What is the Fraction of One Point Compared to an Infinite Line?

  • Context: High School 
  • Thread starter Thread starter CrossboneSRB
  • Start date Start date
  • Tags Tags
    Discussion
Click For Summary

Discussion Overview

The discussion revolves around the concept of comparing a single point to an infinite line, specifically questioning the fraction that a point represents in this context. It also touches on the area of contact between a perfectly round object and a flat surface, exploring both theoretical and mathematical implications.

Discussion Character

  • Conceptual clarification
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • Some participants propose that the fraction of a point compared to an infinite line is 1/∞, suggesting that it represents an infinitesimally small quantity.
  • Others argue that the length of a single point is 0, leading to the conclusion that the ratio of the length of a point to a line segment is 0/(b - a) = 0.
  • One participant emphasizes that division by infinity is not permissible in standard arithmetic, asserting that infinity cannot be treated as a normal number.
  • Another participant introduces the idea of using limits to approach the concept of infinity, stating that the limit of 1/x as x approaches infinity is 0.
  • Regarding the area of contact between a perfectly round object and a flat surface, some participants suggest that if the object is a sphere, the area of contact is zero due to the single point of contact.
  • One participant mentions that the concept of division by infinity can be rigorously addressed through complex infinity on the Riemann sphere.

Areas of Agreement / Disagreement

Participants express differing views on the treatment of infinity and the implications for the fraction of a point compared to a line. There is no consensus on how to interpret or calculate these concepts, indicating ongoing debate.

Contextual Notes

Limitations include the ambiguity in defining the terms used, such as "fraction" and "area of contact," as well as the varying interpretations of infinity in mathematical contexts.

CrossboneSRB
Messages
6
Reaction score
0
So here's a question for you, if on a line we chose one point, then what is the fraction of this point compared to the line?
I think we all agree that between two points there are infinite amount of other points, correct? So what fraction of a line is one point among infinite others? Isn't it 1/∞?

Here's another question, if a perfectly round object is placed on perfectly flat surface, what is the area of contact?
 
Mathematics news on Phys.org
CrossboneSRB said:
So here's a question for you, if on a line we chose one point, then what is the fraction of this point compared to the line?
0. The "length" of a single point is 0.
CrossboneSRB said:
I think we all agree that between two points there are infinite amount of other points, correct? So what fraction of a line is one point among infinite others? Isn't it 1/∞?
No, because we don't calculate length on the basis of how many points are in an interval. We calculate length by subtracting the position of the point on the left from the position of the point on the right. The length of an interval [a, b] between two points (assuming a < b) is b - a.

The ratio of the "length" of a point to the length of the line segment [a, b] is 0/(b - a) = 0.

In any case, division by ∞ is not allowed.
CrossboneSRB said:
Here's another question, if a perfectly round object is placed on perfectly flat surface, what is the area of contact?
Your question isn't very precise. A circular disk is a perfectly round object, so the area of contact would be the area of the disk.

If by "perfectly round object" you mean a sphere, there is only one point of contact, so the area of contact would be zero for reasons similar to what I already gave.
 
Infinity cannot be treated as a normal integer or real number. It is not part of one of these sets of numbers. In that sense 1/ꝏ is meaningless.

You can use the infinity concept in limits. Going to infinity means taken larger and larger values (ꝏ is not a number that can ever reach)

The limit of 1/x as x approaches Infinity is: 0For the second question: when a plane "touches" a sphere they have one point in common. The area of contact is therefore 0
 
The concept of division by infinity can also be made rigorous, instead of using limits, by considering complex infinity on the Riemann sphere.
 

Similar threads

  • · Replies 25 ·
Replies
25
Views
4K
  • · Replies 10 ·
Replies
10
Views
3K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 8 ·
Replies
8
Views
3K
  • · Replies 21 ·
Replies
21
Views
3K
  • · Replies 2 ·
Replies
2
Views
2K
Replies
1
Views
2K
  • · Replies 10 ·
Replies
10
Views
3K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 4 ·
Replies
4
Views
2K