sounds. It doesn't mean the indirect is therefore wrong (although direct measurements are usually seen as more epistemologically sound), and as stated before, many instruments ARE direct observations - this just isn't, as is the galvanometer. You should go reread the posts on it earlier.

Never mind, you can leave, and the rest of us will keep on doing science.

This is merely an ad hominem. If you are going to stoop to casting aspersions, then I really am done. I sincerely asked for explanation of your counter-claims, which you singularly fail to back up. Again, the Newtonian mindset of the Cavendish experiment is explicit, and without assuming it, I doubt it would render what you want. To illustrate, just think of any chemistry experiment, and how different an ancient Greek, an alchemist, or a modern chemist would interpret the result. Still, my initial point stands that it is not directly observed.

 

[Quid est Veritas?]

Science is explicitly making the same kinds of inferences that your brain makes implicitly - except that science also has explicit validations and verifications.

I disagree. Science developed from Roger Bacon and Grosseteste in the 12th, and is not a natural thought process. Humans aren't natural empiricists, and a lot of our thinking isn't relatable to logical inference. This is why we need to instill the style of thinking through years of schooling. Humans are naturally intuitive thinkers initially, and analytical thinking comes later - and does not necessarily follow an empiric path.

 

[FrumiousBandersnatch]

I disagree. Science developed from Roger Bacon and Grosseteste in the 12th, and is not a natural thought process. Humans aren't natural empiricists, and a lot of our thinking isn't relatable to logical inference. This is why we need to instill the style of thinking through years of schooling. Humans are naturally intuitive thinkers initially, and analytical thinking comes later - and does not necessarily follow an empiric path.

When I said the brain is implicitly making inferences, I wasn't referring to conscious thinking but the inductive inference of the unconscious learning and habituation processes that underlie it.

 

[J_B_]

You are assuming a post-Newtonian mindset. Prior to this, the assumption was not that a force was required to counteract another force, but that objects naturally tried to return to a state of rest.

Yeah. Newton wouldn't have been considered revolutionary if the people preceding him thought and worked within a Newtonian mindset. That's why a little knowledge about the history of science is good for these conversations.

One of my favorite pre-Newtonian concepts was "impetus" as formulated by Jean Buridan.

Maybe reading Ernst Mach's writings on this would be more compelling than hearing it from we unwashed poor.

 

[Radagast]

Yeah. Newton wouldn't have been considered revolutionary if the people preceding him thought and worked within a Newtonian mindset.

Well, actually, Newton's first and second law can be found in Galileo's second great book: Discourses and Mathematical Demonstrations Relating to Two New Sciences.

What made Newton revolutionary is that he tackled the problems of force and acceleration with a more sophisticated mathematical toolbox, that of calculus.

The reason why I mentioned Archimedes earlier was that he came remarkably close to several concepts of calculus. If a time traveller was to go back in time and give Archimedes a few hints, he might have done even better. Archimedes also had an understanding of the lever, and knew the concept of forces balancing each other.

 

[J_B_]

Well, actually, Newton's first and second law can be found in Galileo's second great book: Discourses and Mathematical Demonstrations Relating to Two New Sciences.

What made Newton revolutionary is that he tackled the problems of force and acceleration with a more sophisticated mathematical toolbox, that of calculus.

The reason why I mentioned Archimedes earlier was that he came remarkably close to several concepts of calculus. If a time traveller was to go back in time and give Archimedes a few hints, he might have done even better. Archimedes also had an understanding of the lever, and knew the concept of forces balancing each other.

Uh huh. I'm aware of Archimedes' method of exhaustion. I once did a little project where I derived the area of a circle using his method. He was truly a genius, but that doesn't mean he was omniscient. If he was as remarkably close to calculus as you claim, then Newton's use wasn't at all remarkable. You forgot to mention that Leibniz also developed calculus - he and Newton argued over that for years. Then, of course, there was the argument between Newton and Hooke about the nature of fundamental forces (Newton's Law vs. Hooke's Law).

If you're Turkish you'll find Newton in the works of Ali Qushji and if you're Chinese you'll find him in the works of Su Song. Have fun.

 

[Radagast]

Uh huh. I'm aware of Archimedes' method of exhaustion. I once did a little project where I derived the area of a circle using his method. He was truly a genius, but that doesn't mean he was omniscient.

I can still fantasise about a time-traveller giving him a few hints.

You forgot to mention that Leibniz also developed calculus

I'm fully aware of that, and indeed I think Leibniz may well deserve the credit for calculus.

But Newton certainly deserves the credit for applying calculus to physics.

 

[J_B_]

But Newton certainly deserves the credit for applying calculus to physics.

Among other things. God bless.

 

[Subduction Zone]

That does not mean that the attraction of the objects necessarily creates said force, and by stating it satisfies the equation, you are applying Newton's laws - so that supports the hypothesis, but does not mean it was directly observed.

