Today's Hours:
The First Enigma Codebreaker by
The history of Enigma is of interest to many researchers and authors on an international scale. The capture and unraveling of the most hidden secret of the army of the Third Reich that was decisive for the fate of one of the greatest armed conflicts in the history of the world appeals to everyone from the avid historian to Hollywood. So far, other authors' attention has focused on the technical and cryptological issues of Enigma functioning, the fate of the Bletchley Park facility, or Alan Turing's story. Most of the attention was devoted to the events during the Second World War and it is the time frame of this conflict that usually begins and ends the story of Enigma. The First Enigma Codebreaker raises an issue that has never been discussed in greater detail in both international and Polish literature, the story of Marian Rejewski. This biography answers the questions: in what conditions was the ""Enigma conqueror"" brought up, in what circumstances did he manage to decode the machine, what happened to him during the Second World War and why he never ended up in Bletchley Park, what price he had to pay for his discovery in the communist Poland and what he did to make the world know the true history of Enigma. This is the story of a man who made a revolution in cryptology, about the rivalry between man and machine, about powerful history affecting individual lives, and about the life of Marian Rejewski whose story is still waiting to be presented to the public.
The Man Who Saved Geometry by
An illuminating biography of one of the greatest geometers of the twentieth century Driven by a profound love of shapes and symmetries, Donald Coxeter (1907-2003) preserved the tradition of classical geometry when it was under attack by influential mathematicians who promoted a more algebraic and austere approach. His essential contributions include the famed Coxeter groups and Coxeter diagrams, tools developed through his deep understanding of mathematical symmetry. The Man Who Saved Geometry tells the story of Coxeter's life and work, placing him alongside history's greatest geometers, from Pythagoras and Plato to Archimedes and Euclid--and it reveals how Coxeter's boundless creativity reflects the adventurous, ever-evolving nature of geometry itself. With an incisive, touching foreword by Douglas R. Hofstadter, The Man Who Saved Geometry is an unforgettable portrait of a visionary mathematician.
From Counting to Continuum by
Understanding the natural numbers, which we use to count things, comes naturally. Meanwhile, the real numbers, which include a wide range of numbers from whole numbers to fractions to exotic ones like π, are, frankly, really difficult to describe rigorously. Instead of waiting to take a theorem-proof graduate course to appreciate the real numbers, readers new to university-level mathematics can explore the core ideas behind the construction of the real numbers in this friendly introduction. Beginning with the intuitive notion of counting, the book progresses step-by-step to the real numbers. Each sort of number is defined in terms of a simpler kind by developing an equivalence relation on a previous idea. We find the finite sets' equivalence classes are the natural numbers. Integers are equivalence classes of pairs of natural numbers. Modular numbers are equivalence classes of integers. And so forth. Exercises and their solutions are included.