Logical argument using infinity

How can the infinite plane exist?
Well, for one, it's well-defined, so it passes the hurdle where the infinite circle idea seems to fall flat.

How do you construct it?
Probably something along the lines of taking the set of all points that have two real numbers as their orthogonal coordinates, or something along those lines.

The Euclidean plane is infinite. How did I make that jump? Is it to infinity?
Again, you seem to be laboring under severe misconceptions about limit taking. You didn't start with a finite plane that you extended to infinity, so no, you didn't take a limit here.
 
Almost right: you are extending the circle towards infinity. That's taking the limit of the radius to infinity.
No I'm extending the circle indefinitely, without limit. I don't need a function that relates the radius to the curvature. All I need is indefinite extension (hell, I don't even need infinity, because that's implicit).
Again, you seem to be laboring under severe misconceptions about limit taking.
And you seem to be unable to distinguish between the modern concept in calculus, of the limit of a function, and the ancient Greek concept of indefinite extension.
You didn't start with a finite plane that you extended to infinity, so no, you didn't take a limit here.
I didn't start with a finite plane, because I can't--the plane is infinite.

But your orthogonal coordinates and pairs of real numbers is a construction, right? In the infinite plane? So how do you know where to put the origin (I know that's a stupid question, but here we are).
The answer to the stupid question is: it doesn't matter; the plane is infinite in extent. So then it doesn't matter where you stand (anywhere will do), it doesn't matter where you point, there is a circle of directions over every point.

Where is the circle of directions? It doesn't matter where it is because you can prove it exists . . .
Since it doesn't matter where it is, the circle can be at infinity.
 
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No I'm extending the circle indefinitely, without limit.
More misconceptions. Please look up what "taking the limit to infinity" means.

I don't need a function that relates the radius to the curvature.
Actually, you already have set that up in your OP. That you didn't realize that doesn't mean you didn't do it.

All I need is indefinite extension
Which is exactly what limit taking is...:rolleyes:

(hell, I don't even need infinity, because that's implicit).
If you don't need infinity, you can't have an infinite circle. Are you now abandoning your infinite circle claims completely?
 
If you construct an actual circle around a point and call it a circle of directions, does it need to have a finite radius?
Yes, if you need to construct the circle.

What if you just need to prove there is a circle of directions? Where does the circle "need" to be?
What, if anything, does this have to do with taking a limit?
 
If you construct an actual circle around a point and call it a circle of directions, does it need to have a finite radius?
I don't know; "circle of directions" is something you came up with, so why don't you answer your own question?

Yes, if you need to construct the circle.
Well, there you go, I guess?

What if you just need to prove there is a circle of directions? Where does the circle "need" to be?
What, if anything, does this have to do with taking a limit?
I have no clue what a "circle of directions" is, so I can't provide you with any answers regarding that.
 
I have no clue what a "circle of directions" is, so I can't provide you with any answers regarding that.
Oh bullshit.
You know what a direction is I assume? And what a circle is?
Stand at the centre of a given circle. How many directions can you point in? Is there a semantic problem with calling this set of directions "a circle of directions"?

No? Well, there we are then. You can also call the set of circles of directions, on some manifold, a circle bundle (whoa, I just did!).
 
(Again, please stop adding to your post after posting it!)

And you seem to be unable to distinguish between the modern concept in calculus, of the limit of a function, and the ancient Greek concept of indefinite extension.
Since I understand that limit taking can be seen as an generalization of indefinite extension, I'm perfectly capable of distinguishing the two, thank you very much.

I didn't start with a finite plane, because I can't--the plane is infinite.
So why were you talking about limit taking there then?:?

But your orthogonal coordinates and pairs of real numbers is a construction, right?
I suppose, yes.

In the infinite plane?
Wrong. It's "of the infinite plane". I'm constructing it; that was the task you asked of me. One cannot construct a thing inside the thing that one is trying to construct; that's ridiculous.

So how do you know where to put the origin (I know that's a stupid question, but here we are).
What do you mean, "where"? It's not like I'm placing points into an already existing space. In fact, the origin is an arbitrary choice, so I guess you could answer "anywhere you want"?

