How heavy is your data?

Russ Swan of Russ Swan fame, mentioned recently that he had taken part in NASA’s Face in Space program as he’d always dreamed of being an astronaut and this was probably as close to getting into space as he was ever likely to achieve. “A picture of my ugly mug is currently orbiting the Earth on board Endeavour,” he said. Of course, Swan’s near doppelgänger Virgin Galactic’s Richard Branson might be looking for volunteers for the test flights of his “space ship”…

Swan and Branson - space-race dreams

Anyway, Swan is looking forward to downloading his certificate of flight, although he concedes that it’s all just a little misleading, as the picture in question is a massless digital file. Weightless perhaps, but massless? I wasn’t convinced by that assertion and mused on the possibility that some kind of relativistic effect might come into play when data are added to a storage medium, increase the potential energy by adding information and that would equate to an increase in mass according to Einstein’s famous equation E = mc^2…possibly.

Swan was not convinced and asked, “Is my camera’s memory more massive when I’ve taken a picture? Does the stored image have mass? I’m pretty sure that taking my picture with them, as a digital file, has no payload implications for the Shuttle…Flash drives are set to a binary 1 by default, and a 0 is set by applying a voltage. This is like opening or closing a door on the memory cell, and involves no stored charge (as far as I know), so I think there isn’t even an electron’s mass difference between the two states.” However, he qualified his response with the phrase, “But I could be wrong…”.

So, I talked to a physicist friend, Nykolai Bilianiuk, who explains that most storage media would not gain mass when data are added to them, in fact, some might actually lose mass. All is not lost in the mass debate, however.

“For EEPROM and Flash media, data is stored by trapping electrons after injection through an oxide, a state from which they cannot easily quantum-tunnel their way out. In this case, changing the content of a memory does change the number of electrons stored in that cell, and therefore obviously the mass is changed,” Bilianuk explains, “The same holds for dynamic RAM and photographic CCDs, which store data in the form of buckets of electrons in tiny capacitors.”

So, while your data might be weightless in outer space it may not be massless. Swan’s mugshot could very well be adding to fuel consumption aboard Endeavour after all!

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1 thought on “How heavy is your data?”

  1. Swan’s almost instantaneous riposte was to point out a flaw in the logic:

    “I don’t think EEPROM and Flash actually store data by trapping electrons, but rather by changing the gate condition at the memory cell. This may incidentally lead to electrons finding themselves in a semiconductor cul-de-sac, but it is the gate not the electrons that store the data. This is how they can be semi-permanent. The same would presumably also be true when a memory cell is re-written, so you could argue that formatting a Flash drive would notionally *increase* its mass, and a full SD card may actually be lighter than an empty one,” he says.

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