On rainbows. Part 3 on June 29, 2018 Alexander's Dark Band atmospheric optics double rainbow primary rainbow raindrop refraction secondary rainbow +
Collaboration Day 6 on February 11, 2017 Alexander's Dark Band Descartes Goethe objective prismatic experiments rainbow subjective prismatic experiment +
Collaboration Day 4 on September 11, 2016 Alexander's Dark Band Descartes double rainbow primary rainbow secondary rainbow +