Understanding 2D Worlds: The Perception of Shapes in Flatland

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Discussion Overview

The discussion revolves around the perception of shapes in a two-dimensional world, specifically how inhabitants of such a world would recognize a three-dimensional object, like a ball, as a circle. The conversation explores theoretical implications of dimensional perception and the methods by which flatlanders might identify shapes based on their limited sensory experiences.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions how flatlanders could recognize a circle if a ball were to enter their world, suggesting they might only see a dark outline.
  • Another participant proposes that flatlanders could identify the shape by maneuvering around it, noting that the absence of corners would indicate it is a circle.
  • It is suggested that binocular vision could allow flatlanders to visualize the shape of the circle, with shading providing additional clues, similar to how humans perceive spheres.
  • One participant expresses skepticism about recognizing a shape without height, acknowledging the difficulty in imagining such a perception.
  • Another contribution mentions that elite flatlanders could identify shapes based on characteristic lighting patterns in their environment.
  • A generalization is made about dimensional perception, stating that beings in any dimension perceive a hyperplane of one dimension lower, implying that two eyes are sufficient for dimensional understanding.
  • A participant recalls that if the flatlanders' plane were to pass the object, they would see a circle as the line would widen and narrow, although they admit to not fully engaging with the source material.
  • There is a clarification that the question pertains to how flatlanders would perceive the shape as a circle rather than other geometric forms, emphasizing the importance of their perceptual interpretation.

Areas of Agreement / Disagreement

Participants express varying viewpoints on how flatlanders could perceive a circle, with no consensus reached on a definitive method of recognition. Multiple competing explanations are presented, reflecting differing interpretations of the scenario.

Contextual Notes

Some assumptions about sensory perception and the nature of dimensionality remain unexamined, and the discussion does not resolve how flatlanders would definitively distinguish between different shapes in their environment.

Pflip
[SOLVED] Flatland question

In Hyperspace, Mr. Kaku makes several references to a 3D object entering a 2D world. If the object is say, a ball, he notes that the 2D people would see a giant, dark circle.

My question is how they can tell it's a circle. It would seem that if the ball were to come down in front of them, all they would see is a darknesss on the horizon. How could they possibly get a "bird's eye view" and see the outline of the object?

Thanks,
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In Flatland they would maneuver around it and discover it has no corners, and thus discover it's a priest - i.e. what we call a circle. After all, what they could see of each other was only a dark stripe too- recognition was tactile.

BTW, Welcome to the forums. Nice to have you.
 
They don't even have to maneuver around the circle - having two eyes, they could make out the shape of the circle using binocular vision to visualize the shape inside their head. Shading would also give clues to its shape. We do these same things in the third dimension when we see spheres. Hold a ball in front of yourself and ask yourself how you know it is a sphere and not a disk.

You can get more explanations of the dimensional interactions at my website:

Fourth Dimension: Tetraspace
 
OK, I can buy both explanations, of course the examples in the book don't mention the flatlanders moving around, merely that they see a giant circle appear.

As for knowing the ball is a sphere and not a disk, I could only do that if it were close enough.

It's a little hard to imagine seeing something that has NO height. But these are fascinating concepts to consider. I look forward to many more discussions.

>>>--mark-->
 
The elite flatlanders practiced the art of identifying the shape based on lighting; the omnipresent fog would dim the figure before them in a characteristic pattern and those who trained in sight recognition could tell the shape from the color pattern.
 
Generalizing, a person of dimension n will see a hyperplane of dimension n-1 (flatlanders see a line, we see a plane, "tetronians" see a "realm"). Thus, a being in any dimension would only need 2 eyes, because the combination of the two images in the brain adds the last dimension and brings the image up to dimension n.
 
Originally posted by Pflip
My question is how they can tell it's a circle. It would seem that if the ball were to come down in front of them, all they would see is a darknesss on the horizon. How could they possibly get a "bird's eye view" and see the outline of the object?
I don't remember precisely but I believe he said that if their plane was to
pass past the object then they'd "see" a circle - the line would first get
wider and then narrower again. (Couldn't read past the middle of that book,
all that art stuff bored me to death, I guess I should finish reading it sometime.)

Live long and prosper.
 
i think the question was how the flatlander could perceive the shape as a circle, as opposed to them thinking it was a line, square, triangle, or any other shape. If they thought it was a line, then they would see a line grow & shrink instead of thinking it was a circle doing that.
 

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