When Purdue University senior Marcos Kohler skipped a physics class to attend a concert in Chicago, he didn't have to borrow a classmate's notes to catch up.
Instead, he connected his iPod to a computer, downloaded the lecture, and from the comfort of a campus coffee shop, listened to the two-hour discussion on particle physics.
"It re-creates the entire class experience," said Kohler, 22, who missed another lecture at the West Lafayette, Ind., campus when he overslept for the 1:30 p.m. class. A video conference class would be even better, he said, but "to go from paper printouts to audio, this is a step in the right direction."
It's a step that a small but growing number of professors are trying. By turning class lectures into podcasts--free audio recordings that students can download to their iPods or other portable players--students can skip the lecture hall but still hear the lecture. Supporters say podcasts help students who miss a class or want to review the material, while professors get points for being flexible and using the latest, hippest gadget.
More traditional academics fear that by listening to lectures on the run, students will miss out on learning that can happen only when students and instructors come together.
Professors have posted lecture notes, PowerPoint slides and other written class material online for years, but instructors only recently began testing the best uses of the popular audio technology.
At Drexel University in Philadelphia, a chemistry professor assigns podcasted lectures, recorded last semester, for homework, then uses class time to review problems. At the University of Michigan, lectures can be automatically delivered to dentistry students' computers or portable devices.
And at the University of Hawaii, hundreds of students in a computer science class are required to show up at a lecture hall only twice a semester--for the midterm and final. Instead of a textbook, they buy a small iPod at the bookstore, though most students already have one, the course professor said.
Universities have found other ways to test podcasting, using it to publicize campus news and broadcast Sunday mass.
A newscast about coming events at Allegheny College begins: "Sit back, relax, enjoy. If you're in the car, drive safely while you listen. If you're at the gym ... stay focused on what you're doing and be safe."
The California Institute of Technology admissions office last week released an 11-minute podcast for prospective students that leaves listeners with the impression that the school is nerdy, in a hip kind of way.
Rick Bischoff, admissions director at Caltech, said a podcast is a perfect way to grab the attention of busy high school seniors.
"I want high school students to listen and imagine, `That is a community I want to be part of.' Or say, `That doesn't sound like any place that I want to be a part of.'"
Some universities, such as Purdue and North Carolina's Duke University, have university-wide programs that make it easy for professors to podcast.
Purdue this fall introduced a podcasting service called BoilerCast that records and downloads lectures to the school Web site at professors' requests. About 60 professors are using the service, and their students can access the lectures as soon as 10 minutes after class.
Since Aug. 22, when the program began, the Web site has had more than 34,000 downloads, said Michael Gay, Purdue's manager of broadcast networks and services.
Erica Carlson, one professor podcasting her lectures, said attendance in her 22-student seminar class on thermal and statistical physics has not declined.
Carlson downloads her lectures to iTunes as well as the Purdue site. After she was featured on the home page of the iTunes Web site, the number of subscribers to her podcast shot up to 750 from 100. A history major e-mailed to say he enjoyed her lectures, as did an engineer who graduated from college years ago.
"When I saw the subscribership shoot up to 750, I started getting nervous. I love an audience, but an audience of 750 that I can't read or get feedback from is intimidating," Carlson said.
Her two-hour class hasn't changed, she said.
"We run the course just like we did before. Just now it is more accessible."
Duke University professor Richard Lucic, who has 27 students in an introductory computer science course, podcasts lectures and also requires students to listen to independent podcasts related to class topics.
The easy availability of his lectures hasn't affected attendance, he said, probably because class participation counts for 15 percent of a student's grade.
Meredith Tenison, a Duke senior in Lucic's class, has missed only one class but still downloads and listens to the lectures before writing weekly papers and putting together presentations required for the course.
"If there is a gap in my notes, I go back to get the context," said Tenison, who also listens to podcasts about wine, South Africa and Duke basketball. "You can be doing your laundry or doing your homework. It's amazing how efficient you can be with your time."
But Naomi Baron, an American University linguistics professor, said podcasting lectures makes it too easy for students to cut class or mentally check out. It also condones the idea that a student can learn just as well by listening to a lecture on a couch as in a classroom.
"I want to believe that what I'm doing in class is not canned and has something to do with the people who are there," said Baron, an expert in language and computer technology.
Tenison's mother, who is paying for her daughter's education, also said she doesn't see a podcast as a substitute for class.
"I would be rather upset with that," said Elizabeth Tenison, who said she isn't worried about her daughter skipping class. "Part of going to a university is hearing alternate points of view ... and that would be lost in large part if students didn't attend. They would hear it, but they wouldn't be participating."
For the 600 students in David Nickles' two computer science classes at the University of Hawaii, there are no traditional lectures. Nickles records lectures from his office and students listen to them on the bus, on the beach, in dorm rooms.
In his orientation podcast, after an intro drumbeat, he explains the unconventional style.
"We will be taking lecture out of the lecture hall and putting it into your pocket," he said. "This approach will open up your schedule in that you will have the lecture with you all the time. When you have time to listen to lecture, you listen to it."
In a throwback to the old ways, he shows up at a lecture hall once a week to hold optional review sessions.
About half the students join him -- for extra credit.