image credit: Jon Bird;&lt;a href=&quot; http://www.phys-astro.sonoma.edu/graduates/baker/southpolefoucault.html&quot; target=&quot;_blank&quot;&gt; Image source&lt;/a&gt;; &lt;a href=&quot;http://www.physicstogo.org/images/features/foucaultlarge11-26-072.jpg&quot; target=&quot;_blank&quot;&gt; larger image&lt;/a&gt; 