Between 2 and 4 p.m., Sever 113 was supposed to host students shopping Government 1093: “Ethics, Biotechnology, and the Future of Human Nature.” But by 3:30 p.m., Sever 113 was empty. Three words were written in chalk on the blackboard: “Go to Sanders.”

Government 1093 was one of many unexpectedly crowded courses that attracted students on the first day of shopping period on Monday.

Madison L. Coveno ’14 was shopping the class for a friend whose flight was delayed. When Coveno went to Sever 113, she found a “ridiculously crowded” classroom.

“I overheard someone saying something along the lines of, ‘I thought I had found a hidden gem, but it looks like a lot of people felt the same way,’” Coveno said.

Kerstin Haase, one of six teaching fellows for the class, said that when students started piling into Sever, they spilled out of the corridors into Tercentenary Theater.

“People were sort of pouring out of the room. That’s how crowded it was,” Haase said. “One you left the room, it was sort of hard to get back in.”

While Haase estimated the number of students to be around 600, Julia Kete ’13, a Crimson magazine writer, estimated slightly less than 1,000.

After twenty minutes, during which government professor Michael J. Sandel and stem cell and regenerative biology professor Douglas A. Melton made phone calls to explore the possibility of changing rooms, the class was moved to Sanders Theater.

The professors said they will try to reserve Sanders Theatre and recruit more teaching fellows in an effort to accommodate all the students who want to take the course.

Several other courses suffered from overcrowding. Jeremy Ying ’13 left Societies of the World 24: “Global Health Challenges: Complexities of Evidence-Based Policy” after five minutes because he decided it wasn’t worth it to stand by the door, where he couldn’t see the class slides.

Public health professor Sue J. Goldie estimated that 350 to 400 students attended the lecture, packing the stairs, floor, and outside hallway.

“It seems popular because it is an interesting, relevant topic, and Professor Goldie is really enthusiastic and gives the class great energy,” wrote Peter Grogan ’15 in an email to the Crimson. “The class is done by lottery, which is disappointing to some degree because as a freshman it will be hard for me to get in, but I understand the system.”

Although not nearly as crowded as Government 1093 or Societies of the World 24, Science of the Physical Universe 22: “The Unity of Science: From the Big Bang to the Brontosaurus and Beyond” provided a light-hearted option for 70 to 100 shoppers. University Professor Irwin Shapiro’s lecture, which included the use of a blowtorch, a magician’s hat, and a wand, was followed by a round of applause—a first for Shapiro.

“That was a shock to me, I must say. It was nice,” Shapiro said. “I like to inject humor when it’s appropriate...but I don’t have any more top hats.”

—Staff writer Gina K. Hackett can be reached at ghackett@college.harvard.edu.