Earth revolves in eliptical path?

[wasi-uz-zaman]

hi , how earlier scientist figure out that Earth has elliptical motion rather than circular around sun?

 

[mfb]

You can track the relative position of Earth and sun relative to stars - the orbital speed depends on our distance to the sun, if that changes the orbit has to be a (true) ellipse.
You can use observations of other planets as well, but that is tricky as those move significantly within a year.

 

[Dr_Morbius]

http://en.wikipedia.org/wiki/Kepler's_laws_of_planetary_motion