This is one of those sci-fi interactions that seems simple when you view it, but then on analysis it turns out to be anything but. So set aside some time, this analysis will be one of the longer ones even broken into four parts.

The Eye of Agamotto is a medallion that (spoiler) contains the emerald Time Infinity Stone, held on by a braided leather strap. It is made of brass, about a hand’s breadth across, in the shape of a stylized eye that is covered by the same mystical sigils seen on the rose window of the New York Sanctum, and the portal door from Kamar-Taj to the same.

We see the Eye used in three different places in the film, and in each place it works a little differently.

• The Tibet Mode
• The Hong Kong Modes
• The Dark Dimension Mode

The Tibet Mode

When the film begins, the Eye is under the protection of the Masters of the Mystic Arts in Kamar-Taj, where there’s even a user manual. Unfortunately it’s in mysticalese (or is it Tibetan? See comments) so we can’t read it to understand what it says. But we do get a couple of full-screen shots. Are there any cryptanalysists in the readership who can decipher the text?

The power button

Strange opens the old tome and reads “First, open the eye of Agamotto.” The instructions show him how to finger-tut a diamond shape with both hands and spread them apart. In response the lid of the eye opens, revealing a bright green glow within. At the same time the components of the sigil rotate around the eye until they become an upper and lower lid. The green glow of this “on state” persists as long as Strange is in time manipulation mode.

Once it’s turned on, he puts the heels of his palms together, fingers splayed out, and turns them clockwise to create a mystical green circle in the air before him. At the same time two other, softer green bands spin around his forearm and elbow. Thrusting his right hand toward the circle while withdrawing his left hand behind the other, he transfers control of the circle to just his right hand, where it follows the position of his palm and the rotation of his wrist as if it was a saucer mystically glued there.

Then he can twist his wrist clockwise while letting his fingers close to a fist, and the object on which he focuses ages. When he does this to an apple, we see it with progressively more chomps out of it until it is a core that dries and shrivels. Twisting his wrist counter clockwise, the focused object reverses aging, becoming younger in staggered increments. With his middle finger upright, the object reverts to its “natural” age.

Pausing and playing

At one point he wants to stop practicing with the apple and try it on the tome whose pages were ripped out. He relaxes his right hand and the green saucer disappears, allowing him to manipulate it and a tome without changing their ages. To reinstate the saucer, he extends his fingers out and gives his hand a shake, and it fades back into place.

Tibet Mode Analysis: The best control type

The Eye has a lot of goodness to it. Time has long been mapped to circles in sun dials and clock faces, so the circle controls fit thematically quite well. The gestural components make similar sense. The direction of wrist twist coincides with the movement of clock hands, so it feels familiar. Also we naturally look at and point at objects of focus, so using the extended arm gesture combined with gaze monitoring fits the sense of control. Lastly, those bands and saucers look really cool, both mystical in pattern and vaguely technological with the screen-green glow.

Readers of the blog know that it rarely just ends after compliments. To discuss the more challenging aspects of this interaction with the Eye, it’s useful to think of it as a gestural video scrubber for security footage, with the hand twist working like a jog wheel. Not familiar with that type of control? It’s a specialized dial, often used by video editors to scroll back and forth over video footage, to find particular sequences or frames. Here’s a quick show-and-tell by YouTube user BrainEatingZombie.

Is this the right kind of control?

There are other options to consider for the dial types of the Eye. What we see in the movie is a jog dial with hard stops, like you might use for an analogue volume control. The absolute position of the control maps to a point in a range of values. The wheel stops at the extents of the values: for volume controls, complete silence on one end and max volume at the other.

But another type is a shuttle wheel. This kind of dial has a resting position. You can turn it clockwise or counterclockwise, and when you let go, it will spring back to the resting position. While it is being turned, it enacts a change. The greater the turn, the faster the change. Like a variable fast-forward/reverse control. If we used this for a volume control: a small turn to the left means, “Keep lowering the volume a little bit as long as I hold the dial here.” A larger turn to the left means, “Get quieter faster.” In the case of the Eye, Strange could turn his hand a little to go back in time slowly, and fully to reverse quickly. This solves some mapping problems (discussed below) but raises new issues when the object just doesn’t change that much across time, like the tome. Rewinding the tome, Strange would start slow, see no change, then gradually increase speed (with no feedback from the tome to know how fast he was going) and suddenly he’d fly way past a point of interest. If he was looking for just the state change, then we’ve wasted his time by requiring him to scroll to find it. If he’s looking for details in the moment of change, the shuttle won’t help him zoom in on that detail, either.

