1/2 + 1/4 + 1/8 + 1/16 + ⋯

Proof

As with any infinite series, the sum :\frac12+\frac14+\frac18+\frac{1}{16}+\cdots is defined to mean the limit of the partial sum of the first n terms :s_n=\frac12+\frac14+\frac18+\frac{1}{16}+\cdots+\frac{1}{2^{n-1}}+\frac{1}{2^n} as n approaches infinity, if it exists. By various arguments,\right] = 1+\left[s_n-\frac{1}{2^{n}}\right]. Subtracting sn from both sides, one concludes s_n = 1-\frac{1}{2^{n}}. Other arguments might proceed by mathematical induction, or by adding \frac{1}{2^n} to both sides of s_n=\frac12+\frac14+\frac18+\frac{1}{16}+\cdots+\frac{1}{2^{n-1}}+\frac{1}{2^n} and manipulating to show that the right side of the result is equal to 1.}} one can show that each finite sum is equal to :s_n = 1-\frac{1}{2^{n}}, and as n approaches infinity, the term \frac{1}{2^{n}} approaches 0 and so sn approaches 1.

History

Zeno's paradox

This series was used as a representation of two of Zeno's paradoxes.Field, Paul and Weisstein, Eric W. "Zeno's Paradoxes." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/ZenosParadoxes.html For example, in the paradox of Achilles and the Tortoise, the warrior Achilles was to race against a tortoise. The track is 100 meters long. Achilles could run at 10 m/s, while the tortoise only 5. The tortoise, with a 10-meter advantage, Zeno argued, would win. Achilles would have to move 10 meters to catch up to the tortoise, but the tortoise would already have moved another five meters by then. Achilles would then have to move 5 meters, where the tortoise would move 2.5 meters, and so on. Zeno argued that the tortoise would always remain ahead of Achilles. Similarly, Zeno's dichotomy paradox arises from the supposition that to move a certain distance, one would have to move half of it, then half of the remaining distance, and so on, therefore having infinitely many time intervals.Field, Paul and Weisstein, Eric W. "Zeno's Paradoxes." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/ZenosParadoxes.html

In both cases, each time interval is a term of this infinite geometric series, and so even in the limit of infinite terms it would sum to a finite total time. This is sometimes considered to resolve Zeno's paradoxes. However, insofar as Zeno was concerned with the problems of division of a continuum into an actual infinity of sub-parts, rather than the problem of their sum, it may not address the philosophical heart of Zeno's argument.

The Eye of Horus

The parts of the Eye of Horus were once thought to represent the first six summands of the series.

In ''Zhuangzi''

A version of the series appears in the ancient Taoist book Zhuangzi. The miscellaneous chapters "All Under Heaven" include the following sentence: "Take a chi long stick and remove half every day, in a myriad ages it will not be exhausted."

Notes

References

References

1. Abramowitz, M.; Stegun, I. A., eds. (1972). ''Handbook of Mathematical Functions with Formulas, Graphs, and Mathematical Tables'' (9th printing). New York: Dover. p. 10.
2. Huggett, Nick. (2010). "Zeno's Paradoxes: 5. Zeno's Influence on Philosophy".
3. Papa-Grimaldi, Alba. (1996). "Why Mathematical Solutions of Zeno's Paradoxes Miss the Point: Zeno's One and Many Relation and Parmenides' Prohibition". The Review of Metaphysics.
4. Stewart, Ian. (2009). "Professor Stewart's Hoard of Mathematical Treasures". Profile Books.
5. "School of Names > Miscellaneous Paradoxes (Stanford Encyclopedia of Philosophy)".