# John Horton Conway

##
Conway's Circle Theorem (click to go straight to it)

Conway's Proof of Morley's Theorem (click to go straight to it)

Colm was fortunate to spend quality time with the late John H. Conway (1937-2020) about a dozen times between April 1995 (when JHC visited Spelman College) and August 2017 (in NYC), taking in a July 1999 trip to Glendalough (Ireland) along the way.

Colm speaks about John as part of the BAAM! tribute (Sat 25 April 2020)

See his *Guardian
* obituary, and
Siobhan Roberts' *NYT*
obituary.
Also Numberphile has many fine Conway videos, along with a new
tribute here, featuring some previously unaired recordings of John himself
alongside reminiscences from Siobhan Roberts, David Eisenbud and Tony Padilla.
Hear here for BBC Radio 4's *Last Word* tribute (featuring Roger Penrose, it starts 14 minutes in).

Numerous articles in MAA journals, written by and about John and his friend and collaborator Richard Guy (1916-2020), have been collected and shared here courtesy of Don Albers.

John Conway posed and solved problems in a great variety of mathematical areas, one knotty one was only recently solved by Lisa Piccirillo .

16 May 2020, NYT published an extensive "Martin Gardner worthy" article by Conway
biographer
Siobhan Roberts called *Travels
with John Conway, in 258 Septillion Dimensions* which further explored his legacy.

The following day, Jim Propp published Confessions of a Conway Groupie.

On 23 May, *Nature* published a Conway Obit by
Manjul Bhargava.

Conway was sometimes described as magical. Here he is enjoying playing with the "anti-gravity decks of cards", at MOVES conference at MoMath in NYC, August 2017. (Photo courtesy of Ibrahim Dulijan.) He loved a good prank too.

## Conway's Circle Theorem

On 4 May 2020, Doris shared a new proof which we highlight below, saying "It's much nicer and more convincing. One that I think Conway would have been more likely to produce."

As for other proofs of this result predating the recent interest in the theorem,
Matt adds: "A small amount of internet detective work turned up a 2013 paper by Francisco
Capitán which does provide a proof of Conway's circle theorem, albeit in a
rather indirect and non-elementary way. In fact, that paper establishes a
generalization of Conway's result in which a certain set of six points is
defined relative to an arbitrary interior point **P** of any triangle.
These points are then shown to lie on a conic, and that conic turns out to be
a circle if and only if **P** is the incenter of the circle (in which case
the six points coincide with the ones Conway defined)."

On 7 May 2020, the *Aperiodical* ran a proof
without words of the result contributed by Colin Beveridge. Matt Baker responded,
"That's one of the most beautiful Proofs Without Words I've ever seen". An
associated
video (with words!) followed on 11 Jun 2020.

## Conway's Proof of Morley's Theorem

John Conway announced a simplified
proof in 1995, which Alexander
Bogomolny explains.
Though it was in circulation for over a decade, it remained unpublished until
2009, when it apppeared in Martin Gardner’s *Sphere Packing, Lewis Carroll,
and Revresi* (Cambridge University Press), an update of *New Mathematical
Diversions from Scientific American* from 1966. Below is editor Peter Renz's
Postscript of the material in Chapter 17 ("H. S. M. Coxeter"). Peter recalls,
"I went over the final version of the ms with John in Princeton when I was
returning from the Joint Mathematical Meetings in Washington, D.C., in January
of 2009. He made several nice suggestions which I was able to work into the
book before publication. This was the first publication of his proof of Morley’s
Theorem."

*Mathematical Intelligencer*published John's take on it, illustrated with an obtuse triangle.