Habitable sphere and fine structure constant
  Future space missions, TPF and Darwin will focus on searches of signatures of life on extrasolar planets. In this paper we look for model independ definition of the habitable zone. It will be shown that the radius of the habitable sphere depends only on the constants of the Nature.   Key words: Habitable sphere, fine structure constant. 
Miroslaw Kozlowski, Janina Marciak-Kozlowska