3-sphere two 3-balls. This construction is analogous to a construction of a 2-sphere, performed by gluing the boundaries of a pair of disks. A disk is a 2-ball, and the boundary of a disk is a circle (a 1-sphere). Let a pair of disks be of the same diameter. Superpose them and glue corresponding points on their boundaries. Again one may think of the third dimension as temperature. Likewise, we may inflate the 2-sphere, moving the pair of disks to become the northern and southern hemispheres. After removing a single point from the 2-sphere, what remains is homeomorphic to the Euclidean
Public sphere public sphere involves what is the basic theoretical structure of the public sphere, how information is deliberated in the public sphere, and what influence the public sphere has over society. What does it mean that something is "public"? Jürgen Habermas says, "We call events and occasions 'public' when they are open to all, in contrast to closed or exclusive affairs". This notion of the public becomes evident in terms such as public health, public education, public opinion or public ownership. They are opposed to the notions of private health, private education, private opinion, and private ownership. The notion of the