E-Readers get heavier with each book.
Posted: 01 Nov 2011, 21:45
http://www.telegraph.co.uk/science/scie ... -book.html
...E-readers get heavier with each book
E-readers are meant to let bookworms carry their entire libraries with them without any additional weight – but the devices actually get heavier every time a new text is downloaded.
The weight difference is unlikely to make much difference to holidaymakers' baggage allowances, however, because each new tome is about as heavy as a single molecule of DNA.
Prof John Kubiatowicz a computer scientist at the University of California, Berkeley, explained in the New York Times last week that storing new data involves holding electrons in a fixed place in the device's memory.
Although the electrons were already present, keeping them still rather than allowing them to float around takes up extra energy – about a billionth of a microjoule per bit of data.
Using Einstein's E=mc² formula, which states that energy and mass are directly related, Prof Kubiatowicz calculated that filling a 4GB Kindle to its storage limit would increase its weight by a billionth of a billionth of a gram, or 0.000000000000000001g.
This is roughly equivalent to the weight of a small virus, while the equivalent number of books – about 3,500 – would weigh approximately two tons.
E-readers could also become slightly heavier in the summer, because they would take on more energy from their exposure to sunlight, scientists explained.
Graeme Ackland, of Edinburgh University, told the Guardian: "If Prof Kubiatowicz is really struggling with the extra weight, he is welcome to come to Edinburgh where it's cooler, and the lack of thermal energy in his Kindle will more than compensate."
