Speed of Gravity?

I want to know if there is data indicating the two points are observed and what the data looks like. The generator at JPL and the help desk at USNO both say the barycenter is what I need and how to get that. Since that point clearly is not the point we are kicking around here I am failing to see how any data indicates that in fact the Earth orbits a point 20" or 600" from the apparent center of the sun. The 600" is about where the barycenter sometimes is located.

<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 />I want to know if there is data indicating the two points are observed and what the data looks like.<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">Planetary radar ranging data taken by JPL and MIT is used to measure the accelerations of the inner planets, Mercury, Venus, and Mars. These acceleration vectors are like arrows that point toward the source of the Sun's gravity. The JPL Development ephemerides such as DE200 are fitted to the radar ranging data, and can then be used to derive the position of the gravitational Sun at any desired moment.

The USNO transit circle data measures the location of the apparent Sun, and it is displaced by 20" from the gravitating Sun because of the propagation delay of light.

Any astronomer who is familiar with "aberration" can confirm that the source of the Sun's gravity and the apparent source of its light are displaced from one another by 20", the "angle of aberration"; and that the reason for this displacement is the relatively slow propagation speed of light (8.3 minutes from Sun to Earth). Gravity has no such propagation delay effect.

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">The generator at JPL and the help desk at USNO both say the barycenter is what I need and how to get that.<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">Another name for "barycenter" is "center of gravity". Perhaps you asked your question in such a way that they thought you were interested in the center of gravity of the solar system. But for this purpose, you are not.

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">Since that point clearly is not the point we are kicking around here I am failing to see how any data indicates that in fact the Earth orbits a point 20" or 600" from the apparent center of the sun. The 600" is about where the barycenter sometimes is located.<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">The offset of the barycenter of the Sun and nine planets varies between 0" and over 2000", and is influenced mainly by the four outer gas-giant planets Jupiter, Saturn, Uranus and Neptune. Their gravitation pulls the Sun in this direction or that relative to the fixed barycenter. However, to a first approximation, the four inner planets are pulled in the same direction by the same amount by these outer planets. So motion relative to the barycenter tends not to affect the direction of either the apparent or the gravitational Sun as viewed from Earth. And the small amount by which it does have an effect does not change the angle between the two Sun directions (true and apparent). -|Tom|-

The orbital generator at JPL/horizons uses two centers(apparent and astrometric) that are not what you are describing-look at the tables there and see for yourself. I have asked USNO help desk about transit circles so far nothing in reply to that query. If you dictate a question I can ask I will try again to access the data you said was at USNO. The other thread on this topic has some interesting ideas.

<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 />If you dictate a question I can ask I will try again to access the data you said was at USNO.<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">I never suggested you could get data that meant anything to you from USNO. They are not a public data archive as NSSDC is. And I already explained in detail all the things you would need to know to treat such data. It would take you years to learn all the types of effects that must be computed.

You keep oscillating between reasonable requests and unrealistic ones. I think I'd like to bow out and let you fend for yourself, since you are not inclined to take my advice anyway. -|Tom|-

I was taking your advice-you said I could get the data from USNO and they do give data to the public which after all owns the place anyway.

I found this about transit circles at USNO:operation of the European Hipparcos satellite effectively obsoleted the transit circles. So, do you think ESA has the data about the two points of the sun? USNO has no data.