And, in the last paragraph of the general scholium, the appendix of the Principia, Newton describes electromagnetism and the role of electrical oscillation in the nervous system. It’s actually the root of the the history of “vibes”
“And now we might add something concerning a certain most subtle Spirit, which pervades and lies hid in all gross bodies; by the force and action of which Spirit, the particles of bodies mutually attract one another at near distances, and cohere, if contiguous; and electric bodies operate to greater distances, as well repelling as attracting the neighbouring corpuscles; and light is emitted, reflected, refracted, inflected, and heats bodies; and all sensation is excited, and the members of animal bodies move at the command of the will, namely, by the vibrations of this Spirit, mutually propagated along the solid filaments of the nerves, from the outward organs of sense to the brain, and from the brain into the muscles. But these are things that cannot be explain'd in few words, nor are we furnish'd with that sufficiency of experiments which is required to an accurate determination and demonstration of the laws by which this electric and elastic spirit operates.”
https://web.archive.org/web/20100524103006/http://www.isaacn...
This is some remarkable intuition. Electromagnetism wasn't even developed as a theory. To observe such varied phenomena like how nerves communicate or what comprises matter or the behaviour of light and postulate they might all have something in common and something to do with the attraction/repulsion seen when objects are rubbed together, is incredible. Was the idea very unique for its time or did scientists at the time hold similar ideas? Do you think it was just a lucky guess in the end that the world didn't turn out to be more complex or was there some reason behind this craziness?
It's tricky in hindsight. He also guessed stuff wrong, and how the biology eventually turned out is not exactly how he imagied. You project a modern understanding on that text but you don't really understand the significance of the phrasing he uses, such as spirit etc. It's a loose match, perhaps better than Democritus and the atom, but still needs hindsight bias.
People had similar theories, like Descartes imagined nerve tubes carrying fluid to act and kind of hydraulic actuation, as well as ancient Greek pneuma theory of vital spirit. Gilbert's work on magnetism and electricity was known, Hooke's work on vibrations.
It's impressive of course but not out of this world unimaginable magic. He plugged his favorite modern theory to biology, replacing the fluid stuff with electric stuff. Tons of people did that kind of thing before and after, sometimes it works, sometimes it leads to nowhere.
The classic “genius effect” where someone is a genius or very good at something and goes do something else and is off base but people will still thing there’s value there.
People just didn’t have the tools to understand this subject at that time.
Nikola Tesla fits this all to well. He was a genius in an very narrow subject and rejected the ideas of his peers in his field. He didn't believe electricity was made of subatomic electrons and it all came from an either. He was even trying to use the Earth as a wireless energy transmitter when it is a grounding source.
Too many people believe that a person really good in context A will be good in context B to Z. Or the Shaolin Monk Fallacy, just because you can do push ups with two fingers and swing a staff does not mean you are instantly good with a pool cue or tennis racket.
Perhaps not instantly good, but there's obviously major skill transfer between domains. In physical domains this is easy to see and understand with countless demonstrations of professional athletes who decide to swap sports and reach a professional level in the new sport with relative ease. And I think the exact same is true in mental domains.
World class expertise in some mental field is not achieved solely by knowledge within that field, but by a distinct ability to process and apply information in a novel way. And that skill is highly transferrable to other fields. Of course you still need to then accumulate information in said other field, which is why it's not instantaneous, but if a world class individual in one field puts their energy towards mastery of another field, I certainly would not bet against their success!
I’m not sure it’s really about skill transfer outside of very related areas. You need to be genetically lucky to hit the very top of a physical or mental field and the odds you have similar gifts in a field with slightly different demands is far higher than average.
Similarly having the drive to actually dedicate yourself to some narrow area could be considered a skill but I think it’s more a personality trait.
"Or the Shaolin Monk Fallacy, just because you can do push ups with two fingers and swing a staff does not mean you are instantly good with a pool cue or tennis racket."
Agreed, it’s astonishing intuition. It’s hard to call it a lucky guess when it is the last paragraph of Newton’s magnum opus. But very hard to explain.
Choosing my words carefully, I think it was a kind of deep and deliberate magic. Of the sort Newton ascribed to Pythagoras as the esoteric discoverer of the inverse square law of gravitation. (see “Newton and the pipes of pan”). Hooke also had a sort of musical, oscillatory, spiraling conception of mental phenomena. So it was in the Zeitgeist.
In any case, it is striking and amazing— and resonant in this age of vibes.
There are some insights, but I think you only feel they are remarkable because you have a much more concrete understanding of how things work and you filled the holes in these vague words with your knowledge.
An ancient Greek philosopher said the matter is made of smallest particles. It doesn't mean he found the concept of atoms as we know.
People like Newton, in earlier eras, would be called prophets. And Newton wasn't do far from the religious aspect himself. He was considered crazy in his time, disliked by most. He was an adherent of the occult, in fact he discovered gravity while specifically looking for ways to move objects from afar. Oh, he found it. Today he is revered, and rightly so, but at the time he was hated though he was respected.
I don't think prophet is the right word. Prophets didn't develop physics or engineering but warned the tribe of God's impending punishment unless they obey better or similar historic predictions of how God will use floods or draughts or enemy tribes to challenge you etc.
> He was considered crazy in his time, disliked by most.
Where did you get that from? As far as I know he was widely respected as a genius in his time and had great professional and social success (including receiving a knighthood of course).
Where is it written that he was considered crazy and disliked?
"Did we know the mechanical affections of the particles of rhubarb, hemlock, opium, and a man, as a watchmaker does those of a watch ... we should be able to tell beforehand that rhubarb will purge, hemlock kill, and Opium make a man sleep; as well as a watchmaker can" -- John Locke
The world was very pious then. To have written that paragraph a century earlier may have resulted in ostracizm. To have written it like that was enough given the limited backing that ould be given. It was enough to influence those around and after Newton, it was, in that sense, remarkable.
