Alan Alda is back at it, challenging the scientific community to answer what some would say are simple questions. But, are they?

The 79-year-old actor has been challenging scientists to answer questions that would satisfy an 11-year-old child since 2011.

This year, Alan Alda is asking the question: What is sound?

Known as the “Flame Challenge” contest, which offers a $1,000 prize, the challenge asks scientists to explain complicated concepts in ways young people can understand.

Alan Alda issues latest science challenge https://t.co/IEl0yUOpaJ pic.twitter.com/cjL1wbgJql

— Gulf News (@gulf_news) November 4, 2015

“I came up with this contest as a fun challenge for scientists to explain a complex thing like a flame in a way that would make it clear to an 11-year-old,” Alda said in a statement. “The idea was to urge scientists to communicate more clearly. I didn’t realize what an extraordinary learning experience it was going to be for the 11-year-olds. By now, tens of thousands of kids from all over the world have excitedly delved into the mysteries of nature as they’ve judged the scientists’ entries.

“There are so many ways in which sounds affect us, so many ways that different animals use sound, and so many kinds of sound,” Alda said. “I can’t wait to see how creatively scientists will explain exactly what sound is. The kids and I are all ears.”

This year’s challenge was announced by Long Island’s Stony Brook University on Monday. The actor currently teaches at the Alan Alda Center for Communicating Science at the school.

In years past, Alan Alda asked scientists to explain time, color, and of course, what is a flame.

.@alanalda's Challenge: Can you Explain Sound to an 11-Year-Old? https://t.co/ZpYlwI9RZz pic.twitter.com/raBKl7EqQY

— Live Science (@LiveScience) November 3, 2015

The Flame Challenge is sponsored by the American Chemical Society (ACS) and the AAAS.

“The ingenuity of the Flame Challenge is that participating students bring a new source of creativity and take away the lesson that science is fun,” said 2016 ACS President Donna Nelson in a statement.

Keziah Job, an 11-year-old sixth grade student from Lynbrook South Middle School in Lynbrook, New York, was one of the students who came up with this year’s question.

“I hope that they tell me what sound is,” said Keziah, when asked what she hopes the contest’s scientists will tell her about her question. “I’m speaking and I want to know what makes up the sound.”

Scientists have until Jan. 19 to submit entries in either written or video form. Eleven-year-olds will judge the entries.

Do you think Alan Alda‘s question is a good one for this year’s Flame Challenge?