Most of us think we have a decent grasp of how big space is.
We have seen the photos, watched science fiction on big and small screens, read the books. Galaxies spiral like pinwheels. Nebulae glow in impossible colors. Rockets lift into a blue sky, as if the rest of the universe were simply waiting a little farther up.
The problem with this picture is scale.
The numbers involved are so large that the mind quietly disengages. Million. Billion. Trillion. We recognize the words, but we do not inhabit them. They drift past like subtitles in an art-house film in a language we do not quite speak.
For most of human history, this limitation did not feel like a problem. The universe was assumed to be tidy and nearby. The Earth sat at the center, and everything else arranged itself accordingly. The heavens were distant but decorative, moving for our benefit and in our honor.
That picture cracked when Nicolaus Copernicus suggested something radical for its time. The Earth was not the center. The Sun was. This was not merely a technical correction. It was a demotion. We were no longer the anchor of the cosmos, just another participant moving along with the rest.
Even then, the universe remained comfortably small. The Sun sat at the center of everything that mattered. The stars were assumed to be fixed, distant, and all part of a single surrounding shell. It would take centuries to understand how incomplete that picture was.
The First Distance That Breaks Intuition
Let us start close to home.
The Sun is about 150 million kilometers away. Light takes a little over eight minutes to reach us.
If the Sun were to disappear right now, we would continue orbiting an empty point in space for eight minutes before noticing anything was wrong. Reality has latency.
When I was a kid growing up in greater Chicago, thunderstorms were part of summer. After a flash of lightning, my father would tell me to start counting. One Mississippi… Two Mississippi… Five seconds meant the storm was about a mile away. It was a simple way to make distance tangible.
Apply that same logic to the Sun and the scale turns absurd. Light takes a little over eight minutes to reach us. Sound, if it could travel through the vacuum of space, would take nearly fourteen years to cover the same distance. Fourteen years of Mississippis. The exercise is hypothetical, of course. Sound does not travel through empty space. The point is not the mechanism. It is the distance.
To make that distance relatable, let us shrink the Sun. The average distance between the Sun and the Earth is called an astronomical unit, or AU.
Using a scale of 150,000,000:1, the Sun is now about 9.3 meters across. On that scale, Earth is roughly 8.5 centimeters wide, about the size of a baseball, orbiting a kilometer away.
One kilometer of empty space.
That emptiness is the point.
Even within our own solar system, most of what exists is distance, not matter. Planets are not lined up like textbook diagrams. They are isolated islands separated by vast, mostly silent gaps.
The outer planets push this further. Neptune orbits roughly thirty times farther from the Sun than Earth does. On this scale, that places it nearly thirty kilometers away. A long bike ride just to reach the edge of the neighborhood.
Beyond that lies the Kuiper Belt, the Oort Cloud, and then interstellar space, where the Sun’s influence finally gives way to the wider galaxy.
The Space Between Us and the Moon
The Moon looms large in the night sky and feels nearby. During a solar eclipse it neatly blocks the Sun, revealing the corona. In reality, the Moon orbits at an average distance of about 384,000 kilometers.
On this scale, that distance is about 2.6 meters. Line up the other seven planets back to back, using their actual diameters and ignoring rings, and you could just about wedge them into that gap. They would fall short by only a few thousand kilometers in real terms, well under one percent. At the Moon’s farthest point in its orbit, they would fit outright.
The Moon is not hovering just overhead. It is circling across a gulf wide enough to frame almost an entire planetary system.
When Kilometers Stop Working
The nearest star system, Alpha Centauri, sits about 4.4 light years away. On this same scale, that places it roughly 275,000 kilometers from Earth.
Alpha Centauri A itself is only slightly larger than our Sun. Scaled down, it would measure a little over eleven meters across. The size is not the point. The distance is. At this range, everyday comparisons quietly stop helping.
Last summer, just after sundown, I watched the International Space Station catch the Sun as it passed over northern Germany. A bright, fast-moving object, a few hundred kilometers away, close enough to feel almost reachable. Now hold that image and shift your attention outward. Alpha Centauri is a star smaller than the ISS on this scale, yet sitting roughly a thousand times farther away than that orbiting station. And this is our nearest stellar neighbor. Not a distant outlier. The closest one. That is where distance stops being a number and becomes something else entirely.
Then there is Deneb. A blue-white supergiant roughly two thousand light years away, give or take, depending on how you measure it. Deneb is the 19th brightest star in Earth’s night sky, and one corner of the Summer Triangle, alongside Vega and Altair.
On this same scale, Deneb would sit tens to hundreds of millions of kilometers from Earth. Scaled down, its diameter would still be just over a kilometer across, even using conservative estimates. By that point, the model has stopped being something you can visualize or walk through. It no longer fits on the page, which is precisely the point.
Discovering That the Milky Way Is Not Alone
Until the early twentieth century, astronomers believed the Milky Way was the universe.
That assumption collapsed when Edwin Hubble measured the distance to what we now call the Andromeda Galaxy and realized it lay far outside the Milky Way. It was not a cloud. It was another galaxy entirely.
That realization quietly multiplied the universe overnight. The Milky Way went from being everything to being one example among hundreds of billions.
How Fast We Actually Move
Human technology is impressive. It is just not impressive on cosmic terms.
The fastest crewed spacecraft ever flown reached nearly 40,000 kilometers per hour.
Voyager 1, the fastest human-made object to leave the solar system, has been traveling for nearly half a century and has barely begun the interstellar journey.
A Look Back
In 1990, as Voyager 1 prepared to leave the solar system, it was commanded to turn around and take one last photograph of Earth. From billions of kilometers away, our planet appeared as a single pixel suspended in a shaft of sunlight.
Carl Sagan called it the Pale Blue Dot.
Space does not diminish us. It contextualizes us.
Author’s note on scale:
All distances and sizes in this piece are shown using a fixed scale of 150,000,000:1, meaning one astronomical unit, the average distance between Earth and the Sun, is represented as roughly one kilometer. Planetary diameters, orbital distances, and stellar sizes are mean values. Orbits vary, stars are not perfect spheres, and some stellar distances remain uncertain. None of that changes the point being illustrated: space is not just large, it is structured around distances that overwhelm everyday intuition.
- “Star Wars” Lucas Films 1977
- The Pale Blue Dot is a photograph of Earth taken Feb. 14, 1990, by NASA’s Voyager 1 at a distance of 3.7 billion miles (6 billion kilometers) from the Sun. The image inspired the title of scientist Carl Sagan’s book, “Pale Blue Dot: A Vision of the Human Future in Space,” in which he wrote: “Look again at that dot. That’s here. That’s home. That’s us.” The above image, “Pale Blue Dot Revisited,” was created in 2020 for the 30th anniversary of the iconic picture. The updated version used modern image-processing software and techniques to revisit the well-known Voyager view, while attempting to respect the original data and intent of those who planned the images.
NASA/JPL-Caltech - Edwin Hubble, 1931 from Brittanica.com
- Triple lightning strike. July 12, 2014. (Barry Butler Photography / FOX Weather)
- Heliocentric model from Nicolaus Copernicus’s De revolutionibus orbium coelestium (On the Revolutions of the Heavenly Spheres) from Wikipedia
- Other images found on Reddit
Discover more from Thoughtful Steward
Subscribe to get the latest posts sent to your email.