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Homo Sapiens
 We humans, as a species, tend to view the universe human-centrically (how else?). Yet as we learn more and more about the universe and get more and more adept at manipulating nature, we are increasingly confronted by scales that are far outside of our everyday human experience. When confronted by these scales, we unconsciously tend to make assumptions derived from our human-centric bias.
That's why, when I say something like "atoms are close together and galaxies are far apart", it sounds reasonable. After all, atoms are tiny and there are lots of them all around us. For instance, a gram of hydrogen has 6 x 1023 atoms in it! And from a human standpoint a gram of hydrogen is tiny! The Andromeda galaxy on the other hand is 1.5 x 1019 miles away! That's 15 quintillion miles! That's pretty far!
Or is it?
Notice that we are judging things in terms of our human scale. What if instead we separated ourselves from our human-centric bias and looked at distances another way. Perhaps we would see nature in a different way.
A Different Measure...
To do this, we'll need a different way to measure length. What if, instead of viewing distances in human terms, we instead measured the distances between objects in terms of the size of the primary objects involved. For instance we could measure intergalactic distances in terms of the size of the Milky Way galaxy. We already do something similar to this with driving and "car lengths". What's to stop us from measuring solar system distances in terms of "Earth Lengths" or intergalactic distances in terms of "Milky Way Lengths". Then, with those values in hand, we could convert them back to a human sized scale to help our understanding. [*Note* I assumed a human to be a 6ft tall by 2ft diameter cylinder for this conversion].
Let's see an example of how this might work.
Atoms in a Molecule
 The human body is filled with organic molecules. Let's look at a common feature of organic molecules, the carbon-carbon bond. A carbon-carbon bond has an average bond length of around 1.5 Å (1.5 x 10−10 m), This can vary slightly based upon the organic molecule. The diameter of a carbon nucleus is around 2.5 fm (2.5 x 10−15 m). In other words, a carbon-carbon bond is about 60,000 carbon nuclei in length (see what I did there?). That means if a human was shrunk down to the size of a carbon nucleus (2.5 fm), they would have to walk about 22.7 miles before they ran into another carbon atom. That's a pretty long walk!
See how this works? Let's do some more.
Planetary Distances
The diameter of the Earth is roughly 8000 miles. The distance from the Earth to the closest planet to us, Venus, at it's closest approach, is about 24 million miles. in other words Venus, at it's closest approach to us, is about 3000 Earth diameters away. That means if a human was the size of the planet Earth, they'd have to walk 1.1 miles to get to Venus. The Sun would be about a 4.4 mile walk away. Jupiter (at it's closest) would be about 18.5 miles away. Pluto (at it's closest) would be 126 miles away.
Distances Between Stars
The diameter of the Sun is roughly 860,000 miles. The distance to the next closest star, Proxima Centauri is about 4.24 light years away, which is about 25,000,000,000,000 miles. So if we were the size of the Sun, we'd have to walk the equivalent of 1,835.2 miles (Wow!). Wolf 359 (of Star Trek TNG fame) is 7.78 light years away which would be the equivalent of 3,367.4 miles.
Distances Between Galaxies
The diameter of the Milky Way Galaxy is around 100,000 light years (though this measurement has recently been called into question). The closest nearest major galaxy is Andromeda, at approximately 780 kiloparsecs (2.5 million light-years). Or in other words, Andromeda is 25 Milky Way Galaxies away (not bad, right?). If the Milky Way Galaxy was a human, it would only have to walk about 50 feet to get to Andromeda. The Milky Way and Andromeda are both in the Local Group, a collection of over 54 galaxies (most of them dwarf galaxies) of which Andromeda, the Milky Way, and the Triangulum Galaxy are the largest. The local group is only 10 million light-years in diameter (100 Milky Ways). A human the size of our Milky Way would only have to walk 200 feet to walk across our Local Group. (Local indeed!)
Distance Between Galactic Clusters
The next closest galactic cluster is the Virgo Cluster, which is 53.8 Million Light Years away, or around 5 Local Groups away. If we made a human as big as the Local Group, the Virgo Cluster would be only 10 feet away!
If you wanted to, you could apply this way of thinking to the distance between super clusters, the distance between nodes like the Great Attractor. The size of the cosmic voids. I won't go that far in this blog.
Conclusion
Now that we've measured distances in this different way, let's go back and take a look at our earlier statement.
"Atoms are close together and galaxies are far apart"
Obviously from a human-centric point of view this statement is correct. Atoms are tiny and galaxies are huge. On the other hand, if you were to shrink a human to the size of a carbon atom, they'd have to walk 22.7 miles before they got to another carbon atom. Whereas if a human was as big as a galaxy, they'd only have to walk 50 ft to get to another galaxy! That's a staggering difference! We tend to think of the space between galaxies as big and empty, but that space pales in comparison to the lonely emptiness that surrounds an atom!
So there you have it. Sometimes it's helpful to think about things in a different way to gain a new perspective on them. Hopefully you've found all this entertaining. Till next time! -R
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