At the edge of our solar system's inner reaches, the smallest planet is quietly becoming smaller still — and faster than our models had prepared us to understand. New research reveals that Mercury's interior is cooling and contracting at a rate that outpaces prior scientific estimates, unsettling long-held assumptions about how rocky worlds age and evolve. This discovery invites us to reconsider not only Mercury's story, but the broader narrative of how terrestrial planets — including our own — carry the slow weight of geological time.