2679: Quantified Self

xkcd explained, properly

Title text: It's made me way more excited about ferris wheels,

subways, car washes, waterslides, and store entrances

that have double doors with a divider in the middle.

Explanation

Cueball has joined the popular lifestyle of the quantified self, that promotes monitoring oneself with devices and data to promote well-being. However, he does so in a unusual and humorous way, with help from what appears to be a wristband-like device attached to his right arm.

Typically, wearable devices and mobile fitness apps track physical activity, estimating such things as number of footsteps taken, distances walked or run, calories burned, and even mood, etc., via proxy measurements such as acceleration (or the device), heart rate, blood oxygenation level, blood pressure. By giving direct feedback and offering goals to attain (e.g. a goal to walk 3 miles each day) this can promote health and fitness. However, Cueball has chosen to track an unusual modified "distance traveled" metric. His device tracks his path in three-dimensional space and is aware of physical objects that comprise topological tunnels (as in 2658: Coffee Cup Holes and 2625: Field Topology). Software in his device (or its cloud service) performs post-processing by contracting his path, respecting topological constraints.

In the comic strip we see that, over the course of his week, Cueball has looped through his house twice (by leaving through the door that we see, and returning via another door in back), passed under two highway overpasses, passed under a trestle highway sign, and looped through something resembling the St. Louis Gateway Arch, and is now back near home. All other meanderings are not shown, the path having been "pulled taut" wherever possible, except that it must remain looped around those structures that have a topological genus of 1.

For example, he might have left the house by the front, spent a while in the front yard, and returned back into the house through the front door, but this meandering can be reduced or eliminated without changing the topology of the closed path. As another example see xkcd 100: Family Circus. The dotted lines going to the red ball can be reduced to nothing (what topology calls a "null-homotopic path") because Jeffrey re-entered through the same door, however when he went to the swing-set he returned by a different door so that loop will remain.

An "imaginary thread" connecting a person to where they came from (as portrayed in this comic, distinct from a mystical [silver cord]) has been¹ attested² by some experiencing OCD conditions (see also 245: Floor Tiles, 100: Family Circus).

The title text mentions several things that would make the red path longer: passing (one way) through a tube (water slide) or tunnel (subway or car wash), riding on a ferris wheel, or entering a building through one door and exiting another, in all cases the imaginary string would be "captured" and make the total distance longer.

$Transcript&

[A red path links two red Cueballs. It start from the left Cueball, does two loops through a small house, under a first road bridge, under a gantry sign, under a second road bridge, under the Gateway Arch, and to a second red Cueball on the right. That Cueball is looking at a smart watch or a mobile device.]

Red Cueball's watch or mobile device: Good job! You hit your weekly goal for "total length of your path through space if you minimize its length by pulling it taut, maneuvering it around solid objects but not through them."

[Caption below the panel:] I'm into the quantified self, but only for really arbitrary quantities.

My Personal Perspective

I had a preoccupation with this sort of thing, for a while as a child. My "red line" was a remnant of the umbilical cord, with one end permanently anchored in the hospital where I was born. I had little or no knowledge of the fundamental nature of matter and just thought of it as a rubber band that was too small to see or feel. Like in this comic and the description above, it could magically stretch as much as needed and would un-stretch when possible. I did not consider changing behaviour (e.g. choosing which door to leave a building) because I had no desire for it to be longer or shorter, and it was clearly far too late to make a significant difference. I did spend quite some time thinking of all the places the thread must have gotten caught (as in this comic) and estimating its total length. I did not consider airports, or my estimate would have been far longer.

It must have been after I learned about umbilical cords and before learning about atoms (and the electromagnetic nature of covalent bonds) — my magic string was inert to all forces, and therefore electrically neutral, and far thinner than the space between atoms — so it would have passed through solid matter as easily as through air. However, as soon as I learned of the inseparability of quarks I should have re-imagined my magic thread as a gluon tube. Why did this not happen? Perhaps I accept the consequences of Color confinement, or perhaps I don't even believe in gluons.

Footnotes

1 : https://www.reddit.com/r/OCD/comments/1ve309/invisible_thread_attached_to_my_back_am_i_the/ Reddit discussion titled "Invisible thread attached to my back... am I the only one who does it?", 2014 Jan 16.

2 : https://www.reddit.com/r/xkcd/comments/xs50yr/xkcd_2679_quantified_self/ Reddit discussion on xkcd 2679 "Quantified Self", 2022 Sep 30.

This page was written in the "embarrassingly readable" markup language RHTF, and was last updated on 2022 Oct 01.

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