So they’re protesting their future selves?

CAMBRIDGE — Harvard University locked the gates to its storied yard tonight to prevent protesters, including students, from erecting tents as part of the national Occupy movement.

University officials said at 9:20 p.m. they planned to allow students with identification cards back into the yard soon, but were concerned about a possible uprising from protesters not affiliated with Harvard. Some had appeared at a rally at Harvard Law School earlier in the evening.

After that rally, several hundred students and other protesters found themselves temporarily locked out of the yard. They chanted and waved signs as flashbulbs went off. Police closed a gate the protestors were trying to open, provoking cries of ‘‘let them in’’ and ‘‘the whole world is watching.’’

Harvard University Police briefly detained one demonstrator, Jeff Bridges, who yelled, ‘‘I’m a student!’’ Bridges, a third-year divinity student, said he had pushed his way in, waving his ID.

‘‘I think what they’re doing is wrong and immoral, and as a divinity student I should know,’’ he said. Police allowed him to stay inside.

Harvard students met repeatedly — sometimes for three or four hours at a time — in recent weeks to hatch their plan to occupy the university’s yard. A rotating group of undergraduates and graduate students had planned to reside in the tents for days, leaving at intervals for class or visits with family and friends. They are calling on the university to amend its investment practices and to negotiate a new contract with custodial workers.