September 16th, 2024

Why Gauss wanted a heptadecagon on his tombstone

Mathematician Johann Carl Friedrich Gauss proved the constructibility of a heptadecagon at 18, solving a long-standing problem. His legacy is symbolized by a 17-pointed star in his birthplace.

Read original articleLink Icon
CuriosityAdmirationFrustration
Why Gauss wanted a heptadecagon on his tombstone

Mathematician Johann Carl Friedrich Gauss, known for his significant contributions to mathematics, particularly in geometry, desired a regular heptadecagon (17-sided polygon) to be etched on his tombstone. This shape represented a major achievement in his work, as he proved its constructibility using only a compass and straightedge, a problem that had perplexed mathematicians for over 2,000 years. Gauss's proof, completed at the age of 18, demonstrated that the length required to construct a heptadecagon could be expressed using basic algebraic operations. This breakthrough not only established the heptadecagon's constructibility but also led to a broader understanding of which regular polygons can be constructed with these tools. Gauss's work was later validated by Pierre Wantzel, who confirmed the impossibility of constructing certain polygons, including the heptagon and hendecagon, with a compass and straightedge alone. Although Gauss's wish for a heptadecagon on his tombstone was not fulfilled, a monument in his birthplace features a 17-pointed star, symbolizing his legacy in mathematics.

- Gauss wanted a heptadecagon on his tombstone to symbolize his mathematical achievements.

- He proved the constructibility of the heptadecagon at age 18, solving a problem that had stumped mathematicians for centuries.

- His work established criteria for which regular polygons can be constructed with a compass and straightedge.

- Pierre Wantzel later confirmed Gauss's findings regarding the impossibility of constructing certain polygons.

- A monument in Gauss's birthplace features a 17-pointed star in lieu of the heptadecagon.

AI: What people are saying
The comments on the article about Gauss and the heptadecagon reveal several key themes and discussions.
  • Many commenters express a desire for more recognition of Middle Ages mathematicians, contrasting them with Greek and Renaissance figures.
  • There is curiosity about the limitations of compass-and-straightedge constructions, particularly regarding polygons with odd numbers of sides.
  • Some users share resources, such as videos and links, to further explore Gauss's proof and related mathematical concepts.
  • Discussion includes the aesthetic and practical aspects of geometric constructions, with recommendations for hands-on practice.
  • Questions arise about the symbolism of Gauss's legacy, including the presence of a 17-pointed star on his headstone.
Link Icon 15 comments
By @zansara - 5 months
By @libraryofbabel - 5 months
A surprising related fact is that 200 years after Gauss and with a vast amount of progress in mathematics, we still don’t know the largest regular polygon with an odd number of sides that can theoretically be constructed in the Euclidean manner. For the curious, this is because the answer reduces to combinations of multiples of Fermat Primes, and nobody knows if there are any Fermat Primes beyond 3, 5, 17, 257, 65537. (See https://en.m.wikipedia.org/wiki/Constructible_polygon)
By @empath75 - 5 months
There's a series of two excellent videos on youtube about this proof:

Detailed description of the problem of constructable regular polygons and a gloss of the proof. https://www.youtube.com/watch?v=EX7U0DGBmbM

A full explanation of the proof: https://www.youtube.com/watch?v=Gdy1u4lsjDw

By @peter_d_sherman - 5 months
>"Can a compass and straightedge construct a line segment of any length? By Gauss’s time, mathematicians knew the surprising answer to this question.

A length is constructible exactly when it can be expressed with the operations of addition, subtraction, multiplication, division or square roots applied to integers.

[...]

Remarkably, the rudimentary tools that the ancient Greeks used to draw their geometric diagrams perfectly match the natural operations of modern-day algebra: addition (+), subtraction (–), multiplication (x), division (/) and taking square roots (√).

The reason stems from the fact that the

equations for lines and circles only use these five operations

, a perspective that Euclid couldn’t have envisioned in the prealgebra age."

Related:

https://en.wikipedia.org/wiki/CORDIC

By @kqr - 5 months
I recommend anyone to try to work through a few compass-and-straightedge constructions. It can be really satisfying and meditative.

Oliver Byrne made an insanely pretty colourful version of Euclid's Elements, which is available online. Grab a pen, paper, a string to make circles, and the edge of a book to draw straight lines, start with Proposition 1 and go as far as you'd like: https://www.c82.net/euclid/book1/#prop1

(There is also a physical facsimile of Byrne's Elements (ISBN:9783836577380) – it is one of the best additions I've ever made to my library. It is simply gorgeous.)

By @jordigh - 5 months
Does Gauss's headstone actually have a 17-pointed star on the back? I can't find any pictures of this online.
By @wwarner - 5 months
To me, the result is exciting because it shows how algebra, over hundreds of years, came back round to improve Euclidian geometry. Without the background, I wouldn't even know why it was an interesting problem. The motivation is very similar to that of the Langlands program.
By @teleforce - 5 months
If you read most of the mathematics articles you will be forgiven to think that there is no contributions made by the Middle Ages mathematicians ever. For some unknown reasons the writers will always mention and not missing Greek mathematicians contributions in this case Euclid, and then conveniently and ignorantly skipped about a thousand years by going straight to the Renaissance mathematicians in this particular case Gauss, who's the main character of the article.
By @zengid - 5 months
This is really interesting.. does anyone who knows more about Gauss's proof know why you can construct a 5 sided polygon with ruler and compass, but not a 7 or 11 sided polygon? Why do some primes work and others not?
By @yarg - 5 months
Seven sided never seemed that problematic to me?

You can't do it exactly, but you can do it to arbitrary degrees of accuracy; at least about as far as you can go without bumping into the precision limits of a compass and straightedge.

1/7 = 1/8 + 1/64 + 1/512 + 1/4096 + 1/32768... as you can see this will hit the limits of human precision in short order.

In general any fraction 1/(2^n - 1) can be expressed as an infinite sum (or a series that comes infinitesimally close)

1/(2^n - 1) = the sum from x equals one to infinity of 1/(2 ^ (x * n)). And we all know how to section any arch-length into fractions over powers of 2.

So starting with a complete loop, segment take the first piece, then take the second piece, segment and take its first piece... keep on adding all the little pieces together until it's so close enough to 1/7 that you can take a compass measure and use that to resegment the rest of the pie - making sure that you recurse enough that after you've market out 6 additional ones, you get near enough a collision to the first that you're not really worried.

But yeah, I'd be surprised if you could compass and straightedge even to a precision of one part in 4096 - and there's no way in hell that anyone's ever pulling off one part in 32768.

By @sbussard - 5 months
Ok hear me out - headstones are installed after someone dies. It’s still after his death, so the problem can still be corrected for future generations
By @jmclnx - 5 months
Nice read and explains what Yitang Zhang did in a manner I can almost understand!

Everytime I hear about Yitang Zhang, I cannot help but be amazed by his accomplishment.

https://en.wikipedia.org/wiki/Yitang_Zhang

By @calini - 5 months
Are we sure it wasn't just a low poly cirlce? :)