I read this morning of a French nun who survived the 1918 influenza and just healed from the Covid-19 on her 117th birthday. Just last week, I learned of the book The Longevity Economy by Joseph F. Coughlin, about the ever increasing life spans being experienced today.
At the same time, I see that worldwide communication and news outlets are opening more and more doors and views and needs and hopes. As the books Too Big to Know and Everyday Chaos by David Weinberger show, knowledge, opinions and causes, not to mention groups and alliances, emerge and seek members more and more broadly and rigorously and imaginatively.
I got to thinking about how many people I can actually know simultaneously. The definition of "knowing a person" matters, of course. I can see how a man like our 45th president could attend a rally of 7000 - 9000 and think more people like him than do. I wondered if a person lives to age 85 and gets to know an average of 1 new person a day, how many people would that make? 365 days times 85 years = 31025 people, 31046 if you use 365.25.
Somewhere, I got the idea that a typical number of people a person "knows" is 150. I have more than 800 names in my contacts database but I do find that some of the names are of people I can't recall. I looked up the question of how many people one person can know and found ambiguous answers, of course. Recent research shows that people can reliably tell which faces they have seen before and which they haven't with 5000 faces.
Numbers of this size get me to thinking about familiarity with statistical thinking. I think the best book I know for developing such thinking is "The Improbability Principle" by David Hand. I began this post with longevity. Long lives increase both contacts and years to forget contacts.
