Causality (physics) - Basic Concepts of Cause and Effect

Basic Concepts of Cause and Effect

Humans have a practical interest in their surroundings, and tend to be resistant to the idea that things "just happen". If one or more sheep die, humans will attempt to discover why. Learning what has killed the sheep is an important step in protecting the flock. The question can be phrased as, "What caused the sheep to die?" The answer may be "The wolves broke their necks," or "Eating too much clover caused them to bloat." These explanations assume the presence of an agent of some kind. In cases where an obvious cause is not discovered, humans may attribute the events to miracles or to evil supernatural agencies, or create an ungrounded theory to present something as a causative agent. There is a learned preference for some alternative to saying that something occurred without there being a reason for it. Any event that stands as 'uncaused' may motivate us to understand the salient events in the environment of that event.

When trying to answer questions such as, "Why is the water boiling?" it is tempting to search for a single responsible figure: "Mother lit the gas burner under the tea kettle." However, closer examination shows that the lighting of a flame is not the only feature that must be accounted for. Closer study shows that the ambient air pressure is a controlling factor, the Earth's gravity holding the water in the pot is a controlling factor, the temperature to which the water has been heated is a controlling factor, etc.

Given a situation in which water is already sitting in a tea kettle on top of a gas burner, then someone lighting the gas under the kettle may be perceived as the "cause" of the water's boiling. But in the same situation the water would also boil if the air pressure were sufficiently reduced. In more complicated situations, more factors that influence outcomes may be involved. Underlying the expectations that most people hold in regard to the interactions of these several factors are everyday experiences in which someone succeeds in producing a desired result. "If I turn this key, the motor will start." This may be a true statement, but underlying it is a very complicated set of conditions that must all be in place. So the idea of "cause" tends to focus on foreground events and leave out necessary factors that reside in the background.

Real world factors can intervene to challenge simplistic ideas of causation. Water in a pressure cooker will not boil at 100 degrees Celsius. The key is turned but the car motor will not start. So at this level of sophistication, it is not difficult to gain acceptance of a more refined idea of causation. And, in practice, few individuals expect to get a desired outcome without having fulfilled the conditions necessary to earn it. People may wish for a million dollars, but they do not wish for hot toast to emerge from a cold and empty toaster.

The most abstract form of the argument from experience is: (1) Do something and get a certain result. (2) Do not do it and do not get the result. Hence, a cause is both sufficient (1) and necessary (2) in order that the event happen.

Another lesson consistent with everyday experience is that these sequences do not work in reverse. For instance, if a cup of boiling water is allowed to sit at room temperature then it will cool to room temperature, but if a cup of room temperature water is allowed to sit at room temperature it will not warm to the point that it boils. So there is a 'sequentiality' in events familiar to humans from their everyday experience. Whenever this 'sequentiality' is detected or believed to be present, the temporally prior change is said to be a cause, and the temporally posterior change is said to be an effect.

One crack in this belief system has been produced by radioactivity. An atom of some radioactive substance such as radium will eventually decay, and in the process it will emit energy. But there is no known triggering event that could serve as the cause of this decay event. In a large collection of radium atoms the rate of decay can be accurately predicted, but the identity of the decayed atoms cannot be determined beforehand. Their decay is random and was considered to be uncaused in an older framework of quantum theory. Under the new formulation spontaneous emission, for example, is initiated by vacuum fluctuations.

Another crack in this belief system has been produced by quantum mechanical events such that the same sequence of causal events (or causal factors) regularly produces different effects (i.e., results), but the results may repeat themselves in some random (unknowable) sequence. Furthermore, the percentages of results of each kind can be calculated and they are highly predictable.

Results of this kind are seen in the macro world of human beings only in the case of crooked roulette wheels or other such crooked gambling devices since legitimate roulette wheels should have an equal probability of stopping at each position.