We all know that time only moves forward. If we see a movie where a pile of broken glass rises up to a table and becomes a drinking glass we know that it’s being shown in reverse. But the laws of physics tell us that time, like left and right or up and down, should work in either direction. So is that really the case? The axion, a subatomic particle, may help explain both time and dark matter. That is, if it can be detected.