Newton leaving it to “future work” is iconic, like casually predicting neuroscience. Meanwhile, French mathematician Lagrange solved orbital parking mechanic over a century before we sent rockets into space
People today are confused by the word spirit because the word fields quietly replaced it, and they are just as mysterious because we don’t know if they are real.
At the time, 'spirit' was used to mean 'low-viscosity fluid' and 'vapor'. Alcohol and various distilled fluids were called spirits. He didn't necessarily mean 'intangible'.
"Field" is a less mysterious term because it's not polysemous with a supernatural being (ghost) or a distilled alcoholic beverage (soluble liquid).
Sure, it's polysemous with "a cultivated expanse of land", but AFAIK there is no popular, problematic pseudoscientific quackery about suggesting our bodies possess rows of oats.
> Wenn wir das Wesen des Baumes suchen, mĂĽssen wir gewahr
werden, daĂź jenes, was jeden Baum als Baum durch waltet, nicht
selber ein Baum ist, der sich zwischen den übrigen Bäumen antreffen läßt.
It's how a lot of science was written, and knowing that makes strong Sapir-Whorf a really funny joke. We didn't derive our ideas about science from our language. Developing our ideas of science shaped our language so it could communicate them efficiently.
(Weak Sapir-Whorf is still a perfectly fine observation, but it's a lot less predictive as a hypothesis.)
In some sense, yes. I've seen portions of works by people like Newton etc. You had to be a philosopher to read them, much less understand them. In a lot of cases, the same "material" that we learn today required someone to come along later and work out a notation that we can read and teach. My favorite example is the Algebra of Al-Khwarizmi, which contained no numbers, much less equations, but was just a wall of text. In fact, equations were invented later. Also, I think the electromagnetism of Maxwell was reformulated into the equations that we love and cherish by Heaviside.
The principa and the scholium were written in NeoLatin, the version of Latin adopted from the Renaissance through the 1900s to write scientific, philosophical and other treatises
Yeah, so I’m working on a piece about this. Of course, “cosmic sympathy” and “harmony of the cosmos” goes back to the stoics and Pythagoreans. The direct use of the term vibration in the context of mental activity (“thought vibrations”) is from the American New Thought Movement and Theosophy — that’s where The Beach Boys got it from. But it extends back over the centuries to Newton and then Willis (who used sympathetic vibrations as the basis of his introduction of associationism in psychology).
To me, the funniest part of why Principica was bankrolled by Edmund Halley is that is was supposed to be funded by the Royal Academy. Only, their previous publishing project "The history of fishes" had faceplanted and they had no money.
Also, when Principica was funded and Halley was himself short on cash, RA decided that they could not afford to actually pay him money (he was the RA secretary). Instead he would get copies of The History of fishes
wait! wait!
so you are saying that there is an official exchange rate for fish books to pounds strerling, guinies?
all I can say is that hopefully someone keeps a copy of the fish book next to a copy of the Principica as a demonstration/proof of the vast leap and gap that suddenly occured
Back in 1987 I was standing outside Thorns Bookshop in Newcastle upon Tyne.
In its window was a display of books by Professor Paul C. W. Davies.
I was saying to someone beside me that Davies wrote too many books for them to be any good.
Then I turned round and almost bumped into the man himself.
Fortunately he hadn't heard what I'd said and just carried on his way.
He was hurrying to give a lecture at the university commemorating the 300th anniversary of Newton's Principia.
Several years later I was to revise my view of his writings after reading his 'Fifth Miracle' which I enjoyed very much.
> Halley’s intervention saved science from being reduced to “things fall down because they do” for another century.
Well, that might be stretching it. Speaking as someone who has done a little university level physics the understanding still seems to be basically that things fall because they do - we haven't made much progress beyond a firm strike-through of the word "down".
Newton's contribution was a very precise description of how rapidly they fall, and how we can calculate and understand the direction that things fall in complex multidimensional settings.
You’re correct. Newton wasn’t proposing a mechanism or deeper cause for gravity; he just described its effects. Einstein did add a “why” of sorts, with general relativity, he reframed gravity not as a force but as the curvature of spacetime caused by mass and energy. That’s closer to a mechanism, but even there we might ask: why does mass curve spacetime? And we don’t have a deeper answer to that.
Is "why" really a meaningful question? These are all models. The best we can do is to show how to derive the phenomenon from the (hopefully simple) rules of our model.
I think so. The why can be a powerful and compact way to express the elements of a model, when a model can be applied, and when the model might break down. A complicated model without a WHY might not be easily understood by others. A surprising, new result with a good WHY can point the way to other aspects of the model that might be confirmed or disproved.
Think about how much our understanding of atoms has changed. I think the why is an important part of the development. If you're interested in that topic, how about a 35 min nuclear physics primer from Angela Collier (I love her videos!): https://www.youtube.com/watch?v=osflPlZdF_o
It's relative. I operationalize "why is X true?" as "update my worldmodel to the point that X is not surprising". The typical way to do that is to show a more general rule that applies, and which implies X. But yes, you can keep asking the question about the more general rule.
Why do things fall? -> A special case of the general law of gravitation.
Why does reality adhere to the general law of gravitation? A implication of matter distorting the shape of spacetime.
Why is reality such that matter distorts space-time?
If you want something that won't fall down, your only options are (1) luck into noticing something that already does that, or (2) understand why things fall down, so you can prevent your thing from falling.
