gravity effects

Picking up on the remarks by TVF on the dynamics of the Earth/sun orbit-I see several perplexing issues. The acceleration of the Earth by the sun is not equal to the acceleration of the sun by the Earth so the fact that two bodies fall as the same rate seems to be applied in different ways for both bodies. The force of gravity is greater on the sun than on Earth so this is also applied different for both bodies. There are different ways the math is applied to the two bodies. I think you(TVF) say the sun and Earth orbit a barycenter and also say this is not real. This is still another way math is applied in different ways. It is my opinion that the mass of the sun is not being pushed around a barycenter and the model requires this action. Another example of misuse of math to suit the end result.

<BLOCKQUOTE id=quote><font size=2 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote>The acceleration of the Earth by the sun is not equal to the acceleration of the sun by the Earth so the fact that two bodies fall as the same rate seems to be applied in different ways for both bodies.<hr height=1 noshade id=quote></BLOCKQUOTE id=quote></font id=quote><font face="Verdana, Arial, Helvetica" size=2 id=quote>

No, it is applied in identical ways to the two bodies. Only the amounts differ, just as you say.

<BLOCKQUOTE id=quote><font size=2 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote>The force of gravity is greater on the sun than on Earth so this is also applied different for both bodies.<hr height=1 noshade id=quote></BLOCKQUOTE id=quote></font id=quote><font face="Verdana, Arial, Helvetica" size=2 id=quote>

Is that a typo? In any case, in gravitation, forces are not observable, and are therefore a theoretical distraction. Only accelerations matter for determining orbits. And obviously, the Sun's acceleration due to Earth is much smaller than Earth's acceleration due to the Sun.

<BLOCKQUOTE id=quote><font size=2 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote>There are different ways the math is applied to the two bodies.<hr height=1 noshade id=quote></BLOCKQUOTE id=quote></font id=quote><font face="Verdana, Arial, Helvetica" size=2 id=quote>

No, the math is applied identically. Only the amounts differ.

<BLOCKQUOTE id=quote><font size=2 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote>I think you (TVF) say the sun and Earth orbit a barycenter and also say this is not real.<hr height=1 noshade id=quote></BLOCKQUOTE id=quote></font id=quote><font face="Verdana, Arial, Helvetica" size=2 id=quote>

A barycenter is also a mathematical abstraction, and is not observable. It is useful for some purposes, but is just a distraction in this discussion. Forget barycenters here.

<BLOCKQUOTE id=quote><font size=2 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote>This is still another way math is applied in different ways.<hr height=1 noshade id=quote></BLOCKQUOTE id=quote></font id=quote><font face="Verdana, Arial, Helvetica" size=2 id=quote>

I have no idea what the basis for this claim might be, or even what it means.

<BLOCKQUOTE id=quote><font size=2 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote>It is my opinion that the mass of the sun is not being pushed around a barycenter and the model requires this action. Another example of misuse of math to suit the end result.<hr height=1 noshade id=quote></BLOCKQUOTE id=quote></font id=quote><font face="Verdana, Arial, Helvetica" size=2 id=quote>

I would say "another example of your not understanding dynamics", because you continue to state that dynamics makes absurd claims. Claiming something absurd, then knocking the studding out of it, is called a "straw man argument".

Barycenters have no forces or accelerations, and nothing gets "pushed around a barycenter". Eliminate barycenters from your thinking. You have to understand the basics first. Those basics consist of Newton's acceleration law: acc. = GM/r^2, applied to both bodies in the system. (M = Sun's mass to get Earth's acceleration, or Earth's mass to get Sun's acceleration.)

What problems do you have with this basic picture? -|Tom|-

There is data at JPL Horizons that clearly shows the barycenter model in operation. It is the Earth/Moon orbit and the Earth is nearer the sun at Full Moon than at New Moon. This can be drawn on paper also. This is the one of the problems and I think the generator of the data- that is the barycenter model needs to push or how else do the results occur? I'm quite willing to forget this model for this forum, however. So onward-The force is as you say F=ma. Doing the math here I get a greater force exerted on the Earth from the sun than the Earth exerts on the sun. The force can be calculated and I suspect observed if you look in the right place. F=ma for the Earth is very small compared to the force exerted by the sun. Is this OK so far? If so-I think the sun is not moved by the Earth. The force is too small and tidal effects absorb the force. I know you tell me the motion is measured so I am wrong here. Thats fine if the data exists that indicates the motion then I'll rethink my idea. I'm very open to anything that makes sense and rebel against unproven theory. I also know Newton designed most of this stuff and I'm aware of LaPlace, Einstein and others.

<BLOCKQUOTE id=quote><font size=2 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote>There is data at JPL Horizons that clearly shows the barycenter model in operation. It is the Earth/Moon orbit and the Earth is nearer the sun at Full Moon than at New Moon. This can be drawn on paper also. This is the one of the problems and I think the generator of the data- that is the barycenter model needs to push or how else do the results occur?<hr height=1 noshade id=quote></BLOCKQUOTE id=quote></font id=quote><font face="Verdana, Arial, Helvetica" size=2 id=quote>

Forget the barycenter and just look at the accelerations actually occuring. During two weeks of each month, the Moon pulls Earth in the same direction as the Sun. That eventually results in the Earth getting closer to the Sun than it would if only the Sun were pulling it. Right? Two forces are stronger than one, right?

