Cantabrigians who turned their eyes skyward on Friday and Sunday were treated to a laser light show courtesy of the summer school.

From the eighth floor of the science center, members of a summer school class entitled Visu S177, "Lasers in Art, Design and Architecture" aimed a laser beam at the dome of Eliot House on both nights, and on Sunday they held a full-fledged show on the side of William James Hall.

The show served as the final exam for the class, according to Paul Earls, and MIT professor who teaches the summer school course.

"All of the work on William James was work the students actually did," Earls said. "[The purpose was] to give students an experience with working with professional equipment."

Earls said he did not publicize the show because he wanted to avoid making the students nervous about their laser show debut.

"I didn't want to put that pressure on the students," he said. "I wanted it to be a surprise."

"Our instructor decided he would just do it, and kind of be mysterious," said John H. Jones, one of the class' seven students.

And the dazzling display did stun a few passerby. Jones said he overheard several people hypothesizing on the cause of the eerie light when he went walking in the Square on Sunday night. "I heard some alien comments," he said.

Jones said that the weekend drizzle added a special, unexpected effect. "The laser beam hitting the drops of water made it look like it was sparkling," he said. He said the element of surprise was crucial to the overall effect of the show.