No, it isn't. That sounds strange, right? But here is an explanation what
eternauta3k probably meant: In modern physics, there is a kind of consensus that asking “why” has often been inappropriate or even misleading and should be therefore left to philosophers. The real questions are: Does our current model describe all observations? If not, can we find a model that does? And, even better, can that new model make predictions that we can verify?
Newton’s title has philosophy in it. It’s probably a modern error to separate all the fields and ignore philosophy when doing science etc and vice versa.
> The real questions are: Does our current model describe all observations? If not, can we find a model that does? And, even better, can that new model make predictions that we can verify?
But every prediction your model can make comes from a "why" question that the model answers.
It’s interesting how it’s not turtles all the way down (as I understand it at least). The things you learn of one scale do not completely translate to the next but serve as the “shadow” projected by the next level down the line. And this probably brings up the complexity that lets us exist and perceive. I say probably because who knows what else is going on in the universe.
All this to say who knows if we are ever going to learn the fundamental why if there is one.
Yes, general relativity explains gravity pretty darn well, tying it to the fundamental fabric of causality that makes up the universe. It goes from “it just happens” to “it must happen and there is no other way it could be.”
There is no notion of causality in our laws of physics, and from all we know gravity could certainly be different, or absent. You could have a universe with just the other three forces.
Modern physics says little about causality. The fundamental laws are all field equations. Those set constraints about how the physical state of a system can evolve between two points in time, but there is no notion of causation, only of consistency or (im)possibility.
I think we are talking past each other. Defining how the system evolves is defining how initial conditions must lead to (cause) intermediate and final states. That’s causality in the logical sense.
What I’m talking about is most similar to the “Causal Explanation” section at the end of the article you link.
Maybe? That's one theory - but what is "spacetime", and what does it mean to "bend", or "fall into" something like that? In many ways we've just given things names as if that suddenly means they're understood.
And even then how can that be measured and proven vs other theories? Is it some other mechanism that simplifies to "close enough" that it measures similarly? We didn't really see the effects of relativity until we got to a sufficient accuracy of measurement, Newtonian mechanics was sufficient to explain things to the accuracy they could reproduce for a very long time.
Einstein couldn't have done anything like what he published if he didn't have evidence from new (at the time) equipment suggesting there was something wrong with the current model. And then testing proposed new models against those same measurements.
It was less of a counterexample and more of an inaccuracy. It wasn't immediately obvious as to whether the theory was at fault or our measurements or even knowledge of celestial objects (e.g. maybe Mercury had some nearby object that was changing its orbit).
Also, there wasn't any alternative, so a theory that explains almost everything is going to be accepted. Modern theories are also accepted if they explain things with more accuracy or over wider ranges than alternatives - often it's the shortcomings of theories that gives us clues as to a better theory. (e.g. the ultraviolet catastrophe)
I've always been a bit flummoxed we haven't expanded a ton on this given how long it's been.
I'm not sure if it's wrong or right, and not smart enough to posit much, other than it -feels- wrong. But it wouldn't take a ton to convince me otherwise.
You'd think by now we'd have more supporting evidence of such a concept.
Do you mean evidence for general relativity? Because there's a lot: gravitational waves, black holes, gravitational redshift, the bending of light by gravity, the expansion (or contraction, depending on density) of the universe, are all new phenomena predicted by GR and experimentally verified
Oh I meant expanded it down, if that makes any sense, applying it to more things that we'd normally learn in high school.
At least in my case, you're taught gravity as this standalone force, and even the Newtonian idea in high school. Not until later college do they then throw that away and go into gr and the ideas you mention.
Though I guess this is more a failing of public education than science at large.
Ah, right. I would guess that's because it's just a much more complicated theory, and is well-approximated by Newtonian gravity for weak fields, e.g. like in the solar system. So applying GR to more everyday phenomena would just be a much more complicated way of saying almost the same thing.
GR is written in the language of differential geometry, and before even beginning you need a good grasp of Newtonian gravity, special relativity, multivariable calculus, and ideally electromagnetism too, so it needs a fair bit of preparation. And in fact the methods of Newtonian mechanics aren't thrown away, but incorporated into the more general framework. In that sense Newtonian mechanics is a conceptual foundation for GR, so that's why it's still taught first at school
I think it’s kinda more that (in 3D with time moving at a constant rate) space “falls” into the gravity well, and matter goes with it. In 4D this looks like spacetime being bent.
The "river model" you mean isn't very general, as one eventually becomes interested gravitating systems where there isn't a suitable congruence, e.g. in close binary compact objects. In such systems, one has to add terms analogous to turbulence, frustrating calculability (and the development of relativistic intuition). It also doesn't deal well with tides: for example, Schwarzschild infaller worldlines (even on a body like the moon, where there is no horizon) on widely separated radial trajectories converge in a way that is unlike the confluences of rivers and their tributaries. These models really only assist in understanding a single (spatial) radial line with possibly multiple successive "rafts" of matter bound to it (at different times), and in a set of PG-like coordinates useful for a particular distant observer. From there one symmetrizes: all observers and all radial lines are identical (speherical symmetry) and successive "rafts" all take the same radial line (static spacetime). Without this symmetrization, a black hole is an infinite number of slightly different rivers, and then you might as well solve the equations of motion in the standard way.
For understanding a handful of highly symmetrical systems, it might help a student understand some intuitions about what Killing vector fields and congruences (notably those made by choosing the velocity vector field of a set of geodesics) are, and tends to lead into an investigation of what the shift vector in a 3+1 decomposition represents.
For calculating things like the spherical orbits around or the photon surface of a real black hole like our galaxy's central Sgr A*, the river model seems outright unhelpful. For example, how does a river model help to understand https://duetosymmetry.com/tool/kerr-circular-photon-orbits/ ?
