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# Continuum

The term "continuum" has (at least) two distinct technical meanings in mathematics.

The first is a compact connected metric space (Kuratowski 1968; Lewis 1983, pp. 361-394; Nadler 1992; Prajs and Charatonik).

The second is the nondenumerable set of real numbers, denoted . The continuum satisfies

 (1)

and

 (2)

where is aleph0 (Aleph-0) and is a positive integer. It is also true that

 (3)

for . However,

 (4)

is a set larger than the continuum. Paradoxically, there are exactly as many points on a line (or line segment) as in a plane, a three-dimensional space, or finite hyperspace, since all these sets can be put into a one-to-one correspondence with each other.

The continuum hypothesis, first proposed by Georg Cantor, holds that the cardinal number of the continuum is the same as that of aleph1. The surprising truth is that this proposition is undecidable, since neither it nor its converse contradicts the tenets of set theory.

Aleph-0, Aleph-1, Compact Space, Connected Space, Continuum Hypothesis, Continuum Theory, Decomposable Continuum, Denumerable Set, Hereditarily Decomposable Continuum, Indecomposable Continuum, Irrational Number, Metric Space, Rational Number

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## References

Kuratowski, K. Topology, Vol. 2. New York: Academic Press, 1968.Lewis, W. "Continuum Theory Problems." Topology Proc. 8, 361-394, 1983.Nadler, S. B. Jr. Continuum Theory. New York: Dekker, 1992.Prajs, J. R. and Charatonik, W. J. (Eds.). "Open Problems in Continuum Theory." http://web.umr.edu/~continua/.

Continuum

## Cite this as:

Weisstein, Eric W. "Continuum." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/Continuum.html