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].

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

Published April 13, 2017 Occasional ClosedTags: 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’

### 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].