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It’s a long way from planet Earth to the Universe’s edge.
The extent of the visible Universe now goes on for 46.1 billion light-years: the distance that light emitted at the instant of the Big Bang would be located from us today, after a 13.8 billion year journey. As time marches on, light that’s even farther away, that is still on its way to us, will eventually arrive: from slightly greater distances and with slightly greater redshifts. We see into the past when we look out to great distances because the light emitted from distant objects must traverse those great intergalactic distances at a finite speed: the speed of light.
Our tiny home world, seemingly massive, is merely 12,742 km (7,917 miles) across.
This image, taken from the International Space Station by astronaut Karen Nyberg in 2013, shows the two largest islands on the southern part of the Mascarene Plateau: Réunion, in the foreground, and Mauritius, partially covered by clouds. To see a human on Earth from the altitude of the ISS, a telescope the size of Hubble would be needed. The scale of a human is less than 1/5,000,000 the scale of Earth, but Earth is just a proverbial drop in the cosmic ocean, with a diameter of only a little over 10,000 kilometers.
We typically think linearly: where the Sun is ~10,000 times farther away than Earth’s diameter.
While all of the planets in the Solar System orbit the Sun in the same direction, Venus, uniquely, rotates in the opposite direction. For each orbit completed by Venus, although it is the slowest-rotating planet, it experiences roughly two “days” of sunrises and sunsets.
But cosmically, logarithmic scales — where each multiplicative factor of “10” defines our cosmic ruler’s next mark — serve us far better.
The Earth, at nearly 13,000 kilometers (8,000 miles) in diameter, is tiny compared to the cosmic distances between the Earth-and-Moon or, more spectacularly, the Earth-and-Sun. But a logarithmic scale gives us a vastly different perspective, enabling us to reckon with disparate distance scales in a single visual image.
On a logarithmic scale, the Sun, Mercury, and Mars are practically equidistant.
The inner Solar System, including the planets, asteroids, gas giants, Kuiper belt, and more, is minuscule in scale when compared to the extent of the Oort Cloud. Sedna, the only large object with a very distant aphelion, may be part of the innermost portion of the inner Oort Cloud, but even that is disputed. On a linear scale, depicting the entire Solar System in a single image is incredibly limiting; to characterize the orbit of a faraway bound object requires years or even centuries of data.
Another factor of ~10,000 in distance takes us to the Oort cloud.
In the Solar System, we typically measure distances in Astronomical Units (AU), where the Earth-Sun distance is 1 AU. Mercury and Mars are also about ~1 AU from Earth, with Saturn at ~10 AU, the Kuiper belt ending before ~100 AU, and the Oort cloud largely existing at ~10,000 AU. It’s an enormous distance on a linear scale, but only a small set of “factors of 10” away on a logarithmic one.
A short logarithmic jump takes us from the Solar System to the stars.
This long-exposure image captures a number of bright stars, star-forming regions, and the plane of the Milky Way above the southern hemisphere’s ALMA observatory. The nearest stars are only a few light-years away: less than a factor of 10 from the edge of the Oort cloud. But more distant stars and features, still visible with the naked human eye, can be tens of thousands of light-years away instead.
Many of the brightest stars in Earth’s skies are under 1,000 light-years away.
Many of the brightest nearby stars to Earth are members of the Orion arm, which itself is a minor spur of the larger, grander Perseus arm of the Milky Way. From the nearest stars, a few light-years away, to these arms, a few thousands of light-years away, represents only three factors of “10” on a logarithmic scale.
Another small logarithmic jump brings us to our nearest spiral arms.
By viewing the Milky Way in infrared wavelengths of light, we can see through large amounts of the galactic dust and view the distribution of stars and star-forming regions behind them. As revealed by the 2 micron all-sky survey (2MASS), the densest collections of galactic dust can be seen tracing out our spiral arms, but the center of the plane of the Milky Way is where the dust is densest. Infrared and visible light views both showcase this, but in vastly different ways.
Beyond that lies the full Local Galactic Group.
The Perseus spiral arm leads into the full-scale Milky Way, with other galaxies in the Local Group lying only a single factor of “10” beyond the full-scale Milky Way. Another factor of 10 beyond that takes us to large galactic groups and even approaches the closest galaxy cluster.
Rapidly, neighboring galaxies become ubiquitous.
This illustrated map of our local supercluster, the Virgo supercluster, spans more than 100 million light-years and contains our Local Group, which has the Milky Way, Andromeda, Triangulum, and about ~60 smaller galaxies. The overdense regions gravitationally attract us, while the regions of below-average density effectively repel us relative to the average cosmic attraction. However, the individual groups-and-clusters are not gravitationally bound together and are receding from one another as dark energy dominates the cosmic expansion.
Subsequent cosmic steps reveal large-scale galaxy clustering.
There are only a few factors of “10” in logarithmic distance that separate the nearest galaxies, located a few hundred thousand to a few million light-years away, to large-scale clustering features on the scales of hundreds of millions or possibly one billion light-years. At these scales, the Universe’s largest bound features begin to come into view.
Eventually the largest structures of all are revealed: the great cosmic web.
Over time, gravitational interactions will turn a mostly uniform, equal-density Universe into one with large concentrations of matter and huge voids separating them. For as long as radiation is still important, exerting an outward pressure even once the Universe becomes matter-dominated, the growth of matter imperfections is very small.
Many of these features are only apparent: dark energy will tear these pseudostructures apart.
The largest features seen here, like “great walls” and “large quasar groups” may not be cosmologically bound structures, but rather apparent pseudostructures, where gravitation due to their cumulative masses will be insufficient to keep them bound. Dark energy, on the largest cosmic scales, will drive all things apart.
At the cosmic limits, the edges of time are revealed: the earliest moments after the hot Big Bang.
From objects within our Solar System to stars within our galaxy to distant galaxies as far as our telescopes can see, space is populated with objects at a specific location in space that emit light. We can only observe the light that is arriving right now: after journeying through the expanding Universe. However, the leftover light from the Big Bang, the CMB, was emitted from all locations at a specific moment in time. With each passing moment, light from a slightly more distant location than the previous moment arrives.
Thanks to artist Pablo Carlos Budassi for creating this brilliantly illustrated cosmic journey.
This vertically oriented logarithmic map of the Universe spans nearly 20 orders of magnitude, taking us from planet Earth to the edge of the visible Universe. Each large “mark” on the right side’s scale bar corresponds to an increase in distance scales by a factor of 10.
Mostly Mute Monday tells an astronomical story in images, visuals, and no more than 200 words. This article was first published August of 2022. It was updated in September of 2025.
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