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Thread: Newton on Barycenter

  1. #31
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    Remarkable that they were able to discover those treatments in 1600, I guess it just shows how badly they wanted pure gold!

  2. #32
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    Quote Originally Posted by Ken G View Post
    Remarkable that they were able to discover those treatments in 1600, I guess it just shows how badly they wanted pure gold!
    I think they're considerably more ancient: the sulphur method was described by Theophilus in the eleventh century.

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  3. #33
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    But it was in other, independent, lessons in alchemy references they mention Aqua Regia was specifically referred to as "the wolf" in the old texts.

    (I was tested on it in class!)

    You can use dragon's blood too. You mix impure gold with it, then heat the mixture as well, as with the sulfides.

    That's the method of choice with the "artisanal" gold miners in Brazil.
    Time wasted having fun is not time wasted - Lennon
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  4. #34
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    Hmmm, I'm starting to think much more of this is going to get us hollered at...
    Time wasted having fun is not time wasted - Lennon
    (John, not the other one.)

  5. #35
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    We do not see any cases in the rest of the cosmos of a larger object revolving around a smaller object. The reason we do not see any such phenomena is that there is only one place where it could be true – at the barycenter of the universe?

  6. #36
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    Quote Originally Posted by wd40 View Post
    We do not see any cases in the rest of the cosmos of a larger object revolving around a smaller object.
    You must mean a more massive object revolving around a less massive one.
    The reason we do not see any such phenomena is that there is only one place where it could be true – at the barycenter of the universe?
    Why could it be true there?
    Last edited by Ken G; 2018-Jan-14 at 05:32 AM.

  7. #37
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    The second part of the question: it's correct that the the mass centre of the solar system moves in a complex spiral, sometimes well outside the sun and should be easy to find in any search for solar system barycentre. My first ATM post a few years ago was using the effect of Jupiter in particular (plus Saturn) with its eccentric orbit to cause differing Coriolis effects in the radial flows of the sun. But the sunspot record did not support my hypothesis.
    sicut vis videre esto
    When we realize that patterns don't exist in the universe, they are a template that we hold to the universe to make sense of it, it all makes a lot more sense.
    Originally Posted by Ken G

  8. #38
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    https://phys.org/news/2015-03-solar.html
    that link is to a discussion od sunspots and includes the barycentre diagram.
    sicut vis videre esto
    When we realize that patterns don't exist in the universe, they are a template that we hold to the universe to make sense of it, it all makes a lot more sense.
    Originally Posted by Ken G

  9. #39
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    Quote Originally Posted by profloater View Post
    The second part of the question: it's correct that the the mass centre of the solar system moves in a complex spiral, sometimes well outside the sun and should be easy to find in any search for solar system barycentre. My first ATM post a few years ago was using the effect of Jupiter in particular (plus Saturn) with its eccentric orbit to cause differing Coriolis effects in the radial flows of the sun. But the sunspot record did not support my hypothesis.
    No, it's the Sun that is moving in the complex spiral. The center of mass is stationary or at most moving at virtually constant velocity in an inertial frame of reference.

  10. #40
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    Quote Originally Posted by Hornblower View Post
    No, it's the Sun that is moving in the complex spiral. The center of mass is stationary or at most moving at virtually constant velocity in an inertial frame of reference.
    well in a closed system like the solar system you can take any point of reference. That diagram is heliocentric of course but the barycentre could also be used as a centre in which case, yes the sun would appear as the spiral being the heaviest mass, the corrected motion of the planets would not make much difference. If you used the fixed stars as a reference from some way out external viewpoint, Voyager one perhaps, the barycentre would move and the sun would move of course.
    sicut vis videre esto
    When we realize that patterns don't exist in the universe, they are a template that we hold to the universe to make sense of it, it all makes a lot more sense.
    Originally Posted by Ken G

  11. #41
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    Quote Originally Posted by profloater View Post
    well in a closed system like the solar system you can take any point of reference. That diagram is heliocentric of course but the barycentre could also be used as a centre in which case, yes the sun would appear as the spiral being the heaviest mass, the corrected motion of the planets would not make much difference. If you used the fixed stars as a reference from some way out external viewpoint, Voyager one perhaps, the barycentre would move and the sun would move of course.
    If I am not mistaken, we do just that as needed for the demands of the task at hand. For a satellite in low Earth orbit, where the orbital radius is small compared with the distance to the Moon and other bodies, the Earth's center of mass is a good place for the focus of the starting reference ellipse, with small empirically determined terms for the perturbation from the other bodies in the solar system. For Mercury, the Sun's center of mass should be a good choice for the same sort of drill. For Voyager 2, the overall center of mass should be good. For a main belt asteroid, all bets are off. I don't know what point would be best for a starting reference ellipse.

  12. #42
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    Yes, that's right. It's just what I mean about the need to answer "what is a center" before we say what the center is. We so often treat language like that as if it were absolute, when in actual practice it is generally contextual instead. Mistaking contextual language for absolute language is a bugbear that has hounded physics for its entire history, and continues to do so today in many of the threads on this very forum! I know of one thread that is about 100 times longer than it needed to be, entirely because of people making that same mistake.

  13. #43
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    “Mass there governs inertia here.” (Hoyle, Nicolaus Copernicus p73). If we add to our galaxy the billions of other galaxies present in the universe, they will certainly have a substantial effect on determining the universe’s barycenter.

  14. #44
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    Quote Originally Posted by wd40 View Post
    “Mass there governs inertia here.” (Hoyle, Nicolaus Copernicus p73). If we add to our galaxy the billions of other galaxies present in the universe, they will certainly have a substantial effect on determining the universe’s barycenter.
    I'm pretty sure that would just be the barycenter of whatever galaxies' masses (edit - and distances) you measured, not the universe's barycenter.
    Solfe

  15. #45
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    Quote Originally Posted by wd40 View Post
    “Mass there governs inertia here.” (Hoyle, Nicolaus Copernicus p73). If we add to our galaxy the billions of other galaxies present in the universe, they will certainly have a substantial effect on determining the universe’s barycenter.
    Yes, in the sense that "the barycenter" always depends on the mass distribution you are talking about. So the barycenter is not "a thing" in itself, it is something that arises once a decision has been made, a decision about what matters in the context at hand. The very surprising thing is, as you broaden the context to more and more of the universe, the meaning of a barycenter becomes less important, until by the time you get to the whole universe, the very concept of a barycenter itself appears to evaporate into irrelevance. Which leaves us with the question, which is more fundamental to existence, the presence of a barycenter, or the absence of one? One answer is, that also depends on context, the context of how one looks at existence. As in, is there a difference in the concept of "existence" when it applies to something, as opposed to when it applies to everything.
    Last edited by Ken G; 2018-Jan-15 at 11:10 PM.

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