How much did you pay for your last pair of glasses?

Probably way too much, by the standards of Oxford physics professor Josh Silver, who has developed a wearer-adjustable set of eyeglasses that use water-filled plastic bags as lenses. They're so cheap that they can be distributed freely in underdeveloped and impoverished communities, which is exactly what Silver is doing, to the tune of 30,000 units so far. No visit to the optometrist and no custom lens grinding, just a standard pair of specs that you adjust once to your own visual comfort, using a small syringe, and then seal shut.