In the time before computers (BC) various ingenious devices were invented for aiding the extensive calculations required in astronomy, navigation and commerce. In addition to calculators and logarithms, several nomograms were devised for specific applications, for example in meteorology and surveying.
Archive for April, 2017
A Geometric Sieve for the Prime Numbers
Published April 27, 2017 Occasional ClosedTags: Number Theory, Primes
The Water is Rising Fast
Published April 20, 2017 Irish Times ClosedTags: Fluid Dynamics, Geophysics
Seventy percent of the Earth is covered by water and three quarters of the world’s great cities are on the coast. Ever-rising sea levels pose a real threat to more than a billion people living beside the sea. As the climate warms, this is becoming a greater threat every year [TM113 or search for “thatsmaths” at irishtimes.com].

Mean Sea level in Seattle from 1900 to 2013
Torricelli’s Trumpet & the Painter’s Paradox
Published April 13, 2017 Occasional ClosedTags: Analysis, Geometry, Recreational Maths

Torricelli’s Trumpet
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’
The Improbability Principle
Published April 6, 2017 Irish Times ClosedTags: Probability, Statistics
Extremely improbable events are commonplace.
“It’s an unusual day if nothing unusual happens”. This aphorism encapsulates a characteristic pattern of events called the Improbability Principle. Popularised by statistician Sir David Hand, emeritus professor at Imperial College London, it codifies the paradoxical idea that extremely improbable events happen frequently. [TM112 or search for “thatsmaths” at irishtimes.com].

From front cover of The Improbability Principle