If you could see trails of light left behind by the photons that are crisscrossing the room in front of you right now, they would be heading in all directions, constantly passing through each other without noticeable effect In that one room (or for that matter in your backyard if you're reading this outside) there will be visible light heading in all directions as it reflects from objects all around you.
And with all that light, somebody sees you.
I happened to be reading Brian Clegg's book while I was sitting on the back porch overlooking the backyard. Clegg saw me in his imagination. And, for a moment, it was weird, I felt I was being observed.
source: Before the Big Bang: the prehistory of our universe by Brian Clegg