Speed of Gravity?

So, can we say the Earth orbits a center that is located 20" from the apparent center of the sun? That seems to be what you are saying. I need to pin this detail down so I can get on with my research. One sure thing there is a lot wrong with the JPL generator. I wish data was easier to get out of data banks.

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by Jim</i>
<br />So, can we say the Earth orbits a center that is located 20" from the apparent center of the sun?<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">Correct. -|Tom|-

OK then if the gravity cnter of the orbit of the Earth/moon system is in fact about 20" from the apparent center an accurate measurement of the distance between those two points will give the speed of gravity as you say. Where can I find that data? It must vary a little since the Earth/sun distance is not always the same 8 light minutes apart. If I had that data a lot of puzzles would resolve themselves.

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by Jim</i>
<br />Where can I find that data?<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">I already answered that question in my first post to you on 22 May in this thread.

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">It must vary a little since the Earth/sun distance is not always the same 8 light minutes apart.<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">That is correct. It does vary by about 3% because of the eccentricity of Earth's orbit.

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">If I had that data a lot of puzzles would resolve themselves.<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">We've been over this before, Jim. Your choices are either processed data that someone has published in a technical article and you can find in a library search, for which you must assume that the processing was done competently and correctly; or raw data that no one has fooled around with. The latter is in the National Space Sciences Data Center, but is affected by nearly everything: precession, nutation, aberration, parallax, orbital motion, planetary perturbations, relativity, ... Computing each of these and removing their effect from the observations requires programming and computer skills and lots of astronomical knowledge. The formulas and explanations are found in the "Explanatory Supplement to the Astronomical Ephemeris".

There is a reason one must study for years to master these arts. The total number of people in the world who have done so number in the hundreds, and they hold international meetings to discuss their craft and latest findings every few years. Shortcuts can be taken, such as picking up other people's canned programs to compute these things (orbits, precession, etc.) for you. But then, you are back to assuming that the people who have studied this and acquired these skills and wrote the programs knew what they were doing.

There was one "Star Trek New Generation" episode in which Leonardo da Vinci -- a bright human if ever there was one -- is recreated outside the holodeck and experiences a 24th century world. But in the end, Picard has to answer some key questions from da Vinci with "that is beyond your understanding". Of course, da Vinci was smart enough to learn everything Picard knew. But it would have taken years to fill him in on everything da Vinci needed to know to understand what his new existence, centuries beyond everything he had been taught, was all about. I am reminded of that scene by some of your questions about data. Unless I misunderstand what you are really after, the answer you will have to live with is "that is beyond your understanding". -|Tom|-

It is also beyond my understanding, Jim.

But I know THAT it is (beyond my understanding). And I know WHY it is.

And I work around it. Mostly I rely on the competence of others (risky, but what else are you going to do?). But I always keep in mind the possibility that that other guy could have made a mistake. When things don't look right, I reassess the risks.

Someday I may decide to spend the years needed to bring such things within my understanding. Probably not, but you never know.

Or, perhaps someone will write a computer program that can allow specialists in other fields to process raw data with a toolbox of canned functions. Then all you need to know is which processing function(s) need to be applied. And Why. And in what order. And how to recognize bad results. Still not easy, but not nearly as hard as it is now.

There actually are some programs available that might be described as early attempts at this sort of thing. They are expensive, and it takes years to master them (although you can begin to get some kind of results within a few days). Formal training helps a lot, but often costs 2 to 10 times what the program itself costs.

And they are not always suited to a particular task. (Usually, the task they are not well suited for is the one you are working on. Sigh.)

Regards,
LB

LB/TVF, I understand you very well and agree for the most part that things could be a lot better and simpler and will be someday when the right software is constructed. I am more into Alice and the card game being playedin her story I think than Startrek BS. What are the rules in that card game? Anyway, back to the data problem, since the 20" distance does vary by 3% it seems to me right there you can determine the speed of gravity and see if it is instant or not. If it is instant than why not agree it is not in motion at all?