Measuring sun's true direction

<BLOCKQUOTE id=quote><font size=2 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote> [tvf] The Sun's motion is entirely in the plane of the ecliptic by definition of "ecliptic" (the Earth's orbital plane). <hr height=1 noshade id=quote></BLOCKQUOTE id=quote></font id=quote><font face="Verdana, Arial, Helvetica" size=2 id=quote> I see from your prior post showing the calculation of the aberration that you are measuring aberration caused by the earth's orbital motion, whereas I was thinking about the Sun's 220 km/sec motion through the galaxy, which must be at an angle relative to the ecliptic since the Milky Way in the night sky is not aligned with the ecliptic (is my reasoning OK?). (We could also consider the galaxy's motion.) Wouldn't this (net) motion of the Sun also result in aberration? Shouldn't therefore the net aberration due to the earth's orbit plus the Sun's motion be detectable as an angle tilted to the ecliptic? I have doodled circles and arrows all over my desk. I'm going to have to find an orrery on a moving track...

<BLOCKQUOTE id=quote><font size=2 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote>I was thinking about the Sun's 220 km/sec motion through the galaxy, which must be at an angle relative to the ecliptic since the Milky Way in the night sky is not aligned with the ecliptic (is my reasoning OK?). (We could also consider the galaxy's motion.) Wouldn't this (net) motion of the Sun also result in aberration?<hr height=1 noshade id=quote></BLOCKQUOTE id=quote></font id=quote><font face="Verdana, Arial, Helvetica" size=2 id=quote>

Sure, but it is unobservable because Sun and Earth share the same motion, and aberration depends on <i>relative</i> speed. -|Tom|-

Oh...right. I think I was assuming that an ether wind would allow us to detect a difference between the direction we need to look to see the Sun and the direction from which we feel its gravity. Thanks.

My math is poor but I have calculated the time and distance that 20 sec of arc and 30,000m/s triangulate out to and they seem to indicate the speed of gravity(by your method of determing this)is less than a billion times the speed of light. Did you do this calculation and if so what is your result?

<BLOCKQUOTE id=quote><font size=2 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote>My math is poor but I have calculated the time and distance that 20 sec of arc and 30,000m/s triangulate out to and they seem to indicate the speed of gravity (by your method of determing this) is less than a billion times the speed of light. Did you do this calculation and if so what is your result?<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 you mean by "your method", or what information you are using to estimate the speed of gravity. But for the figures listed, 20 arc seconds is an angle of 1/10,000 radians, and 1/10,000 of the speed of light, 300,000,000 m/s, is the orbital speed of the Earth, 30,000 m/s. So the measured aberration angle for the Sun from Earth does correspond to the ratio of Earth's speed to the speed of light.

But where do you see the speed of gravity in any of that? Measuring the speed of gravity requires an experiment. There are six experiments available. The strongest of those is the binary pulsar experiment, which sets the "20 billion c" lower limit for the speed of gravity. -|Tom|-

I don't see a speed of gravity myself and I'm only trying to figure out the location of the sun relative its apparent position which is a 500 seconds distance apart. The speed of gravity enters the picture from the left of the difference in the two locations.