The underappreciated science: unraveling the cosmic forces at work during a "blood moon"

The "Blood Moon" is a mesmerizing celestial event that transforms the night sky into a masterpiece, a demonstration of how Earth's atmosphere paints the light of the sun. This reddish glow is not a mere coincidence, but a result of Earth's atmosphere acting as a giant, spherical lens and filter.

During a lunar eclipse, the moon passes through Earth's shadow, which consists of the penumbra and the umbra. As the moon enters the umbra, it doesn't completely darken; instead, it transforms into a reddish, glowing disc, known as the "Blood Moon".

The red glow is caused by the light component of red wavelengths continuing its path relatively undisturbed, while shorter blue wavelengths are filtered out and scattered away when sunlight traverses Earth's atmosphere at the day-night boundary. This phenomenon is known as Rayleigh scattering, named after the physicist who described the effect causing the red coloration of the Moon during a total lunar eclipse, although his name is not explicitly mentioned in the search results.

Rayleigh scattering primarily occurs in Earth's atmosphere at nitrogen and oxygen molecules. Mie scattering, named after German physicist Gustav Mie, describes the scattering of electromagnetic waves by particles of a size comparable to the wavelength and can influence the intensity and hue of the reddish light during a blood moon.

The exact color and brightness of the blood moon can vary, from a bright copper red to a deep, almost black dark red, depending on the state of Earth's atmosphere. A dusty or aerosol-enriched atmosphere along the terminator results in a darker blood moon, while a clean atmosphere leads to a brighter and more vividly colored eclipse.

The brightness of the Moon during totality is approximately 600,000 times less than that of a normal full moon, requiring an increase of about 19 f-stops in exposure for photographers to achieve a correctly exposed image. If photographed from the Moon during a total lunar eclipse, Earth would appear as a pitch-black disc surrounded by a glowing red ring.

The next opportunity to witness this breathtaking spectacle will be on New Year's Eve 2028 in Germany. So, mark your calendars and prepare to be amazed by the enchanting display of the Blood Moon.