By engaging with all the videos within this series, you will effectively complete a full undergraduate course in astronomy, equipping yourself with the knowledge and skills necessary to navigate the night sky with confidence, learning all the basics and many advanced topics! We look now at Isaac Newton’s contributions and his perspective on light. In 1666, Isaac Newton began his experiments with light using prisms, aiming to disprove the wave theory of light. He believed light consisted of particles, which he called corpuscles. Newton demonstrated that light behaves like particles by showing how it reflects off surfaces, akin to bouncing balls. Newton’s experiments with prisms revealed that sunlight passing through a prism splits into a spectrum of colors (red, orange, yellow, green, blue, indigo, violet). By using a second prism, he recombined the spectrum into white light, arguing that the glass of the prism did not corrupt the light. Despite attacks from Robert Hooke, who favored the wave theory, Newton persisted. By 1672, he presented his findings to the Royal Society, advocating for the corpuscular nature of light. Meanwhile, Christiaan Huygens sought to incorporate refraction and reflection into the wave theory, encountering difficulties explaining certain phenomena like the behavior of calcite crystals, which produced double images. Despite his success in many scientific areas, Newton’s corpuscular theory was eventually replaced as further advancements in understanding light were made.