You're thinking of the Banach-Tarski Theorem, sometimes called a paradox.  Mentioned here several times.<p><a href="http://searchyc.com/banach+tarski" rel="nofollow">http://searchyc.com/banach+tarski</a><p>Same connection was made last time: <a href="http://news.ycombinator.com/item?id=416765" rel="nofollow">http://news.ycombinator.com/item?id=416765</a>