Is it theoretically possible that the metric in the whole universe would be described by Kruskal extension of Schwarzschild solution of Einstein equation and in the universe would be no matter at all (vaccum solution everywhere). What's the interpretation of parameter m characterising Schwarzschild solution in this case? Does the matter need to be somewhere in the universe in case of this solution because we don't want to have white hole? Are there also other arguments for placing matter in some regions. What about the statement that matter (stress energy tensor) is the source of gravitational field. Are nonflat global solution of vaccum Einstein equation acceptable in whole universe (theoretically) or if there was vaccum everywhere in the universe it would have to be flat. Thanks.