Astronomy Help

[andyfox]

Just trying to teach myself a little astronomy and I came across the "ecliptic." My book says: "The Sun appears to circle the celestial sphere once each year on a simple path called the ecliptic."

I understand that, since the earth circles the sun once a year, the sun would be seen from a different spot each day, and thus it would be seen against a different background of stars (were the stars visible during the day). But I don't get how the "path" is determined. As the sun appears to move through the sky from sunrise to sunset, what spot is used to determine it's daily location on the ecliptic?

Thanks for any help.

[daryn]

intuitively i think it's all about the tilt of the earth at the time, in other words, what season we're in.


the ecliptic is higher in the sky during the summer, that is why the summers are hotter than the winters. ironically, the sun is actually closer to earth during our winter, and farther away during our summer.


anyway i'm pretty sure this is all due to the precession of the earth as it rotates on its own axis as it flies around the sun in it's elliptical orbit.

[goofball]

wow, something i may be able to give a real opinion on. However I need you to more precisely define "celestial sphere"

Is that just the sky? If so, I believe the claim is teh following. If you took a picture of the sun's place in the sky at the same time every day for a year, then animated it to watch the changes in the placement of the sun at that particular time of day as the year progressed, you would see an elliptical path. THat's just what it seems to be saying though. I have no idea whether or not this is true, and actually, I don't think it's something astronomers are typically concerned about.

[Zeno]

The Celestial sphere is a conceptional construction to give some reference to the movement of stars and planets etc. Think of it as the dome of the sky with the ends at the horison. The ecliptic is the path of the sun across that sphere or half-dome. Anyway here are two websites that explain this very well: The Ecliptic (http://www-spof.gsfc.nasa.gov/stargaze/Secliptc.htm)

The Celestial Sphere (http://csep10.phys.utk.edu/astr161/lect/celestial/celestial.html)

Hope this helps.

-Zeno

[brassnuts]

[ QUOTE ]
As the sun appears to move through the sky from sunrise to sunset, what spot is used to determine it's daily location on the ecliptic?

[/ QUOTE ]

This is just a guess, but I would think the zenith.