They came, many said, because “Bill Nye the Science Guy” helped shape their lives. “He was probably the one who inspired me to keep going in the science career track,” said Betsy Salmon, the first person in line at one entrance to the auditorium. She majored in animal ecology.

Kaci McCleary, an “aspiring neurobiologist, or neuro-something,” said that Mr. Nye was “a very inspiring person in the field of science — he tells people to make science part of their lives, even if it’s not their career.” Ms. McCleary, who knitted as she waited to be let in, said a friend had joked to her, “I hope to be able to touch the hem of his lab coat, so he could cure me of my stupid.”

Mr. Nye did not disappoint. In a lecture that gave evidence of his stand-up roots, he started out with rambling asides on his his family and its generations-long fascination with sundials. He talked about the bluish tinge of shadows on Earth compared with the orangy shadows on Mars, and described the sundial that he convinced NASA to send up with the Curiosity rover. He got a little risqué with a joke about the gnomon — the part of the sundial that sticks up, you know — and bounced into a discussion of the hellish heat of Venus and that planet’s high concentration of greenhouse gases.

He told the students that if they figured out ways to solve problems like greenhouse gases and global warming, “You could — dare I say it? — change the world!” And what’s more, he added, throwing his head back for a hearty mad-scientist laugh, “you could get rich!”

Over the hour-and-a-half talk, those statements started out as a laugh line that got funnier through increasingly manic repetition. But he shifted his tone gradually, from goofy to fervent. By the end of his speech, it was an exhortation, a command: Change the world.

During the question-and-answer session, a student brought up Mr. Nye’s comments on evolution and creation. The problem, he explained, is that some people advocate requiring public schools to teach religious apologia as science.

“The earth’s not 4,000, 6,000, 10,000 years old,” he said. “I’ve got no problem with anybody’s religion. But if you go claiming the earth is only 10,000 years old, that’s just wrong.”

The students roared their approval. As the audience streamed out — did those dudes really rip off their shirts to show that they had painted, in all capital letters, “Bill Nye” on their chests and “science” on their backs? — Mr. Nye looked like someone who had just run a triathlon. And then it was time for more pictures.

Earlier in the day, he had marveled at the chain of events that made him the Springsteen of the nerds. “I was making a TV show. It had commercials for toys.” Yet, he noted, “It stands the test of time. It’s very gratifying.”

What he did then, and what he does now, are all part of the same crusade, he said. “There’s nothing I believe in more strongly than getting young people interested in science and engineering,” he said — “for a better tomorrow, for all humankind.”

He stopped, realizing that sounded grandiose, or at least corny.

“I’m not kidding,” he said.

(http://www.autoadmit.com/thread.php?thread_id=2285364&forum_id=2#23422316)