My favorite school test question came from my high school history teacher (waves at PVO) who asked us to describe how the colonization of America would have changed if the Pilgrims had landed in California instead. I loved this question. It really made me think about the things we had learned about the early settlers -- their need for fresh water, the Indian tribes they encountered, the climate and physical conditions they endured. Among other things, I remember writing that the Rocky Mountains would have posed a formidable challenge for those early explorers.
This is a fun exercise. Take any widely held assumption and ask yourself, what if it weren't true? Keeping this in the realm of science:
What if people walked on their heads instead of their feet? How would the design of cars be different? How would the circulatory system have adapted?
What if the sky were green instead of blue? Would the rest of the world look different? How? Would chlorophyll still be useful?
What if the earth was colder at the equator and hotter at the poles? What would have to change for this to occur? Is it physically possible?
One thing I like about this exercise is that everyone gets a chance to answer. Since it's all theoretical, we're just making some best guesses here. And that gives everyone a chance to play.
Which makes me wonder ... What questions are you thinking up right now?