Two dozen people took the stage at the Paramount Theater on Friday to explore how the world could change if people asked themselves “What if?”

That two-word question was the theme of the third annual TEDx Charlottesville, a day-long series of short talks held by a nonprofit group that puts on these events across the country.

“What if we could reinvest in communities without displacing, replacing and erasing their cores?” asked Dan Rosensweig, president of Charlottesville’s Habitat for Humanity.

Rosensweig, who is also on the city Planning Commission, spoke about the experience of converting a Charlottesville trailer park into a mixed-income community called Sunrise Court.

He said many social issues could be addressed by finding ways to get people of different incomes to live in the same communities.

“Right here in Charlottesville, we’re doing just that,” Rosensweig said, adding that the original plan for Sunrise Court was to build luxury condominiums until Habitat bought the property.

Speaker after speaker talked about how they are pushing the boundaries in fields ranging from solar system research to the future of medicine.

The head of research and development at HemoShear talked about the challenges of solving rare diseases through biotechnology.

“It’s not science fiction,” said Dr. Brian Wamhoff, describing how it is possible to replicate diseases in the laboratory to study them and attack them at the molecular level.

“This means we can cut years off the development of medicines for our patients,” said Dr. Marshall Summar, chief of genetics and metabolism at the Children’s National Medical Center.

The future of medicine also was the topic of another speaker.

“What if there were years to shave off the time it takes to develop a treatment?” asked Dr. Neal Kassell of the Focused Ultrasound Foundation, which promotes the use of ultrasound technology as an alternative to radiation and surgery.

The audience then heard from Kimberly Spletter, the first person in the country to undergo the treatment for Parkinson’s disease. She took the stage to explain how she’s been able to move again after the disease had taken away her ability to be active.

Anne Verbiscer of the University of Virginia’s astronomy department spoke about seeing Pluto up-close as part of the New Horizons team. The spacecraft took almost 10 years to travel to the dwarf planet for a one-day flyby.

“Pluto was instantly transformed into a world that we could explore, with a surface that we could never have imagined would be there,” Verbiscer said.

Other local speakers included Deirdre Enright of the Innocence Project at UVa and Maddie Walls, a freshman at Western Albemarle High School who spoke about the figurative masks people place on themselves and other people.

University of Virginia student Martese Johnson reflected on how his life changed after his controversial arrest by state Alcoholic Beverage Control agents March 18 outside Trinity Irish Pub.

Johnson, whose charges were later dropped, began his talk by describing how he saw an African-American man lying dead for hours on a street in Chicago, his hometown.

He said many of the students he grew up with are now disgruntled because of their experiences. Only five of the 30 students in an advanced program he was enrolled in at Gompers Elementary School made it to college.

“Somehow, I made it and I still have to figure out why,” Johnson said. “Eventually, I had to realize that I wasn’t special or different. I was lucky.”

Johnson followed his best friend to an advanced middle school where he said he saw male role models for the first time. He received academic training, but there were only a handful of slots to go around and other children did not have the same opportunity.

“Somehow, I made it to the University of Virginia,” Johnson said. “Upon getting to the university, I began experiencing setbacks immediately.”

Johnson said he was the only African-American student in his first-year dorm and that he experienced social barriers. He said he was told by many fellow students that they believed he was only admitted because of affirmative action. Still, he said he was dedicated to finishing and began to assimilate so that he could do so, establishing what he called his “sanctuary.”

But then came the incident when that was all shattered outside a Corner bar.

“Before having any real conversation, I was grabbed by the three ABC officers and slammed to the pavement across from my university,” Johnson said. “I realized at the moment that that sanctuary had never even existed.”

Johnson said he believes he could be treated the same way again at any time.

“We have to wake up and realize this is a prevalent issue in our society,” Johnson said. “Every child deserves a fair chance, and we have the power to give them that.”

“What if all of you stood with me today?” he asked.