I'm realizing that it's quite common here at TED to go from 'glass half full' to 'waiter, my glass is empty!' in just a matter of minutes. As you might imagine, this afternoon's panel on 'What Will Tomorrow Bring?' was no exception.

Peter Schwartz is possibly the most optimistic person to ever take the mike at a TED event, which is largely filled with hopeful, if not completely optimistic, people. It's a good thing, then, that his job is as a professional futurist.

I won't begin to guess how one becomes a futurist, but what he had to say will help me sleep like a baby tonight. There are four big questions that we want answered about what the world holds for us in the next 50 years:

Will there big a big world war?
Will the global economic growth continue?
Will the fruits of that growth be evenly spread?
Can we achieve that growth in an ecologically sustainable manner?

According to Schwartz, the answer to each of these questions is a resounding YES. So, stop worrying.

But next up was Gregory Petsko, a biochemistry professor at Brandeis University, who had just three minutes to convince us that by 2050 the world will experience an epidemic of neurological diseases as the population ages. Took the air right out of my bubble, anyway.

Perhaps these two should square off in some sort of optimism debate.

Finally, Walter Isaacson, the former Time magazine editor who is now a biographer and the chief executive of the Aspen Institute, gave a talk on the future of the narrative.

The web hasn't changed much about our content, he suggested. We've just been putting old wine in new bottles. Even blogs like HuffPost and sites like YouTube are still just providing a new way to deliver the old stuff (written stories, video).

Which is why he's decided his next book will be "one of the first books for the electronic age." Taking a page from the wiki model, it will be published online in some format, and will be available for anyone to edit, enhance, or destroy as they wish. They can share with friends and republish it as they wish. It will be fully collaborative and interactive. This new type of book will be "always evolving and improving."

It's a fun concept, but it's unlikely that any publishing house will be jumping to sign Isaacson for his new venture. "I'm not sure what the business model will be," he admitted.

By Megan Barnett