China , the world’s most populous nation, already is an economic and military force to be reckoned with. But this may well be the Chinese century. Over the next few decades, China is poised to become a global superpower on a par with—or perhaps even surpassing—the United States . At the same time, it must struggle with societal and political change. Join in the discussion of China ’s rise and what it will mean to the rest of the world.

Tell us what you think about the subject and discuss how the problems can be solved.

35 years after President Nixon declared a federal "war on cancer," we're still struggling with the nation's second-biggest killer. What are the latest developments in prevention and treatment? How have attitudes about cancer evolved? Join in the discussion.

Since September 11, 2001 the U.S. has been locked in a war against Islamic extremists that may go on for decades. Who's winning, and at what cost? Are the Bush Administration's strategy and tactics correct or misguided? Offer your opinions here.

If you're an American you live in one of the most powerful, prosperous countries on earth. What does that mean to you? What's it like to be an American in the 21st century?

What's it like to view America from outside its borders? How does our foreign policy affect the rest of the world? Weigh in here.

This IS Discovery after all, so let's get our hands dirty. Are you concerned about the state of the environment? Have you taken steps to reduce your impact? Be part of the discussion -- and solution -- here.

What do you think of Koppel on Discovery? What topics would you like to see covered? What ignites your interest in a particular issue?