Parallax
Deeply Nested will be on vacation next week, returning on September 2. Please feel free to revisit a recent technical (Traversal Order, Safety) or non-technical (Swimming Upstream, Wasting Time) post, and remember you have access to the archives.
Movement, in absolute terms, is an illusion. Each of us stands at the origin of our own frame of reference, within which we are still. This principle applies not only to physical movement, but to progress of any kind.
Things fall apart; the centre cannot hold
—William Butler Yeats, The Second Coming
The most facile way to assess our own velocity is relative to whomever or whatever is nearby, yet it is no more meaningful to say we are flying past others than it is to say they are flying past us. In the moment, it is not always clear which way is forward, and which reverse.
I didn't leave the Democratic Party. The party left me.
Observing progress relative to big things, rather than close ones—mountains in the distance, stars in the sky, or the events of the distant past—is hard, because distance obscures detail. Ever wonder why it seems like music/movies/media were better in some other decade? It’s because, in hindsight, the hits seem closer and closer together, even as the interstitial noise is slowly forgotten.
The phenomenon by which objects appear closer to each other the farther they are from us is called perspective. The related phenomenon by which we seem to move faster relative to nearby objects than to distant ones is called parallax.
💡The parsec, an astronomical unit of distance, is an abbreviation of “parallax second.” It is how close another star would have to be to the plane of our orbit around the sun to seem, from our perspective, to have moved through two arcseconds (0.0003% of the way across the sky) in six months. During that time, we travel nearly 300,000,000 km, yet a parsec is over 30,000,000,000,000 km. There are no stars so close.
Although we cannot meaningfully assess our progress relative to others, what we can determine are changes in our own velocity. Changes in velocity are called acceleration, and like all derivatives with respect to time, acceleration is fundamentally an instantaneous property: We know, in any given moment, whether we are speeding up or slowing down. The sensation is often visceral.
If there is a lesson to be learned from all these observations, it is that progress is an illusory thing. Measuring progress in a changing world, or comparing our own progress to that of other people—or worse yet, other people’s progress relative to ours—is a fool’s errand. The question we can answer is whether we’re doing better than we were yesterday. Whether “doing better” means moving faster or slower… well, that’s up to you.