Unit conversion: 0.04oz is approximately 1.14g, which sounds pretty impressive. But it can't be much heavier because a common swift typically only weighs around

Unit conversion: 0.04oz is approximately 1.14g, which sounds pretty impressive. But it can't be much heavier because a common swift typically only weighs around 35-56g (that's 1¼–2oz) according to http://www.commonswift.org/swift_english.html http://www.commonswift.org/swift_english.html According to the Wikipedia article linked by mongol, these devices can be as light as 0.3g. It's a battery, a phototube, a clock, and a recording chip. Longitude can be reconstructed from the time of most/least light, whereas the length of day and night allow reconstruction of latitude. Battery life is between 6 months and 5 years.