Why are we unable to see light except if we are looking at the light source or a source that is reflecting the light? For example; say we set up a powerful laser but we cannot see the origin or the end point. The a vacuum is produced in the room to remove all possible particles that might reflect the laser's light. We switch the laser on but we cannot see the beam of light passing from one point to the other. You cant really say that its because the particles are so small because if you take into account a lightsource like the sun, the light radiation and packets of quanta pretty much saturate anything in direct lines from the source (or anything reflecting the source). So I guess the more appropriate question is why cant we quanta in transit?