Rummaging around, I found this in ChatGPT.
Construction of the Cantor Set
- Start
with a line segment: Begin with the interval [0,1] on the
real number line.
- Remove
the middle third: Remove the open interval (1/3,2/3), leaving two closed intervals: [0,1/3] and [2/3,1].
- Repeat
the process: For each remaining interval, remove its middle third. For
example:
- In
the next step, remove (1/9,2/9) and (7/9,8/9).
- This
process continues indefinitely.
The Cantor set consists of all points that are never removed
during this process.
Properties of the Cantor Set
- Uncountable:
Despite appearing "small," the Cantor set is uncountably
infinite. It contains as many points as the real numbers in [0,1].
- Zero
measure: The total length of the intervals removed adds up to 1, so
the Cantor set has Lebesgue measure zero. It is "small" in this
sense.
- Nowhere
dense: The Cantor set is nowhere dense in [0,1], meaning it
does not contain any intervals of positive length.
- Self-similar:
The Cantor set is a fractal. It looks "the same" at all scales
and can be described by recursive patterns.
- Perfect
and closed: The Cantor set is a perfect set (every point is a limit
point of the set) and a closed set (it contains all its limit points).
- Ternary
representation: A point in [0,1] belongs to the Cantor set
if and only if it can be written in base 3 (ternary) without using the
digit 1.
The Cantor set is a fundamental example in mathematics for
illustrating ideas about infinity, measure, and topology. It is also used to
demonstrate the concept of a set that is uncountably infinite yet has no
"length" in the traditional sense.
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