How do you provide a higher education when students and professors cannot physically meet? The American ivory tower has been forced to figure that out as its denizens — and much of the world — have responded to the coronavirus pandemic by hunkering down at home. This has left really only one option: online learning. The questions to be dealt with now are whether mass online learning is sustainable, and if so, whether it should be sustained.

So far, though most professors seem to have adjusted to online video chatting platforms such as Zoom, some horror stories, like Zoom bombing, have emerged. Also, some professors uncomfortable with real‐​time presentation apps have prerecorded their lectures. On the flip side, pioneering online learning organizations have stepped up. EdX is offering free courses to universities within its partnership, and Coursera is furnishing free courses to universities inside and outside of its network.

What does history tell us about a pandemic taking online learning to a wider scale? Perhaps the closest analog to the current situation is Hurricane Katrina in 2005, which devastated New Orleans and severely disrupted about 20 colleges. The Sloan Consortium, an association of institutions supporting online education, offered free virtual classes from about 100 schools to 1,700 students to help them keep up with their studies.

Of course, Katrina was very different from the current situation. Fifteen years ago, there were relatively few options for online learning. In 2019, in contrast, 2.4 million undergraduates, or 15% of the total undergrad student body, studied entirely online, and another 3.6 million took online courses along with on‐​campus classes. Online learning is much more of a thing than it was in 2005.

The second major difference, of course, was that the effects of Katrina were limited geographically, whereas the coronavirus is a worldwide disrupter. The demand for online education is orders of magnitude greater and far fewer colleges are in positions to help their peers.

What do we know about the effectiveness of online learning? Most research suggests in‐​person instruction leads to better performance. Students who took the same course online and in‐​person at DeVry University earned an average of a C if online but B- if in‐​person. Students across the board suffered lower performance in online classes at Washington State, but males, younger students, Black students, and students with lower grade point averages especially struggled. A 2019 paper reported that online education failed to keep pace with in‐​person, especially for more at‐​risk groups such as low‐​income students.

Some research is more encouraging. Students who took an MITx physics course online learned more than lecture‐​based students. Also, a recent Gallup‐​2U survey found that graduates of 2U‐​powered online programs were just as likely as graduates from traditional universities to agree that they had professors who made them excited about learning, and that they were challenged academically. Finally, a recent study found that online STEM courses in Russia produced similar student learning outcomes to traditional in‐​person instruction at a much lower cost, though student satisfaction was lower with online courses.

A major benefit of mass migration online may be innovation that vastly improves outcomes; necessity, after all, is the mother of invention. But assuming the academic effects of online education remain worse than in‐​person, can widespread use still be a net gain, even after the major COVID-19 threat passes? Yes, because it can dramatically improve accessibility by overcoming physical distance. In 2016, more than half of all first‐​time, full‐​time, first‐​year students at four‐​year schools attended institutions 100 or fewer miles from their homes. Online education could put institutions geographically much farther away at students’ fingertips.

Second, unlike a dorm or lecture hall, there is no limit to the number of students who can fit inside a pre‐​recorded online lecture. If a course is popular, it could essentially enroll an infinite number of students. It could also give far more students access to the same teacher, reducing differences in teaching quality. And students could interact and collaborate outside of class on Zoom and chat rooms.

The ability to serve more students, coupled with a declining need for expensive‐​to‐​maintain physical campuses, could yield major cost savings down the line. As Vance Fried has noted, some online providers charge as little as $50 per credit hour, whereas the average price at a four‐​year public institution is $325 and at a four‐​year private it is $1,039.

That said, there are some clear limits to the potential reach of online education. One major bottleneck is grading, especially of involved assessments such as research papers or exams with essay questions. The lecture of one professor may be seen by millions, but a single professor can only grade so much. Another limit is that some courses must have a physical component. It is very difficult to master chemistry without a lab. Engineers need to put stuff together.

Right now, for many colleges, online learning is just a lifeline. When the pandemic subsides, should it grow beyond its pre‐​COVID level? That depends on what students demand, of course. But we may well see the quality of online college improve, and even if not, it makes higher ed accessible to far more people than brick‐​and‐​mortar schooling. So online is probably here to stay, and its expansion would almost certainly be a good thing.