Ha, catchy title, sounds very authoritative, I like it. But seriously, it’s entirely true. What a dimension really is, is often misunderstood by the population, thanks mostly to the overuse of the misnomer in science-fiction since the ’40s. So, yeah, the sci-fi people take the hit for this one. But we can correct this mistake.
X, Y, and Z are variables that represent a point in a 3 dimensional system, they are dimensions. We live in three dimensions, or more precisely we perceive three dimensions, we infer the fourth, as a coordinate, from the constant, steady, and measurable effect it has on everything we perceive.
The apple left to rot on the table is not being moved by any external force, but as time ticks on, its three dimensional coordinates change. In other words, the apple was something different yesterday than what it is today, yet it’s still the same apple. So there you have it, three plus one dimensions. That’s all dimensions are. They are not a magical place where people wear goatees.
The places, the other words, the ‘other realities’ concepts most people think of when they hear ‘dimension’ is called something different. Wikipedia says it well:
Many-worlds is an interpretation of quantum mechanics that asserts the objective reality of the wavefunction, but denies the reality of wavefunction collapse (In layman’s terms, there is a very large—perhaps infinite—number of universes, and everything that could possibly have happened in our past, but didn’t, has occurred in the past of some other universe or universes.) It is also known as MWI (Many Worlds Interpretation), the relative state formulation, theory of the universal wavefunction, parallel universes, many-universes interpretation or just many worlds.
So, to all my science-fiction writer friends out there, please, we’re in 2010, let’s stop referring to those weird worlds where our characters suddenly find themselves thanks to a strange mirror, gateway, or even closet, with the antiquated and incorrect ‘parallel dimensions’ label. Let’s start using the correct ‘parallel universes’ designation, or better yet MW for short. It’s our fault that everyone now makes the ‘dimension’ mistake. We should work to correct that.
It’s also in part why I think some physics grad students always seem angry when talking to science-fiction writers. They seem to blame us for all the woes that bad science in science-fiction created in their lives.
To quote a certain Physicist I know: “Because of Dan Brown, I now have to explain to every person I meet who learns that I’m a particle physicist that, no, CERN will not create a miniature black hole that will fall to the center of the Earth and destroy the the planet!”
(Extra note for hardcore sci-fi writers: Interesting loopholes for creating really weird realities (in relatively scientifically plausible ways) exist within Dr. Lisa Randall’s Brane Theory. She’s my hero! Read her book!)