<p>Banach-Tarski Paradox</p>
<p>Start with 1 ball in 3D space, split it into finite number of pieces, and you can put them back together to form 2 identical copies of the original ball.</p>
<p>How? ^</p>
<p>Tan char</p>
<p>the proof involves set theory, and I won’t go into that</p>
<p>Here’s a layman’s approach</p>
<p>[Banach-Tarski</a> Paradox – Math Fun Facts](<a href=“http://www.math.hmc.edu/funfacts/ffiles/30001.1-3-8.shtml]Banach-Tarski”>http://www.math.hmc.edu/funfacts/ffiles/30001.1-3-8.shtml)</p>