Mordred said:Drakkiths comment on learn what GR teaches, is a good solid point. Here is a statement from Einstein that applies.
"According to the general theory of relativity, the geometrical properties of space are not
independent, but they are determined by matter. Thus we can draw conclusions about the
geometrical structure of the universe only if we base our considerations on the state of the
matter as being something that is known."
keep in mind this line was written prior to the cosmological constant. Which is in essence a negative pressure influence, gravity being a positive pressure influence.
However the above statement is still true provided you also consider the cosmological constants added influence on the average densities of matter.
this isn't the best book to study GR and SR even though its written by Einstein, however it is a free for distribution book. As well as a good historic reference article. Much of the explanations in it are easily read so its a good starting point.
http://www.marxists.org/reference/archive/einstein/works/1910s/relative/relativity.pdf