John Stachel Image source: John Stachel John Stachel is an American physicist and science historian who is director of the Center for Einstein Studies and wrote ‘Einstein and the Quantum’. Quotes by John Stachel in Time OneThe reconciliation of gravitation and quantization is still one of the most intractable problems in contemporary theoretical physics. More about John Stachel Wikipedia “The Other Einstein” (PDF) “How Did Einstein Discover Relativity?” “A World Without Time: The Forgotten Legacy of Gödel and Einstein” Michael Sprague Henry Stapp