Understand the concept of time dilation using the relativistic time dilation formula.
1. If one has two clocks at "infinity" and makes sure they run the equal, and after that lets one fall, what speed will the falling one have as it reaches the ground relative to the one at infinity?
2. Utilize those results to estimate how much slower a clock goes near the earth than one, which is higher up. (Put in the speed from question 1 into the special relativistic time dilation formula. I use the word "estimate" since the true answer is in fact a little different, but to get that would take much more math than we want to use here!)