The six degrees of separation theory ------------------------------------
On social networks, general-purpose ones like Facebook or professional ones like LinkedIn, we can define a relational distance by treating the network as a graph. The nodes of this graph are the individuals in the network, and two individuals are joined by an edge if they are directly connected.
In the small network above, the distance between A and B is 1, the one between A and C is 2, and the one between A and F is 3. In 1929, the Hungarian writer Frigyes Karinthy (1887–1938) claimed, albeit in more literary terms, that the distance between two people in such a graph was never greater than 6. This idea is known as the six degrees of separation theory. It holds approximately true on social networks and in the famous (for mathematicians!) Erdős number, where the relationships are joint authorship of a paper. In that case, no one is known, among people who have co-signed a mathematics paper, to be more than 7 steps away from Erdős himself. This world is small, and so are the others!
Women gifted at mathematics -----------------------------------------