Two guys cross the playing field in the half-dark, heading for the train station. Bishop Markham Village glows amber from the night-lights on South Street, and there’s nothing moving on Summer Street, where the houses face the park like homesteads on the edge of their fields. The big tree-less bowl and floor of the Common opens upwards to the sky, offering a clear shot to the constellations. Walking there, I sometimes think of the scene in the classic science-fiction movie “The Day the Earth Stood Still,” with the silver saucer ship scattering ballplayers and picknikers as it descends and lands on a vast lawn in the middle of Washington, D.C.  The sky seems to come right down to the ground in a wide open space like this. With the sun slightly chinning the eastern horizon, the tall pines circling the Common are substantial black shapes, their conical look like the top part of the electric green Christmas tree strung from the giant smokestack at Wannalancit Mills, visible beyond the roof lines to the north.