This paper analyzes the history and impact of the double-slit experiment on the world of physics. The experiment was initially created by Thomas Young in the early nineteenth century to prove that light behaved as a wave, and the experiment’s findings ended up being foundational to the classical wave theory of light. Decades later, the experiment was replicated once more with electrons instead of light and shockingly demonstrated that electrons possessed a dual nature of behavior in that they acted in some instances as particles and in others as waves. Despite numerous modifications and replications, the dual behavior of electrons has never been definitively explained. Numerous interpretations of quantum mechanics all offer their own explanations of the double-slit experiment’s results. Notably, the Copenhagen Interpretation states that an observer measuring a quantum system, such as the double-slit experiment, causes the electrons to behave classically (i.e. as a particle.) The Many Worlds Interpretation offers that multiple branching worlds come into existence to represent the physical occurrence of all probable outcomes of the double-slit experiment. In these and other interpretations, explanations of the double-slit experiment are key to proving their respective dogmas. The double-slit experiment has historically been very important to the worlds of both classical and quantum physics and is still being modified and replicated to this day. It is clear that it will continue to remain relevant even in the future of physics.

Activists seeking to create social change must decide whether to expend more resources trying to change the behavior of individuals or institutions. For example, a climate activist could spend their days urging people to stop flying in airplanes, or they could spend their days urging the government to outlaw excessive flying. Some social change theorists argue that the second tactic is more effective than the first. Are they correct? I use the environmental movement and the animal liberation movement as case studies to examine this question from an empirical perspective. I conclude that while attempts to change individual behavior should not be entirely abandoned, they should be used with caution because of their tendency to distract the public from the need for institutional reform and their tendency to alienate potential allies. Seeing that, for decades, the animal movement’s main strategy has been to urge individuals to change their dietary behavior, this movement would greatly benefit from this knowledge.