Of course, for the other two weeks, the Moon pulls opposite to the Sun, which eventually results in the Earth getting farther away from the Sun than it would be if there were no Moon. Right?

So without any barycenter or any pushes or centrifugal forces or anything at all expect simple Newtonian gravity, we get the observed behavior shown in the models.

<BLOCKQUOTE id=quote><font size=2 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote>I'm quite willing to forget this model for this forum, however. So onward-The force is as you say F=ma. Doing the math here I get a greater force exerted on the Earth from the sun than the Earth exerts on the sun. The force can be calculated and I suspect observed if you look in the right place. F=ma for the Earth is very small compared to the force exerted by the sun. Is this OK so far?<hr height=1 noshade id=quote></BLOCKQUOTE id=quote></font id=quote><font face="Verdana, Arial, Helvetica" size=2 id=quote>

Solar system gravitational forces are not observable and cannot be observed, even in principle. So let's stick to observable accelerations or we will not be able to explain the basics. Forces and barycenters are unnecessary, advanced concepts introduced for special purposes where they are useful. They cannot help us understand the fundamentals.

The acceleration law is not F = ma. (Forget you ever learned that. It has no value for gravitation.) The acceleration law for any target body in a gravitational field is acc. = GM/r^2, where M is the mass of a source of gravity and r is the distance of a target body from the source mass. Because every mass in a system can be a source mass, every body in the system must take its turn as a target body, and that acceleration formula must be applied to it. So everything moves, no matter how big or small it is.

<BLOCKQUOTE id=quote><font size=2 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote>If so-I think the sun is not moved by the Earth. The force is too small and tidal effects absorb the force. I know you tell me the motion is measured so I am wrong here. Thats fine if the data exists that indicates the motion then I'll rethink my idea. I'm very open to anything that makes sense and rebel against unproven theory.<hr height=1 noshade id=quote></BLOCKQUOTE id=quote></font id=quote><font face="Verdana, Arial, Helvetica" size=2 id=quote>

We all rebel against unproven theory. But most of us accept theory that has proved itself.

** 300 years ago, the acceleration law was new, and it was amazing to see that the planets and their moons all obeyed it so well.

** 200 years ago, comets and asteroids could be added to the list of successful predictions, even though observations were an order of magnitude better.

** By 100 years ago, the acceleration law was known to apply to many double stars and to certain laboratory experiments; and observations had become another two orders of magnitude more accurate. The acceleration law had been used to predict Neptune, leading to its discovery in 1845. Remaining anomalies indicated that at least one additional planet remained to be found.

** By 50 years ago, the acceleration law was verified to eight decimal places of accuracy. But is was found inaccurate (finally) in going from the eigth to the ninth decimal. This led to Einstein's correction to explain (among other things) why Mercury's elliptical orbit had a slight precession that the acceleration law did not predict. The acceleration law was extended to stellar clusters and even galaxy dynamics.

** In the last 50 years, we have added another four orders of magnitude to the accuracy of the observations. GPS, VLBI, laser ranging, and spacecraft data are accurate to meters, or even centimeters in some cases, even over distances of billions of meters. Yet the acceleration law (except for Einstein's small corrections) has still lived up to its name: the <i>universal</i> law of gravitation.

Instead of just thinking about these matters, why not get a few books and read up on the state of the field today? That is really the only way to get up to speed. If you want to make a contribution, you will first have to see where everyone else is and how they got there. Then you can lead the pack in some new direction. But you cannot just go off in a new direction and expect anyone in the pack to follow. The route to where the pack is now is straightforward, easy to follow, and known to be safe because it was forged by geniuses. To the pack, those who go off in other directions before they get to the safe place where the pack is appear "mad" because all other directions have been explored many times before, and no one who went that way has every returned.

So either enjoy your adventure -- alone -- or learn the basics so you can communicate your original ideas to others. -|Tom|-

The issue is still the same and here at least there a a tiny window that is open to the issue. Lets not bring the baggage from the other forum here- that is why I left the paradox forum and started this one. I want to know dynamics-not dogma-not how egnorant "they" are. Do that at the other forum. So, TVF-you say F=ma is not an issue in orbital dynamics? I ask you,"is that a typo"?

<BLOCKQUOTE id=quote><font size=2 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote>[Jim]: you say F=ma is not an issue in orbital dynamics? I ask you, "is that a typo"?<hr height=1 noshade id=quote></BLOCKQUOTE id=quote></font id=quote><font face="Verdana, Arial, Helvetica" size=2 id=quote>

No, it is not a typo, but I'm glad you asked.<img src=icon_smile.gif border=0 align=middle> In astronomy, all of dynamics can be done with the acceleration law I quoted. Forces are never needed and cannot be observed, so it can be quite confusing to invoke them. In the case in point, your understanding of concentional dynamics would be greatly enhanced if you eliminated all thought of forces and Newton's 2nd and 3rd laws of motion from your thinking. That throws out the equivalence principle too, in case that matters to you.

What is left is the pure motions of bodies -- their accelerations -- and the single, simple rule that governs them. Once you understand what these motions are, and how the rule governing them has been verified (that list of observation techniques I gave in my last message), you will understand the basics of conventional dynamics. And once you understand conventional dynamics, you will be in a position to criticize it if there is something not right. -|Tom|-