From Twitter https://twitter.com/drsekula:

RT @NobelPrize: Today=100th anniversary of Einstein's presentation on theory of general relativity. A.E. Q&A http://www.nobelprize.org/nobel_prizes/physics/laureates/1921/einstein-faq.html?utm_source=twitter&utm_medium=social&utm_campaign=twitter_tweet https://twitter.com/NobelPrize/status/669454441913966592/photo/1 https://chirp.cooleysekula.net/attachment/4349