Speed of Gravity?

Astro, Both JPL and USNO have generators using the barycenter as you have said. If the Earth orbits that point would it be able to stay in the orbit it is in? The observation has been made that it would not and Earth orbit is centered either at the apparent center of the sun or 20" from that point. JPL and USNO refuse to comment on any of these points. Can you comment on weather or not the orbit of Earth can be stable if the center of the orbit is at the barycenter?

The Earth's orbit is neither centered at the Sun's apparent position nor at the Sun's true position 20" away. The Sun is actually at one of the foci of the Earth's orbit.

--Astro

Sorry about the improper use of the terms here, but you get the point, I hope. The sun being at the center of one focus of the eliptical orbit of Earth means the barycenter is not the center of gravity-right? The center of gravity is the center of the sun so is that the apparent center or the true center? Or somewhere in the midway 20" range?

<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 />The speed of gravity will be clearly noted as a difference between 20" and whatever the difference from instant is measured. For example if the distance is 19" then the speed of gravity is 20 times light.<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">What you say in these sentences is clear and correct.

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">If gravity is not instant then the 20" stuff is not correct.<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">This is wrong. Every measurement has uncertainty because no measurement can be perfect. The eclipse experiment measures the angle of aberration to be 20" (an approximation of the true value) +/- 1". This allows the speed of gravity to be as slow as 20 times light, as you say. But one of the other experiments measured 20" +/- 0.0001", which limits the speed of gravity to be at least 200,000 c. And the most sensitive experiment implies 20" +/- 0.000000001", making the speed of gravity greater than or equal to 20,000,000,000 c.

Obviously, only the most sensitive experiment matters in setting the final value. -|Tom|-

I have been studying the generators at JPL and USNO to see where they locate the focus of Earth's orbit. They say it is focused at the barycenter but the generator locates it at the center of the sun. There is no reference to the point TVF makes clear-the sun is 20" from where it appears to be. So, where exactly is the focus of Earth's orbit seems a point worth measuring somehow.

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by tvanflandern</i>
The observations proving that the Sun's gravity acts from the center of its circular path through the stars, and not from the delayed position of the Sun, are radar ranging observations. But that fact was never in doubt because Newton's law of gravity would have failed long ago if that were not true. -|Tom|-
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
One does not really need observations to prove this because the concept of a force would be inconsistent if static forces do not act instantaneously (see my page www.physicsmyths.org.uk/retard.htm ). Just imagine that the sun is suddenly removed from the solar system. It is just inconceivable that the earth would continue in its orbit for another 8 min without any physical object present to provide the required gravitational attraction and hence force balance.

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