Science and technology

Associated Press
This April 3, 2013 photo shows bitcoin tokens at 35-year-old software engineer Mike Caldwell's shop in Sandy, Utah. Caldwell mints physical versions of bitcoins, cranking out homemade tokens with codes protected by tamper-proof holographic seals, a retro-futuristic kind of prepaid cash. With up to 70,000 transactions each day over the past month, bitcoins have been propelled from the world of Internet oddities to the cusp of mainstream use, a remarkable breakthrough for a currency which made its online debut only four years ago. (AP Photo/Rick Bowmer)

View gallery

500 photos

Astronomy, meteorology, environment, archaeology, electronics, computers and gadgets

View Comments (0)