Just last month, in an essay for the New York Review, I wrote the following sentence about Google and secrecy:
None of these books can tell you how many search queries Google fields, how much electricity it consumes, how much storage capacity it owns, how many streets it has photographed, how much e-mail it stores; nor can you Google the answers, because Google values its privacy.
As of today, that’s out of date. Google has decided to reveal the answer to two of those questions. James Glanz reports in the New York Times that the company’s data centers worldwide consume just under 260 million watts of electricity and field something over a billion searches a day.
This works out (Google says) to about three-tenths of a watt-hour per search. Google had given out that per-search figure before, in hopes of quieting people who wildly estimated that a single search consumes as much energy as bringing half a kettle of water (however much that is) to boil, or running a 100-watt light bulb for an hour.
Now, 0.3 watt-hours isn’t nothing, but it isn’t much. It sounds worse in joules: about a thousand. You yourself, if you are doing nothing more strenuous than reading this item, dissipate that much energy every twenty seconds or so. Google points out (with considerable justice, in my opinion) that any one search has the potential to save vast amounts of energy—a gasoline-powered trip to the library, for example.
It may feel as though there’s something apples-and-orangish about all this. Energy and information. I hear an echo of something I noted in The Information: that at the dawn of the computer era, in 1949, John von Neumann came up with an estimate for the minimal amount of heat that must be dissipated “per elementary act of information, that is per elementary decision of a two-way alternative and per elementary transmittal of one unit of information.” It was a tiny number; he wrote it as kTln 2 joules per bit.
Oh, and by the way, von Neumann was wrong; Charles H. Bennett and Rolf Landauer have explained why. But energy and information are tightly bound. Of that, at least, there is no doubt.