Why Soccer Players Are Training in the Dark

I stand in the darkened silence of a rectangular chamber, 8 meters long and 6 meters wide, balanced on the tips of my toes. On the wall in front of me are the outlines of two circles. Beyond these walls is an enormous insulated hangar decked with artificial grass and filled with highly paid professional soccer players. I brace, as though waiting for the Death Star to ready its superlaser. I turn, and it takes another two touches before I've brought the ball fully under my control. A professional player would have managed it in one, and would have done so without making a sound.