Tuesday, March 11, 2008

Earth, Water, Air and Factcheck

Dan Phiffer's blog posts this image he found on an Internet message board. On the left is all of Earth's water gathered in one place. On the right, all the air. Both are set relative to the scale of the planet.

The image is getting a lot of attention (I found it via BoingBoing). But a question remained. Is it accurate?


A reader, Pat Stanton, does the math:

My son sent me a link to the image of spheres representing all the water and air on Earth. He was skeptical and suspected it was an example of “tree-hugger shock media.”

I decided to do the math, starting with the data provided by Andrew Nowicki. The math appears to verify the posted image. Although I applaud my son’s skepticism, tree-hugger shock media sometimes brings us an important and informative message.

General approach:

  1. Measure the spheres representing Earth, water and air in the image. Obtain the diameter in pixels of each sphere. Also, identify relevant physical constants.

  2. Starting with data independently provided by Andrew Nowicki, calculate the diameters of spheres that would contain Earth’s water and air.

  3. Normalize the results from Step 2 into pixels and compare with measurements from Step 1.

Detailed results
Pat details his calculations in the full post -- and the image is legit. Impressive work all around. The image does emphasize the thin film our known biomass occupies.

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