Consider two spheres:
Earth Sphere
The earth is a sphere slightly flattened at the poles. If it was possible to drill a core through the earth, it would be 7,918 miles long. The earth's diameter is about 7,918 miles across.
Water Sphere
If every water molecule on earth was contained by a sphere, the sphere would be much smaller than the earth sphere. Visualized as a sphere, earth's water would be 860 miles across.
 |
| Volume of all earth's water as compared to the earth's volume. US Geological Survey |
| Water as a sphere | Earth as a sphere |
| 860 mile diameter | 7,918 mile diameter |
The tiny blue sphere located east of the much larger total water sphere represents all of the fresh water found in the ground, lakes, swamps, and rivers. The fresh water sphere is 169.5 miles in diameter.
You could not step twice into the same rivers; for other waters are ever flowing on to you.
― Heraclitus of Ephesus
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