A Wandering Rainbow

I found a heavy glass tumbler resting right where the bright sun hits the windowsill. I paused first, tilting sideways to see if the shimmer was moving on its own? When I leaned my shoulder against the smooth glass to give it a gentle nudge, a tiny curved rainbow jumped across the white paint. It flickered right beside my feet like a quiet little star. We stood together for a long time, watching the colors stay completely still.