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#Mon Aug 09 11:42:17 CEST 2010
Text__WxEPYKOaEd-WfYQ0GneCwQ_text=A mass curves the surrounding space time. <p></p>Light propagates on shortest paths in this geometry and thus appears deflected. <p>The observer  perceives two images, situated on the left and right hand side of the source. </p>
Text__WxEPYKOaEd-WfYQ0GneCwQ_title=Why does a mass act like a lens ?