SCALE OF THE UNIVERSE 3 - SCIENTIFIC CATALOG
37 independently framed reference scales. Reviewed 3 November 2026.

01. The Planck length
1.6 × 10⁻³⁵ m | derived natural length scale | derived
The combination ℓP = √(ℏG/c³) defines a natural length of approximately 1.616 × 10⁻³⁵ metres. Dimensional arguments suggest that quantum effects of gravity may become important near this scale. No experiment has established that distance is discrete, that shorter lengths are impossible, or that spacetime has the foam-like structure illustrated here. This is the lower reference of this guide, not an experimentally established floor of reality.
Limit: Derived from physical constants, including the measured gravitational constant G. The numerical scale is meaningful; a minimum length and quantum foam remain theoretical. The animation is a metaphor, not measured geometry.
NIST — Planck length
https://physics.nist.gov/cgi-bin/cuu/Value?plkl

02. A fundamental string
≈10⁻³⁴ m | illustrative model-dependent length | hypothetical
String theory proposes that every particle is one vibrating filament, and that which note it plays decides whether we call it an electron or a photon. It is mathematically beautiful and entirely untested: no string has been detected, and no experiment yet devised can reach this scale. It belongs in this journey as an honest question mark.
Limit: No fundamental string has been observed. The 10⁻³⁴ m placement is an illustrative near-Planck reference, not a universal prediction of string theory. Other entries, including the Oort Cloud and cosmological distances, also involve inference.
CERN — supersymmetry & string theory
https://home.cern/science/physics/supersymmetry

03. An up quark
< 10⁻¹⁹ m | illustrative compositeness limit | upper-limit
Quarks are the constituents of protons and neutrons. Every experiment to date — including the highest-energy collisions at the LHC — is consistent with quarks having no internal structure at all. The number here is the finest resolution our instruments have achieved; the true size, if any, lies somewhere below it. Quarks are never found alone: pull two apart and the energy in the bond creates new quarks instead.
Limit: 10⁻¹⁹ m is a representative compositeness reference, not a universal measured quark radius. Bounds depend on the interaction, dataset and assumed model. The rendered spheres and gluons are symbols, not observed surfaces.
Particle Data Group — quark review
https://pdg.lbl.gov/2024/reviews/rpp2024-rev-quarks.pdf

04. An electron
< 10⁻¹⁸ m | representative structure bound | upper-limit
The electron is as close to a true point as physics has found. Precision measurements of its magnetic moment agree with theory to twelve decimal places, the most accurately verified prediction in all of science, and that agreement would break if the electron had internal structure. Yet it is not a tiny ball orbiting anything: bound to a nucleus, it exists as a standing wave of probability.
Limit: This conservative 10⁻¹⁸ m placement is a representative upper-limit reference, not a measured radius or universal best bound. Precision limits depend on the assumed interaction. The probability cloud is illustrative; it is not a particle surface.
Particle Data Group — lepton review
https://pdg.lbl.gov/2024/listings/rpp2024-list-electron.pdf

05. A proton
≈1.7 fm | charge diameter | exact
A proton is three valence quarks inside a boiling sea of gluons and quark–antiquark pairs. Add up the masses of those three quarks and you get roughly one percent of the proton's mass — the other 99% is the binding energy of the strong force, mass made from motion. Resolving the proton's radius took decades and produced a genuine scientific crisis when two methods disagreed; muonic hydrogen measurements settled it near 0.84 fm.
Limit: Twice the root-mean-square charge radius is a reference diameter, not a hard boundary. The displayed valence quarks and gluons are an interpretation. Decay limits depend on the decay channel.
US DOE — the proton radius puzzle
https://www.energy.gov/science/np/articles/new-measurement-fits-another-piece-proton-radius-puzzle

06. A carbon nucleus
≈5.4 fm | diameter | typical
Twelve nucleons — six protons, six neutrons — bound into a drop so dense that a sugar-cube volume of it would weigh about 400 million tonnes. Every carbon atom in your body was assembled inside a star through the triple-alpha process, a reaction so finely balanced that its discovery was predicted from the mere fact that carbon-based observers exist.
Limit: Nucleons are drawn as touching spheres to convey packing; in reality they are smeared quantum wavefunctions with no distinct boundaries.
IAEA — nuclear data services
https://www-nds.iaea.org/