There are also free-spin jog wheels, which can specify absolute or relative values, but since Strange’s wrist is not free-spinning, this is a nonstarter to consider. So I’ll make the call and say what we see in the film, the jog dial, is the right kind of control.

So if a jog dial is the right type of dial, and you start thinking of the Eye in terms of it being a video scrubber, it’s tackling a common enough problem: Scouring a variable range of data for things of interest. In fact, you can imagine that something like this is possible with sophisticated object recognition analyzing security footage.

• The investigator scrubs the video back in time to when the Mona Lisa, which since has gone missing, reappears on the wall.
• INVESTIGATOR
• Show me what happened—across all cameras in Paris—to that priceless object…
• She points at the painting in the video.
• …there.

So, sure, we’re not going to be manipulating time any…uh…time soon, but this pattern can extend beyond magic items a movie.

The scrubber metaphor brings us nearly all the issues we have to consider.

• What are the extents of the time frame?
• How are they mapped to gestures?
• What is the right display?
• What about the probabilistic nature of the future?

What are the extents of the time frame?

Think about the mapping issues here. Time goes forever in each direction. But the human wrist can only twist about 270 degrees: 90° pronation (thumb down) and 180° supination (thumb away from the body, or palm up). So how do you map the limited degrees of twist to unlimited time, especially considering that the “upright” hand is anchored to now?

The conceptually simplest mapping would be something like minutes-to-degree, where full pronation of the right hand would go back 90 minutes and full supination 2 hours into the future. (Noting the weirdness that the left hand would be more past-oriented and the right hand more future-oriented.) Let’s call this controlled extents to distinguish it from auto-extents, discussed later.

What if -90/+180 minutes is not enough time to entail the object at hand? Or what if that’s way too much time? The scale of those extents could be modified by a second gesture, such as the distance of the left hand from the right. So when the left hand was very far back, the extents might be -90/+180 years. When the left hand was touching the right, the extents might be -90/+180 milliseconds to find detail in very fast moving events. This kind-of backworlds the gestures seen in the film.

That’s simple and quite powerful, but doesn’t wholly fit the content for a couple of reasons. The first is that the time scales can vary so much between objects. Even -90/+180 years might be insufficient. What if Strange was scrubbing the timeline of a Yareta plant (which can live to be 3,000 years old) or a meteorite? Things exist in greatly differing time scales. To solve that you might just say OK, let’s set the scale to accommodate geologic or astronomic time spans. But now to select meaningfully between the apple and the tome his hand must move mere nanometers and hard for Strange to get right. A logarithmic time scale to that slider control might help, but still only provides precision at the now end of the spectrum.

If you design a thing with arbitrary time mapping you also have to decide what to do when the object no longer exists prior to the time request. If Strange tried to turn the apple back 50 years, what would be shown? How would you help him elegantly focus on the beginning point of the apple and at the same time understand that the apple didn’t exist 50 years ago?

So letting Strange control the extents arbitrarily is either very constrained or quite a bit more complicated than the movie shows.

Could the extents be automatically set per the focus?

Could the extents be set automatically at the beginning and end of the object in question? Those can be fuzzy concepts, but for the apple there are certainly points in time at which we say “definitely a bud and not a fruit” and “definitely inedible decayed biomass.” So those could be its extents.

The extents for the tome are fuzzier. Its beginning might be when its blank vellum pages were bound and its cover decorated. But the future doesn’t have as clean an endpoint. Pages can be torn out. The cover and binding could be removed for a while and the pages scattered, but then mostly brought together with other pages added and rebound. When does it stop being itself? What’s its endpoint? Suddenly the Eye has to have a powerful and philosophically advanced AI just to reconcile Theseus’ paradox for any object it was pointed at, to the satisfaction of the sorcerer using it and in the context in which it was being examined. Not simple and not in evidence.

Auto-extents could also get into very weird mapping. If an object were created last week, each single degree of right-hand-pronation would reverse time by about 2 hours; but if was fated to last a millennium, each single degree of right-hand-supination would advance time by about 5 years. And for the overwhelming bulk of that display, the book wouldn’t change much at all, so the differences in the time mapping between the two would not be apparent to the user and could cause great confusion.

So setting extents automatically is not a simple answer either. But between the two, starting with the extents automatically saves him the work of finding the interesting bits. (Presuming we can solve that tricky end-point problem. Ideas?) Which takes us to the question of the best display, which I’ll cover in the next post.