Matters of Scale - The Measure of All Things
Estimated number of human cells in an average human body | 100,000,000,000,000 |
Number of bacteria cells in and on an average human body | 1,000,000,000,000,000 |
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Total biomass of oceanic cyanobacteria | ~44,000,000,000 |
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Total biomass of humans, metric tons | ~250,000,000 |
Total biomass of Antarctic krill | ~500,000,000 |
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Age of the horseshoe crab | 300,000,000+ |
Age of the cyanobacteria | 3,500,000,000+ |
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Age of human species (homo sapiens sapiens), years | ~130,000 |
Average age of a mammalian species at extinction | ~5,000,000 |
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Number of species estimated by Linnaeus (1758) | ~20,000 |
Number of species recorded today | ~1,500,000 |
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Estimated total number of species | 4,000,000 to 100,000,000 |
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Number of planets conceived of (in Europe) in 1500 | 7 |
Estimated number of Earth-like planets in the universe in 2005 | ~3,000,000,000,000,000,000,000 |
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Assumed distance of humanity from the center of the Universe (Earth)
in the time of Copernicus (1473–1543), kilometers | 0 |
Assumed distance of humanity from the center of the Universe (the Sun)
in the time of Galileo (1564–1642), kilometers | ~149,000,000 |
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Current estimated distance from Earth to the center of the Milky Way galaxy, light years | 8,000 |
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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 Peter-son, Demonic Males, and Kentucky Geological Survey
classroom activities website (www .uky.edu/KGS/education/timeline_short.html).
Biomass: Biology Daily website (www.biol ogydaily.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.