What we would like to prove:

You can't jump higher than Rollins Chapel

What we can actually prove:

If you're loaded with a heavy backpack, then you can't jump higher than the Empire State Building

Why is it so hard to prove that something can't be done? What are the challenges involved in proving such lower bounds? Find out this Spring, in CS 85/185: "You Can't Do That: Lower Bounds in Computer Science". Maybe you will be inspired to solve something that has vexed computer scientists for decades, and will become rich and famous! Details at www.cs.dartmouth.edu/~cs85.