The LEGO Technic Planet Earth and Moon in Orbit (42179) is an engaging and educational model that brings the mechanics of our solar neighborhood to life. This 526-piece set builds a detailed orrery of the Earth, Moon, and Sun, driven by a manual crank that simulates Earth’s orbit around the Sun and the Moon’s orbit around Earth.
The gearing is surprisingly accurate for a LEGO model, representing an Earth year at about 364.5 days—within roughly 0.2% of reality—while also approximating the Sun’s rotation at around 25–27 days and the Moon’s orbital period at about 27 days. The model correctly maintains Earth’s axial tilt to demonstrate how seasons work, and even includes a tidally locked Moon that always shows the same face to Earth. Printed month and moon-phase elements round out the build, making it both an impressive display piece and a hands-on learning tool for budding astronomers.