Zealandia submerged microcontinent New Zealand

An inertial navigation system works out a submarine’s position from its motion sensors, without outside information once aligned. Weather and jamming do not disrupt it. But small errors build over time, so the system needs occasional position fixes.

Researchers have demonstrated a way to heat polyethylene—the plastic used in many bags and containers—so it breaks down into hydrogen gas and graphene, a form of carbon just one atom thick. The approach could turn waste plastic into two useful materials, although scaling it up remains a challenge.