For billions of years, the moon's soil has quietly recorded the behavior of Earth's invisible magnetic shield, and now humanity is learning to read that record. China's Chang'e 6 mission returned samples from the lunar farside that, when compared with nearside soils, reveal Earth's magnetosphere does not simply block the solar wind — it slows it, cutting particle velocities nearly in half before they reach the moon's Earth-facing hemisphere. This discovery, drawn from the thermal signatures of noble gases trapped in ancient regolith, reframes our understanding of planetary magnetism and opens