|
 previous / next column
A PHYSICIST WRITES . . .
(April 2003)
When you are watching TV, do you ever think what a miracle of technology it is, allowing you to see pictures from around the world without leaving your chair? Indeed so, but it’s nothing compared with the ‘natural’ technology that is at work in your brain, enabling you to view and understand the TV picture — together with everything else around you.
Just compensating for the optical irregularities in your eyes is a big enough task for the brain! Normally you do not notice that your sight is rather fuzzy everywhere except at the centre of your gaze, where it is sharp (if you are lucky). Very probably you are unaware that each eye has a blind spot, not far from the centre of view.
Certainly you are not conscious that this page is being projected by a lens onto the back surface of the eye (the retina) upside-down, as in a camera, in order that your brain can read the words. Nor can you tell that the whole scene in front of you is actually highly distorted in this picture on the retina, because of the curvature of the eyeball.
Somehow the brain manages to disguise all these peculiarities, so that you get the firm impression that you are simply looking out directly at your surroundings as if through a single open window (not even through two separate eyes!). The truth could hardly be more different — but it will have to wait until another time. Meanwhile, what is the message in this for drivers?
At the wheel your gaze tends to be attracted along the road into the distance, perhaps because this is the most restful part of the scene to look at. This line of sight probably also helps you to steer the most accurate course. But many hazards — not to mention signs — appear at the side of the road, where your view will be indistinct if you are gazing ahead. To demonstrate this to yourself, try focusing on one WORD and notice how few other words around it you can see clearly at the same time.
And then there is the effect of the blind spot I mentioned, in each eye: hold your right hand spread out (palm towards you) at about arm’s length, look hard at the thumb, then cover your right eye with your left hand (or else just close it), and you will lose sight of at least part of a finger. You rely totally on your right eye to detect anything appearing in this particular direction — perhaps a dog wandering at the roadside — and similarly on the right eye, for things on the left.
Hence the advice that we are given as advanced drivers: keep sweeping your gaze from side to side, just as you might do when not concentrating on a task. Then there is a good chance that you will see that dog clearly and in good time, instead of as a blur, or not at all. Don’t be blind to Spot!
Peter Soul
previous / next column
|
