Have you seen the adverts for the new Marvel Super Heroes 4D experience at Madame Tussauds?
4D! That's one whole dimension more than 3D. If you take this mathematically, we're talking about the tesseract; if you take it physically, it's time. Before you know it, you're stretching into multidimensional territory - string theory and quantum physics. Who knew Madame Tussauds had it in it?
Then you read the small print. "Marvel's Super Heroes 4D unites amazingly realistic 3D animation with state-of-the-art digi-star projection and then adds in an extra-sensory fourth dimension. The action will spill out of the screen over the audience and [there are] thrill-enhancing special effects - from water and smoke to tremors beneath the feet."
So, 4D is not the discovery of a fourth spatial dimension. No. It is more like the sensation of the building falling down while you sit in an oversized cinema, having bought a comically overpriced ticket. What a shame. But it's quite fun to imagine how it's done. I picture beleaguered Tussauds staffers in the wings of the former planetarium, chucking buckets of water over the audience. "But I wanted a fourth dimension!" some outraged parent will shout. "I wanted access to a parallel universe, to see beyond our finite conception of time and space!" In return, an usher will blow smoke into his eyes and jiggle his chair.
I suggest the Madame Tussauds complaints department rapidly work on its PR strategy and sample a little Kant to throw at detractors: "That everywhere space (which is not itself the boundary of another space) has three dimensions, and that space in general cannot have more dimensions, is based on the proposition that not more than three lines can intersect at right angles in one point. This proposition cannot at all be shown from concepts, but rests immediately on intuition and, indeed, on pure intuition a priori because it is apodictically [demonstrably] certain."
Translation: obviously there are only three dimensions, numpty. 4D is marketing. Now go home and watch reruns of Quantum Leap to cheer yourself up.