The Basics of Sailing
The Science
The actual science behind sailing is very complicated and involves lots of physics. People can easily comprehend that a sailboat can sail downwind or with the wind, because everyday we see evidence of how the wind is pushing things. For example, the wind will blow a plastic bag down wind, but do you ever see the wind pushing a plastic bag upwind or against the wind? No, but a sailboat can still go upwind by trimming or setting the sails in the proper position, so that it will make low and high pressure air pockets to push the sailboat upwind. Fortunately, sailors do not have no know all of the complicated physics behind sailing. They just have to know how the boat reacts to the wind and learn from that.
How to Sail
A sailboat can sail in all direction except forty-five degrees or less to the wind. If the boat is closer then forty-five degrees to the wind then it is called "in irons" and the sail will be flapping and the boat will probably be floating backwards. Here is a diagram that illustrates how to sail in the different directions.
As the diagram shows, the more upwind the boat is sailing, then the closer in the sail should be. If the boat is going downwind, then the sail should be farther out. Someone might ask how do you sail to your destination if it is directly into the wind. Well you would position the boat forty-five degrees to the wind on a close hauled direction and then zig-zag upwind, which is called tacking. Sailing upwind might take you twice the distance compared to a motor boat, due to the zig-zags, but it is twice as much fun. The best way to learn to sail is to go out on the water on a calm day and see how the sailboat reacts to the wind.