From both a philosophical and a scientific perspective, we’re taught to doubt, question, and be skeptical of everything. Even the reality of ourselves and our own experiences cannot be taken for granted, as we must make certain assumptions about how trustworthy our measurement sensors — and our own senses, for that matter — actually are in order to arrive at any satisfactory conclusions. Sure, certain things might appear real, but it’s also possible that those “real” appearances are deceiving us, and that quantities or concepts that we take for granted might be nothing more than very convincing illusions. When we consider our physical reality, however, these sorts of questions take on a different meaning. We’ve learned lots of surprising and counterintuitive lessons from our investigations of time. Time is relative, not absolute. Time always marches forward, never backward, but we still lack an explanation for the perceived arrow of time. Thermodynamically, the Universe has an arrow of time, which “flows” in the same direction as increasing entropy. And when we investigate the Universe on an …