Robert Hazen, experimental mineralogist George Mason University and Carnegie Institution of Washington
In our recent book, Why Aren't Black Holes Black?, Maxine Singer and I discuss 14 great unanswered questions that challenge scientists today. My top five unanswered questions are:
Extraterrestrial life: Are we alone?
Development: How do we develop from a single cell?
The Brain: What are the physical origins of memory?
Origins: How did life arise?
Environment: How many people can Earth sustain?
Each of these questions is the subject of intense research today, and probably still will be 25 years from now. But it is equally likely that the most exciting scientific question in 25 years will be something that no one has yet imagined. We can only ask questions about what we know we don't know, but many of the most exciting scientific discoveries reveal new unexpected objects or phenomena. Fifty years ago no one could have predicted quasars, plate tectonics, homeoboxes, lasers . . . the list goes on and on. The most exciting part of the scientific adventure will continue to be the discovery of things we didn't know we didn't know.