Fixed the Safari bug, replaced CSS transform-origin (broken in Safari on SVG) with native SVG animateTransform which works everywhere.
Also, you can now drag the "Year" slider on the main table to see how the periodic table looked at any point in history. Undiscovered elements fade to near-invisible. Ancient elements (no known discovery date) stay visible.
Also, i think in the timeline you should show a summary of the discovery on hovering over the element, so you don't have to click then go back.
Otherwise — nice!