The Weight of Literature: Part 2

Quoting from The Week Issue 843 12 November via the New York Times. . .

E-readers enable people to carry around their libraries - but adding extra books makes devices heavier. They are, however, unlikely to get too heavy: filling a 4GB Kindle to its full capacity, a scientist has calculated, would increase its weight by about a billionth of a billionth of a gram. Storing new data involves holding electrons in a fixed place in the device's memory, and keeping them still rather than letting them float around takes up extra energy, Professor John Kubiatowicz of the University of California, Berkley told the New York Times. Using Einstein's E=MC2 formula, which implies that energy and mass are related, he calculated that each additional weighs about the same as a molecule of DNA.