Light travels in all directions at the same time so it serves as a bad example; because of its dual nature as a particle and a wave (its particle nature allows it to travel in every direction at the same time, BTW), we find it difficult to compare it to objects that are ruled primarily by newtonian physics. Therefore, your example does not fit in here. (BTW, the speed of light is 186285 mph)
The fact is that if you buy at market and the thing goes up 25 cents immediately, it may take significant sellers to sell the stock back down to where it was. Or, for it to come back down again, you may require massive pulling of bids so that even in a market that is not trading high volume, you see erratic price movements.
Think of it this way: you drive 100 miles south. In order to get 100 miles north of where you started, you actually have to drive 200 miles north. I'm just saying that it behooves you to buy strength and sell weakness....unless you do so on the wrong side of a pivot point (as i've been doing lately).
