What makes a question active?
I realized that some questions are bounced to the top, as if they were posted just now. I thought this would occur whenever a new answer is posted, but somehow this is not true.
Questions are bumped when they are Answered, when the question or any of it's answers are Edited, or when a Bounty is offered.
Additionally, the Community user bot will periodically bump questions with no upvoted answers.
Also take note that question won't be 'bounced back' if you're on the newest questions tab.