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Are Refinements to Newton’s Calculations Necessary?

  1. May 9, 2003 #1
    Since I really displayed my ignorance of astrophysics and Newton in my first post “Gravity of the Sun?”, some of you may decide not to consider this one. I really was lost for a while and didn’t keep my argument on target. I am not a physicist by trade. The study of Physics is a hobby and the area of least interest to me is astrophysics. I try to focus on electrons, electricity and electromagnetic fields.

    I did refine my argument based on what I learned from you and other research of Newton, his life and his laws. So the following may or may not be significant in real life. It is simply a question that I am trying to find an answer to. I know that if the result were truly significant, some of you may be able to get a grant from NASA to answer the questions below. It is quite possible that the question has already been answered and someone could just point me to a website to learn the answers.

    I want to thank WazZy for trying to pull my foot out of my mouth in the last post but I seemed determined to keep it there. I also want to thank the people who really tried to help me understand Newton’s calculations (securitysix, FZ+, Zefram, enigma, Janus, Zefram and Drag).

    Are Refinements to Newton’s Calculations Necessary?

    To say that there are errors in Newton’s calculations for gravity would be extremely unfair. Newton’s calculations for gravity are elegant due to their sheer simplicity and they accurately predict the positions of astrological objects.

    There are things, however, that we know today that were not known in Newton’s time. Because Newton’s calculation is so elegant and it works there is no reason to question the calculation.

    Or, is there?

    With Newton’s calculation of mass, later discoveries were already compensated for. Refining a mass calculation is not necessary unless you intend to land on a planet. The trajectory of the landing must take into consideration the gravity of the planet. The structural capabilities of the craft also must account for the stresses involved in the landing. And, if we are attempting to land people on a distant planet, they could be stranded forever if we do not consider all of the factors that may have a bearing on our calculations.

    There are behavioral differences in the objects in our solar system. The Sun is quite different than the rest of the planets. The Sun is the source of electromagnetic radiation in our solar system and may cause the orbits of planets to change from where they “should” be.

    Consider this hypothetical problem.

    I have two perfectly round planetary objects of equal weight each made of a different substance. Planet A is composed of iron. Planet B is composed of aluminum. Neither planet has an atmosphere. According to Newton’s calculations, both objects would be in the same orbit about the Sun.

    But the properties of each planet are different which may have an effect on their orbit and cause the mass calculation for Planet A to be different than Planet B and the gravity difference may cause difficulty in landing on either planet.

    The physical differences that may affect the orbit are as follows:
    1. Iron is attracted to electromagnetic fields. The Sun has an enormous amount of electromagnetic energy. Planet A, our iron planet, may have a tendency to move into a closer orbit around the Sun than Planet B since aluminum has no attraction to electromagnetic fields.
    2. Planet B will be larger than Planet A due to the fact that it is composed of a less dense material. The atomic material expelled by the Sun at light speed will hit a larger surface area on Planet B than on Planet A. Planet B may be pushed into an orbit that is farther from the Sun than it should be.

    Viewing these two objects from earth and calculating their mass will produce errors that may only be significant if you were trying to land on one or both of the objects.

    The characteristics of earth introduce a variety of errors in our orbit.

    Unlike Planet A and B, the earth has a large liquid surface that can absorb the Sun’s energy. Earth also has an atmosphere that deflects and absorbs the Suns’ force. Earth also has an iron core that is significantly larger than many planets.

    It is likely that the earths’ orbit is closer to the Sun than it “should” be based only on Newton’s mass calculations.

    What affect does the quantity of iron have on a planet’s orbital position?

    What affect does the outward force of the Sun have on a planet without a “shock absorber” atmosphere or surface?

    Have we based the calculation of the mass of other planets on the earths’ orbital position?

    If so, what errors are introduced in the calculation?

    Is the error significant? (Only if it is large enough to throw off calculations for landing!)
  2. jcsd
  3. May 9, 2003 #2


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    Staff: Mentor

    You're talking about errors in assumptions, calculations, and measurements. These are certainly all issues and all different depending on the circumstances. But there is a problem with Newton's law itself: it doesn't account for Einstein's Relativity. That presents some real problems that have to be corrected in many circumstances.
  4. May 9, 2003 #3


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    Staff Emeritus
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    Gold Member

    Let's be more specific than "iron is attracted to electromagnetic fields." After all, light is nothing more than a ripple in the electromagnetic field. Do you propose that iron is attracted to light? The bottom line is that iron is ferromagnetic. You should perhaps do some additional reading on what it means for a material to be ferromagnetic.

    You continue to insist that somehow electromagnetics have something to do with the planets' orbits, and the simple fact is that they do not. There really is no room to question this fact.
    The larger flux received by the larger planet will indeed result in a slightly large force. The larger planet will be pushed outwards more so than will the smaller planet.
    The only forces acting upon a planet are a) the centripetal force and b) the radiation pressure from the Sun. The centripetal acceleration is a function of mass, while the radiation pressure is a function of cross-sectional area, and area alone. It does not matter if the planet is composed of air, water, or iron.
    I still don't know exactly what a "mass calculation" is, but I see no reason to believe the Earth is doing anything abjectly non-Keplerian.
    Your idea of a "shock absorber" is flawed. Perhaps it is time to learn some mechanics.
    No. Orbital position has nothing to do with mass.

    - Warren
  5. May 9, 2003 #4


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    Staff: Mentor

    Re: Re: Are Refinements to Newton’s Calculations Necessary?

    You know, this equation:

    Newton + Kepler = mass
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