In modern society there are few people who are not familiar with the theory of 6 handshakes. Now that the Internet has erased all boundaries in the communication of people who, otherwise, might never have met, this theory can be renamed the 6-click rule. However, few people know that it was described long before its appearance in the novel of the famous Hungarian writer Frides Carinti. The work belonged to the genre of fiction and was published when no one even thought about the theory of 6 handshakes and its essence.
Theory 6 Handshakes
It is difficult to argue with the assertion that the world is small. Few people did not encounter a situation when, while in an unfamiliar society, they met common acquaintances. No one thinks about the fact that, in fact, human society is not infinite, it is limited by a certain framework and is somewhat closed. In theory, each of us can be acquainted with any person on the globe through mutual acquaintances or relatives.
It would seem impossible. However, do not rush to conclusions. There is a theory of 6 handshakes, which consists in the fact that all the people of the planet Earth are familiar with each other through 5 people, which is 6 levels of communication.
The world is small
Despite the fact that this theory looks fantastic at first glance, it has existed for a long time and has repeatedly found confirmation.
It is difficult to say when the expression "The world is small" appeared. Most likely, it originates from those times when people lived only on their territory and practically did not go beyond its borders. 
Over the years, the borders have expanded, people began to visit each other first, and then move from their homes in search of a better life. However, in new places either countrymen or other people met whom they once knew. In an extreme case, conversations with new people almost always had common acquaintances. Since then, this concept has entered our vocabulary.
Milgram experiment
The rule of close ties of mankind is connected with the names of American psychologists Stanley Milgram and Jeffrey Travers, who in 1969 proposed a concept that came to us as a theory of 6 handshakes. 2 years before the results of the experiment were published, Milgram conducted a study whose purpose was to determine the length of the chain connecting people to each other. Calling it “The World is Small,” the scientist developed a special algorithm designed to calculate the number of connections between two people.
Experiment progress
The sites where the Milgram experiment was conducted were the cities of Omaha and Wichita, which are located, respectively, in the states of Nebraska and Kansas. The addressee was chosen by a resident of Boston. Scientists explained their choice by the fact that, despite the small remoteness of cities from each other in terms of geography, their inhabitants were divided by a whole chasm in terms of living and education.
The experiment consisted of randomly sending residents of Omaha and Wichita letters inviting them to take part in a scientific experiment. In the event that they agreed, they should write their details on the form enclosed in the letter. Then this letter had to be sent to a resident of Boston, whose name was indicated on the envelope. If the addressee knew him personally, he should have forwarded the letter to him, and if not, then it was necessary to send a message to the person who is more likely to know him. The only condition was that the envelope should be sent only to a person who is personally known to a person or relative.
Experiment results
The main difficulty of the study was the number of those who agreed to forward the letter further.Moreover, the failure occurred at various stages of the experiment. As a result, out of 296 letters sent with an invitation to participate, the final recipient received 64. The length of the chain of friends averaged 5-6 people. 
It is noteworthy that many people, choosing the next addressee, came from the one who lives closer to the city of the addressee, and just in this case, the letter did not reach the final goal. It took 2 years to formulate the law of six handshakes, which with the advent of the Internet received a new meaning.
6 emails
Already at the present stage of development of society, scientists decided to repeat the Milgram experiment using new technologies. A group of Columbia University employees sent 24,613 emails to different parts of the world. The point of the study was that the people who received these letters had to find one of the 20 recipients. Data on them was minimal: name, surname, education, occupation, place of residence. 
The first success of the research was brought by a volunteer from Australia, who managed to find his secret addressee in Siberia with just 4 messages. Thus, the second time the theory of 6 handshakes was confirmed, which was interesting for many sociologists to verify.
Confirmation of the theory of 6 handshakes in social networks
In 2011, the rule of six handshakes decided to check the most famous social network Facebook. Another study was conducted in conjunction with the University of Milan. According to its results, the number of links in the human chain is even less than 6 and averages 4.74. Thus, a resident of a planet living on one point on the globe is connected with a resident of another point through “friends of friends”. The only condition is registration in the global virtual community.
The next study of the reliability of the theory was conducted among users of the Russian social network VKontakte. Here the chain of friends numbered 3-4 people on average. Surprisingly, there was not a single excess of the number 6 in the human chain. Given the territorial limitation of this virtual community, it can be argued that the results of the study also confirm the theory of 6 handshakes.
Criticism of the law 6 handshakes
Like any study, this rule has been criticized more than once by both scientists and ordinary people. The main argument, to which the category of doubters referred, is that the links of the human chain have been repeatedly interrupted in all experiments. However, in this case, the failure to conduct the study occurred only due to the refusal of participants to pass the baton.
Another argument cited by critics concerns research on social networks. In this case, the object of doubt is the assignment to the category of acquaintances of all people on the list of friends of the participants. This is a rather controversial statement, but still, if someone is among the friends on your page in any social network, it means that you still have some relation to each other.
Thus, the arguments of critics opposing the law of 6 handshakes are not weighty enough to give a serious rebuttal to the theory.
Truth or myth
Believe it or not the law of 6 handshakes, everyone decides for himself. However, it is worth considering that in the scientific world they take it more than seriously. Moreover, scientists who favor this theory work in various fields, often far from the sociology with which it all began. One of the most striking examples of this attitude of the scientific world is the game “Erdös Number”, named after the Hungarian mathematician, who wrote many scientific works. The meaning of the game lies in the fact that you need to find the shortest human chain that leads from any random scientist to Erdesh himself. For example, a scientist is assigned the first number if he worked with the founder of the game at any time.The second number is given to the scientist who worked with a scientist who, in turn, worked with Erdös himself. It is noteworthy that most of the Nobel Prize winners have small numbers for this game.
By the way, anyone can check this theory, and for this you do not need to be a scientist at all. All that is needed for this is to create your own “dating map”. It is desirable that the link not lower than the fourth is familiarity with a celebrity. The more its popularity, the higher the likelihood of meeting a huge number of people, including high-ranking people, who, in turn, have no less friends.
Thus, perhaps we are all familiar through 6 handshakes. Due to a detailed study of all the results of experiments conducted at different time intervals and by various methods, the popular joke about getting to know the Queen of England no longer seems fantastic. Think about a celebrity who until this time seemed completely unattainable, you might be familiar with, according to this theory. It is likely that the result of your own research will greatly surprise you.
