Odds are that Andrei D. Sakharov won't soon be delineating the intricacies of pi-mesons, quarks or even Soviet repression against maverick scientists to bleary-eyed Harvard students in Science Center C.

But the unlikelihood of Kremlin powers reversing their decision to place the prominent physicist and dissident in internal exile didn't deter the Physics Department from inviting Sakharov to spend a semester here as a Loeb Lecturer.

"I don't think anyone feels this invitation in itself will have any effect," one Physics professor said, "but we hope it is a gesture of support which he might welcome."

One of the scientists who helped develop the hydrogen bomb for the Soviet Union, Sakharov broke with his country's policies in the '60s and won the Nobel Peace Prize in 1975 for his human rights efforts. Another Nobel laureate, Sheldon L. Glashow, professor of Physics, said yesterday, "I hope the Russians realize they stepped on a lot of toes when they put this man in Gorky."

Glashow, who met Sakharov at a 1974 scientific conference in Moscow, called the invitation a "risky gesture" because Harvard may become a university non grata to Soviet leaders. In retaliation, he said, the Soviets will probably not permit their scientists to visit or work with Harvard academics.

However, that possibility won't be tested until the U.S. Soviet political climate allows full scientific exchanges to resume.

For the moment, scientists at Harvard said this week, official exchanges have dropped off sharply

But personal contacts with scientists--many of whom support Sakharov--will continue. "It's important to keept a line of communication open," commented Richard Wilson, professor of Physics. "While you're talking, you can't drop bombs."