December 17, 2013
by Tim Knight
Flatland – A Post by Erik Shofer (Year 2 Math HL Student)In Flatland, a book that is now a movie about a square in a 2D world, the 2 dimensional shapes like the square see each other in 2D and are unable to process the existence of a 3D sphere that comes into their world. Similarly, some line segments that exist on a 1 dimensional line in the 2D square’s world see each other in 1 dimension only and are unable to believe that the world is 2D. I think that, while the idea of different beings existing in different dimensions is an interesting thought (and a good political satire), but I think that the way the shapes see in the book and movie is incorrect.
In Flatland, the shapes on the 2 dimensional plane see each other in 2 dimensions. This is shown by how they know that they are squares, circles, hexagons and so on. However, I believe that if two 2 dimensional shapes were to look at each other, they would only see a line. As they exist in a 2D space, they can only see along their 2D plane. The reason this would cause a line can be explained like this: If you have a plane (or paper) with shapes on it and you looked at it from a parallel plane, (or look at the paper while it is facing you) you would see shapes. However, if you then turned the plane (or paper) so that you were viewing it from a perpendicular plane, (or viewing the paper while it is flat at eye-level) you would merely see a line as from your plane (or view), you would only see the second plane along the line where the two planes (one being your sight and the other being the paper) intersected. This is how the creatures that exist in the 2D plane would see as they can only see along their plane, not from the side, and therefore would only see lines in front of them.
Furthering on that idea, the creatures that existed in 1 dimension would not see each other as lines, but rather as points. An example would be to take a line (or piece of string) that is divided by colors into segments and view it from a perpendicular line (or hold the string straight away from you at eye-level). It would look like a point (or just the end of the string) because from your line (or view), you would only see the other line at the point where it intersects. This is also how a creature existing in 1 dimension would see, a single point in front of it hiding the rest of the line from view. The 1 dimensional creature would also only ever see one point because, no matter where it moves (it can only move along its own line), the lack of a second dimension means that it can never go around the line segment in front of it.
These two earlier statements would make it seem that a 3 dimensional creature would see in 2 dimensions. This would be true, except for one thing. A 3 dimensional space allows for multiple viewpoints facing the same area or general direction, but at different angles (i.e. 2 eyes). These multiple viewpoints allow the view to be transformed into 3 dimensions inside a brain by using the difference between the two views to add depth. A person missing one eye however, would only be capable of seeing in 2 dimensions as they would have no second viewpoint to compare their one view to.
A 2 dimensional shape would still view a 3 dimensional shape as a line because, the 2 dimensional shapes can only see a small part of the 3D shape (the part intersecting with the plane) at a time. A 1 dimensional shape would similarly see everything as a point, even if it was a 2D or 3D shape as it could only view part of it at a time.
This raises the question, what does a 4 dimensional being see?
My answer is that, based on the pattern above, a 4 dimensional shape sees in 3 dimensions. While this seems odd as we 3D creatures see in 3D, it makes sense because we don’t see in 3D. We simply see in 2D twice (each eye) and then compare the two to make a 3D image inside of our brains. A 4D creature would see everything in true 3D. Unlike the movies where true 3D means adding depth, a creature seeing in true 3D would see objects from every possible 3D angle at once. It would be like viewing a cube from below, above, the left side, the right side, behind, in front and every other possible viewpoint all at the same time. Unfortunately, this is something that the human brain is incapable of conceiving or imagining as the furthest dimension it can think in is 3D. It is likely impossible that a human will ever be able to understand, let alone view objects in or from a 4th dimension.
And if a 4 dimensional creature sees in true 3D, what would a 5 dimensional creature’s view be? That is, if it there are even 5 dimensions.