rlm@1: #+title: A Universe of Human Experience
rlm@1: #+author: Robert McIntyre
rlm@1: #+email: rlm@mit.edu
rlm@2: #+description: How many man-years are in a year?
rlm@2: #+keywords: man-year man-month man-hour universe human experience philosophy
rlm@1: #+setupfile: ../../aurellem/org/setup.org
rlm@1: #+include: ../../aurellem/org/level-0.org
rlm@2: #+babel: :results output :exports both
rlm@1: 
rlm@3: * What is a Man-Hour?
rlm@2: 
rlm@2: A [[http://en.wikipedia.org/wiki/Man-hour][/Man-Hour/]] is a term from the field of Management.  It is one hour
rlm@2: of work by one person for a certain task. 
rlm@2: 
rlm@2: For example, if I have a nine-to-five programming job at Initrode, but
rlm@2: I slack off most of the time and only /actually/ work from
rlm@2: 10:00-11:00, then I only put in one man-hour of work a day.
rlm@2: 
rlm@2: If my task is simply existing, then I put in 24 man-hours of work
rlm@2: every day.
rlm@2: 
rlm@2: 
rlm@2: * Experience
rlm@2: 
rlm@2: I've often wondered what it would feel like to have more than one
rlm@2: body, and to experience the same day from different perspectives. 
rlm@2: 
rlm@2: For example, there are around twenty different majors available at
rlm@2: MIT. If you had ten different bodies, and each of them double-majored
rlm@2: in different subjects, then in only four short years you would
rlm@2: graduate with a degree in every field MIT has to offer. You would have
rlm@2: experienced forty man-years of college in the process.
rlm@2: 
rlm@2: How many man-years does the entire MIT class experience every year?
rlm@2: [[http://web.mit.edu/fnl/volume/192/century.html][There were around]] $4585$ undergraduates at MIT in the fall of 1982.
rlm@2: 
rlm@2: $4585$ students $\times$ $1$ year $=$ $4585$ man-years.
rlm@2: 
rlm@2: One person could help lay the first blocks of [[http://en.wikipedia.org/wiki/Great_Pyramid_of_Giza][great Pharaoh Khufu's
rlm@2: tomb]] and live to see [[http://www.burjkhalifa.ae/][Burj Khalifa]] and they would accrue the same
rlm@2: amount of experience as the MIT class of '82 did in one year.
rlm@2: 
rlm@2: 
rlm@2: * Forever in a Day
rlm@2: 
rlm@2: How many man-years does everyone experience in a day? There are almost
rlm@2: 7 billion people around today, according to [[http://www.census.gov/main/www/popclock.html][www.census.gov]]. 
rlm@2: 
rlm@2: #+begin_src clojure
rlm@2: (ns lifespan)
rlm@2: (use '[clojure.contrib [pprint :only [cl-format]]])
rlm@2: 
rlm@2: (cl-format *out* "Man-years per day: \n ~R"
rlm@2:            (* 6969492979 ;; people on Earth
rlm@2:               (/ 1 365)  ;; years-per-day
rlm@2:               ))
rlm@2: #+end_src
rlm@2: 
rlm@2: #+results:
rlm@2: : Man-years per day: 
rlm@2: :  nineteen million, ninety-four thousand, five hundred one
rlm@2: 
rlm@2: Together, we experience almost 20 million years every day!
rlm@2: 
rlm@2: A week in the lives of the people of Earth is enough to reach back to
rlm@2: the age of the dinosaurs.
rlm@2: 
rlm@2: 
rlm@2: * The Infinite Stories of Humanity
rlm@2:   
rlm@2: How many man-years is the sum total of human experience? That is, how
rlm@2: many man-years has every human who has ever lived experienced?  
