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What they mean is that you may take whatever point in space to be your immobile frame of reference and describe all motion with respect to that point. It happen

by aluren 7y ago

What they mean is that you may take whatever point in space to be your immobile frame of reference and describe all motion with respect to that point. It happens to be convenient to take the center of the Sun as such a point when doing calculations relevant to the solar system but it's not more 'valid' than literally any other point in the universe. You just have to change the equations a bit.

acqq 7y ago
No, they actually dispute the „physical reality“ which is completely wrong: the actual words: “there's no particular physical reality to the matter”
- onion2k 7y ago
  The "physical reality" of describing motion is transformations relative to a frame of reference. The origin (eg where you put 0,0,0) of that frame is a mathematical choice; it's not a real physical thing.
  - acqq 7y ago
    That the formulas can be calculated relative to any reference point doesn’t change the fact that the physical reality is ellipsoid movement of planets around the Sun. https://spaceplace.nasa.gov/barycenter/en/ https://spaceplace.nasa.gov/barycenter/en/
    - pishpash 7y ago
      Even as you insist on choosing a privileged reference frame for, say, aesthetic reasons, it's still not all the planets moving around the Sun. Did you not read the article? It's all the planets and the Sun moving around the barycenter. If you try to think through what your words even mean, you'll realize that they don't even mean anything, much less describe a physical reality.
      - acqq 7y ago
        > you'll realize that they don't even mean anything, much less describe a physical reality. Wrong. https://en.wikipedia.org/wiki/Ellipse#Planetary_orbits https://en.wikipedia.org/wiki/Ellipse#Planetary_orbits "In the 17th century, Johannes Kepler discovered that the orbits along which the planets travel around the Sun are ellipses with the Sun [approximately] at one focus, in his first law of planetary motion. Later, Isaac Newton explained this as a corollary of his law of universal gravitation. More generally, in the gravitational two-body problem, if the two bodies are bound to each other (that is, the total energy is negative), their orbits are similar ellipses with the common barycenter being one of the foci of each ellipse. The other focus of either ellipse has no known physical significance. The orbit of either body in the reference frame of the other is also an ellipse, with the other body at the same focus." The existence of barycenter it a physical reality. The elliptic movement is a physical reality. Compared to all other distances, the barycenter is for all the motions of all the planets effectively Sun. Even it it is approximation, it's a good approximation. Even if it moves and is sometimes a little outside of the Sun surface, it's still compared to the other distances practically there. Sun. It was known even three centuries ago, but now some "philosophers" think that they "relativize" that away. No. It's there.
        fenomas 7y ago
        > The existence of barycenter it a physical reality. A barycenter is a mathematically defined point that we choose because it makes equations simpler. There's nothing physically real (i.e. directly observable) at the location. Consider: if you fire a cannonball it will follow a parabolic path, and that parabola will have a focus, right? But that doesn't mean there's anything physically real about the focus of the parabola - it's a mathematically abstraction we invent because it's useful for describing the cannonball. > some "philosophers" think that they "relativize" that away. The relativity we're talking about comes from Einstein, not philosophers. Deciding whether the Earth revolves around the sun or vice-versa ultimately boils down to choosing a frame of reference, and one of the grand results of relativity is that there really is no absolute frame of reference we can measure from.
        7y ago
- yorwba 7y ago
  The laws of motion are the same in every reference frame, which means that statements like "X revolves around Y and not vice versa" are not "physically real" in the same way as "X and Y attract each other gravitationally" is, because they select one reference frame as privileged.
  - saagarjha 7y ago
    > The laws of motion are the same in every reference frame Inertial reference frame, right? Otherwise you need to add in fictitious forces.
  - Retric 7y ago
    Rotation is different from motion. Rotating around a point still applies in any frame of reference. Spin a top and the axes of rotation is independent of your frame of reference. Pick an atom on that top and it’s rotating around a specific point in any frame of reference.
    - ironSkillet 7y ago
      This goes back to the ambiguity of the definition of orbit. If I have a system with two points involved in some sort of rotational motion, then there isn't a "best choice" for which point should be considered the origin of my coordinate system.
      - deleted 7y ago
        [deleted]
      - Retric 7y ago
        If you mean exactly 2 abstract points in Euclidean geometry then sure. 3D objects are not points which is the first issue. Relatively also cares about accelerating or rotating reference frames which applies to both point masses. The center of mass in a two body system is a nice inertial reference frame which simplifies calculations.
- cassianoleal 7y ago
  No, they said "there is no physical reality to the matter", where, judging by context, "the matter" is the question of whether the Earth revolves around the Sun. The conclusion that there is no physical reality to this is based on the what @aluren mentioned - you can take any immutable point of reference and describe the movements of the others from it using the same laws of physics, thus "the matter" becomes one of philosophy and choice of point of reference rather than physics itself. You may disagree with this point but I don't think anyone disputed the existence of a physical reality, they simply moved one particular question out of its domain.
  - brokenkebab 7y ago
    Changing the point of reference will change your mathematical model, sure, but it will still describe a movement around a barycenter, and the statement remains true whatever your philosophy. Numerous ways to model a phenomenon don't deny its existence.
    - cassianoleal 7y ago
      Again: not denying the existence of the phenomenon, only removing it from the realm of physical reality to that of philosophy and mathematical point of reference. Still very much existent.

