# Bill Casselman’s Column Archive

Here are Bill Casselman’s older Feature Columns. Bill’s newest columns may be found here.

- January 2021 – Am I really uninfected? COVID-19 and rapid testing (Math and the Sciences, Math and Nature, Probability and Statistics)
- September 2020 – Does He Have It?: Sensitivity, Specificity, and COVID-19 Testing (Math and the Sciences, Math and Nature, Probability and Statistics)
- May 2020 – Mathematics and the Family Tree of SARS-Cov-2 (Math and the Sciences, Math and Nature, Discrete Math and Combinatorics)
- January 2020 – More Measles (Math and Nature, Discrete Math and Combinatorics)
- November 2019 – Why 95% ? (Probability and Statistics, Math and Nature, Discrete Math and Combinatorics)
- June 2019 – Understanding Kepler III–Predecessors (History of Mathematics, Math and the Sciences)
- February 2019 – Understanding Kepler II–Earth’s Motion (Math and the Sciences, History of Mathematics)
- November 2018 – Understanding What Kepler Did–Part I (History of Mathematics, Math and the Sciences)
- June 2018 – Reading the Bakhshali Manuscript (History of Mathematics)
- February 2018 – Jakob Bernoulli’s Zoo (Discrete Math and Combinatorics, History of Mathematics)
- November 2017 – Solar Daze (Calculus and Analysis, History of Mathematics, Math and the Sciences)
- June 2017 – The Joy of Barycentric Subdivision (Geometry and Topology, Probability and Statistics)
- February 2017 – Assembly Required (Discrete Math and Combinatorics, Geometry and Topology)
- November 2016 – Circles and Squares … and Primes (Calculus and Analysis, Algebra, History of Mathematics)
- June 2016 – The Legend of Abraham Wald (Probability and Statistics, History of Mathematics)
- February 2016 – It Just Keeps Piling Up! (Probability and Statistics, Discrete Math and Combinatorics)
- November 2015 – Circles and Squares (History of Mathematics, Geometry and Topology, Algebra)
- June 2015 – Sums and Integrals: The Swiss analysis knife (Calculus and Analysis, History of Mathematics)
- February 2015 – The Mathematics of the Rainbow, Part II (Math and Nature, History of Mathematics)
- November 2014 – Why Do We Expect Lots of Twin Primes? (History of Mathematics, Calculus and Analysis)
- June 2014 – Feeling Your Way Around in High Dimensions (Linear Algebra, Geometry and Topology)
- February 2014 – Stereographic Projection (Geometry and Topology, History of Mathematics)
- December 2013 – The Polish Attack on Enigma II: Zygalski sheets (History of Mathematics)
- June 2013 – More ENIGMA (History of Mathematics)
- February 2013 – How to Read QR Symbols Without Your Mobile Telephone (Linear Algebra, Math and Technology)
- November 2012 – Can You Do Better? (Geometry and Topology, History of Mathematics)
- June 2012 – What Does a Circle Look Like? (History of Mathematics, Geometry and Topology)
- February 2012 – Archimedes on the Circumference and Area of a Circle (Geometry and Topology, History of Mathematics)
- November 2011 – Fragments of Greek Mathematics (History of Mathematics)
- June 2011 – What’s Normal? (Calculus and Analysis, Probability and Statistics)
- February 2011 – Why Only Five? (History of Mathematics, Geometry and Topology)
- June 2010 – How Did Escher Do It? (Math and the Arts)
- February 2010 – Crypto Graphics (Math and Technology, Linear Algebra)
- November 2009 – Marian Rejewski and the First Break into Enigma (History of Mathematics)
- June 2009 – How Much Longer Can This Go On? (Algebra, Discrete Math and Combinatorics)
- February 2009 – The Mathematics of Rainbows (Math and Nature)
- November 2008 – From Bézier to Bernstein (Calculus and Analysis)
- June 2008 – The Mathematics of Surveying: Part II. The Planimeter (With John Eggers) (Calculus and Analysis, Math and the Sciences, History of Mathematics)
- February 2008 – What is the Length of a Year on Planet Sitnikov? (Calculus and Analysis, Math and the Sciences)
- November 2007 – Strange Associations (Geometry and Topology, Discrete Math and Combinatorics)
- August 2007 – Time and the Hour Running Through Rough Days (History of Mathematics, Geometry and Topology)
- February 2007 – All for Nought (History of Mathematics)
- June 2006 – Simple Chaos – The Hénon map (Calculus and Analysis)
- February 2006 – Variations on Graph Minor (Geometry and Topology, Discrete Math and Combinatorics)
- October 2005 – Mental Calculation (Math and Technology, Calculus and Analysis)
- May 2005 – Slingshots and Space Shots (Calculus and Analysis, Math and the Sciences)
- March 2001 – A New Solution to the Three Body Problem – And More (Calculus and Analysis, Math and the Sciences)
- December 2000 – Packing Pennies in the Plane (Geometry and Topology)