How much information could you store on every technological device in the world? Every hard drive, book, video tape and microchip on a credit card? A research team from the University of Southern California has estimated that figure, in 2007, to have been 256 exabytes of data.

That's a 256 billion gigabytes, the equivalent of 1.2 billion average PC hard drives, enough CDs to make a stack which would reach beyond the moon and 15 libraries for every person on the planet.

As for broadcasting information, like TV and GPS, humankind sent approximately 1.9 zettabytes of information in 2007. In that same year, we shared 65 exabytes of data through two-way communications, like phones. In terms of computing, the world's general-purpose computers performed 6.4 x 10^18 instructions per second. If you did all that by hand, it would take 2,200 times the period since the Big Bang.


To come up with these staggering numbers, study author Martin Hilbert and his team at the University of Southern California estimated the amount of data held on 60 different digital and analogue technologies -- including x-ray films and floppy disks -- from 1986 to 2007. They then used this data to look at trends and growth rates.

For example, 2002 was the year digital storage capacity overtook the world's total analogue capacity. By 2007, almost 94 percent of the world's data was stored in a digital format.

The team also saw computing power grow by 58 percent a year -- ten times faster than the gross domestic product of the United States -- and telecommunications and storage capacity grew 28 percent and 23 percent annually respectively.

However, as impressive as those numbers are, they're dwarfed by the information processing and storage seen in nature. That mammoth 295 exabyte figure is less than 1 percent of the information stored in all the DNA molecules of a single human being.


The number of calculations performed by the world's computers? A human brain could do that, by itself. And it would be impossible, says Hilbert, to write down the names of every star in the known universe, even if you had access to every storage medium on the planet.

If, duly humbled, you want to see the research, it was published in the 10 February issue of the journal

Science.