The answer to the stupid question is: it doesn't matter; the plane is infinite in extent.
How can you have an infinite plane when you are still busy constructing it? You are making no sense.

So then it doesn't matter where you stand (anywhere will do), it doesn't matter where you point, there is a circle of directions over every point.
What is a "circle of directions"?

Where is the circle of directions?
The more I read "circle of directions", the less coherent the term becomes. How can a circle be constructed out of directions?

It doesn't matter where it is because you can prove it exists . . .
Please provide that proof then! I've asked you multiple times for proof now, and you continue to refuse while also continuing to claim the proof exists. It's approaching intellectually dishonesty, to be frank.

Since it doesn't matter where it is, the circle can be at infinity.
A circle being located at infinity doesn't mean the circle is infinite in size, so I don't know why you are bringing this up?
 
Oh bullshit.
You know what a direction is I assume? And what a circle is?
Well, obviously.

Stand at the centre of a given circle. How many directions can you point in?
360 degrees, obviously.

Is there a semantic problem with calling this set of directions "a circle of directions"?
Yes, because if you read the definition of circle I gave earlier, this obviously isn't one.

Please stop redefining words mid-conversation without telling anybody.

No? Well, there we are then.
Actually, not "no".

You can also call the set of circles of directions a circle bundle (whoa, I just did!).
Why do you feel the need to start defining things that are irrelevant to the discussion at hand? Are you trying to pull this thread off-topic?
 
Wrong. It's "of the infinite plane". I'm constructing it; that was the task you asked of me. One cannot construct a thing inside the thing that one is trying to construct; that's ridiculous.
There's a difference between "in the infinite plane", and "of the infinite plane"? That's pretty cute.
And you are "constructing" the infinite plane? That's even cuter.
It's not like I'm placing points into an already existing space.
Ha ha hah . . . etc
 
Yes, because if you read the definition of circle I gave earlier, this obviously isn't one.
You aren't very well-read, are you? A circle of directions isn't that common a term, but it is well understood (and not really hard to understand, unless you're too cute to be bothered).
Why do you feel the need to start defining things that are irrelevant to the discussion at hand? Are you trying to pull this thread off-topic?
Why should I accept what you say about relevance? Who TF are you?
 
There's a difference between "in the infinite plane", and "of the infinite plane"? That's pretty cute.
And you are "constructing" the infinite plane? That's even cuter.Ha ha hah . . . etc
Post #59: You: "How can the infinite plane exist? How do you construct it?"

So yeah, I'm sorry I took up your challenge. It's becoming more and more clear you are just trolling. Have fun with that!
 
I'm not convinced you would necessarily step along the line. Let's say the line lies at an angle of 30 degrees; if I take an infinite (straight) step at 45 degrees from a point on the line, how can I end up back on the line? Euclidean geometry says that's not possible: two non-parallel straight lines can only have on intersection, and that's where I started from. Please explain how you see this being possible.
But the diameter of the circle also becomes infinite, no? Why not an infinitely large curved plane?

Take a small completed circle and expand the circle infinitely large. Does it cease to be a circle? Will the circle break at some point and become parallel lines?
 
But the diameter of the circle also becomes infinite, no?
A circle with an infinite radius would also have an infinite diameter, yes.

Why not an infinitely large curved plane (space)?
That would be non-Euclidean; I've explicitly stayed away from that in this thread.

Take a circle and expand the circle infinitely large. Does it cease to be a circle?
That's what the whole discussion between arfa brane and me was about. It seems that both of us have come up with arguments why infinite circles can't exist, without having found any counter-arguments, so it seems that if such a thing is possible, then yes, it ceases to be a circle.
 
NotEinstein said:
It seems that both of us have come up with arguments why infinite circles can't exist, without having found any counter-arguments, so it seems that if such a thing is possible, then yes, it ceases to be a circle.
It seems that it's a matter of choice whether an infinite circle is still a circle; some say no it can't be, by definition, some say it is a circle "at infinity", but loses most of the properties of a circle.

