Rather than starting with a monologue full of scientific jargon Tuesday evening, noted astrophysicist Neil deGrasse Tyson - the man once named People magazine's "Sexiest Astrophysicist Alive" - began by posting to his Twitter feed.
"You can play baseball on the airless Moon, but only if you find a way not to suffocate & if you don't care about curve balls," he tweeted in front of a packed crowd of hundreds.
Tyson, a Harvard University alumnus and the director of the Hayden Planetarium in New York, then gave what he called a "cosmic update," discussing advances in space research.
Tyson talked about how scientists are interested in other celestial objects that have ice -- such as Mars and Jupiter's moon Europa -- to learn about the possibility of life outside of Earth.
But he criticized Hollywood for being unimaginative about what aliens would look like, complaining that movie aliens have similar features to humans.
"If you were a jellyfish looking at a human and ET, you would not be able to tell us apart," he said.
Tyson also told the audience about an asteroid that is expected to get close to Earth in 2029 and has a one in 300,000 chance of crashing into the Pacific Ocean in 2036. Scientists have created a plan to deflect the asteroid's orbit, he said.
Americans have fears about science and numbers, he said. Tyson criticized the notion that the world will end in 2012 due to a Mayan prediction by noting that the Mayan civilization was destroyed.
"If they had prognosticating abilities, they should have seen that coming," he said.
Earlier in the day, Tyson had lunch with Chattanooga State Community Collegefaculty members and held a question-and-answer session with students where he mainly discussed science literacy, said Phyllis Mescon with Chattanooga State student affairs.
At the end of his presentation, Tyson noted that the United States is producing fewer scientific papers than it has in the past.
"All the sciences need support," he said.
After he spoke, he allotted about half an hour to a question-and-answer session.
When an 8-year-old girl approached a microphone, Tyson asked her if her teachers called Pluto a planet.
"They said that Pluto was a dwarf planet," the girl responded.
The answer pleased Tyson, who has been a leading supporter of the notion that Pluto is not a planet.
The crowd gave Tyson a standing ovation before and after he spoke. After the question-and-answer session, a long line of people waited to get Tyson's autograph.
Sarah Wood, 22, came to see Tyson from Knoxville, where she is a physics major at the University of Tennessee.
"It was awesome," she said. "He was nerdy as his pictures show him to be and I love it."