From the Great Pyramids and the Sydney Opera House, people, institutions and landmarks around the globe powered down from 8:30 to 9:30 local time Saturday night in order to raise awareness about the benefits of energy conservation and the issue of climate change.

The annual event, which was started in Sydney in 2007, has now spread to a number of U.S. college campuses — including, as of last year, Yale.

The Yale Student Environmental Coalition, the Student Taskforce for Environmental Partnership and the Yale College Council held myriad activities to entice students out of their darkened dorm rooms. But the lights gleaming from dorm windows, Payne Whitney Gymnasium and Linsley-Chittenden Hall during this year’s Earth Hour suggested that the level of participation was only mediocre.

About 15 students gathered in the Branford common room for ice cream and a screening of “Planet Earth.” Most students said, however, that the main draw was the free dessert.

David Sydlik ’10, one of the attendees, said he planned to return to his room and work on his computer with the lights out — but admitted that, since he would have to plug it in to use it, this would negate the effects of turning off his lights.

Ezra Stiles, Morse and Calhoun colleges banded together around a makeshift campfire of candles in paper cups. The group of about 30 tossed around a glow-in-the-dark Frisbee and sang original songs about global warming composed by Laura Zax ’11 (“The world is melting, kids will have to swim to school”).

YCC member Sarah Selem ’11 said while she did not know whether Earth Hour would directly impact the problem of energy waste, it does promote awareness.

“There’s obviously an energy crisis in a world where there’s a growing population with limited resources, so we should definitely promote conservation,” she said. “Anything we can do is great.”

Bianca Rolon ’11, who was playing Uno with a group of friends at the campfire gathering held behind Morse and Stiles, said she was planning to do homework, but when she heard about the event she decided it would be a nice study break.

Trumbull College hosted an study break with S’mores in the college’s buttery during Earth Hour. Davenport and Pierson colleges organized a game of ultimate Frisbee; players sported flashing blue necklaces in order to avoid painful run-ins with one another in the courtyard.

This year’s Earth Hour was also the kick-off event to the astronomy department’s celebration of the International Year of Astronomy, being held in honor of the 400th anniversary of Galileo Galilei’s first use of the telescope.

The Astronomy Department took advantage of the coincidence of the two events to raise public awareness about the negative impact of light pollution on astronomical observing by inviting the public to use its telescopes and take advantage of the unusually darkened sky Saturday night.

In an e-mail, astronomy professor Michael Faison said he was amazed at the degree to which light pollution is an American problem.

“Energy conservation is second nature in most other countries,” he said. “For example, if you use a public restroom in Europe, the lights are almost always on timers or at least motion sensors.”

According to its Web site, over 4,000 cities and towns in 88 countries — which includes hundreds of millions of people — participated in Earth Hour 2008.