> time moving at a constant rate
This is another way of saying slicing of a Lorentzian (4d) spacetime into non-overlapping spaces organized along an arbitrarily chosen future-directed non-spacelike worldline. That is, this is a 3+1 slicing. We can slice along your worldline, or on that of a neutral hydrogen atom floating in intergalactic space, or on that of a high-energy cosmic ray, or on that of a CMB photon. It's arbitrary, and each can give markedly different spatial slices through the same spacetime (in particular particle counts on slices will differ where the choices of index axes are anywhere accelerated with respect to one another).
When we decompose in this way, and take an <https://en.wikipedia.org/wiki/ADM_formalism> approach, we will tend to think of the shift vector as how we associate a point one one slice (everywhere in space at a coordinate instant in the spacetime) with its successor slice (everywhere in space at the next coordinate instant int he spacetime), which is helpful when spacetimes expand or contract in one or more spatial directions along the arbitrarily chosen time axis.
Oh come on. Things fall down because matter has a property called gravity that attracts other matter, and below us is a giant earth with a lot of matter. And it has more of a net effect on us than any other matter in the universe because gravity scales with distance and mass in that particular way. That's as darn good of an explanation of why we fall down as one could possibly give. "But why does mass have gravity?" Why does Newton have to have all the answers to every other question too? Maybe ask that and someone will answer that question in a few hundred years? He answered your original question, he didn't claim he can answer every subsequent question you think of. It's quite ridiculous to suggest Newton just tautologically concluded "things fall down because they do" just because he doesn't go on and explain the "why" of every sub-question ad infinitum.
I'd just throw in that this idea of universal gravitation coupled with the laws of motion and dodgy ideas like force and momentum enabled a wide range of phenomena to be described and some predictions to be made that could be compared with observations.
Yes, ideas like 'force' and 'momentum' were a bit dubious but the resulting theory was effective[1] within its domain of applicability.
Newton’s physics is still taught and used everywhere because it’s simple and accurate enough for 99% of practical situations. Einstein’s relativity isn’t a better explanation, it just extends it to extreme conditions. NASA still uses Newtonian law to launch rockets.
"Alleged eyewitness reports of Joseph's levitations are noted to be subject to gross exaggeration, and often written years after his death."
That sounds super reliable. ;0)
"Poisoning due to the consumption of rye bread made from ergot-infected grain was common in Europe in the Middle Ages. It was known to cause convulsion symptoms and hallucinations. British academic John Cornwell has suggested that Joseph had consumed rye bread (see ergot poisoning). According to Cornwell "Here, perhaps, lay the key to his levitations. After sampling his own loaves he evidently believed he was taking off–as did those who partook of his high-octane bake-offs.""
Eilmer of Malmesbury showed a bit more commitment to his flying:
“In the 337 years since, Newton’s ideas have been used for all sorts of fussy yet vital activities: building bridges that don’t collapse, plotting planetary orbits, and explaining why toast inevitably lands butter-side down.
NASA still uses Newton’s framework today. They strap adventurous humans into enormous cylinders, set off controlled explosions underneath, and fling them into space—because three centuries later, it’s still the best idea we’ve got.”
Relativity isn’t needed because rockets never get anywhere near the speeds or gravitational extremes where Einstein’s equations matter. At rocket speeds, Newtonian mechanics is so accurate the difference is negligible, so why make things harder? NASA sticks with Newton because it’s simpler, faster to calculate, and gets the job done perfectly for launching rockets into orbit.
It was just ELI5-style writing and I was being tongue in cheek about it. Newtonian physics are fine for determining how much propellant will launch a rocket into orbit, but you couldn’t build a GPS satellite without accounting for space time distortion.
For the record, Newton was vastly conceptually wrong which is not the same as saying his work is useless because being wrong in a precise way is science. Time does not "flow immutably from one moment to the next" and there are no gravitational "forces" acting magically at a distance. Even if the linear approximatiins he made hold on a narrow domain they offer little in the way of conceptual framework. In fact, mostly Newton played mathematical parlour tricks.
If you are waiting for science to tell you "why" things happen you will wait forever because science answers "how" things happen.
There is no way for a successor scientific theory to completely subsume all of the predictions of its predecessor because they are often incommensurable. Which is to say that there is simply no way to define one in the terms and concepts of the other.
If you think of GR as some extension or modification of Newton's work you're doomed to misunderstanding the mathematical facts.
Only for a useless definition of "wrong". Modeling reality well is an end in itself, and to the extent that model predicts well and "factors" reality cleanly into distinct mechanisms, it is conceptually right. This is all "conceptually right" needs to mean. You can not, as I'm sure you'll agree, even hope to explain the "root cause" of motion and time-evolution. at some point you have to base any theory on some postulate or assumption about why things happen at all. But the point of work like Newton's is to get things right above that level, and he was enormously successful at this.
> mostly Newton played mathematical parlour tricks.
Only for a useless definition of "parlour tricks". The hard part of new ideas (1) is getting to the point where you're posing the right problem and thinking about it the right way. Once you get that right, the predictions (2) hopefully fall out as simple tricks! Then they have to be validated (3) against data—also hard. Newton pulled off all three, the hard parts and the tricks. Not single-handedly, mind you, but almost.
To bring such a big picture into view and fill out its details with credibility was a monumental task. I think of it as akin to evolution developing a new organ system—the genome usually has to find its way down on a very long limb to get there and to be stable enough to stay there. For a species this can happen over many generations, but for a human thinker it is has to happen by imagining and testing many subsequent ideas. Newton did an enormous amount of this on his own, over decades.
