When NASA climate scientist James Hansen spoke up about climate change in the 1980s, he risked the loss of his job & reputation. But, he says, it was worth it -- because he could not be silent about something so important.

Social psychologist Adam Galinsky studies why it's so daunting to speak up -- and what can help. He says the most powerful factor that compels us to take that risk is "moral conviction."

Clint Smith is a poet and doctoral candidate at Harvard. As a high school English teacher, he taught his students the dangers of staying quiet and the importance of finding their voice.

After 9/11, Dalia Mogahed saw an increase in negative perceptions of Muslims in the media, so she made it her job to speak up for her faith and fight prejudice with better understanding.