Why do stars shine? The man across the table at breakfast, heaping great gobs of grape jelly onto his bread, is the man who provided humankind with the answer.

Hans Albrecht Bethe is now 75 and not only active but impatient when asked to talk about his days during the disastrous German inflation of 1923, about his getting away from the Nazis in 1933, or about his regret over helping to build the hydrogen bomb. Through his good-humored smile he says, "Let's not spend too much time on ancient history. I'm still working, you know."

But since the shining of our local star provides the Earth with virtually all its energy Bethe's current work on America's energy troubles still does not stray far from his famous problem, and the solution that gave him the Nobel Prize.

Bethe is in Washington for a party in his honor given by the Americans for Energy Independence.

His newest career began before the oil embargo of 1973. The year before, he had gone out to buy gas for his car several times and found the pumps dry.

The experience recalled his childhood in Germany, and his concern and intensity about energy problems come partly from the sense of just how bad things can get.

When the economic disaster in Germany reached bottom in fall of 1923, economy had forced Bethe's school to close in the mornings. So he was given a family job.

"You could count on inflation doubling every day, which is almost inconceivable," Bethe said. It amounts to a little less than five percent an hour. His father got paid every three days, with the amount adjusted for the inflation since the last check, to help preserve the value of the marks. But to wait a day or two to spend the money would have almost canceled its value.

"The critical time was 1 o'clock. My job was collecting my father's money and spending it before 1 o'clock," he said. At 1, "all stores would close for one hour, and when they opened again everything was twice as expensive. If I missed 1 o'clock, then we couldn't eat, or at least only half of what we needed."

Bethe's mother and grandparents were Jewish, so by 1933 a job in the public university was no longer open to him, and there were no private universities in Germany.

So Bethe chose to leave, via England, for Cornell University. He arrived in 1935 and discovered that the physics department was much in need of help, especially in sorting out the meaning of experiments. He then created an extraordinary document, later called "Bethe's bible," which reviewed the entire state of man's knowledge of nuclear physics.

The review made him one of America's greatest scientific resources, even before he began to think about things beyond Earth. Then in 1938, he says, two friends, Edward Teller and George Gamow, told Bethe they were bored with the topic for their annual Carnegie Institution meeting on theoretical physics in Washington.

So they changed the subject to the stars, Bethe says as he scoops egg between bread and fork.

There was a sense among astrophysicists that what ran the furnace stars might have something to do with nuclear reactions of some kind. But they did not know what.

It took Bethe about six weeks of work. The answer came, he says, rather easily. For stars like the sun, the chief reaction was between two hydrogen atoms. When their nuclei collide under the pressures and temperatures in the sun, they fuse, and in the process of the collision, some matter is annihilated.

Einstein's E=mc2 says annihilated matter squirts out as energy. In this case, what comes out is starshine.

It is not surprising that Bethe, who has lived intimately with particles and their reactions, should like the notion of nuclear power. "It is beautiful," he says, "and it is still a little cheaper than coal." He realizes that since no nuclear plants have been ordered in recent years, there may be no nuclear future.

Unexpectedly, he is not much interested in solar power. It is simply not practical for anything but small uses at the moment, he says.

After walking outside in the sun to have his picture taken, Bethe remarked that the light falling on us as we stood there was rather old.

"About 10 million years," he said. It takes that long for a particle of light created in the center of the sun to make its way out through the dense matter to the surface of the sun. Then, it is an eight-minute leap down to our faces as we gaze out at the fumes from the cars on Connecticut Avenue.

At the party for Bethe last night in the new building of the Library of Congress there was talk of his years of work on disarmament and of his mountain climbing, which he still enjoys despite his age. Guests included Sen. Spark Matsunaga (D-Hawaii), Rep. Melvin Price (D-Ill.), Danny Boggs, senior policy adviser for natural resources in the White House, Nunzio Palladino, chairman of the Nuclear Regulatory Commission, and students and friends.

Ralph Lapp, physicist and nuclear consultant, recalled one evening with Bethe many years ago. "I said, well, you are the first man to work out the elemental energy source of the universe. How do you feel?" Bethe replied that when he was finished with the weeks of calculation necessary to do the job, he wondered why no one had done it before.

After food, drinks, several little speeches and notes from the president and other notables were read, Bethe spoke briefly to the assembled. "The main danger, I suppose, is that I might believe all the things you have said about me. I assure you I believe less than half of it."