Scales of the Universe

  • The 13 scales that define our physical universe;
  • A video that maps the Milky Way onto the United States, where on that scale our sun would fit between the ridges of a fingerprint;
  • Recalling again the famous Powers of Ten video from 1977;
  • And “Religion” from Philip Glass’ Naqoyqatsi.

Some sciency bits today. I’ve always been fascinated by timelines and by scales of time and space. Here are a couple new ones.

Big Think, Ethan Siegel, 14 Aug 2023: The 13 scales that define our physical Universe, subtitled “The visible Universe extends 46.1 billion light-years from us, while we’ve probed scales down to as small as ~10^-19 meters.”

Key Takeaways, per the usual Big Think format:

• On the smallest of physical scales, we have the fundamental, elementary particles, which build up to assemble nuclei, atoms, molecules, and even larger structures. • On larger scales, we have planets, stars, stellar systems, galaxies, clusters of galaxies, and vast voids between them, all contributing to the enormous cosmic web. • Overall, there are many different scales to view the Universe on. Here’s the grand cosmic tour, from the extremely tiny to the unfathomably large.

I’ll list the 13 scales, but the article has lots of cool graphics to go with them.

  1. Fundamental, elementary particles. Down to 10-19 meters, these quanta have never been divided.
  2. Nuclear scales. On femtometer (~10-15 m) scales, individual nucleons, composed of quarks and gluons, bind together.
  3. Atomic scales. Angstrom-sized (~10-10 m), atoms compose all matter on Earth.
  4. Molecular scales. Nanometers (~10-9 m) and larger, molecules contain multiple atoms bound together.
  5. Microscopic scales. Below 0.0001 meters (human hair width), tools beyond human eyes are required.
  6. Macroscopic scales. Our conventional perceptions extend from sub-millimeter to several kilometer scales.
  7. Sub-planetary scales. Where gravity cannot defeat electromagnetism, free-floating bodies can reach several hundred kilometers.
  8. Planetary scales. Spheroidal because of self-gravitation, planets are typically ~1000-200,000 kilometers across.
  9. Star-sized scales. From 0.08-to-2000 times the Sun’s size, these nuclear furnaces light up the Universe.
  10. Stellar system scales. Extending up to ~2 light-years away, extended Oort-like clouds probe the limits of individual stellar systems.
  11. Galactic scales. From ~100-to-1,000,000 light-years, normal and dark matter hold galaxies together.
  12. Cluster-and-void scales. 10-to-100 million light-years wide, they’re the largest gravitationally bound structures.
  13. Truly cosmic scales. The fully observable cosmic web extends ~92 billion light-years across.

Humans are comfortable only with what are called here “macroscopic scales” — which range from, in human terms, tiny to very large, reflecting the experience of human life at its particular scale. (Intermediate? Hmm.) Just as humans don’t intuit the difference between million and billion and trillion (they’re all just really big numbers), so humans don’t intuit anything below or above those macroscopic scales.

This perception, or lack of perception, is one of those cognitive biases that I wish there was a specific term for (if there is I can’t find it), though perhaps it’s not a bias in the same way the others are, but more of a psychological disability, an intellectual skill for which there was no reason evolution should build into us. It’s akin to the way humans can think linearly, but not exponentially. This is true even when we resort to exponents to refer to very small or large numbers.


I came across this in my Facebook feed. Hadn’t heard of him before, but he has a channel there.

Eric Spaceman: The scale of the Milky Way

This is pretty good, especially in how he shows that (with the naked eye) we see virtually none of the universe besides stars in our own galaxy, and most strikingly in mapping the size of the Milky Way to the continental United States, on which scale our own solar system would span a fingertip. And he quotes Carl Sagan.

The analogy of scales works very well at overcoming human lack of intuition about vast sizes and numbers. (I’ll keep this in mind.) Many other such models have been done, one of the most famous the Cosmic Calendar of Carl Sagan.

That most people don’t understand or care about such matters is one reason those of us who do have little patience with the likes of Star Wars, or even Star Trek, which not only ignore these expanses, but imply that they don’t exist. The Enterprise arrives at a new planet every week (even as rationalized by its stardate system), and ships in Star Wars seem to get anywhere in 15 minutes. It’s not only irresponsible, it’s dishonest.

And this might be why most people have no concept of the vastness of space, and of time. Even when you explain it to them. This inability to think beyond the intuitive and familiar, at its worst, is why some people can’t understand the shape of the world and insist, rationalizing frantically and dishonestly, that the Earth is flat.


The granddaddy of all such videos, as far I know, is Powers of Ten, from 1977. Which I’ve mentioned before.


Finally for today, the best cut from Philip Glass’s Naqoyqatsi. I’ve discussed this before.

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