When different lines cross, interesting things happen.
And so it happened that when Wah Chang, the artist, sculptor and master prop maker, crossed paths with Dr. Oster through Edmund Scientific, an army surplus outlet that specialised in supplying lenses and telescope kits, more than just a prop’s dynamic eye-candy resulted: something of huge scientific relevance was built into the Star Trek props.
Chang didn’t need to spend too much time leafing through the 1965 Edmund Scientific catalogue 661 to work out if it had what he needed; the cover told him what he was looking for would be inside – Science, Optics, Math – the catalogue’s byline pretty much describes the tricorder’s functions. From a prop-building perspective, Edmund Scientific was an Aladdin’s cave of useful goodies, but the feature on moiré patterns on page 74 must have jumped out at Chang. Simply sliding those evenly spaced lines over each other quickly creates the most dynamic and mesmerisingly technical patterns of billowing arcs perpetually bubbling out of every edge of the image.
When putting our communicator moiré together we had the incredible help of HeroComm, who kindly loaned us an original 1965 “Educator’s and Designer’s Moiré Series (A)-Deluxe Kit”. The amazing resources on the HeroComm website helped us cut the moiré from exactly the right position from Pattern #4, but when it came to the tricorder, we had to work things out for ourselves. In order to replicate the moiré pattern as seen in all the known photos of the hero prop, a close-up of the studio photo from “The Making of Star Trek” book, corrected for perspective, was overdrawn with lines to pinpoint the centre of the pattern.
We knew that the moiré pattern was created from two discs cut from the same Edmund Scientific moiré sheet as the comm had been, but had been cut from a different part of the pattern. By overlaying our line drawings on Pattern #4, we were quickly able to see where to take the tricorder’s moiré discs from.
While the tricorder has a moiré disc similar to the communicator, given the lack of space for a communicator-style pocket-watch drive mechanism behind the tricorder prop’s front panel, it is clear that the tricorder’s moiré never actually rotated. Nevertheless, as the static pattern we see in the photographs is clearly made from two discs sitting on top of each other, it was never in question that our tricorder’s moiré should rotate to bring that pattern alive. With the two patterns overlaid and moving, the evolving fringes turn out to be very exciting and do have the look of strange magnetic flux lines, perhaps displaying some otherwise-unseen aspect of a subspace signal.
The stepper motor we chose to drive the tricorder’s moiré is much larger than the one we used for the communicator. Space inside the communicator is very limited: the moiré driving motor has to sit just under the moiré disc, on top of the speaker. Only the smallest stepper motor would fit. In the tricorder there is much more space behind the moiré panel which meant we could select a much bigger motor. The larger motor is actually less expensive and more robust, so it’s possible to connect directly to the moiré base disc, making it mechanically simpler and assembly easier.
A stepper motor is needed because small DC motors function at high speed and as a result have to be heavily geared to achieve the low rotational speeds required to replicate the pocket-watch driven moiré motion seen in the communicator. The meshing of many tiny gears is a noisy business. The stepper motor is quieter and has the added benefit of accurate digital control of not just the speed, but also individual rotational steps. This provides another benefit for the tricorder’s function as a cabinet display piece.
In use, without additional mechanical complexity and moiré position sensors, it is not possible to know at which position the moiré has stopped. For the perfect display experience, the ideal situation would be for the moiré pattern to replicate the ‘X’ shape seen in the various images of the hero prop. With the stepper motor’s fine control, we are able to include a mode that will allow the user to manually adjust the rotation of the base disc to get the moiré pattern to look just right.
The further we pushed into the design of this hero prop, the more we got to realise the scientific thinking that underpinned the design choices Wah Chang made. Beyond expensive watered taffeta that gave these shimmering patterns their name, the moiré’s interference fringes are actually a highly scientific phenomena that have had a huge impact in many areas of technology and exploration. Moiré patterns have taken humans from the discovery that light travels in waves, when in 1801 Thomas Young inferred the wave half of the wave-particle duality by observing interference fringes created as beams of light shone through slits, all the way to the 21st century interferometry used by huge telescope arrays that peer deep into the most distant corners of the universe – further from our home planet than Kirk could have ever dreamed.
When different lines cross, interesting things happen.
Coming next time
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