“Spacetime tells matter how to move; matter tells spacetime how to curve.”
John Archibald Wheeler (1911–2008) American physicist
Wheeler's succinct summary of Einstein's theory of general relativity, in Geons, Black Holes, and Quantum Foam (2000), p. 235. http://books.google.com/books?id=zGFkK2tTXPsC&lpg=PA1&pg=PA235