> are often incommensurable
Newton being absorbed into relativity is like the one case where they are commensurable. Newton is a clear limiting case! The "ways of thinking" about reality are perhaps not, but nobody (except cranks) is still stuck on Newtonianism at this point.
> as some extension or modification
Obviously it contains new math and new abstractions, as needed to match empirical reality on new data. Its content doesn't extent logically out of Newton, because how could it? The data wasn't there. But the conceptual gesture of devising a mathematical framework which can handle the data is the same one Newton used.
Postscript: philosophy of science folks always like to show up in physics discourse ready to fight various tired, old battles which mostly mattered in the context of the particular ideological dispute of some decade or another. The matter in question is always how to generalize the success of physics by fitting various philsci "models" to the "data" of physics' history. This can be interesting, but they never contribute much to the physics itself, which has always proceeded by its own internally-coherent and immensely-successful logic.
The definition of wrong is given in the second part of the sentence you quote. Newton was usefully wrong in a scientific sense; His theory and ontology of time as immutably flowing from moment to moment is fine for beings in a relatively stable gravitational field but fails miserably anywhere else. GR is a theory that gets time less wrong, but entails completely different ontology wherein "forces" disappear. In your parlance, Newton put time below "that level" when he should have lifted it into that which must be reasoned about physically. This means he was wrong conceptually in taking something as an absolute when it was not so.
'Only for a useless definition of "parlour tricks".'
If you look at Newton's work it amounts to little more than a first order approximations, rules to model linear portions of a nonlinear reality. I think you have a very romantic picture of Newton's work. Don't get me wrong, Newton was a giant in his time he had mastered linear curve fitting and to some extent I think he knew what he was doing and that it would be supplanted. I actually think if Newton stood here today he would disagree with you, side with me and take up GR straight away.
"Newton being absorbed into relativity is like the one case where they are commensurable."
Newton's theory was not absorbed, it was supplanted. One cannot absorb the idea of a "force" into GR. This is precisely what incommensurability means.
"Obviously it contains new math and new abstractions..."
It is not about the data, Newton was wrong because non-euclidian geometry wasn't there,
"Postscript"
I have degrees in electronic engineering and theoretical physics. I graduated number one in my class both times. I am not a philosophy interloper as you point out in your ad-hominid attack.
IF you want to make progress in your understanding of physics you best heed the words and thoughts I have provided.
The point of my argument was to express a "practical" epistemology in which Newton's successes represent exactly what they accomplished, instead of some failure to live up to an ideal "truth", a view which I consider useless and pedantic.
> One cannot absorb the idea of a "force" into GR.
Yeah you can, tho I never learned the specifics. IIRC, a force is a Lagrange multiplier representing a constraint on the extremization of action. When you extremize a joint system (two particles A and B interacting) you just get some exchange of momentum between them and no force appears. But if you extremize just A w.r.t to a known and fixed trajectory of B, B's influence on A appears as an "external force" term. This is actually all "forces" ever were—constraints relating dp_A/dt and dp_B/dt—but this fact is obscured in Newton because we typically think of systems with their external forces factored out, which of course lets us apply useful approximations for gravity, air resistance, friction, etc.
You can certainly do the same operation in GR of isolating a subsystem of a joint system and you will find a "force" term, it has to be there just as a logical consequence of the extremization process. I thought this was well known. Or do you mean "one cannot absorb..." in some other sense?
My mistake tagging you as a philsci person, tho. I regret the error!
dr_dshiv – 19 hours ago
“And now we might add something concerning a certain most subtle Spirit, which pervades and lies hid in all gross bodies; by the force and action of which Spirit, the particles of bodies mutually attract one another at near distances, and cohere, if contiguous; and electric bodies operate to greater distances, as well repelling as attracting the neighbouring corpuscles; and light is emitted, reflected, refracted, inflected, and heats bodies; and all sensation is excited, and the members of animal bodies move at the command of the will, namely, by the vibrations of this Spirit, mutually propagated along the solid filaments of the nerves, from the outward organs of sense to the brain, and from the brain into the muscles. But these are things that cannot be explain'd in few words, nor are we furnish'd with that sufficiency of experiments which is required to an accurate determination and demonstration of the laws by which this electric and elastic spirit operates.” https://web.archive.org/web/20100524103006/http://www.isaacn...
potamic – 17 hours ago
bonoboTP – 16 hours ago
People had similar theories, like Descartes imagined nerve tubes carrying fluid to act and kind of hydraulic actuation, as well as ancient Greek pneuma theory of vital spirit. Gilbert's work on magnetism and electricity was known, Hooke's work on vibrations. It's impressive of course but not out of this world unimaginable magic. He plugged his favorite modern theory to biology, replacing the fluid stuff with electric stuff. Tons of people did that kind of thing before and after, sometimes it works, sometimes it leads to nowhere.
mlinhares – 11 hours ago
People just didn’t have the tools to understand this subject at that time.
yndoendo – 10 hours ago
Too many people believe that a person really good in context A will be good in context B to Z. Or the Shaolin Monk Fallacy, just because you can do push ups with two fingers and swing a staff does not mean you are instantly good with a pool cue or tennis racket.
somenameforme – 10 hours ago
World class expertise in some mental field is not achieved solely by knowledge within that field, but by a distinct ability to process and apply information in a novel way. And that skill is highly transferrable to other fields. Of course you still need to then accumulate information in said other field, which is why it's not instantaneous, but if a world class individual in one field puts their energy towards mastery of another field, I certainly would not bet against their success!
