How many zettabytes can dance on the head of a pin?

Attempts to put the size of a zettabyte into perspective fall a few petabytes short

Perhaps you've seen the headlines: The petabyte will soon need to step aside in favor of the zettabyte for use in describing humankind's ever-expanding yearly output of digital information.

And, as we all know (ahem) a zettabyte equals 1 trillion gigabytes, or a 1 followed by 21 zeroes.

So what do we make of that? ... No, really, what does a zettabyte mean in the meaningful sense of mean? EMC took a swing answering the question this week in releasing an IDC report it commissioned called "The Digital Universe Decade - Are you ready?"

Let's just say they did the best they could.

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In a general, I understand that a zettabyte is really big and that the comparisons being offered are really big things, too, albeit big things that might be a tad more accessible to my limited grasp of such scale. The comparisons are helpful, all right; it's just that they don't help all that much. Let's take a look at what was offered in an EMC press release: "The amount of digital information created in 2010 (1.2 zettabytes) will equal: "

"The digital information created by every man, woman and child on Earth 'tweeting' continuously for 100 years ."

The first problem with this is you need to know the world's population, which today straddles the 7 billion mark, depending on which guesser you want to cite. You also need to know that there's nothing other than trendiness calling for all the world's people to drop what they are doing and spend a full century tweeting, as opposed to say, sending e-mail or writing haiku. And, of course, the fact that the calculation comes out to a nice round 100 years - not 96.5, not 103.7 - suggests that maybe someone decided to wing it here, because, well, who's going to even try to check the math on this one?

The next attempt borrows more from the tried-and-true football field approach, placing the 1.2 zettabytes of data on a lot more iPads than Apple could even think about building before meeting its unmet commitment to jilted international buyers:

"75 billion fully-loaded 16 GB Apple iPads, which would fill the entire area of Wembley Stadium to the brim 41 times, the Mont Blanc Tunnel 84 times, CERN's Large Hadron Collider tunnel 151 times, Beijing National Stadium 15.5 times or the Taipei 101 Tower 23 times."

What have we learned here? OK, 75 billion iPads would be more than enough to give seven to every man, woman and child on the planet, provided Apple can ramp up production. Nothing to sneeze at. But the clearest thing we learn is that the Beijing National Stadium could steal Wembley's lunch money.

Next up, we turn to TV for a familiar reference point.

"A full-length episode of FOX TV's hit series '24' running continuously for 125 million years."

This didn't help at all in my quest to understand the magnitude of a zettabyte, perhaps because I've never watched so much as a nanosecond of "24."

And here's the last one:

"707 trillion copies of the more than 2,000-page U.S. Patient Protection and Affordable Care Act signed into Law in March 2010. Stacked end to end, the documents would stretch from Earth to Pluto and back 16 times or cover every inch of the United States in paper 3 feet deep."

That just made my head hurt. Let's give up.

(Update: A reader comes to the rescue.)

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