India and the zero

The concept of zero as a number and not merely a symbol or an empty space for separation is attributed to India, where, by the 9th century AD, practical calculations were carried out using zero, which was treated like any other number, even in case of division. (source: Wikipedia)

Ché Guevara – Fidel Castro: One-time pad cipher

Ché Guevara used a number code when communicating with Fidel Castro. He transposed each letter in the text to a number […]. He then wrote those numbers one behind the other. Below that line he wrote a second line of numbers, known only to him and Castro, which was used only once. He then added both lines, number per number, and below each set of numbers he wrote (the last digit of) the sum. This give a third line of numbers. Only that row was transmitted. When Castro subtracted the second line from the third, he had the first line as the result.

The Ché method cannot be cracked because the key (the second line of numbers) is random, as long as the message, is only used once.


Here is a photo of the original manuscript:

More details: (in Spanish)

Ready for your ultimate post

After the comments of today, you have to write a new post with more information and the images that will appear in your final panel.


  • Try to follow the points of the “list of topics”. You can select some of them.
  • Use short sentences.
  • Put interesting photos and explain them.

Deadline: Monday 24th November 2014

Let’s start!

Now you have got a topic, you must start the work. The first thing I want you to do is to write a post with a picture and a brief explanation of it. Obviously, it must be related with your topic.

For example, let’s imagine that I’m working on the topic “Fractals”.  Then, I would post something like this:

  • A fractal is a mathematical object that exhibits a repeating pattern that displays at every scale.
  • Fractals can be seen in Nature.
  • For example, have a look at this Romanesco broccoli. Each of the smaller buds is made up of even smaller buds.


Deadline: Monday 17th November 2014

Teams and topics

Here are the topics for each team:

  • Team A: Fermat’s last theorem (*)
  • Team B: Numerical Systems
  • Team C: The Tablet Plimpton 322
  • Team D: Pythagoras’ Theorem
  • Team E: Zero (**)
  • Team F: Cryptography

(*) You should have posted something.

(**) Team F was faster than you and they also chose the topic of Cryptography.