The New York Times writes:
A new research paper seeks to answer a riddle for publishers, editors and even readers: when does new news become old news?
In the case of a news article on the Internet, the answer is surprisingly long: 36 hours on average, according to the paper, The Dynamics of Information Access on the Web, which appeared in the June issue of Physical Review E, the journal of the American Physical Society.
More precisely, 36 hours is the amount of time it takes for half of the total readership of an article to have read it, the paper found. The physicist who led the research, Albert-Lszl Barabsi of the University of Notre Dame, said that the papers conclusion should give journalists hope, even in the era of instant news.