Retric – 7 hours ago
Similarly having the drive to actually dedicate yourself to some narrow area could be considered a skill but I think it’s more a personality trait.
vjvjvjvjghv – 7 hours ago
It doesn't even mean you are good at fighting :-)
dr_dshiv – 17 hours ago
Choosing my words carefully, I think it was a kind of deep and deliberate magic. Of the sort Newton ascribed to Pythagoras as the esoteric discoverer of the inverse square law of gravitation. (see “Newton and the pipes of pan”). Hooke also had a sort of musical, oscillatory, spiraling conception of mental phenomena. So it was in the Zeitgeist.
In any case, it is striking and amazing— and resonant in this age of vibes.
ahazred8ta – 10 hours ago
https://www.enotes.com/topics/theology/criticism/criticism/j...
dr_dshiv – 12 hours ago
raincole – 12 hours ago
An ancient Greek philosopher said the matter is made of smallest particles. It doesn't mean he found the concept of atoms as we know.
dotancohen – 16 hours ago
bonoboTP – 16 hours ago
dotancohen – 12 hours ago
olddustytrail – 10 hours ago
Where did you get that from? As far as I know he was widely respected as a genius in his time and had great professional and social success (including receiving a knighthood of course).
Where is it written that he was considered crazy and disliked?
dotancohen – 7 hours ago
You should read about his experiments and beliefs in the occult.
I'm of the opinion that the story of the apple falling on his head, started as a jab.
Onavo – 14 hours ago
ahazred8ta – 10 hours ago
"Did we know the mechanical affections of the particles of rhubarb, hemlock, opium, and a man, as a watchmaker does those of a watch ... we should be able to tell beforehand that rhubarb will purge, hemlock kill, and Opium make a man sleep; as well as a watchmaker can" -- John Locke
throwaway843 – 16 hours ago
eirikbakke – 15 hours ago
TMEHpodcast – 15 hours ago
SoftTalker – 5 hours ago
mensetmanusman – 14 hours ago
ahazred8ta – 11 hours ago
gavmor – 11 hours ago
Sure, it's polysemous with "a cultivated expanse of land", but AFAIK there is no popular, problematic pseudoscientific quackery about suggesting our bodies possess rows of oats.
mensetmanusman – 7 hours ago
gavmor – 4 hours ago
— Martin Heidegger, Die Frage Nach Der Technik
nilamo – 15 hours ago
chowells – 6 hours ago
(Weak Sapir-Whorf is still a perfectly fine observation, but it's a lot less predictive as a hypothesis.)
analog31 – 12 hours ago
dr_dshiv – 9 hours ago
windowshopping – 17 hours ago
?
dr_dshiv – 17 hours ago
phrotoma – 12 hours ago
dr_dshiv – 4 hours ago
NoToP – 18 hours ago
progre – 19 hours ago
Also, when Principica was funded and Halley was himself short on cash, RA decided that they could not afford to actually pay him money (he was the RA secretary). Instead he would get copies of The History of fishes
perihelions – 17 hours ago
https://archive.org/details/francisciwillugh00will/page/n321...
moffkalast – 9 hours ago
metalman – 17 hours ago
dotancohen – 16 hours ago
Many in academia might like to remember this example.
ykonstant – 18 hours ago
zabzonk – 18 hours ago
tristramb – 16 hours ago
roenxi – 22 hours ago
Well, that might be stretching it. Speaking as someone who has done a little university level physics the understanding still seems to be basically that things fall because they do - we haven't made much progress beyond a firm strike-through of the word "down".
Newton's contribution was a very precise description of how rapidly they fall, and how we can calculate and understand the direction that things fall in complex multidimensional settings.
Micoloth – 19 hours ago
> Why apples fall, why planets don’t wander off, and why we aren’t all quietly drifting into space every time we sneeze.
Newton didnt really explain the why.. Einstein added something much later, but it might be that really we still don’t have a clue.
All we can do is measure how fast it happens, very precisely
TMEHpodcast – 15 hours ago
eternauta3k – 21 hours ago
brianpan – 19 hours ago
Think about how much our understanding of atoms has changed. I think the why is an important part of the development. If you're interested in that topic, how about a 35 min nuclear physics primer from Angela Collier (I love her videos!): https://www.youtube.com/watch?v=osflPlZdF_o
SilasX – 20 hours ago
Why do things fall? -> A special case of the general law of gravitation.
Why does reality adhere to the general law of gravitation? A implication of matter distorting the shape of spacetime.
Why is reality such that matter distorts space-time?
thaumasiotes – 19 hours ago
...of course?
If you want something that won't fall down, your only options are (1) luck into noticing something that already does that, or (2) understand why things fall down, so you can prevent your thing from falling.
tralarpa – 15 hours ago
No, it isn't. That sounds strange, right? But here is an explanation what eternauta3k probably meant: In modern physics, there is a kind of consensus that asking “why” has often been inappropriate or even misleading and should be therefore left to philosophers. The real questions are: Does our current model describe all observations? If not, can we find a model that does? And, even better, can that new model make predictions that we can verify?
mensetmanusman – 14 hours ago
thaumasiotes – 6 hours ago
But every prediction your model can make comes from a "why" question that the model answers.
725686 – 22 hours ago
bravesoul2 – 21 hours ago
We can never say why. Just produce better and better models.
The whys never end!
DanielVZ – 20 hours ago
All this to say who knows if we are ever going to learn the fundamental why if there is one.
adastra22 – 19 hours ago
layer8 – 13 hours ago
adastra22 – 11 hours ago
Maybe you are confusing causality for the arrow of time?
layer8 – 10 hours ago
Causation in physics is a complex and problematic notion: https://plato.stanford.edu/entries/causation-physics/
adastra22 – 10 hours ago
What I’m talking about is most similar to the “Causal Explanation” section at the end of the article you link.
noman-land – 22 hours ago
kimixa – 21 hours ago
And even then how can that be measured and proven vs other theories? Is it some other mechanism that simplifies to "close enough" that it measures similarly? We didn't really see the effects of relativity until we got to a sufficient accuracy of measurement, Newtonian mechanics was sufficient to explain things to the accuracy they could reproduce for a very long time.
