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> 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

by roenxi 1y ago

> 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.

725686 1y ago
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.
- bravesoul2 1y ago
  It's funny. We don't float away. We can never say why. Just produce better and better models. The whys never end!
  - DanielVZ 1y ago
    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.
- adastra22 1y ago
  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.”
  - layer8 1y ago
    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.
    - adastra22 1y ago
      There absolutely is. The speed of light is the speed of causality. It is very tightly integrated into the framework of modern physics. Maybe you are confusing causality for the arrow of time?
      - layer8 1y ago
        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. Causation in physics is a complex and problematic notion: https://plato.stanford.edu/entries/causation-physics/ https://plato.stanford.edu/entries/causation-physics/
        adastra22 1y ago
        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.
noman-land 1y ago
Doesn't mass bend spacetime (do we know why? No idea) and cause matter to "fall" into the gravity well?
- kimixa 1y ago
  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.
  - silisili 1y ago
    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.
    - griffzhowl 1y ago
      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
      - silisili 1y ago
        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.
eternauta3k 1y ago
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.
- SilasX 1y ago
  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?
- thaumasiotes 1y ago
  > 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.
  - tralarpa 1y ago
    > ...of course? 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 1y ago
      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.
    - 1y ago
Micoloth 1y ago
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
- TMEHpodcast 1y ago
  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.
dataflow 1y ago
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.
- 2b3a51 1y ago
  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 https://en.wikipedia.org/wiki/Effective_theory
- tralarpa 1y ago
  > 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).
  - TMEHpodcast 1y ago
    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.
- sanderjd 1y ago

by roenxi 1y ago

725686 1y ago

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.

bravesoul2 1y ago
It's funny. We don't float away. We can never say why. Just produce better and better models. The whys never end!
- DanielVZ 1y ago
  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.
adastra22 1y ago
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.”
- layer8 1y ago
  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.
  - adastra22 1y ago
    There absolutely is. The speed of light is the speed of causality. It is very tightly integrated into the framework of modern physics. Maybe you are confusing causality for the arrow of time?
    - layer8 1y ago
      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. Causation in physics is a complex and problematic notion: https://plato.stanford.edu/entries/causation-physics/ https://plato.stanford.edu/entries/causation-physics/
      - adastra22 1y ago
        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.

noman-land 1y ago

Doesn't mass bend spacetime (do we know why? No idea) and cause matter to "fall" into the gravity well?

kimixa 1y ago
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.
- silisili 1y ago
  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.
  - griffzhowl 1y ago
    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
    - silisili 1y ago
      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.

eternauta3k 1y ago

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.

SilasX 1y ago
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?
thaumasiotes 1y ago
> 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.
- tralarpa 1y ago
  > ...of course? 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 1y ago
    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.
  - 1y ago

Micoloth 1y ago

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

TMEHpodcast 1y ago
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.

dataflow 1y ago

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.

2b3a51 1y ago
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 https://en.wikipedia.org/wiki/Effective_theory
tralarpa 1y ago
> 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).
- TMEHpodcast 1y ago
  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.
sanderjd 1y ago