Different times of sunset at the same location due to elevation Me and my friend were watching the sunset on the same location (at my country the latitude is approximately 40 degrees). I am at sea level and my friend is at an elevation. He observed the sunset with a difference of about 4 minutes than me. He is a physicist so he challenged me to find out his elevation. Any ideas on how to use these information and win the challenge? 
I found some information on Wikipedia here but cannot understand a lot.
Any idea on how to solve this will be appreciated. Thanks in advance for your help.
The page you refer to is about sunrise/sunset throughout the year, but what you really care about is differences in the geometry on one day. This is sometimes expressed as different observers seeing the horizon at different distances, or sometimes as an angle, a “dip” of the horizon when seen from higher altitude.  Thinking about that geometry should get you started on working out the answer.