资料题：What does the passage mainly discuss（　）。

During the past few years, scientists the world over have suddenly found themselves productively engaged in a task they once spent their lives avoiding- writing, any kind of writing, but particularly letter writing.Lured by electric mail's seductive blend of speed, convenience and economy, people who never before touched the stuff are routinely, skillfully, even cheerfully taping out a great deal of correspondence.Electronic networks have been woven into the fabric of scientific communication these days.Anyone with a personal computer, a modem and the software to link computers over telephone lines can sign on.An estimated five million scientists have done so, communicating through a bundle of interconnected domestic and foreign routes known collectively as the internet, or net.E-mail is starting to edge out the fax, the telephone, overnight mail and, of course land mail.It shrinks time and distance between scientific collaborators, in part because it is conveniently asynchronous (writers can type while their colleagues across time 2ones sleep.) fit is not yet speeding discoveries, it is certainly accelerating disclosures.Jeremy Bernstein, the physicist and science writer, once called e-mail the physicist's umbilical cord.Lately other people, too, have been discovering its connective virtues.Folklorists are studying it; college students are lining up the computer center for accounts, and sure sign that it has come of age, the New Yorker has celebrated its liberating presence with a cartoon- anappreciative mutt seated at a keyboard, saying happily,''On the Internet, nobody knows you are a dog.”