Science and video games, together! Minecraft can be a great tool for visualizing complicated subjects, such as the speed of light. Using a straight track and simple math, we can see how the universe might be limiting speeds for very fast things, such as light. The "doors" metaphor is admittedly, imperfect. While they do limit speed outside of "acceleration", they falsely imply that there is something "in space" that slows things down, which does not appear to be the case at the moment. From 'spumwack'.