Einstein couldn't have done anything like what he published if he didn't have evidence from new (at the time) equipment suggesting there was something wrong with the current model. And then testing proposed new models against those same measurements.
hermitcrab – 18 hours ago
dotancohen – 12 hours ago
ndsipa_pomu – 8 hours ago
Also, there wasn't any alternative, so a theory that explains almost everything is going to be accepted. Modern theories are also accepted if they explain things with more accuracy or over wider ranges than alternatives - often it's the shortcomings of theories that gives us clues as to a better theory. (e.g. the ultraviolet catastrophe)
mixmastamyk – 9 hours ago
kimixa – 9 hours ago
And then you need other examples to test new theory predictions on as they come about.
silisili – 20 hours ago
I'm not sure if it's wrong or right, and not smart enough to posit much, other than it -feels- wrong. But it wouldn't take a ton to convince me otherwise.
You'd think by now we'd have more supporting evidence of such a concept.
griffzhowl – 16 hours ago
silisili – 8 hours ago
At least in my case, you're taught gravity as this standalone force, and even the Newtonian idea in high school. Not until later college do they then throw that away and go into gr and the ideas you mention.
Though I guess this is more a failing of public education than science at large.
griffzhowl – 4 hours ago
GR is written in the language of differential geometry, and before even beginning you need a good grasp of Newtonian gravity, special relativity, multivariable calculus, and ideally electromagnetism too, so it needs a fair bit of preparation. And in fact the methods of Newtonian mechanics aren't thrown away, but incorporated into the more general framework. In that sense Newtonian mechanics is a conceptual foundation for GR, so that's why it's still taught first at school
thaumasiotes – 19 hours ago
The jargon term for this is "dormitive potency" or, more originally, "dormitive virtue".
https://en.wiktionary.org/wiki/dormitive_virtue
taneq – 21 hours ago
raattgift – 15 hours ago
For understanding a handful of highly symmetrical systems, it might help a student understand some intuitions about what Killing vector fields and congruences (notably those made by choosing the velocity vector field of a set of geodesics) are, and tends to lead into an investigation of what the shift vector in a 3+1 decomposition represents.
For calculating things like the spherical orbits around or the photon surface of a real black hole like our galaxy's central Sgr A*, the river model seems outright unhelpful. For example, how does a river model help to understand https://duetosymmetry.com/tool/kerr-circular-photon-orbits/ ?
> time moving at a constant rate
This is another way of saying slicing of a Lorentzian (4d) spacetime into non-overlapping spaces organized along an arbitrarily chosen future-directed non-spacelike worldline. That is, this is a 3+1 slicing. We can slice along your worldline, or on that of a neutral hydrogen atom floating in intergalactic space, or on that of a high-energy cosmic ray, or on that of a CMB photon. It's arbitrary, and each can give markedly different spatial slices through the same spacetime (in particular particle counts on slices will differ where the choices of index axes are anywhere accelerated with respect to one another).
When we decompose in this way, and take an <https://en.wikipedia.org/wiki/ADM_formalism> approach, we will tend to think of the shift vector as how we associate a point one one slice (everywhere in space at a coordinate instant in the spacetime) with its successor slice (everywhere in space at the next coordinate instant int he spacetime), which is helpful when spacetimes expand or contract in one or more spatial directions along the arbitrarily chosen time axis.
Braeck & Gron 2012 have a good bit of pedagogy about the river analogy and a fine set of references <https://arxiv.org/abs/1204.0419> and of course point to Hamilton & Lisle 2008, as originators of the analogy <https://arxiv.org/abs/gr-qc/0411060>.
dataflow – 17 hours ago
sanderjd – 14 hours ago
To me, the right word for this sentence is clearly "how", not "why".
2b3a51 – 17 hours ago
Yes, ideas like 'force' and 'momentum' were a bit dubious but the resulting theory was effective[1] within its domain of applicability.
[1] https://en.wikipedia.org/wiki/Effective_theory
layer8 – 13 hours ago
We’re still trying to figure out why exactly energy distorts spacetime.
[0] https://en.wikipedia.org/wiki/Stress%E2%80%93energy_tensor
tralarpa – 16 hours ago
Well, around two hundred years later they found out that it is not a good explanation (which of course in no way diminishes Newton's achievements).
TMEHpodcast – 15 hours ago
Simon_O_Rourke – 19 hours ago
hermitcrab – 18 hours ago
That sounds super reliable. ;0)
"Poisoning due to the consumption of rye bread made from ergot-infected grain was common in Europe in the Middle Ages. It was known to cause convulsion symptoms and hallucinations. British academic John Cornwell has suggested that Joseph had consumed rye bread (see ergot poisoning). According to Cornwell "Here, perhaps, lay the key to his levitations. After sampling his own loaves he evidently believed he was taking off–as did those who partook of his high-octane bake-offs.""
Eilmer of Malmesbury showed a bit more commitment to his flying:
https://en.m.wikipedia.org/wiki/Eilmer_of_Malmesbury
zabzonk – 17 hours ago
> Eilmer said he had "forgotten to provide himself with a tail."
mattmaroon – 14 hours ago
NASA still uses Newton’s framework today. They strap adventurous humans into enormous cylinders, set off controlled explosions underneath, and fling them into space—because three centuries later, it’s still the best idea we’ve got.”
