Assertion: celestial sphere | /r/HasProperty | useful tool
Facets:
value: extremely
type: DEGREE
Source sentences:
text: The Celestial Sphere is an imaginary concept that is a useful tool for understanding some workings of the sky. ...
text: The celestial sphere is still useful even though it is no longer accepted as physical reality.
text: The Celestial Sphere is an imaginary concept that is a useful tool for understanding some workings of the sky: Sphere of infinite radius with Earth at center.
text: Hence, the celestial sphere is an extremely useful tool if one plans to observe the sky — which is exactly why we have built a working model of it!