by aluren 7y ago

acqq 7y ago

No, they actually dispute the „physical reality“ which is completely wrong: the actual words: “there's no particular physical reality to the matter”

onion2k 7y ago
The "physical reality" of describing motion is transformations relative to a frame of reference. The origin (eg where you put 0,0,0) of that frame is a mathematical choice; it's not a real physical thing.
- acqq 7y ago
  That the formulas can be calculated relative to any reference point doesn’t change the fact that the physical reality is ellipsoid movement of planets around the Sun. https://spaceplace.nasa.gov/barycenter/en/ https://spaceplace.nasa.gov/barycenter/en/
  - pishpash 7y ago
    Even as you insist on choosing a privileged reference frame for, say, aesthetic reasons, it's still not all the planets moving around the Sun. Did you not read the article? It's all the planets and the Sun moving around the barycenter. If you try to think through what your words even mean, you'll realize that they don't even mean anything, much less describe a physical reality.
    - acqq 7y ago
      > you'll realize that they don't even mean anything, much less describe a physical reality. Wrong. https://en.wikipedia.org/wiki/Ellipse#Planetary_orbits https://en.wikipedia.org/wiki/Ellipse#Planetary_orbits "In the 17th century, Johannes Kepler discovered that the orbits along which the planets travel around the Sun are ellipses with the Sun [approximately] at one focus, in his first law of planetary motion. Later, Isaac Newton explained this as a corollary of his law of universal gravitation. More generally, in the gravitational two-body problem, if the two bodies are bound to each other (that is, the total energy is negative), their orbits are similar ellipses with the common barycenter being one of the foci of each ellipse. The other focus of either ellipse has no known physical significance. The orbit of either body in the reference frame of the other is also an ellipse, with the other body at the same focus." The existence of barycenter it a physical reality. The elliptic movement is a physical reality. Compared to all other distances, the barycenter is for all the motions of all the planets effectively Sun. Even it it is approximation, it's a good approximation. Even if it moves and is sometimes a little outside of the Sun surface, it's still compared to the other distances practically there. Sun. It was known even three centuries ago, but now some "philosophers" think that they "relativize" that away. No. It's there.
      - fenomas 7y ago
        > The existence of barycenter it a physical reality. A barycenter is a mathematically defined point that we choose because it makes equations simpler. There's nothing physically real (i.e. directly observable) at the location. Consider: if you fire a cannonball it will follow a parabolic path, and that parabola will have a focus, right? But that doesn't mean there's anything physically real about the focus of the parabola - it's a mathematically abstraction we invent because it's useful for describing the cannonball. > some "philosophers" think that they "relativize" that away. The relativity we're talking about comes from Einstein, not philosophers. Deciding whether the Earth revolves around the sun or vice-versa ultimately boils down to choosing a frame of reference, and one of the grand results of relativity is that there really is no absolute frame of reference we can measure from.
        7y ago
yorwba 7y ago
The laws of motion are the same in every reference frame, which means that statements like "X revolves around Y and not vice versa" are not "physically real" in the same way as "X and Y attract each other gravitationally" is, because they select one reference frame as privileged.
- saagarjha 7y ago
  > The laws of motion are the same in every reference frame Inertial reference frame, right? Otherwise you need to add in fictitious forces.
- Retric 7y ago
  Rotation is different from motion. Rotating around a point still applies in any frame of reference. Spin a top and the axes of rotation is independent of your frame of reference. Pick an atom on that top and it’s rotating around a specific point in any frame of reference.
  - ironSkillet 7y ago
    This goes back to the ambiguity of the definition of orbit. If I have a system with two points involved in some sort of rotational motion, then there isn't a "best choice" for which point should be considered the origin of my coordinate system.
    - deleted 7y ago
      [deleted]
    - Retric 7y ago
      If you mean exactly 2 abstract points in Euclidean geometry then sure. 3D objects are not points which is the first issue. Relatively also cares about accelerating or rotating reference frames which applies to both point masses. The center of mass in a two body system is a nice inertial reference frame which simplifies calculations.
cassianoleal 7y ago
No, they said "there is no physical reality to the matter", where, judging by context, "the matter" is the question of whether the Earth revolves around the Sun. The conclusion that there is no physical reality to this is based on the what @aluren mentioned - you can take any immutable point of reference and describe the movements of the others from it using the same laws of physics, thus "the matter" becomes one of philosophy and choice of point of reference rather than physics itself. You may disagree with this point but I don't think anyone disputed the existence of a physical reality, they simply moved one particular question out of its domain.
- brokenkebab 7y ago
  Changing the point of reference will change your mathematical model, sure, but it will still describe a movement around a barycenter, and the statement remains true whatever your philosophy. Numerous ways to model a phenomenon don't deny its existence.
  - cassianoleal 7y ago
    Again: not denying the existence of the phenomenon, only removing it from the realm of physical reality to that of philosophy and mathematical point of reference. Still very much existent.