One hypothetical model that explains how so many dimensions can exist in our universe is the idea of compactification. Picture a big oil or natural gas pipeline stretching across a vast plain: when you stand next to it, it clearly has the three dimensions of length, depth, and height. By moving away a few feet, it increasingly seems like the pipeline has only length and height; moving still farther away, it may seem like it only has one dimension, length. In a sense, two of the pipeline’s three dimensions have now been “compactified.” They are still there, but they are too small to be observed. The same concept might apply to dimensions beyond those of observable space and time. This idea has been around for decades. However, it might be impossible to confirm the existence of other dimensions because scientists would have to observe size scales smaller than the Planck length to see the amount of compactification necessary for the universe to behave as it does.