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Friday, 29 May 2015

Seven - six degrees of separation - network science

Some days ago, I received my daily email from Barry Ritholtz's The Big Picture. One of his topics was the "emergence of network science". It contains a Cornell University "documentary unfolding the science behind the idea of six degrees of separation. Originally thought to be an urban myth, it now appears that anyone on the planet can be connected in just a few steps of association. Six degrees of separation is also at the heart of a major scientific breakthrough; that there might be a law which nature uses to organize itself and that now promises to solve some of its deepest mysteries." (source)

The topic of six degrees of separation has been a draft blog of mine for several months now but I felt that something was missing. After seeing the Cornell University documentary on network science, it suddenly struck me: you need to have seven (7), to have six degrees of separation.

There is something odd about the number 7:
- Seven is the most significant number across religions and cultures;
- It also appears in some of the world's favourite fictional works;
- A poll of 30,000 people reveals 7 is overwhelmingly our favourite number.
Source: Daily Mail

Some remarkable examples with respect to the number 7:
- Bible: the universe was created in 6 days and on the 7th day the work was finished.
- 7 continents: North America, South America, Europe, Africa, Middle East, Asia and Australia.
- 7 seas: Arctic, North Atlantic, South Atlantic, Indian, North Pacific, South Pacific and the Antarctic.
- In physics there are 7 SI base units. These are a coherent set of units defined to measure 7 basic physical properties: metre, kilogram, second, ampere, kelvin, mole, candela. The 7 SI base units are used to define all other SI units, which are known as SI derived units.
- 7 colours of the rainbow: red, orange, yellow, green, blue, indigo, and violet (Isaac Newton)
- Biology: there are 7 types of virus according to the Baltimore classification
- The number seven is of particular significance within Cherokee cosmology.
- The Seven Lucky Gods refer to the seven gods of good fortune in Japanese mythology.
- The Seven Virtues: chastity, temperance, charity, diligence, kindness, patience, and humility.
- The Seven deadly sins: lust, gluttony, greed, sloth, wrath, envy, and pride.
Source: Wikipedia

That Wikipedia article even forgets the 7 senses clusters: sight, smell, taste, hearing, touch, vestibular and proprioception (source). Actually, I prefer to combine the latter 2 in spatial visualisation ability and to add intuition (source). 

I suppose that 7 is the maximum number for any cluster to be efficient and effective. Each cluster has a hub that cooperates / coordinates with the hub of other clusters. Together they form networks and - ultimately - living organisms. A failing hub causes a failing network and - ultimately - a failing organism (e.g., sicknesses).

The Cornell University documentary states that understanding network science may cause major scientific breakthroughs. They make a compelling case for that. Please see their video.