That is as good as it gets in the world of science and is far superior than any other alternative. Of course I could be wrong. What would top that?

I defined direct and indirect observations above, and most scientific instruments are direct observation, in that they can be directly related to sensory observation in calibration of the instrument for that measurement. This most certainly cannot, and requires computation and application of relations in addition to simple measurement with a calibrated device.

Actually you only hand waved a bit. But it appears that you just contradicted yourself. By your standards in this part of your post gravity has been directly observed.

 

[Quid est Veritas?]

The formal definition of direct observation in Physics, as per the work of Dudley Shapere:

x is directly observable if information is received or can be received by an appropriate receptor; and that information is or can be transmitted directly, i.e., without interference, to the receptor from the entity x which is the source of the information.

This leaves three things to consider if directly observable: the release of information by the x, the transmission of information, and the receptor. The assumption being that experiments are theory-laden, so that it can be determined based thereon the source of the information was from x, that the receptor was appropriate, and no interference occured. The point being that Observation usually has a perceptual and epistemic role, to establish support as evidence for beliefs. In Physics, the perceptual role can only apply to what humans can perceive by sense-data, and any other information has of necessity, to be converted into a form we can perceive. For this reason, the definition sometimes adds that the information must be convertable into human accessible information which is perceived by a human being (though tautological in a way, and Shapere argues that the observation itself is inseparable from the inference of the theory). So in practice, physics weakens the perceptual role by generalising Observation via inference and reason, to focus on an epistemic role to allow further building on the nested hypotheses and inferences upon which Science in general is built. In quotidian and Philosophic usage, the perceptual aspect of Observation takes greater precedence, often in support of the epistemic - so for instance, it makes little sense to say I have observed the centre of the sun usually, but in scientific circles, it can be said - from inference of other observations.

Circling back to my original post, I stated: "It should be remembered that Gravity is itself an hypothetical construct, inferred from acceleration or weight, but not directly observed. Another how many inferred Forces is just as possible, and people had been investigating physics empirically for centuries prior to Newton." This remains a valid statement, applying the philosophical and quotidian meaning of observation as the context demands, as inference is without a doubt essential to any 'observation', or a better word perhaps such as detection, of Gravity. In discussing the possibility of additional forces inferred, such forces would have to be be applied into experimentation to be 'observed'. The whole point of this thread was to challenge the epistemic framework of current physics and its four forces.

But to return to the definition. The pragmatic usage is to use the strongest form of language until doubt arises as to the validity thereof. The application of whether something is directly observed, depends upon the theory-ladeness of it. So to Galileo observing the moons of Jupiter, using a telescope, his contemporaries rightly critisised it as not directly observed, but once we established it better, we no longer have qualms in calling it thus. The more inferences required though, the less secure an observation epistemically. Whether something is directly observed or not, depends upon how much leeway you grant to the gulf of inferences and interactions between actual perception by human sense organs and the initial x. The epistemic ground we grant in physics, determines largely whether we term it direct or not. Earlier in this thread, I took a fairly hard approach to this, which I must concede, was likely coloured significantly by my philosophic point. On Cavendish's experiment, it seems clear to me that Archimedes could not directly observe Gravity as per definition, but Cavendish being post-Newton could. Whether Cavendish's experiment is a direct observation in Physics, I concede it could be so construed if Gravity is merely defined as a mathematical description therein, as @Radagast did, and granting the inference of balanced forces. If defined more as curvature of space/time as per Relativity theory, then it certainly doesn't; and any observation of this, runs into the limit of its failure to adhere to quantum mechanics. So the epistemic footing to exclude interference in the transmission between x and the receptor, or even the interactions of x and the receptor itself, is lacking.

I hope that clears the air a bit, and I apologise for my intransigence. I think that concludes this tangential discussion.

 

[Radagast]

The formal definition of direct observation in Physics, as per the work of Dudley Shapere:

x is directly observable if information is received or can be received by an appropriate receptor; and that information is or can be transmitted directly, i.e., without interference, to the receptor from the entity x which is the source of the information.

But he points out that prior knowledge comes in to building a receptor. So we can use prior physics (e.g. the theory of levers) to design an instrument for testing theory A.

What we can't do is assume theory A in the instrument that tests theory B, and at the same time assume theory B in the instrument that tests theory A. Modern physics sometimes looks like it's in danger of being circular in that way.

Circling back to my original post, I stated: "It should be remembered that Gravity is itself an hypothetical construct, inferred from acceleration or weight

I'm still taking issue with that, because I think Cavendish-style instruments directly observe the force.

Of course, the nature and explanation of the force are still left up in the air by Cavendish-style experiments. If we were pedantic, we wouldn't say "gravity," we would say "the attractive force that's proportional to the masses of objects and inversely proportional to the distance between them."

I think we are actually both agreeing on that, using different terminology for doing so.

