The 1577 comet, which remained visible from November 1577 to January 1578. Tycho's observations revealed no measurable parallax, implying that the comet was located beyond the sphere of the moon. His reconstruction of the comet's orbital path , from brightening and dimming and displacement with respect to the background stars, indicated that the comet moved across the concentric planetary crystalline spheres. This supported the notion of a "fluid heaven" and contradicted the physical reality of these spheres as real, hard, transparent, contiguous spherical shells.
-Written and last revised 20 December 1997 by paulchar@ucar.edu.