Time is something that, despite being such a seemingly foundational part of how the universe functions, still manages to perplex us to this day. The fact that we can’t imagine time working any other way than it does is probably part of that, but luckily we have this great tool called physics to help us model things like time. And interestingly, out of all the fundamental laws/equations of physics, there’s only one that shows why time moves forward and not any other way (i.e., backwards or both backwards and forwards).
The video above, made by MinutePhysics, explains how the Second Law of Thermodynamics determines the direction of time and how, because of this, we know it is inevitable that the universe will eventually turn into an empty vacuum. Entropy can be a complicated thing, but the video above explains it very well in terms of time, the universe, and why the universe is on the path it is.