If they miss this morning's introductory biology lecture, Johns Hopkins University students can still catch it this afternoon -- at the lacrosse field, on the light rail, even in bed.
Or wherever they like, whenever they want, provided they have an iPod or some other digital music player.
It's called course "podcasting" -- an amalgam of "iPod" and "broadcasting" -- and Hopkins is one of dozens of universities making classroom lectures almost instantly available on personal computers and hand-held media players, of which Apple Computer's iPod is the dominant brand.
Some education experts and college officials believe that the trend could alter the college experience, from changing students' study and attendance habits to challenging the basic lecture format itself, something that has largely been fixed since the Middle Ages.
"Learning can now happen anywhere, any time," said Sarita Sanjoy, an instructional technologist at the University of Maryland, Baltimore, which is experimenting with podcasting at several of its professional schools.
There is nothing new about the recording of lectures, a practice that dates at least to the reel-to-reel tape era. And as early as the mid-1990s, colleges and universities were experimenting with letting students hear and watch recorded lectures on university Web sites.
The difference with podcasting is that students are no longer tethered to a computer or to the Internet. They can download individual lectures or "subscribe" to an entire course and have the most recent class automatically added to their iPod or other device.
Once the file is downloaded, it can be heard or watched virtually anywhere.
That sounds pretty good to John Ji.
"I'd never go to class at all," the Hopkins neuroscience major said last week, on his way to hear Richard Shingles lecture on the ecological interaction of species. "I'd just sit on the couch and download the podcast and eat potato chips."
The only reason he does show up for general biology -- one of a handful being podcast at Hopkins this semester -- is because Shingles doles out points for attendance, he said.
Those points are awarded through the use of hand-held voting machines, or "clickers," that students bring to class. Ostensibly designed to facilitate teacher-student interaction in large lectures, the clickers also function as electronic attendance monitors, Shingles acknowledges.
"If it weren't for the [clicker], I would stay at home," Ji said.
That attitude makes some professors wary of podcasting altogether.
"It seems this would remove a reason to come to class," said Hopkins philosophy professor Sean Greenberg, who said he would be unlikely to podcast his introductory course on moral philosophy. "I'm not sure we should cater to students' desire to be doing other things during class time."
Such as sleeping in.
Harvard University sophomore Justin Becker said he had no qualms about missing about half of his freshman-year life sciences lectures, knowing he could later watch video recordings of them on a university Web site.
Before exams, Becker would review back-to-back lectures at 1 1/2 times their natural speed to maximize cramming efficiency, he said. He got an A.
Though there are as yet no comprehensive studies of the new phenomenon, podcasting advocates say students such as Ji and Becker are the exception. Anecdotal evidence, observers say, shows that most students will still show up in person to downloadable classes.
"The attendance issue is usually the No. 1 thing that people are concerned about, and frankly, it's a huge debate right now," said Obadiah Greenberg, who manages the podcasting program at the University of California at Berkeley.
"Good students will use this to supplement the class. Bad students will use it as a substitute," Greenberg said. "But the fact is that overall, it is a technology that only enhances the classroom experience."
For better or worse, campus-tech trend-watcher Kenneth C. Green believes that podcasting has shown signs of taking root in a way that previous "course-casting" technologies, such as streaming video over the Web, never did.
"It's really taken off in the last year," said Green, director of the Campus Computing Project, a survey of technological trends in higher education begun in 1990. "Podcasting has really taken it to the next plateau."
The key ingredient is familiarity, said Diana Oblinger, a vice president at Educause, a nonprofit association of about 2,000 higher-education information technology professionals.
College students are comfortable downloading music from the Web and transferring it to iPods and other portable devices. And because there's no technical difference between downloading a pop song and downloading a psychology lecture, today's college-age consumers are old hands at the new technology, Oblinger said: "It's a technology that students are familiar with, and they've already got the tools they need to use it."