picking-up the light

It is mostly dark on my car-trip to work each morning. On this particular morning I was slowing for a traffic light when I saw something on my car seat. It was a small area of light. I thought that perhaps it was a small piece of paper from my pocket the previous day. As I stopped at the signal I reached over to pick up the paper. I tried to get it twice before I realized it was a spot of light. I then heard a small voice whisper to me:
“You can’t pick-up the light by physical means.”