Monday, November 07, 2011

Did you say 4.3 billion people - are you sure?!?

One of my favorite movies is "Back to the Future" and one of my favorite scenes was when Doc Brown realizes the enormous power required to make the Time Machine work.   He starts getting really excited and repeating the amount of energy, or 1.21 gigawatts, while Marty asks what a gigawatt is.   

gig·a·watt/ˈgigəˌwät/ - A unit of electric power equal to one billion (109) watts.


Just like Doc Brown, I was really a bit concerned when I determined in my last post that I have nearly 4.3 billion ancestors, starting from 100 AD..  That just sounds a bit large, so I started looking closer at the numbers and the assumptions.  I kept getting the same number, and even better, the Population Reference Bureau, determined that around 100AD, the earths population was about 300 million.    Further still, the total number of people who have ever lived since the beginning of time, is only estimated to be about 108 billion!

So how is this so far off?    

Well, if we start with the assumed total of 300 million around 100 AD, that means we get about 28 generations.   But even that seems a bit small, since that means each generation is about 70 years, and that is a huge stretch and for now, I am going to look into this further, as something is off.

In showing this analysis, I hope the point hasn't been lost in the math.   While researching your family line, it is important to make assumptions about the story being told, but to be clear and document it in detail, for you to later review and or others to follow.   It is a good practice, to always annotate your sources, state your assumptions and keep clear notes for reference.   This helps others in the future, as well, and they can either confirm or refute what you published.   .
I hope my example was helpful and beneficial.  Stay tuned for more about the mystery of the "overpopulated" world in 100 AD.

Your cousin, Brian

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