most recent 30 from http://mathoverflow.net 2013-05-20T14:03:37Z http://mathoverflow.net/feeds/user/13359 http://www.creativecommons.org/licenses/by-nc/2.5/rdf http://mathoverflow.net/questions/57115/five-points-in-spheres José Araujo 2011-03-02T14:31:24Z 2011-10-04T06:29:15Z

<p>Do there exist five points in the euclidean space ${\mathbb R}^3$ such that every four of these points are in a spherical ball of radius 1, but that the five points are not in a ball of radius 1?</p> <p>Do there exist five points in the euclidean space ${\mathbb R}^3$ such that every four of these points are on a sphere of radius 1, but that the five points are not on a sphere radius 1?</p>