Is a cell really a 2-dimensional creature or is it really egg shaped?
It makes sense in a 2 dimensional world that the cell wall keep the cell intact. But what happens in the 3rd dimension? Is the cytoplasm enclosed completely in a cell wall? If so, is the cell wall just transparent when viewed perpendicularly?
Cells exist in all three dimensions. They are not so much egg-shaped as…“cell-shaped.” Here’s what a nerve cell looks like:
Also, only plant cells have a cell wall (although bacteria are encapsulated in a sugar coating).
The commonly seen 2-D image of a cell is what happens when you squish it between a slide and a slide cover, or make a thin slice of it.
This makes me wonder if there’s anything that takes up space in the 3D world that is not 3-dimensional. No matter how thin it may be if it’s “in space” it just has to have some thickness. What’s wrong with my thinking? Are there examples of 2D objects that exist in 3D space? Even drawings of 2D objects have the thickness of whatever medium is doing the drawing, right?
[QUOTE=cmosdes… If so, is the cell wall just transparent when viewed perpendicularly?[/QUOTE]
Yes, in general cell membranes are usually transparent when viewed perpendicularly, like through a microscope.
They are in reality only a couple of molecules thick.
Zeldar, what about a shadow or a projected image on a flat surface? Those could be considered strictly two dimensional, in a way.
Good example. Now the question becomes “Does a shadow exist in 3D space?” I would point out that the light falling on things not included within the confinces of the shadow, and the lack of light falling within the confines of the shadow, is/are what make the shadow appear to exist. It is not even a dimensional entity, but some other type of thing (like an idea or a wish or some other abstract entity) that has a name but doesn’t exist in 3D space.
What’s wrong with my thinking?
Do numbers exist in 3D space? (not those carved out things that represent numbers, but numbers themselves)
More than you ever wanted to know or dreamed that could be known about the 2-D vs. 3-D nature of shadows and their existence or non-existence in the real world.
Shadows are regions of greater and lessor illumination on the surface of 3d objects. That makes them 3d in my book.
Your way of saying this makes it hard to argue that the shadow appears in the 3D world and therefore to whatever degree it exists it does so in the 3D world. I’m still maintaining that the shadow has no 3D properties. It has no depth. You could mark off the perimeter of a shadow like they do dead bodies with chalk, but what is its thickness, its third dimension?
Shadows have length and width. That’s two dimensions. My definition of an object would require three dimensions, so an object that has only two dimensions wouldn’t make much sense. Therefore, a projection of an object (such as a shadow) is as 2 dimensional as it gets.
But it does have depth. It does not have thickness there is a difference.
care to expound?
Is a shadow an object or a perception? Do shadows happen any place other than in human brains? There are many variations of light intensity that aren’t called shadows, so I submit that a shadow is really the name of a kind of relationship and not an object in the objective sense. Subjectivists need not apply.
A shadow is a region of lower lighting that exists on a surface. All real world surfaces have exist in 3 dimensions therefore they have depth. Therefore the shadow on the surface has depth. The shadow does not exist except at the surface so it is not like a coating that has thickness.
I have been thinking a little more about this and depending on what you want to call the shadow it can exist in 3 dimensions. There are some uses of the word shadow that refer to the volume of space where the light is blocked by another object. “He was difficult to see because he moved into the shadow of the doorway.”
Clever demonstration of the “depth” of a shadow that’s hard to fault.
If you see the shadow on the ground where its only visible dimensions are the outline it makes on the ground, can you make an argumant for that to have depth or thickness?
I am not sure what you are asking here. The ground is not perfectly flat therefore this edge that goes around the region of shadow will exists in 3 dimensions and thus have depth.
Yeh, I think we’re delving into the murky depths of semantics now. I think we’d all agree that a shadow is merely a projection of any 3 dimensional object. The fact that a shadow is projected onto a 3D surface, doesn’t mean the perceived shadow has another dimension other than its length and width. (especially if you only thought of it in terms of its topology).
As to the OP, anything that is made up of matter is going to have “thickness”. Especially at the relatively HUGE dimensions a cell has compared to that of a single molecule.
Numbers are an abstract concept that exist only in our minds, which we represent using printed symbols such as “4” and “83” and that we use to solve problems and answer questions about the world. The numbers themselves, though, don’t exist in any kind of space.
Okay, let’s try it this way. Lay out a big slab of plywood on the ground. As carefully as you can, do a topo map of the surface of that plywood, noting every dent and crease and other irregularity that keeps that plywood from being perfectly flat and smooth. Next stand some object next to the plywood and shine a light on the object so as to cast a shadow of the object onto the plywood.
Are you prepared to describe a technique that will re-measure the surface of the plywood to find the thickness of the shadow on the plywood? If so, you may have a patentable device/method. If not, I suspect the idea of a shadow’s thickness will rely on something more subtle than this demonstration.
I am not saying that shadows have thickness, I am saying that they are a surface that has depth. In your plywood example the shadow has length and width along the plywood but also depth due to the roughness of the plywood.
