Recall what was said in the reader’s letter: “I am a newcomer at the wheel. And then I ran into a mystery. In the evening I park the car on the roadway of the street parallel to the curb, and the next morning I see that the side facing the road is clean, and the opposite was doused with water from a puddle. I have not yet been able to catch the hooligans. What will you advise?»Since there is no education to answer this task, the correct solutions are almost one hundred percent. In cities, public utilities are watching the cleanliness of the streets. When the watering machine does its job, the jets of water hit on the surface of the roadway, knock down dirt from it – and, passing under the bottom of a parked car, they can reach the curb stone. Further depends on the deployment of the object. When its threshold hangs over the curb, the side is practically not sprayed, the water and dirt that reflected from the obstacle fall only on the bottom of the machine. If you park further from the border, then the dirt reflected up is easily sprayed by the side. Therefore, many suggest parking a car with a partial race on the sidewalk – unless, of course, this is prohibited by road signs. It would seem that the answer to the task is quite clear. But…The authors of some answers seemed to have not heard about the features of city life. Some accepted the words about hooligans for a pure coin – and tell the complainant how to act. So, a certain citizen, having sat in an ambush for a couple of nights, caught the villain – the tenant of his own entrance, who believed that his place in the courtyard was occupied “illegally”, so the alien car was dirty. There were other versions: “Imagine that after the rain a deep puddle formed on the road. If a flow of transport moves along it, then the parked car will be a plague from all sides. But, while the puddle has not been scooped to the bottom, the side facing the road will be cleaner, because it is continuously watered! And on the other side the dirt accumulates…»We did not study this theory deeply, since there is not enough introductory to work on the dissertation here. There are other ideas: “The car in the morning fades from the difference in temperature. The side facing the road is blown by passing by transport and remains dry, and dew on the opposite for a long time collects dust…“But another version is much more romantic:“ If the side of the car facing the road looks east, then after sunrise the loss of dew quickly dries out. And the Western West for a long time collects dust from passing machines “.