Line segment of length pi (Just a thought I've had)

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Discussion Overview

The discussion revolves around the concept of a line segment with a length of pi, exploring the implications of pi being an irrational number. Participants examine the nature of measurement, the distinction between physical and geometric lines, and the philosophical considerations of length in relation to irrational numbers.

Discussion Character

  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants propose that a line segment of length pi must be finite, despite pi being an irrational number with infinitely many decimals.
  • Others argue that the inability to measure the segment precisely does not imply that it can become indefinitely long.
  • A participant questions the meaning of "precisely measure," suggesting that while physical measurement may be imprecise, mathematical definitions allow for intervals of length pi to be considered precisely measured.
  • One participant emphasizes that while approximations of pi can be longer than others, they do not equate to pi itself, thus the segment does not get longer indefinitely.
  • Another participant asserts that at very small scales, atomic dimensions and quantum uncertainty prevent the possibility of measuring exactly pi, which applies to any irrational number.
  • A later reply highlights the distinction between physical lines and geometric lines, arguing that claiming a physical segment has an irrational length is meaningless.

Areas of Agreement / Disagreement

Participants express multiple competing views regarding the nature of line segments with irrational lengths, the implications of measurement, and the distinction between physical and abstract concepts of lines. The discussion remains unresolved.

Contextual Notes

Participants note limitations related to measurement precision, the abstract nature of geometric lines versus physical representations, and the implications of quantum uncertainty on measurements of irrational lengths.

eg2333
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If you were to imagine a line segment of length pi, I would guess it would have to be finite. But since pi is an irrational number, it has infinitely many decimals so can't you just keep sort of zooming in on the end of the segment so that it sort of keeps on getting longer indefinitely?

Pi is just an example, but I'm sure any irrational number would bring up the same idea. Any thoughts on this?
 
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NOT being able to precisely measure the length of the segment in this case, does not imply that the segment is/gets indefenitely long(er).
 
But what do you mean by "precisely measure"? If you are talking about using some kind of measuring device then, of course, it cannot be "precisely measured". No interval can in that sense. If you mean "mathematically", in the same sense that we talk about an interval "of length 1", then it can be "precisely measured". Measure out an interval of length 1 and construct a circle about one end of that interval having the interval as radius. The circle will be of length ]pi. An interval of length "pi" is no different from an interval of any other length.
 
eg2333 said:
If you were to imagine a line segment of length pi, I would guess it would have to be finite. But since pi is an irrational number, it has infinitely many decimals so can't you just keep sort of zooming in on the end of the segment so that it sort of keeps on getting longer indefinitely?

Well, 3.141592653 is certainly longer than 3.1415, but 3.1415 isn't pi, so no, it is NOT getting longer.
 
No, because at sufficiently small scales, atomic dimensions and quantum uncertainty would prevent the possibility of having something mesuring exactly \pi. The same applies for any irrational number.
 
JSuarez said:
No, because at sufficiently small scales, atomic dimensions and quantum uncertainty would prevent the possibility of having something mesuring exactly \pi. The same applies for any irrational number.

Huh, are people aware that physical lines and geometric lines are two different things?

Lines and line segments are abstract ideas. They're not what you draw on a piece of paper, nor are they anything that we see. To say that a physical line segment has irrational length is completely meaningless, as it is to say that a physical segment has some precise length.
 

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