07. A gamma-ray photon
1 pm wavelength | wavelength | typical
A photon is a quantum excitation of the electromagnetic field, with no established hard radius. The one-picometre wavelength selected here corresponds to approximately 1.24 MeV through E = hc/λ. Such radiation can ionise atoms and, under suitable conditions, produce an electron–positron pair while conserving energy and momentum. A photon wave packet may have a spatial extent that is distinct from its wavelength. Gamma radiation occurs in nuclear processes and high-energy astrophysics.
Limit: The wave is an electromagnetic-field metaphor. Its wavelength is the selected comparison length; the packet width, colour and animation speed are illustrative.
NASA — the electromagnetic spectrum
https://science.nasa.gov/ems/

08. Electron Compton wavelength
2.426 pm | wavelength | derived
The electron Compton wavelength λC = h/(mₑc) is approximately 2.426 pm. It is a mass-derived scale, not the size of the electron. Relativistic localisation arguments commonly use the reduced Compton wavelength ℏ/(mₑc), which is smaller by 2π. Pair creation requires sufficient energy and a process that conserves momentum; an isolated photon cannot create a pair in empty space.
Limit: A conceptual relativistic interaction, not a quantitative scattering simulation. λC differs from the reduced Compton wavelength by 2π. The electron is not a sphere of this diameter.
NIST — Compton wavelength
https://physics.nist.gov/cgi-bin/cuu/Value?ecomwl

09. An X-ray photon
0.1 nm wavelength | wavelength | typical
You cannot see anything much smaller than the wavelength you look with, which is why no optical microscope will ever show you an atom. X-rays solve this by having a wavelength about the size of an atomic bond, and when they diffract off a crystal the pattern encodes where every atom sits. That technique revealed the double helix of DNA, the folded architecture of haemoglobin, and the structure of nearly every protein we understand.
Limit: 0.1 nm is a selected wavelength. Adjacent scenes are independently framed; their apparent sizes are not a scale comparison. Field thickness and colour are illustrative.
NASA — the electromagnetic spectrum
https://science.nasa.gov/ems/

10. A hydrogen atom
≈0.106 nm | diameter (2 Bohr radii) | typical
Hydrogen has one proton and one electron. Twice the Bohr radius, approximately 0.106 nm, provides a useful characteristic diameter; the electron probability density has no sharp boundary. Hydrogen nuclei formed during primordial nucleosynthesis in the first minutes, while neutral atoms became abundant around 380,000 years later. Orbital shapes describe quantum states rather than paths followed by tiny orbiting balls.
Limit: The cinema render illustrates an orbital shape, not a measured density or a scale-calibrated ground-state atom. The 2a₀ value is a conventional ground-state length reference, not the diameter of every excited orbital. The nucleus is greatly enlarged for visibility.
IUPAC Gold Book — Bohr radius
https://goldbook.iupac.org/terms/view/B00693

11. A water molecule
≈0.28 nm | van der Waals width | typical
If water were straight it would be a symmetric, nonpolar gas and biology would be impossible. The bend puts the oxygen's negative charge on one side and the hydrogens' positive charge on the other, making every molecule a tiny magnet that grips its neighbours. That grip is why water is liquid at the temperatures where life happens, why ice floats so lakes freeze from the top, and why proteins fold into the shapes that do the work of being alive.
Limit: Atoms are drawn at van der Waals radii; molecules have no solid surfaces and this one vibrates and rotates constantly.
NIST Chemistry WebBook — water
https://webbook.nist.gov/cgi/cbook.cgi?ID=C7732185

12. The DNA double helix
≈2 nm wide | helix width | typical
The width never changes, because every rung pairs one large base with one small one — A with T, G with C. That constant geometry is what lets the molecule be read, copied and repaired by machinery that does not need to know what the message says. Uncoiled, the DNA in a single human cell would stretch about two metres; the DNA in one body would reach to the Sun and back dozens of times.
Limit: Shown as idealised B-form DNA. Real DNA bends, supercoils, and is wound around histone proteins; base colours are a convention.
NIH — the structure of DNA
https://www.genome.gov/genetics-glossary/Deoxyribonucleic-Acid

