Time impacts every aspect of our lives. Yet, despite our seemingly intimate relationship with time, many would be hard-pressed to define it. So, exactly what is time?
For millennia, philosophers and scientists have proposed and argued theories about time, but very few have resulted in any kind of consensus. And while there still remains no complete definition, in its strictest sense, time is a unit of measure. We use it to describe an event, or the duration of or between them. This is true both in everyday matters, as well as in mathematics. Colloquially, we might say something like “time marches on” when speaking about life’s forward movement, while physicists would characterize this perceived experience as the “arrow of time.”
Beyond time’s symptomatic effects, however, the true essence of the phenomenon remains controversial and mysterious. While physicists can use units of time within their equations, questions such as "How does time work?" continue to confound the scientific community. Indeed, as the superficial layers of time get pulled back, common sense and intuitive ideas are challenged, making it difficult to talk about the existential without flirting with something more metaphysical. As a result, the riddle of time has actually led some philosophers and scientists to rethink the entire model of our universe.
In that spirit, let’s explore some scientific theories about time that challenge our own views about reality.