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.
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.
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.
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.
"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.
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.
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.)
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.
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.”
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.
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.
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.
"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.
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.
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.
“Newton and the pipes of pan” (1966) McGuire & Rattansi
https://www.enotes.com/topics/theology/criticism/criticism/j...
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.
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.
Scholars back then had good intution:
"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.
This must be the mother of all "This is left for future work" paragraphs.
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
Left as an exercise for the reader.
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.
Is that how all "science" was written? It's nearly unreadable, the plot (Spirit?) lost in the language.
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.
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.)
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
> It’s actually the root of the the history of “vibes”
?
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).
I had no idea Newton also pioneered British understatement.
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
I enjoyed this anecdote. As gratitude, please accept this copy of History of Fishes
https://archive.org/details/francisciwillugh00will/page/n321...
Eight hundred pages? Well at least he got his money's worth.
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
Or as an example of he who gets the funds, not necessarily being the worthy of the two.
Many in academia might like to remember this example.
He ended up swimming with the history of fishes.
sleeping, surely?
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.
That’s what i though as well
> 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
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?
> Is "why" really a meaningful question?
...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.
Isn't it because of the curvature of spacetime? Not that that means much to a layman, but I think that progress has definitely been made.
It's funny. We don't float away.
We can never say why. Just produce better and better models.
The whys never end!
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.”
Doesn't mass bend spacetime (do we know why? No idea) and cause matter to "fall" into the gravity well?
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.
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.
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.
[1] https://en.wikipedia.org/wiki/Effective_theory
> That's as darn good of an explanation of why we fall down as one could possibly give.
To me, the right word for this sentence is clearly "how", not "why".
The real “why” is because energy distorts spacetime [0], and gravitational acceleration is just uniform motion through that distorted spacetime.
We’re still trying to figure out why exactly energy distorts spacetime.
[0] https://en.wikipedia.org/wiki/Stress%E2%80%93energy_tensor
> That's as darn good of an explanation of why we fall down as one could possibly give
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).
In fairness, he only explained why a vast vast majority of people don't float away. He didn't adequately explain edge cases like Joseph of Cupertino - https://en.m.wikipedia.org/wiki/Joseph_of_Cupertino
"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:
https://en.m.wikipedia.org/wiki/Eilmer_of_Malmesbury
I like Eilmer:
> Eilmer said he had "forgotten to provide himself with a tail."
It's actually 338 years. I turn 38 today and was born in 1987. TIL Newton published the Principia exactly 300 years before I was born.
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“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.”
Someone should tell them about relativity!
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.
NASA does a lot of things.
Sidenote: Is anyone else distracted/unsettled by that faint animated circle of dots that snaps to your mouse whenever it's moving?
He avoided the why. “Hypotheses non fingo”, I frame no hypotheses.
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.
oh, what the hell, I'll argue with you.
> 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.
'Only for a useless definition of "wrong"....'
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.