What causes a blood moon? Earth’s atmosphere refracts red sunlight via Rayleigh scattering during totality.
While the "Blood Moon" often invites high-energy headlines, there is something deeply grounding about the science of a total lunar eclipse. As the moon slips from the pale penumbra into the deep umbra—the darkest part of Earth’s shadow—we are witnessing a global optical filter. Rayleigh scattering, the same physics that gives us our red outback sunsets, bends light around the curve of our planet to reach the moon.
On this March 3 evening, some may even witness a "selenelion"—a rare geometric quirk where atmospheric refraction allows us to see the sun rising and the eclipsed moon setting simultaneously. It is an "impossible" sight that reminds us how our own atmosphere shapes our reality. In a busy world, these celestial events offer Australians a moment of collective pause, reminding us that we all live under the same thin, blue line.
