The golden mean occurs repeatedly in the pentagram [image Wikimedia Commons]
Everyone knows about the golden mean. It must be one of the most written-about numbers, certainly in recreational mathematics. It is usually denoted by
and is the positive root of the quadratic equation
with the value
There is no doubt that is significant in many biological contexts and has also been an inspiration for artists. Called the Divine Proportion, it was described in a book of that name by Luca Pacioli, a contemporary and friend of Leonardo da Vinci.
Continue reading ‘Metallic Means’
Published January 19, 2017
Tags: Arithmetic, Topology
The world has been transformed by the Internet. Google, founded just 20 years ago, is a major force in online information. The company name is a misspelt version of “googol”, the number one followed by one hundred zeros. This name echoes the vast quantities of information available through the search engines of the company [TM107 or search for “thatsmaths” at irishtimes.com].
Artist’s impression of the Library of Babel [Image from Here].
Long before the Internet, the renowned Argentine writer, poet, translator and literary critic Jorge Luis Borges (1889 – 1986) envisaged the Universe as a vast information bank in the form of a library. The Library of Babel was imagined to contain every book that ever was or ever could be written.
Continue reading ‘The Library of Babel and the Information Explosion’
Published December 24, 2015
Tags: Arithmetic, Games
How many ways can a deck of cards be arranged? It is very easy to calculate the answer, but very difficult to grasp its significance.
Continue reading ‘Factorial 52: A Stirling Problem’
The idea of using two numbers to identify a position on the Earth’s surface is very old. The Greek astronomer Hipparchus (190–120 BC) was the first to specify location using latitude and longitude. However, while latitude could be measured relatively easily, the accurate determination of longitude was more difficult, especially for sailors out of site of land.
OSi Mapviewer. XY coordinates indicated at bottom left.
French philosopher, scientist and mathematician René Descartes demonstrated the power of coordinates and his method of algebraic geometry revolutionized mathematics. It had a profound, unifying effect on pure mathematics and greatly increased the ability of maths to model the physical world.
Continue reading ‘Who Needs EirCode?’
Albert Girard (1595-1632) was a French-born mathematician who studied at the University of Leiden. He was the first to use the abbreviations ‘sin’, ‘cos’ and ‘tan’ for the trigonometric functions.
Left: Albert Girard (1595-1632). Right: Pierre de Fermat (1601-1665)
Continue reading ‘Fermat’s Christmas Theorem’