Physics Games is a collection of browser games that all have at least a rudimentary physics model. Some of the games I've enjoyed are Roly Poly Eliminator, Totem Destroyer 1 & 2, Demolition City and Red Ball. Most are fairly simple but some are complex, notably IncrediBots 1 & 2, which might as well require an engineering degree (slight hyperbole). My absolute favorite type of game on this site is the destroy-castles-with-a-trebuchet game, handsomely represented by not one but three games, Castle Clout, Castle Clout: Return of the King (no Tolkien connection) and Crush the Castle. All this is but a small sample of what's on offer.
UniverseNewsFilter: Scientists claim to have detected dark matter! Here are NASA's press release, feature page and multimedia presentation. For an explanation what dark matter is, I refer you to this page. After all that excitement, you can sit down and work out how much dark matter is in the Milky Way.