On Cavendish's experiment, it seems clear to me that Archimedes could not directly observe Gravity as per definition, but Cavendish being post-Newton could.

And my reason for taking issue with that was that the prior knowledge that Cavendish-style instruments assume is the theory of the lever (which Archimedes had) and the concept of torsion (which is implicit in the design of the torsion catapult, which goes back to before Alexander the Great, and which seems to be something that Archimedes had personal experience with).

If defined more as curvature of space/time as per Relativity theory, then it certainly doesn't

And direct observation of "the curvature of space/time" is indeed a whole lot more difficult.

 

[Quid est Veritas?]

I'm still taking issue with that, because I think Cavendish-style instruments directly observe the force.

Not philosophically, as you still need to infer a balance of forces, and thus infer an attractive force.

And my reason for taking issue with that was that the prior knowledge that Cavendish-style instruments assume is the theory of the lever (which Archimedes had) and the concept of torsion (which is implicit in the design of the torsion catapult, which goes back to before Alexander the Great, and which seems to be something that Archimedes had personal experience with).

You are also assuming that he infers a balance of opposite forces, while we know the Greeks assumed the natural state was one of rest, with motion only possible by the constant application of an external force to overcome it. At equilibrium, someone holding this view would think a state of rest achieved, as a product of the natural tendency to return to rest as well as the opposing force. Similarly, the ascribing of the inferred opposing force to the masses of the substances is not a given, either. The ancient Greeks held that the elements had natural motion, to return to rest at their appropriate sphere, determined by weight, density and the medium in which they find themselves. So the torsion could be overcoming this natural movement as well, and varying the mass would be interpreted as varying the elemental composition. As far as I am aware, the Ancient Greeks had no concept of mass in the modern sense, and even ideas like a quantity of matter is a late Roman one, and only under Scholasticism did the ideas of a certain quantity of matter maintaining a certain volume arise.

So a complex equation of a force of torque and a natural tendency to rest would be opposed by a balance of elements moving upwards (air and fire) and downwards (earth and water). While the latter could certainly be equated as an opposing vector, ascribing it to mass would not necessarily occur.

I disagree the prior knowledge required is only the lever and torsion, but he would also need to set aside substantial parts of the prevailing paradigm of Greek physics, and interpret the results in a novel way for his time. Nor do I think you can assume an adequate knowledge of theory based on the practical ability to utilise it in the case of torsion - the Romans built excellent aquaducts and baths, but they certainly didn't understand flow and pressure correctly, for instance.

So Archimedes would have to make inferences different from the prevailing ones in his society, in order to 'directly observe' it. But this is merely a tangential thought, as regardless, my point was that we cannot observe gravity anyway, without making said inferences.

 

[Radagast]

Not philosophically, as you still need to infer a balance of forces, and thus infer an attractive force.

You're disagreeing with what Dudley Shapere says about prior knowledge, then?

You are also assuming that he infers a balance of opposite forces, while we know the Greeks assumed the natural state was one of rest

Like I said, Archimedes was familiar with balance of forces as it occurred in the lever.

And with a balance of forces, there is no actual motion.

At equilibrium, someone holding this view would think a state of rest achieved, as a product of the natural tendency to return to rest as well as the opposing force.

Do you seriously think so? A torsion catapult would have disabused them of that notion in a fraction of a second.

As far as I am aware, the Ancient Greeks had no concept of mass in the modern sense

Their entire financial system was based on measuring the masses of gold and silver.

the Romans built excellent aquaducts and baths, but they certainly didn't understand flow and pressure correctly, for instance

Their knowledge was empirical, but pretty good. They had an empirical feel for the relationship between slope and water velocity.

my point was that we cannot observe gravity anyway, without making said inferences.

I still say we can observe the attractive force.

I agree that observing the "curvature of space" is trickier.

 

[Quid est Veritas?]

You're disagreeing with what Dudley Shapere says about prior knowledge, then?

Not at all. I am in fact applying his point about the necessity of inference, and the difference between the use of 'direct observation' in physics versus philosophy and logic.

Do you seriously think so? A torsion catapult would have disabused them of that notion in a fraction of a second.

Yet it didn't.

Their entire financial system was based on measuring the masses of gold and silver.

Their financial system was based on weights and measures, not mass. The Greeks considered weight a property of individual objects, not as a universal concept.

I still say we can observe the attractive force.

I respectfully disagree.

 

[Radagast]

Not at all. I am in fact applying his point about the necessity of inference, and the difference between the use of 'direct observation' in physics versus philosophy and logic.

I think you are misunderstanding him.

Yet it didn't.

Not so; the Greek misunderstandings related to motion, in part because phenomena like drag make it harder to deduce the principles.

Their financial system was based on weights and measures, not mass.

Their financial system was based on a concept of "amount of gold" or "amount of silver."