plural of celestial sphere

(of a black hole) A region of around a black hole where photons travel in orbits around the singularity, just beyond the event horizon.

plural of crystal sphere

A crystal ball

A fold mirror that is a "sphere", i.e. a spherical mirror

(cosmology) Hubble volume

plural of photon sphere

plural of Klerksdorp sphere

A small object, often spherical to disc-shaped, found in three-billion-year-old pyrophyllite deposits mined near Ottosdal in South Africa.

(topology) A pathological object, a certain embedding of a sphere in three-dimensional Euclidean space, obtained by various modifications of a torus.