User:Johntex/cell division
Taking inspiration from the Drake Equation, I have created the "Johntex equation" in attempt to estimate how many cell divisions have occured since the origin of life on Earth:
| Variable | Description | Value | Source |
|---|---|---|---|
| EarthPop | Current world human population | 6,450,000,000 | http://en.wikipedia.org/wiki/World_population |
| HBC | Cells in an average human body | 1E+14 | http://ask.yahoo.com/20020625.html |
| HBCD | Number of cell divisions needed to make 1 x 10^14 cells | 7.03687E+13 | Math |
| HBCR | Numer of times, on average, each cell in the human body replaced during life | 3 | My estimate |
| PerBio | Percent humans comprise of the world's biomass | 1% | http://www.space.com/scienceastronomy/plant_food_040629.html |
| Years | Years since the origin of life | 4E+9 | http://en.wikipedia.org/wiki/Timeline_of_life |
| Turnover | Number of years needed for world's biomass to turn-over, on average | 20 | My estimate |
| Conclusion | Total number of cell divisions= | 2.72E+44 | =EarthPop * HBC * HBCD * HBCR * PerBio * Years / Turnover |
The total of 2.72E+44 would be just for life on Earth.
If one wanted to also consider the number of cell divisions that have occured in extraterrestrial life, one could multiply by the number of worlds that support life using a modified version of the Drake Equation. To do this, one would ommitt the variables relating to the life forms developing an intelligent culture, for example:
If R=10, fp=0.5, ne=2, fl=1, and L=100,000,000, then the modified Drake equation would give 1E+09.
Multiplying 2.72E+44 by 1E+09, we get 2.72E+53 for the total number of cell divisions of all life anywhere in the Milky Way. By comparison, the total number of stars in the Milky Way is estimated to be something more than 2E+9. By these calculations, the number of cell divisions that have occured in the galaxy would be about 1.36E+44 times more than the number of stars in the galaxy. Johntex\talk 22:22, 18 January 2006 (UTC)
Update - above has been updated with the input of Robert Merkel in the discussion at the Reference desk. Johntex\talk 22:45, 18 January 2006 (UTC)