Timeline: You control this. Periodically answer questions throughout the year.
On the first day I hand out a 3×5 card to every student and ask them to write their name on the card and the ask me three questions on any topic and give them 5 minutes to think and write them down. As they think I encourage them to ask anything they’ve ever been curious about. Why the sky is blue? What is the 53rd digit of Pi? I let them know that I will not mention who asked which questions so don’t be embarrassed. Some students don’t engage and ask silly questions. Some try to stump me. Some students ask incredibly insightful questions. I use the questions to fill gaps that come in scheduling. When the lesson ends 5 minutes early my class wants me to answer more questions. Students really enjoy this activity.