Multiple Higher Dimensions

Alternate universes have long been a popular subject for speculation, but a serious problem for those who believe they exist was why no one could see them. Usually, this was explained by invoking multiple higher dimensions. It went something like this. All dimensions begin with a mathematical point, which has no dimensions. However, string an infinite number of them side by side and you get a line, which has the first dimension of length. Lay an infinite number of lines beside each other and you get a plane, which has the second dimension of width. Stack an infinite number of planes on top of each other and you get a space, which has the third dimension of depth. Finally, arrange an infinite number of spaces around each other and you get a hyperspace, which has a fourth dimension.

While each dimension may be finite in size, it contains an infinite number of lower dimensions. Hence, if we assume each three-dimensional space is a separate universe, a hyperspace would contain an infinite number of independent universes. These universes would be separated from each other across the fourth dimension, which we cannot travel or see through, hence they are invisible to us. For many years, it was thought that the fourth dimension was time, since Albert Einstein had used time as a dimension in his theory of relativity. String theory, however, predicts that our universe has eleven dimensions, ten spatial and one temporal. Time is considered to be the eleventh and highest dimension, so the fourth dimension of a hyperspace would now be an uncharacterized spatial dimension like length, width, and depth.

However, string theory also predicts that only four of the dimensions form the kind of nested hierarchy described above. These are the three spatial dimensions of length, width, and depth, plus the dimension of time. The other seven spatial dimensions are subatomic and are bound up with the strings, so they do not form "higher" dimensions containing infinite numbers of lower dimensions. The idea is that, before the Big Bang, all eleven dimensions were equal in size, strength, and character; in other words, they were symmetrical. During the Big Bang, however, the universe underwent what is called a symmetry breaking event. Seven of the dimensions collapsed in size and shed most of their energy, which was absorbed by the remaining four, causing them to expand to infinite size and turning three into spatial dimensions and one into a temporal dimension. Each Level 1 multiverse that forms in a Level 2 multiverse undergoes a similar symmetry breaking event, but quantum fluctuations cause the number of dimensions to collapse and the kind to emerge to be random.

Parallel universes are now the primary way to explain where the alternative universes exist and why we cannot see them. However, higher dimensions still play an important role in understanding how universes are ordered and arranged into larger structures.

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