USC researcher Martin Hilbert

What do you get if you pile up all those USB thumb drives, CDs, chip-enabled credit cards, moldering videocassettes, library books, and Babylonian clay tablets

About 295 exabytes of storage capacity, that's what. So conclude Martin Hilbert and Priscilla Lopez, researchers at the University of Southern California, who today published in the journal Science their estimate of just how much information humans can store at present.

That number is, of course, big. An exabyte is 1,000 petabytes, and a petabyte is 1,000 terabytes, and a terabyte is about what you'd get in a desktop PC hard drive these days.

And that number is, of course, getting bigger. General-purpose computing storage capacity is growing at about 58 percent per year, according to the study.

But here's an even bigger number: the amount of data that vanishes into the ether. The researchers say humanity broadcast about 1.9 zettabytes of information from sources such as TV shows and GPS satellite location data in 2007. A zettabyte is 1,000 exabytes.

And although humanity has an impressive collective hard drive, it's peanuts compared to what nature has accomplished. Humanity's manufactured storage capacity is just a hundredth of the information capacity of humanity's DNA, the researchers said.