‘Psychologists have hitherto failed to realize that imagination is a necessary ingredient of perception itself.’ –Kant


For centuries, scientists studied light to comprehend the visible world. […] But in the late 19th century all that changed […] the whole focus of physics—then still emerging as a distinct scientific discipline—shifted from the visible to the invisible. […] Today its theories and concepts are concerned largely with invisible entities: not only unseen force fields and insensible rays but particles too small to see even with the most advanced microscopes. […] Theories at the speculative forefront of physics flesh out this unseen universe with parallel worlds and with mysterious entities named for their very invisibility: dark matter and dark energy. […]

…the concept of “brane” (short for membrane) worlds. This arises from the most state-of-the-art variants of string theory, which attempt to explain all the known particles and forces in terms of ultra-tiny entities called strings, which can be envisioned as particles extended into little strands that vibrate. Most versions of the theory call for variables in the equations that seem to have the role of extra dimensions in space, so that string theory posits not four dimensions (of time and space) but 11. As physicist and writer Jim Baggott points out, “there is no experimental or observational basis for these assumptions”—the “extra dimensions” are just formal aspects of the equations. However, the latest versions of the theory suggest that these extra dimensions can be extremely large, constituting extra-dimensional branes that are potential repositories for alternative universes separated from our own like the stacked leaves of a book. Inevitably, there is an urge to imagine that these places too might be populated with sentient beings, although that’s optional. The point is that these brane worlds are nothing more than mathematical entities in speculative equations, incarnated, as it were, as invisible parallel universes. […]

Scientists, of course, are not just making things up, while leaning on the convenience of supposed invisibility. They are using dark matter and dark energy, and (if one is charitable) quantum many-worlds and branes, and other imperceptible and hypothetical realms, to perform an essential task: to plug gaps in their knowledge with notions they can grasp.

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