Do-it-yourself telescope kits might be common nowadays, but you'd be hard-pressed to find parts that cost just $1.95. Brownscope's 100x telescope lens kit, which was suited for refracting telescopes, came with two astronomical eyepieces and one polished objective lens. As if you weren't saving enough money by buying an inexpensive lens, the advertisement also recommended making a profit by charging people to look through your newly-upgraded telescope.
Five amazing, clean technologies that will set us free, in this month's energy-focused issue. Also: how to build a better bomb detector, the robotic toys that are raising your children, a human catapult, the world's smallest arcade, and much more.