rlm@2: 
rlm@2: Using a very rough calculation involving the table from [[http://www.prb.org/Articles/2002/HowManyPeopleHaveEverLivedonEarth.aspx][here]] and the
rlm@2: average human lifespans through the ages found [[http://en.wikipedia.org/wiki/Life_expectancy][here]], I get the
rlm@2: following:
rlm@2: 
rlm@2: #+begin_src clojure 
rlm@2: (in-ns 'lifespan)
rlm@2: (use '[clojure.contrib [def :only [defvar]]])
rlm@2: 
rlm@2: (defvar
rlm@2:   time-periods
rlm@2:   [:start-8000BC
rlm@2:    :8000BC-1    
rlm@2:    :1-1200      
rlm@2:    :1200-1650   
rlm@2:    :1650-1750   
rlm@2:    :1750-1850   
rlm@2:    :1850-1900   
rlm@2:    :1900-1950   
rlm@2:    :1950-1995   
rlm@2:    :1995-2011]
rlm@2:   "The time periods under question.
rlm@2:     'start' here is taken to be 50,000BC")
rlm@2: 
rlm@2: (defvar births
rlm@2:   (zipmap
rlm@2:    time-periods
rlm@2:    [ 1137789769  ;; \
rlm@2:     46025332354  ;;  | 
rlm@2:     26591343000  ;;  |
rlm@2:     12782002453  ;;  |
rlm@2:      3171931513  ;;  | -- from the video at:
rlm@2:      4046240009  ;;  | http://www.prb.org/Articles/2002/
rlm@2:      2900237856  ;;  |    HowManyPeopleHaveEverLivedonEarth.aspx
rlm@2:      3390198215  ;;  |
rlm@2:      5427305000  ;;  |
rlm@2:      2130327622]);; /
rlm@2:   "number of people who existed in the given time periods")
rlm@2: 
rlm@2: ;; Confirm that the sum of people agrees with that in the video.
rlm@2: (assert (= 107602707791 (reduce + (vals births))))
rlm@2: 
rlm@2: (defvar lifespans
rlm@2:   (zipmap
rlm@2:    time-periods
rlm@2:    [33   ;; start-8000BC  \
rlm@2:     22   ;; 8000BC-1      | -- from: 
rlm@2:     30   ;; 1-1200        | http://en.wikipedia.org/wiki/
rlm@2:     32   ;; 1200-1650     /    Life_expectancy
rlm@2:     35   ;; 1650-1750 \
rlm@2:     35   ;; 1750-1850  |-- from:
rlm@2:     45   ;; 1850-1900  | http://www.deathreference.com/
rlm@2:     66   ;; 1900-1950  |    Ke-Ma/Life-Expectancy.html
rlm@2:     66   ;; 1950-1995 /
rlm@2:     70   ;; 1995-2011-------> form:  
rlm@2:          ;;   http://www.prb.org/DataFinder/Topic/
rlm@2:          ;;      Rankings.aspx?ind=6&loc=241
rlm@2:     ])
rlm@2:   "lifespans in years from birth for the various time periods")
rlm@2: 
rlm@2: 
rlm@2: 
rlm@2: 
rlm@3: 
rlm@3: ;; This section is just here to make the result look pretty.
rlm@2: (dorun
rlm@2:  (map println
rlm@2:       (clojure.contrib.string/split
rlm@2:        #"," 
rlm@3:        (cl-format 
rlm@3:         nil "years of human experience: \n ~R years"
rlm@3: ;; Multiply each time-period's total number of people
rlm@3: ;; by those people's average lifespan in years to get
rlm@3: ;; the total number of man-years experienced during
rlm@3: ;; that period, then add them together.
rlm@3:         (reduce + 
rlm@3:                 (map *
rlm@3:                      (map births time-periods)
rlm@3:                      (map lifespans time-periods)))))))
rlm@2: 
rlm@2: #+end_src
rlm@2: 
rlm@2: #+results:
rlm@2: : years of human experience: 
rlm@2: :  three trillion
rlm@2: :  three hundred seventy-one billion
rlm@2: :  ninety-three million
rlm@2: :  five hundred ninety-five thousand
rlm@2: :  one hundred eighty-one years
rlm@2: 
rlm@2: 
rlm@2: 
rlm@2: Humans have already collectively lived far longer than the age of the
rlm@2: universe.