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   Science, of course, depends upon reliable measurement.

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   Here’s how “length” measures up in the 21st century.

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[…with apologies to our metric visitors]

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For very “short,” a proton is 0.04 trillionths of an inch;

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then there’s

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For very “long,” the universe  at 30 billion light-years

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For some things in-between use the DOOR.

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[MORE]

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   No single “yardstick” works well to measure. The measurements below have been adapted and modified from The Illustrated Encyclopedia of Space & Space Exploration (Metro Books, 2014).

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a proton                           .00000000000004  of an inch

an atom                                         .000000004  of an inch

a DNA molecule (width)             .00000008  of an inch

a red blood cell                                               .04  of an inch

a human being                                                72  inches (6 ft.)

Earth (diameter)                                        7928  miles

Solar system  (to ave. orbit of Pluto)   7,340,000,000,000 miles

Milky Way Galaxy                        100,000 light-years¹

Universe                          30,000,000,000 light-years

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   What then is the “take-away’ from this?  Let us suggest 4 things:

   (1)  Sizes of objects and distances between objects vary from unimaginably small to unimaginably large or distant. (And, a scientific argument can be made for such measurements.)

   (2)  The universe as a whole is very large, and most of it (including individual atoms) “contains” a lot of empty space.

   (3)  Humans are sort of in-between very small things and very big things.

   (4)  There’s much “within” and beyond Earth that we don’t know about and are never going to fully understand.

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   ¹ A “light-year” is a unit if distance, not time equal to about 6,000,000,000,000 miles (or 6 trillion miles). It is the distance that light travels in one (Earth) year. Note also that the sun is about 8 light-minutes away. We never “see” the sun. When we view it, we see what it was like about 8 minutes ago. As we’ve  said before, all astronomical observation is a study of history.