Webpages from six historical events over the last three years have disappeared faster than they could be archived.

Hany M. SalahEldeen and Michael L. Nelson

There is a well-known thrill that comes from watching -- nearly in real time -- as big news unfolds on Twitter. Millions upon millions of people pass information around, celebrate it, mourn it, and discuss it. How will this whole process look to historians of the future? Will they be able to recreate and understand what it was like?

The question goes beyond the archiving of the tweets themselves (something the Library of Congress has taken a lead on), though that matters too. But the tweets are only part of the story; where their links bring readers to also needs to be preserved, and that's not happening fast enough, according to a new study (pdf) from Hany M. SalahEldeen and Michael L. Nelson at Old Dominion University in Norfolk, Virginia.

They looked at some one million tweets from six historical events over the past three years (Iranian elections, Michael Jackson's death, the H1N1 outbreak, Obama's Nobel Peace Prize, the Egyptian revolution, and the recent Syrian uprising) and found that archiving is not keeping apace with the web's fast turnover -- as time progressed, the webpages linked to became increasingly unavailable. "We estimate that after a year from publishing about 11 percent of content shared in social media will be gone," they write. "After this point, we are losing roughly 0.02 percent of this content per day."