Celestial sphere
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In astronomy and navigation, the celestial sphere is an abstract sphere that has an arbitrarily large radius and is concentric to Earth. All objects in the sky can be conceived as being projected upon
Celestial globe by Jost Bürgi (1594)
Concentric objects
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In geometry, two or more objects are said to be concentric when they share the same center. Any pair of objects with well-defined centers can be concentric, including circles, spheres, regular polygon
Celestial sphere
…In astronomy and navigation, the celestial sphere is an abstract sphere that has an arbitrarily large radius and is concentric to Earth. All objects in the sky can be conceived as being projected upon the inner surface of the celestial sphere, which may be centered on Earth or…
Ripples in water
Histology of a Pacinian corpuscle, in a typical expanding circular pattern.
Tree rings, as can be used for tree-ring dating