Abstract Confusions

Complexity is not a cause of confusion. It is a result of it.

Tag Archives: Erdos Number

Six Degrees of Separation

How many times you met some stranger and he turns out to be one of your friend’s friend or friend’s – friend’s friend? How many times you meet some one in airport or in rail journey and he turns out to be your school mate or college mate? Many of us might this kind of meetings most often.

So, this post is about the mystery behind such happenings.

Meet Mr Shah

One such incident to reckon. Couple of weeks before, I met Fowzul’s hubby – Mr. Shah on beach. At first he is a perfect stranger to me. All I know was, he studied in a same college where I studied but left it before me joining it. Then when he spoke about his friends, we both came to know that we have common friends. So, it turned out like enquiring about the friends in common.

The question we have now is – “Is it possible to know any given stranger through known people?”, if so, how many such people you need to know to know “the stranger?”. Hold your breath, the answer is a mere six. And that is the maximum number of people for that. That is, you need to know, exactly six people to know any one in the world.

You & A Stranger

Let me put it more specific. Consider a farmer in remote Chinese village. Now, you need find your way to get connected to him with six or less people. There are many examples for these in popular culture and mathematical culture.

Kevin Bacon number is one such very popularly known and discussed. Bacon acted as the famous scientist in “Hollow Man” movie. He once said, he can relate to any actor in the world.

In mathematics, Paul Erdos – a famous mathematician who collaborated with so many people and produced graph theoretical paper had a number named after him. It is known as Erdos number.

Erdos number - An example

Erdos number - An example

Now, how amazing is it? we don’t have a proof for this anyway.