The measure of all things.

The Measure of All Things

Assumed distance of humanity from the                                 0
  center of the Universe (Earth) in the
  time of Copernicus (1473-1543),
  kilometers
Assumed distance of humanity from the                      ~149,000,000
  center of the Universe (the Sun) in
  the time of Galileo (1564-1642),
  kilometers
Current estimated distance from Earth                             8,000
  to the center of the Milky Way
  galaxy, light years

Number of planets conceived of (in                                    7
  Europe) in 1500
Estimated number of Earth-like planets   ~3,000,000,000,000,000,000,000
  in the universe in 2005

Number of species estimated by Linnaeus                         ~20,000
  (1758)
Number of species recorded today                             ~1,500,000
Estimated total number of species              4,000,000 to 100,000,000

Age of human species (homo sapiens                             ~130,000
  sapiens), years
Average age of a mammalian species at                        ~5,000,000
  extinction
Age of the horseshoe crab                                   300,000,000+
Age of the cyanobacteria                                  3,500,000,000+

Total biomass of humans, metric tons                       ~250,000,000
Total biomass of Antarctic krill                           ~500,000,000
Total biomass of oceanic cyanobacteria                  ~44,000,000,000

Estimated number of human cells in an               100,000,000,000,000
  average human body
Number of bacteria cells in and on an             1,000,000,000,000,000
  average human body

SOURCES: Distances: University of Arizona, Educational Resources in
Astronomy and Planetary Sciences website (http://ethel.as.arizona.edu/
~collins/astro/index.html). Planets: Dr. Charles Lineweaver, Planetary
Science Institute, Australian National University. Number of species:
Prof. John Blamire, City University of New York, and Society for
Conservation Biology. Species ages: Wrangham and Peterson, Demonic
Males, and Kentucky Geological Survey classroom activities website
(www.uky.edu/KGS/education/timeline_short.html). Biomass: Biology Daily
website (www.biologydaily.com/biology/Biomass), and J. Overmann and F.
Garcia-Pichel in The Prokaryotes (http://141.150.157.117:8080/prokPUB/
index.htm). Cells: www.nationmaster.com/encyclopedia/Bacteria_in_the_
human_body.

Visit www.worldwatch.org/ww/mos/ to view other archived Matters of Scale.