|
 |
 advertisement
| |
|
|
|
|
|
The Celestial Sphere
By Jeff Kanipe
posted: 30 June 2005
08:12 am
|
Tuesday, June 12Like our ancestors did thousands of years ago, it's quite natural for us to view the night sky as an inverted bowl upon which the stars are fixed, while the Sun, Moon and planets move among them. It requires only a little more imagination to further visualize that this dome is actually the hemisphere of an immense globe -- a celestial sphere -- that turns about an axis that runs through Earth, which is located at the center of the sphere. The celestial sphere concept can be laid at the feet of 5th- and 6th-century Greek philosophers, particularly Pythagoras and Parmenides. Ancient Chinese, Arab, Egyptian and European astronomers also assumed that the stars were fixed to the surface of a globe that lies an immense distance from the observer. Even today, basic observational astronomy is taught using the celestial sphere as an analog for the real sky. Five fundamental axioms of Greek astronomy nurtured this notion: - Earth is a sphere;
- It lies at the center of heaven;
- And it is of negligible size in relation to heaven.
- Heaven, too, is spherical;
- It rotates daily about an axis that passes through Earth.
Cognizant as we are today of the true distances and motions of the stars, we recognize the celestial sphere as a perspective effect that has been handed down through the ages. I wonder -- if we weren't so edified and technologically well endowed, how could we deduce the true depths of space? What would prevent us from thinking that the universe was a vast sphere etched with stars?
|
|
|
|
|
