The longest animal on Earth isn’t what you think. It’s a drifting, gelatinous predator whose reach reshapes how we define size, survival and life in the ocean. In 1865, a dead jellyfish washed onto a Massachusetts beach. When scientists measured it, they discovered that its bell measured 2.1 meters (7 feet) across, making it wider than most doorways. What was more shocking were its tentacles: they stretched... [6134 chars]