Tech UPTechnologyThe world is a handkerchief

The world is a handkerchief

A few years ago, the so-called “Bacon game” became fashionable in the United States because it had actor Kevin Bacon as its central protagonist. It consisted of the following: one of the players thought of the name of a movie actor or actress and the rest had to find the smallest chain of actors that united them. Thus, if the subject had shared a cast with Bacon in a movie, his Bacon Number was 1. If he had never shared a poster with Bacon, but had done so with someone who had, he was assigned the number  Bacon’s number 2. And so on. Therefore, the game consisted of determining the lowest possible Bacon Number corresponding to the chosen actor.

In the Department of Computer Science at the University of Virginia they took the idea of the game to its extreme and developed a program that they baptized with the name of “Oracle of Virginia”. Using the world’s largest actor database, the Internet Movie Database, the Oracle was able to instantly determine the Bacon Number of any actor or actress in the world . For example, introducing our great national actor Fernando Fernán Gómez, the answer would be: “Fernando Fernán Gómez acted in Lead Soldiers (1983) with Assumpta Serna, who acted in Chain of Desire (1992) with Elias Koteas, who at In turn, he acted in Novocaine (2001) with Kevin Bacon.” So Fernando Fernán Gómez’s Bacon number is three.

And not only that. Finding any actor or actress with a Bacon Number greater than three is extremely difficult ; in fact no one has a Bacon number higher than eleven. To calculate the mean number of steps separating a randomly chosen actor, programmers Brett Tjaden and Glenn Wasson computed the number of people one step away (1,469 actors), two steps away (105,800 actors), and They calculated the average: it came out to be only 2.9.

Does this mean that Kevin Bacon is the center of the world cinematic universe? Certainly not. This also happens with any other. Take, for example, Sean Connery. The famous Irish actor has an average number of intermediaries of 2.66, lower than Bacon’s. All this points to the fact that we are facing a dense network where the nodes are the actors and actresses who are “hooked” with each other through threads that represent having worked together.

The extraordinary thing about this game is that we have a group of more than half a million people united professionally and spread all over the planet, in which the “average distance” between any of them is only 3.65 steps. In other words, in this network, to go from one node to any other following the trajectory marked by the threads, we only need to make four jumps. We might think that this is due to the peculiar characteristics of the seventh art, but it is not.

Who has not experienced the surprise that after chatting for a while with the stranger sitting next to us on the bus or train, we have a mutual acquaintance? We might think that this is simply an illusion, but in the 1960s the social psychologist Stanley Milgram concluded a series of pioneering experiments in social networks with which he tried to measure the size of that handkerchief that is the world. Milgram arbitrarily selected individuals in Omaha and Wichita . They were then asked to send a letter to a certain person in Boston. If they knew him personally, they should forward the letter directly to him, but in the most likely case that they did not, the person should think of a friend or relative whom they knew personally and who, in their opinion, they were more likely to know personally. to the recipient.

As we can see, it was an experiment similar to Bacon’s game. It was a scheme similar to Bacon’s game, only with one important difference: what we have is two ordinary citizens who are not united neither for professional nor geographical reasons. How many steps do you think it took to connect them? Or put another way, what number of individuals separated on average two people chosen at random from the entire US population -about 200 million individuals-? The answer is amazing: only six! Since then this result has been known as “six degrees of freedom”, the statistical version of the popular saying “the world is a handkerchief”.

Since then, scientists have found the phenomenon of six degrees of freedom in the structure of the most diverse networks. Analysis techniques have shown that networks such as those of electrical energy, telephone calls, sexual contacts, and many biological networks such as the nervous or metabolic system, or ecosystems , have common structural properties that exhibit the phenomenon of six degrees of freedom. Talking about six degrees of freedom means that the average distance between network components is extremely low, contrary to what our intuition tells us.  On the other hand, that the structure of the framework that presents this property is shown in a very recurrent way in networks of disparate systems.

In 1998, Duncan J. Watts and Steven Strogatz, both in the Department of Theoretical and Applied Mechanics at Cornell University, showed that both networks in the natural world and those in the human world exhibit this small-world property, as This is the case of the nerve network of the nematode (or roundworm) Caenorhabditis elegans, where each nerve cell or neuron, out of around 300, is connected to others with an average number of steps from one neuron to another of only 2.65, and something similar happens with electricity transmission networks. Interestingly, this research began with Watts’ interest in understanding why crickets synchronize their songs, as if they were coordinated by an invisible hand.

This regularity in such disparate phenomena has made scientists think that there are some universal laws operating under the skin of experience.


Watts, D. (2006) Six Degrees of Separation, Paidós

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