National Geographic : 2011 Jun
• Military vision The U.S. military also depends on China's mines. Night-vision goggles (above) require lanthanum, gadolinium, and yttrium. Samarium magnets, which can withstand intense heat, help control Predator drones and Tomahawk cruise missiles. Medical scans Gadolinium also serves as a contrast agent in magnetic resonance imaging, or MRI, helping surgeons distinguish diseased from healthy tissue. In the scan at right it highlights a brain tumor (colored orange for clarity). Green machines Hybrid cars would not exist without rare earth elements---lanthanum for their batteries, neodymium magnets for their electric motors. A wind turbine may contain hundreds of pounds of neodymium; a compact fluorescent lightbulb, much smaller amounts of yttrium and terbium. And much else... such as protecting eyes and beverages from ultraviolet radiation. Praseodymium, erbium, and neodymium tint sunglasses; cerium in wine-bottle glass promotes absorption of UV light. Some power tools rely on neodymium or dyspro- sium magnets to shrink their motors.