visited him in Italy, though not for a while.
Benedict.Pope Emeritus (I think that's what he is still called) broke his silence with a letter to Odilfreddi, see here.
Hence I am two handshakes away from Pope Benedict. It used to be said that there were Six degrees of separation-- for all people a,b there is a path of length at most 6 that links them. The graph varies with you you ask, but it tries to pin down that a and b know each other.
Is six now too big? One measure is how many Google hits
`X degrees of separation' gets
- Six degrees gets 1,760,000 hits
- Five degrees gets 97,300 hits
- Four degrees gets 159,000 hits
- Three degrees gets 605,000 hits
- Two degrees gets 843,000 hits
with the title `Two degrees of Separation' and also a company with that name.
How well two people know each other has to be defined carefully.
- Erdos Numbers- Put an edge between a and b if they have a paper together.
- Bacon Numbers- Put an edge between a and b if they appear in the same movie.
- Handshake Numbers (I am not sure its every been called that)- Put an edge between a and b if they have shaken hands.
- knows-number (likely not defined). Put a DIRECTED edge from a to b if a will return b's phone calls and/or email.
- Twitter Numbers (Not sure if its ever been defined). But a directed edge between a and b if a follows b on twitter.
The following is probably known but I couldn't find it- what is the longest distance between two websites (number-of-links to go from one to the other)?
The average? Are these numbers getting larger or smaller?
ADDED LATER: Christian Sommer emailed me the following two
Diameter of the web and
Tools to study the web graph
The first link claims the avg diameter of the web is 19.