Is there a physical reason we read from left to right?
Is there any reason why we read from left to right? That is, is there something about the mechanisms of brain perception that make it more natural to go in that direction?
Obviously not — witness Chinese and Hebrew. It's just a matter of habit. In fact, I once knew a proofreader who read everything upside down, being either too lazy or too drunk to turn the page over once the typesetter tossed it at him.
Professional busybodies have often suggested that every other line of type on a page should be printed "backwards," so the eye could quietly drop from the end of one line to the beginning of another without having to go zipping back and forth across the column. The authors of some of the earliest known Greek texts wrote in just this manner. This style of writing is called boustrophedon, Greek for "turning of the ox" — the words go back and forth across the page like an ox does when plowing, turning at the end of each row. Actually, it's surprisingly easy to get used to — a couple hours of practice seem to be enough. Maybe we can get to work on this once we're through with the great Metric Conversion. If you want to get a head start, check out this boustrophedon text reader available for Linux, plus this sample page.