There's something about hurtling through space at incredible speeds in such absolute darkness that you cannot see a hand in front of your face, that concentrates the mind wonderfully. This is how I will end, you allow yourself to speculate briefly. No one speaks and in the silence thoughts and imagination are the only outlet.
In another situation -- an amusement park ride -- screams of delight would be issuing from the mouths of the ride participants. Even as they approach the precipice of the tunnel and know that a 200 foot drop into a pool below awaits them, they squeal with anticipation.
My thoughts turn darker and I imagine for a moment that I'm trapped in an airplane plunging towards earth at the mercy of some video game playing captain. But there are no sounds of improperly stowed luggage shifting and banging so I abandon that fantasy, with relief.
At last the subway train begins to slow as it pulls into the light of the next station. Passengers blink and exhale, collectively, and abandoned conversations resume.