Famous Thought Experiments

Schrödinger’s Cat

Throughout history, scientists and thinkers have come up with numerous interesting situations for us to ponder. These scenarios, called thought experiments, are mental concepts or hypotheses used as ways to illustrate very dense concepts. Moreover, thought experiments are most often used in theoretical fields where it is very difficult or impossible to conduct an actual experiment. The scenarios of thought experiments usually make for interesting food for thought and can be a great topic-starter when discussing theoretical concepts. 

The Trolley Problem

In the field of ethics, this thought experiment goes as follows: There are five innocent people tied to a train track, and one innocent person tied to an adjacent track. You are controlling the path of the train and have only enough time to decide either to keep the train on its current course and kill the four people, or pull a lever to divert the train to the other track and kill the one person. Under these circumstances, what would you do? 

This thought experiment was first proposed by the philosopher Philippa Foot and is a clear way to illustrate utilitarian thinking. There are three main responses to this situation: 

- Pull the lever. From a utilitarian standpoint, one should pull the lever, killing one person and sparing the other four, because this consequence does the least amount of harm to human lives. 

- Do not pull the lever. Some other schools of thought, such as deontology, would suggest that the ethical course of action would be not to pull the lever and let the train run its natural course, thereby killing the four people on its original path. This is because some critics of utilitarianism believe that one becomes complicit in pulling the lever, which is an immoral act as the person would now be somewhat responsible for the death of one person, who would otherwise have been alive if the train operator did not make a conscious decision to set the train on their path. 

- Pull the lever, because doing nothing would be just as immoral. Yet others believe that since you are in the situation, you have to choose the least damaging course of action, and to do nothing and let the four people die would be just as immoral as voluntarily killing the one person. As such, even if the train operator was committing an immoral act by pulling the lever and killing one person, they had no choice because none of the available options were wholly moral. 

In the end, the thought experiment of the trolley problem illustrates that in real world situations, we may sometimes have to compromise our own moral standards when faced with a dilemma. Moreover, there may be some situations in which there is no fully moral course of action. 

The Ship of Theseus

This paradox is one of the oldest known thought experiments, originating in the writings of Plutarch. In this thought experiment, an old ship called the Ship of Theseus has remained seaworthy for hundreds of years due to the constant repairs and replacements conducted on it. Whenever one part wore out, a new part would replace it, until the resulting Ship of Theseus no longer had any of its original parts. Can one say that this end product is still the same Ship of Theseus, or is it a completely new ship? If the latter, when did the ship cease being the same Ship of Theseus and become something different? 

The philosopher Thomas Hobbes later posed another question to extend this problem even further: if all the old parts removed from the Ship of Theseus were taken and remade into a new ship, would this new product be the real Ship of Theseus, or would the first ship which had all of its original parts replaced be the real Ship of Theseus instead? 

This thought experiment explores what it means for objects to have an identity. Are objects merely the sum of their parts, or something more? 

Such situations also exist in modern times. Think of a band or an entertainment group that has lasted for many years, until all of the original members have retired one by one from the lineup. Is it still the same group, or is it now a different group? 

Similar examples exist in businesses, schools and organizations that have seen a complete change of personnel until none of the original founding members remain, but continue to operate under the same name. This thought experiment challenges people to question the notion of identity, against the commonly held belief that the identity of an object or an entity is tied to what it is made up of. 

Schrödinger’s Cat

The paradox of Schrödinger’s Cat explores a theory of quantum mechanics and, as its name suggests, was first proposed by the physicist Erwin Schrödinger. In this thought experiment, a cat is placed in a sealed box for an hour, together with a radioactive material, a vial of poison, a Geiger counter and a hammer. There is only a 50/50 chance that the radioactive material will decay during that one hour. If it does, the Geiger counter will detect radiation and trigger the hammer, smashing the vial which will then release the poison and kill the cat. However, since there is an equal chance that this will or will not happen, Schrödinger states that before anyone opens the box and determines what has happened to the cat, the cat will exist in all its possible states – which means that it is simultaneously alive and dead. 

What this means is that as long as there is no one around to witness the results of the experiment, no one can say for sure whether the cat is alive or dead, so it theoretically exists in all possible states simultaneously, which is both alive and dead. This is similar to the riddle that asks, “if a tree falls in the woods and nobody is around to hear it, does it make a sound?”

A common misconception is that Schrödinger supported the Copenhagen Interpretation of quantum mechanics, but in reality, he disagreed with it. Schrödinger came up with this experiment to oppose the Copenhagen Interpretation of quantum mechanics, which states that an object in a physical system exists in all possible configurations until the system is observed, at which point the system collapses and the object is forced into only one of its possible configurations. To prove that the Copenhagen Interpretation was inherently flawed, Schrödinger conceived this thought experiment to illustrate that the rules of quantum mechanics could not apply to large objects such as a cat, because it would be impossible for a cat to be simultaneously alive and dead. 

The paradox of Schrödinger’s Cat has sparked many variant interpretations, such as one hypothesis of parallel universes, which states that the cat is alive in some universes and dead in others, but these worlds will never overlap with one another. 

Famous Thought Experiments Continued