The idea of “other dimensions” is an appealing one. It’s been called on to explain everything from ghosts and paranormal phenomena to UFOs and even Bigfoot. It’s implicit in science fiction concepts such as hyperspace or subspace, which make faster-than-light travel possible. Esoteric teachers often invoke higher dimensions to explain mystical concepts and experiences. Even mainstream scientists talk about “other dimensions” when discussing advanced topics such as relativity and string theory. Despite the huge divergence in the way the concept is used, all these disciplines – science, esoterica, science fiction and the paranormal – can trace their interest in other dimensions to a common origin in the 19th century.
It seems self-evident that we live in a three-dimensional world. A box has three dimensions – length, width and height. Each of those dimensions is at right-angles to the other two. It’s impossible to imagine a fourth dimension at right angles to these three (or at least, it’s impossible for most of us – a few people claim they can do it). On the other hand, it’s easy to picture fewer than three dimensions – if you draw a square on a flat sheet of paper then it has just two dimensions.
You can fold the piece of paper diagonally, so that the two opposite corners – a long way apart in two-dimensional space – are now almost touching. What was previously a long journey from one corner to another becomes a short journey through the third dimension. The science-fictional idea of hyperspace is a logical extension of this – if you could fold or warp three-dimensional space in higher dimensions then you could turn a long journey between the stars into a short one.
The first reference to curved or warped space occurs not in science fiction, but in a work of mainstream science. It was put forward in 1872 by a German astronomer named Karl Zöllner as a possible explanation of a longstanding mystery known as Olbers’ Paradox. If the universe is infinite in extent, why is it dark at night? Zöllner’s explanation for the apparent paradox is that the three-dimensional space occupied by the universe is curved in the fourth dimension. Thus distant stars “disappear over the horizon” just as ships disappear over the horizon on the curved surface of the Earth (this isn’t quite the way modern cosmologists would explain Olbers’ Paradox, although it may be a contributing factor).
Although Zöllner first arrived at the idea of the fourth dimension in a scientific context, he went on to take it in a more mystical direction. He was a great admirer of the English scientist William Crookes, an outspoken proponent of spiritualism. Zöllner went even further than Crookes, by suggesting that spirits live and move in four-dimensional space. What we perceive as ghosts are merely their three-dimensional “shadows”.
With the help of an American psychic named Henry Slade, Zöllner carried out a series of experiments to demonstrate that spirits could accomplish tasks that would be physically impossible without access to the fourth dimension. He published his results in 1878 in a book, dedicated to William Crookes, called Transcendental Physics (available to read online). This was one of the first systematic attempts to study the paranormal using scientific methods – although the modern consensus is that Slade was a fraud, who fooled Zöllner using sleight-of-hand methods.
The concept of the fourth dimension was developed in yet another direction by Charles Howard Hinton. He wasn’t a scientist or a mystic, but a mathematician – albeit a somewhat unorthodox one. He believed that striving to visualize four dimensional objects (which as I said earlier, is all but impossible for most people) was an effective way to expand the mental faculties – a kind of yoga for the mind. Hinton invented various shapes for his students to visualize, including a four-dimensional hypercube which he called a tesseract. His most important work on the subject was a book called A New Era of Thought, published in 1888 (again, the complete book is available to read online). Several people are supposed to have driven themselves insane trying to visualize Hinton’s tesseracts!
As far as mainstream science is concerned, the fourth dimension became firmly established early in the 20th century with the development of Einstein’s theory of relativity. This introduced the concept of a four-dimensional space-time continuum, which combines the three dimensions of space with a fourth dimension representing time. Although the idea of time as the fourth dimension wasn’t a new one, the novelty of Einstein’s theory lies in the fact that time was no longer independent of the other three dimensions. An object moving close to the speed of light becomes compressed in length and “dilated” in time.
In his general theory of relativity, published in 1916, Einstein was able to explain the phenomenon of gravity in terms of four-dimensional space-time. General Relativity was far from being a “theory of everything”, however – for example it could not explain electromagnetic forces. During the 1920s, two scientists named Theodor Kaluza and Oskar Klein proposed a theory involving five dimensions that would unify gravitation and electromagnetism. That was a step forward, but it was still unable to explain things like nuclear forces. Modern “theories of everything” need even more dimensions: the present record is held by M-theory, which invokes no fewer than eleven dimensions.