On a cold night, 6000 ft above the sea, our flashlights danced around in our tent. My numb fingers fumbled with the sleeping bag, craving its promised warmth. My tent-mate’s uneven breathing alternated with my own. For a moment her headlamp flashed on my face. I winced. “Why are we doing this again?” she asks. I laugh, thinking of the answer that mankind has been giving for ages. Because we can.