Things You Thought You Knew – Is Everything Light?

In this episode of StarTalk Radio, Neil deGrasse Tyson dives into the fascinating science of light through three interconnected themes: albedo, light pollution, and the electromagnetic spectrum. Starting with albedo—the measure of reflectivity—Tyson explains how it applies not just to celestial bodies like the moon and Earth, but also to human skin, fashion choices, and even philosophical reflections on race. He reveals that the moon’s low albedo of 0.1 makes it darker than a car tire, and that Earth’s average albedo of 0.3 means 70% of solar energy is absorbed, contributing to climate concerns. The concept of Earthshine—moonlight reflected from Earth—is explored as a beautiful example of albedo in action, first theorized by Leonardo da Vinci. The discussion then shifts to light pollution, where Tyson highlights how artificial lighting disrupts astronomy, wildlife, and our connection to the night sky. He praises the International Dark-Sky Association for promoting efficient, downward-directed lighting to reduce waste and preserve dark skies. Beyond visible light, the episode expands into radio wave and satellite pollution, with the Vera Rubin Observatory’s nightly sky movies now battling streaks from orbiting satellites. Tyson concludes with a deep dive into the electromagnetic spectrum, revealing that all forms of radiation—from radio waves to gamma rays—are fundamentally the same phenomenon: light. He traces the discovery of infrared by William Herschel and emphasizes how our eyes perceive only a tiny fraction of this vast spectrum, making us nearly blind to most of the universe’s signals.