When the Moon Plays Tricks: ALMA Reveals Cosmic Secrets

By European Southern Observatory (ESO) February 16, 2025

Collected at: https://scitechdaily.com/when-the-moon-plays-tricks-alma-reveals-cosmic-secrets/

On the barren Chajnantor plateau, ALMA observes the depths of space, yet the rising Moon reminds us of home. Its seemingly large size on the horizon is merely an optical illusion, but its true influence on Earth is profound — shaping tides, stabilizing seasons, and making life as we know it possible.

The Atacama Large Millimeter/submillimeter Array (ALMA), operated by ESO and its international partners, sits high on the Chajnantor Plateau, where the thin, dry air creates ideal conditions for observing the cold, dark universe. In this stunning image, the plateau’s rolling, rust-colored terrain appears more like the surface of an alien planet than a place on Earth.

Yet, a familiar sight brings us back home — the full Moon rising at sunset. Throughout its phases, the Moon rises and sets at different times, and over the year, it shifts its position along the horizon. When it appears just above the horizon, it often looks unusually large. However, this is merely a well-known optical illusion, not a change in the Moon’s actual size.

Our Moon is a unique body within the solar system; it’s Earth’s only natural satellite and is a particularly large moon at 25 percent of its host’s size. The Moon, then, exerts extra influence on the Earth, stabilizing seasons and climate and producing tides — things without which we might not have life. The Moon is a wonder to admire, indeed.