  A computation of the Casimir effect for a real scalar field in four
situations: on a segment of a line, on a circle and on both standard
commutative and noncommutative two-spheres is given in this paper. The main aim
of this paper is to discuss the Casimir energy on the noncommutative sphere
within the theory with commutative time. The comparison with the noncommutative
cylinder is also done.
