Thisbookismeanttobeneitherencyclopedicnorasourcebookforthemostrecentobservationaldata.Infact,Iavoidaltogetherthepresentationofdata;afterallthedatachangeveryquicklyandareeasilyaccessiblefromnumerousavailablemonographsaswellasontheIntemet.Furthermore,Ihaveintentionallyrestrictedthediscussioninthisbooktoresultsthathaveasolidbasis.Ibelieveitisprematuretopresentdetailedmathematicalconsiderationofcontroversialtopicsinabookonthefoundationsofcosmologyand,therefore,suchtopicsarecoveredonlyataveryelementarylevel.