Musical notes that are simply related to each other have a pleasing effect when sounded together. Each tone has a characteristic rate of oscillation, or frequency. For example, Middle C on the piano oscillates 264 times per second or has a frequency of 264 Hz (Hertz). If the frequencies of two notes have a ratio of two small whole numbers, the notes are harmonically related and sound pleasant when played together.

## Posts Tagged 'Geometry'

### Hearing Harmony, Seeing Symmetry

Published May 11, 2017 Occasional Leave a CommentTags: Geometry, Music

### Torricelli’s Trumpet & the Painter’s Paradox

Published April 13, 2017 Occasional Leave a CommentTags: Analysis, Geometry, Recreational Maths

Evangelista Torricelli, a student of Galileo, is remembered as the inventor of the barometer. He was also a talented mathematician and he discovered the remarkable properties of a simple geometric surface, now often called *Torricelli’s Trumpet*. It is the surface generated when the curve for is rotated in 3-space about the x-axis.

Continue reading ‘Torricelli’s Trumpet & the Painter’s Paradox’

### Voronoi Diagrams: Simple but Powerful

Published February 2, 2017 Irish Times 1 CommentTags: Algorithms, Geometry

We frequently need to find the nearest hospital, surgery or supermarket. A map divided into cells, each cell covering the region closest to a particular centre, can assist us in our quest. Such a map is called a Voronoi diagram, named for Georgy Voronoi, a mathematician born in Ukraine in 1868. He is remembered today mostly for his diagram, also known as a Voronoi tessellation, decomposition, or partition. [TM108 or search for “thatsmaths” at irishtimes.com].

### Unsolved: the Square Peg Problem

Published December 29, 2016 Occasional Leave a CommentTags: Geometry, Topology

The idiom “square peg in a round hole” expresses a mismatch or misfit, often referring to somebody in the wrong profession. It may also indicate a difficult or impossible task but, of course, it is quite simple to fit a square peg in a round hole, hammering it in until the corners are tight against the circular boundary of the hole. Since the peg may be oriented at any angle, there are an infinite number of ways to fit a square within a circle. In contract, for a boomerang-shaped hole, there is just one way to draw a square with its vertices on the curve.

### Kepler’s Magnificent Mysterium Cosmographicum

Published October 13, 2016 Occasional Leave a CommentTags: Astronomy, Geometry, History

Johannes Kepler’s amazing book, *Mysterium Cosmographicum*, was published in 1596. Kepler’s central idea was that the distance relationships between the six planets (only six were known at that time) could be represented by six spheres separated by the five Platonic solids. For each of these regular polyhedra, there is an inner and an outer sphere. The inner sphere is tangent to the centre of each face and the outer sphere contains all the vertices of the polyhedron.

Continue reading ‘Kepler’s Magnificent Mysterium Cosmographicum’

### Heron’s Theorem: a Tool for Surveyors

Published September 8, 2016 Occasional Leave a CommentTags: Geometry

Heron was one of the great Greek mathematicians of Alexandria, following in the tradition of Euclid, Archimedes, Eratosthenes and Apollonius. He lived in the first century, from about AD 10 to AD 70. His interests were in practical rather than theoretical mathematics and he wrote on measurement, mechanics and engineering. He devised a steam-powered device and a wind-wheel that operated an organ. He is regarded as the greatest experimenter of antiquity, but it is for a theorem in pure geometry that mathematicians remember him today.

### The Tunnel of Eupalinos in Samos

Published September 1, 2016 Irish Times Leave a CommentTags: Geometry, Pythagoras

The tunnel of Eupalinos on the Greek island of Samos, over one kilometre in length, is one of the greatest engineering achievements of the ancient world [TM098, or search for “thatsmaths” at irishtimes.com].

Approximate course of the tunnel of Eupalinos in Samos.