The Cathedral's kaleidoscope

As every year, around the winter solstice, the Cathedral of Mallorca gives us an amazing show of a huge kaleidoscope of color. The View from Es Baluard, with permissions of the clouds, is one of the outputs of the prettiest sun that we can see.  

This effect, discovered and studied by the Balear Society of Mathematics SBM-XEIX gathers every year more and more fans and, with the intention of spreading mathematic knowledge, we've prepared this year a morning with an exceptional speaker.