Someone should tell them about relativity!
TMEHpodcast – 14 hours ago
mattmaroon – 12 hours ago
NASA does a lot of things.
xandrius – 6 hours ago
jrowen – 22 hours ago
AStonesThrow – 22 hours ago
Liftyee – 9 hours ago
tiahura – 10 hours ago
d4rkn0d3z – 15 hours ago
If you are waiting for science to tell you "why" things happen you will wait forever because science answers "how" things happen.
There is no way for a successor scientific theory to completely subsume all of the predictions of its predecessor because they are often incommensurable. Which is to say that there is simply no way to define one in the terms and concepts of the other.
If you think of GR as some extension or modification of Newton's work you're doomed to misunderstanding the mathematical facts.
sixo – 12 hours ago
> vastly conceptually wrong
Only for a useless definition of "wrong". Modeling reality well is an end in itself, and to the extent that model predicts well and "factors" reality cleanly into distinct mechanisms, it is conceptually right. This is all "conceptually right" needs to mean. You can not, as I'm sure you'll agree, even hope to explain the "root cause" of motion and time-evolution. at some point you have to base any theory on some postulate or assumption about why things happen at all. But the point of work like Newton's is to get things right above that level, and he was enormously successful at this.
> mostly Newton played mathematical parlour tricks.
Only for a useless definition of "parlour tricks". The hard part of new ideas (1) is getting to the point where you're posing the right problem and thinking about it the right way. Once you get that right, the predictions (2) hopefully fall out as simple tricks! Then they have to be validated (3) against data—also hard. Newton pulled off all three, the hard parts and the tricks. Not single-handedly, mind you, but almost.
To bring such a big picture into view and fill out its details with credibility was a monumental task. I think of it as akin to evolution developing a new organ system—the genome usually has to find its way down on a very long limb to get there and to be stable enough to stay there. For a species this can happen over many generations, but for a human thinker it is has to happen by imagining and testing many subsequent ideas. Newton did an enormous amount of this on his own, over decades.
> are often incommensurable
Newton being absorbed into relativity is like the one case where they are commensurable. Newton is a clear limiting case! The "ways of thinking" about reality are perhaps not, but nobody (except cranks) is still stuck on Newtonianism at this point.
> as some extension or modification
Obviously it contains new math and new abstractions, as needed to match empirical reality on new data. Its content doesn't extent logically out of Newton, because how could it? The data wasn't there. But the conceptual gesture of devising a mathematical framework which can handle the data is the same one Newton used.
Postscript: philosophy of science folks always like to show up in physics discourse ready to fight various tired, old battles which mostly mattered in the context of the particular ideological dispute of some decade or another. The matter in question is always how to generalize the success of physics by fitting various philsci "models" to the "data" of physics' history. This can be interesting, but they never contribute much to the physics itself, which has always proceeded by its own internally-coherent and immensely-successful logic.
d4rkn0d3z – 11 hours ago
The definition of wrong is given in the second part of the sentence you quote. Newton was usefully wrong in a scientific sense; His theory and ontology of time as immutably flowing from moment to moment is fine for beings in a relatively stable gravitational field but fails miserably anywhere else. GR is a theory that gets time less wrong, but entails completely different ontology wherein "forces" disappear. In your parlance, Newton put time below "that level" when he should have lifted it into that which must be reasoned about physically. This means he was wrong conceptually in taking something as an absolute when it was not so.
'Only for a useless definition of "parlour tricks".'
If you look at Newton's work it amounts to little more than a first order approximations, rules to model linear portions of a nonlinear reality. I think you have a very romantic picture of Newton's work. Don't get me wrong, Newton was a giant in his time he had mastered linear curve fitting and to some extent I think he knew what he was doing and that it would be supplanted. I actually think if Newton stood here today he would disagree with you, side with me and take up GR straight away.
"Newton being absorbed into relativity is like the one case where they are commensurable."
Newton's theory was not absorbed, it was supplanted. One cannot absorb the idea of a "force" into GR. This is precisely what incommensurability means.
"Obviously it contains new math and new abstractions..."
It is not about the data, Newton was wrong because non-euclidian geometry wasn't there,
"Postscript"
I have degrees in electronic engineering and theoretical physics. I graduated number one in my class both times. I am not a philosophy interloper as you point out in your ad-hominid attack.
IF you want to make progress in your understanding of physics you best heed the words and thoughts I have provided.
sixo – 11 hours ago
The point of my argument was to express a "practical" epistemology in which Newton's successes represent exactly what they accomplished, instead of some failure to live up to an ideal "truth", a view which I consider useless and pedantic.
> One cannot absorb the idea of a "force" into GR.
Yeah you can, tho I never learned the specifics. IIRC, a force is a Lagrange multiplier representing a constraint on the extremization of action. When you extremize a joint system (two particles A and B interacting) you just get some exchange of momentum between them and no force appears. But if you extremize just A w.r.t to a known and fixed trajectory of B, B's influence on A appears as an "external force" term. This is actually all "forces" ever were—constraints relating dp_A/dt and dp_B/dt—but this fact is obscured in Newton because we typically think of systems with their external forces factored out, which of course lets us apply useful approximations for gravity, air resistance, friction, etc.
You can certainly do the same operation in GR of isolating a subsystem of a joint system and you will find a "force" term, it has to be there just as a logical consequence of the extremization process. I thought this was well known. Or do you mean "one cannot absorb..." in some other sense?
My mistake tagging you as a philsci person, tho. I regret the error!
d4rkn0d3z – 11 hours ago
I can do no such thing. The idea of a "force" as known to Newton, being "action at a distance" by "mutual attraction", is not at all present in GR.