A new study published in the Journal of Neuroscience reveals that the human brain retains a strong instinct for gravity, even after prolonged periods in space. Researchers observed 11 astronauts on the International Space Station for five to six months and found that their brains continued to overcompensate grip force at the top of movements, mirroring Earth-based gravity expectations. This “perceptual illusion” persisted, with astronauts gripping harder at the top of a movement than the bottom, contrary to what microgravity dictates. Astonishingly, upon returning to Earth, astronauts initially exhibited weightless-like gripping, but relearned Earth's environment significantly faster than they adapted to microgravity. These findings, particularly the brain's struggle to unlearn gravity, have critical implications for future long-duration missions to the Moon and Mars, potentially requiring specialized astronaut training for object manipulation in partial gravity.