However it does still have identifiable antipodal points; indeed, the infinite circle is different in that respect because the identifications aren't added, like you can add to a finite circle, but axiomatic. Calling the line at infinity in the projective plane a "circle" is technically incorrect; but given a context (infinite distance), it's well understood what is meant. Then you see there is a kind of logic to it. Oh well.
 
A circle with an infinite radius would also have an infinite diameter, yes.
That would be non-Euclidean; I've explicitly stayed away from that in this thread.

That's what the whole discussion between arfa brane and me was about. It seems that both of us have come up with arguments why infinite circles can't exist, without having found any counter-arguments, so it seems that if such a thing is possible, then yes, it ceases to be a circle.
So, what happens to the plane, it also disappears, no?

Are we looking at a change from a 2D plane to a 1D line. Is that not against some rule?
How about 3D space, inflated infinitely large? What happens to that? Does it change from 3D to an infinity of straight 1D lines in all directions. Originating from where?

Is our description of the universe incorrect or is it not infinite? That would solve the entire exercise, no?
 
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So, what happens to the plane, it also disappears, no?
What plane do you mean, exactly?

Are we looking at a change from a 2D plane to a 1D line. Is that not against some rule?
I don't think there's any 2D plane changing into a 1D line in this situation?

How about 3D space, inflated infinitely large?
Are you "inflating"/expanding the space itself, or things within the space?

What happens to that? Does it change from 3D to and infinity of 1 D lines in all directions
Why would a 3D space change into 1D lines in all directions?

Is our description of the universe incorrect or is it not infinite?
How is this related to anything? Also, are you suggesting you know whether the universe is infinite or not (in spatial size)?

That would solve the entire exercise, no?
No, because we are talking about abstract concepts, not physical reality.
 
What plane do you mean, exactly?
A circle forms a 2 D plane, no? All points equi-distant from the center?
I don't think there's any 2D plane changing into a 1D line in this situation?
Is the center of the circle not in the center of the plane as well as in the center of a sphere?
Are you "inflating"/expanding the space itself, or things within the space?
That would be an example of a 3D sphere inflated infinitely. If the surface expands infinitely, does the sphere cease to be sphere at some point?
Why would a 3D space change into 1D lines in all directions?
Does a sphere not have an infinite number of circumferences, creating a "volume"? Unlike a circle which has just one circumference, creating a "circle"?
How is this related to anything? Also, are you suggesting you know whether the universe is infinite or not (in spatial size)?
No, I'm posing the question. It seems related to the OP and to the current example of a circle, no?
No, because we are talking about abstract concepts, not physical reality.
The argument would still need to be logically sound, no?

If not, it would not be possible, seems to me....:? That's why I am asking....o_O
 
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A circle forms a 2 D plane, no?
A circle lies in a plane, but it isn't one itself. Are you perhaps thinking of a disc?

Is the center of the circle no in the center of the plane?
Not of the plane the circle is in. If you are talking about a disc, then yes.

That would be an example of a 3D sphere inflated infinitely. If the surface expands infinitely, does the sphere cease to be sphere?
I guess if a sphere is defined as all the points with at certain radius from the center or closer, it would remain a sphere, but I'm not sure if that's the proper definition.

Does a sphere not have an infinite number of circumferences?
What do you mean? Are you talking about things like "great circles" ("orthodomes")?

No, I'm posing the question. It seems related to the OP and to the circle, no?
It's not related as far as I can see? How do you figure?

The argument would still need to be logically sound, no?
Well, yes, obviously. But for that trick to work, you'd need to find an infinite circle in reality, and we know that currently can't be done (the observable universe being finite and all that).

If not, it would not be possible, seems to me....:? That's why I am asking....o_O
Not being able to find a physical case of an infinite circle doesn't mean one can't be constructed in abstract, so no this part of your reasoning doesn't hold up.
 
What do you mean? Are you talking about things like "great circles" ("orthodomes")?
No, I just visualize a sphere as being an infinite collection of equal circumferences in all 3 dimensions, equi-distant from the center, completely enclosing the volume of the sphere?

Any single measurement of a circumference of a sphere yields a circle, no?
 
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