What are two Dimensional objects?

[uwekezaji]

Hi all. I am new here. What actually are two dimensional objects? Do they really exist in material world?

[YaDinghus]

A two dimensional object is anything that can be described using vertices (points connecting edges) with only two coordinates. It also counts when vertices with more than two coordinates can be simplified to two coordinates (for instance when they are all in a higher dimensional space, but are located on a plane in this space).

Our material world has no (strictly) 2D objects. You may be able to make a square on a sheet of paper or with a wire frame, but the sheet and the frame have a thickness of their own

An object in our material world can cast a shadow on a plane surface. This shadow is 2D, but it is a pseudo-object

I tried to add a reference to a definition of pseudo-objects, but could only find references to grammar and programming. My naïve, trivial definition regarding this case would be: A Pseudo-object is an object which is generated by another object by blocking or emitting directed rays (e.g. shadow or laser point)

Edited June 5, 2018 by YaDinghus
Shadows

[uwekezaji]

15 minutes ago, YaDinghus said:

A two dimensional object is anything that can be described using vertices (points connecting edges) with only two coordinates. It also counts when vertices with more than two coordinates can be simplified to two coordinates (for instance when they are all in a higher dimensional space, but are located on a plane in this space).

Our material world has no (strictly) 2D objects. You may be able to make a square on a sheet of paper or with a wire frame, but the sheet and the frame have a thickness of their own

An object in our material world can cast a shadow on a plane surface. This shadow is 2D, but it is a pseudo-object

Thanks for your reply. I do not understand when an object like a triangle is drawn on a sheet of paper and called a 2D object because even the ink used to draw it has a thickness!!

[YaDinghus]

6 minutes ago, uwekezaji said:

Thanks for your reply. I do not understand when an object like a triangle is drawn on a sheet of paper and called a 2D object because even the ink used to draw it has a thickness!!

The ink or graphite from your pencil is like the wire frame, and yes it has a thickness of its own. It's not a 2D object in itself, but it is a good representation. That's all you need for math

[uwekezaji]

21 minutes ago, YaDinghus said:

The ink or graphite from your pencil is like the wire frame, and yes it has a thickness of its own. It's not a 2D object in itself, but it is a good representation. That's all you need for math

Thank you

[studiot]

4 hours ago, YaDinghus said:

The ink or graphite from your pencil is like the wire frame, and yes it has a thickness of its own. It's not a 2D object in itself, but it is a good representation. That's all you need for math

Both posts,

Good discussion in answer. +1

[Strange]

4 hours ago, uwekezaji said:

Thanks for your reply. I do not understand when an object like a triangle is drawn on a sheet of paper and called a 2D object because even the ink used to draw it has a thickness!!

The 2D triangle is a mathematical construct or abstraction. When you draw one with a pencil, it is a 3D representation of that abstract concept.

[uwekezaji]

1 minute ago, Strange said:

The 2D triangle is a mathematical construct or abstraction. When you draw one with a pencil, it is a 3D representation of that abstract concept.

That makes sense. Thanks a lot

[StringJunky]

2 minutes ago, Strange said:

The 2D triangle is a mathematical construct or abstraction. When you draw one with a pencil, it is a 3D representation of that abstract concept.

A projection of a triangle onto a screen  would make the triangle 2D since the photon is a point particle.

 

[YaDinghus]

3 minutes ago, StringJunky said:

A projection of a triangle onto a screen  would make the triangle 2D since the photon is a point particle.

 

I try(angle) to be as coherent as possible

3 minutes ago, StringJunky said:

A projection of a triangle onto a screen  would make the triangle 2D since the photon is a point particle.

 

Pseudo-object. Though I would prefer a standalone thread on this subtopic

+1 nonetheless

Edited June 5, 2018 by YaDinghus
Acknowledgement

[uwekezaji]

2 hours ago, YaDinghus said:

I try(angle) to be as coherent as possible

Pseudo-object. Though I would prefer a standalone thread on this subtopic

+1 nonetheless

How does a photon being a  particle lie in 2D? 

[YaDinghus]

3 minutes ago, uwekezaji said:

How does a photon being a  particle lie in 2D? 

A photon is a particle that doesn't have a physically meaningful size, and thus can be considered a point in space. This way you can have a hypothetical 'photon-thick' layer of photons making a 2D object in 3D space. This is a hypothesized scenario by Stephen Hawking about photons orbiting a black hole on the event horizon, where they neither fall into the black hole but can't escape either. Note: a sphere's surface is also a 2D object on a 3D sphere

[StringJunky]

11 minutes ago, uwekezaji said:

How does a photon being a  particle lie in 2D? 

A "Particle" is an excitation in a field really; it just means it has a discrete energy but no spatial extent.

[YaDinghus]

7 minutes ago, StringJunky said:

A "Particle" is an excitation in a field really; it just means it has a discrete energy but no spatial extent.

True, but afaik all fermions have a physically meaningful size, while this can't be said about Photons, and I'm not sure whether this applies to other bosons as well

But we're sorta off topic here. 

Edited June 5, 2018 by YaDinghus

[StringJunky]

6 minutes ago, YaDinghus said:

True, but afaik all fermions have a physically meaningful size, while this can't be said about Photons, and I'm not sure whether this applies to other bosons as well

But we're sorta off topic here. 

I think the upper limit of physical 2D is probably a graphene molecule, which is basically a flat hexagon of carbon atoms.

Edited June 5, 2018 by StringJunky

[YaDinghus]

1 minute ago, StringJunky said:

I think the limit of physical 2D is probably a graphene molecule, which is basically a flat hexagon of carbon atoms.

I should get a t-shirt that says I <3 Graphene

[taeto]

Do you consider the event horizon of a black hole to be a thing that exists in the real world? It might fit the bill pretty close, no?

[studiot]

19 minutes ago, taeto said:

Do you consider the event horizon of a black hole to be a thing that exists in the real world? It might fit the bill pretty close, no?

Any interface is only as rough or smooth as the initiating structure.

[taeto]

5 minutes ago, studiot said:

Any interface is only as rough or smooth as the initiating structure.

But it is an actual boundary more than just an interface. A (non-rotating) black hole at a given time has a precise Schwarzschild radius that depends on its mass, and the event horizon surrounds the singularity spherically at that precise distance. I don't think you are supposed to imagine anything being fuzzy. In which case it qualifies as a 2D surface.

[studiot]

It is the result of a mathematical model that does not take inhomogenity in to acount.

Many such models exist in Physics, such as the water /air interface, the shape of the gravity field on Earth and so on.

These are smooth at the level of the mdoel but bumpy at a molecular or sub molecular scale.

So too would the S Radius be at scale of whatever passes for primary lumps of matter in the black hole.