13. Haemoglobin
≈6.5 nm | diameter | typical
Haemoglobin is a mechanism. When the first oxygen binds to one of its four iron centres, the whole protein flexes, making the remaining three sites bind more eagerly — so it loads greedily in the lungs and unloads decisively in tissue that needs it. A single red blood cell carries around 270 million of these, and the shape is dictated entirely by the one-dimensional sequence of amino acids that folds into it.
Limit: Rendered as a schematic ribbon/surface of PDB entry 1A3N; side-chain detail and solvent are omitted, and colour marks subunits, not chemistry.
RCSB PDB 1A3N — human haemoglobin
https://www.rcsb.org/structure/1A3N

14. Influenza virus
≈100 nm | diameter | typical
A virus carries no metabolism and cannot reproduce by itself. It is a delivery package — eight segments of RNA wrapped in a membrane studded with two proteins, one to pick the lock on a cell and one to escape afterwards. Because those eight segments can be shuffled when two strains infect the same cell, influenza reinvents its own surface faster than immune memory can keep up, which is why the vaccine is reformulated every year.
Limit: Influenza particles are pleomorphic — often filamentous rather than spherical. Spike counts and spacing are representative.
CDC — influenza virus structure
https://www.cdc.gov/flu/about/viruses/types.htm

15. Escherichia coli
≈2 μm long | length | typical
Everything required to live — read the genome, build proteins, harvest energy, sense food, swim towards it, divide — packed into two micrometres with no internal compartments at all. Its flagellum is a true rotary motor, spinning at hundreds of revolutions per second on a molecular bearing, driven by protons falling across the membrane. You carry roughly as many bacterial cells as human ones.
Limit: Internal structure is schematic: the nucleoid is drawn as a compact region, though in life the chromosome is far more diffuse and entangled.
BioNumbers — E. coli dimensions
https://bionumbers.hms.harvard.edu/bionumber.aspx?id=100004

16. A human cell
≈20 μm | diameter | typical
Every one of your roughly thirty trillion cells runs the same genome and reads a different part of it. Inside: a nucleus holding the archive, mitochondria that were once free-living bacteria and still carry their own DNA, a folded membrane factory stamping out proteins, and a skeleton that hauls cargo along molecular rails. It all turns over constantly — most of the molecules in this cell will have been replaced within weeks.
Limit: Organelle counts, sizes and spacing are illustrative. A real cell is crowded to the point of being almost solid, not open as drawn here.
NCBI Bookshelf — the size of cells
https://www.ncbi.nlm.nih.gov/books/NBK26880/

17. A human hair
≈70 μm wide | width | typical
A hair is the smallest thing most people can see unaided, which is why it has become the universal yardstick for "very small". It is also a scale boundary: below roughly fifty micrometres your eye cannot resolve detail, and everything in this journey so far has required an instrument to see at all. Each strand is dead keratin, extruded by a living follicle beneath the skin.
Limit: Hair width varies by a factor of three or more between individuals and across the body; 70 μm is mid-range.
NIST — hair as a length reference
https://www.nist.gov/how-do-you-measure-it/how-do-you-measure-very-small-things

18. A grain of sand
≈0.5 mm | diameter | typical
Sand is what remains after everything softer has been ground away and everything more soluble has washed out to sea. Most grains are quartz, and some have been eroded, buried, lifted and eroded again across hundreds of millions of years. Geologists define sand strictly by size on the Wentworth scale: from 1/16 of a millimetre to 2 millimetres, regardless of what it is made of.
Limit: Grain shape and colour vary enormously by source; this is one illustrative quartz grain, not a type specimen.
USGS — the Wentworth grain scale
https://pubs.usgs.gov/of/2006/1195/htmldocs/nomenclature.htm

19. An ant
≈5 mm | body length | typical
Scale is not just a number — it rewrites which forces matter. An ant's muscles are strong relative to its weight because strength scales with cross-section while weight scales with volume, so it lifts many times its own mass. It cannot be hurt by a fall, because air resistance caps its speed almost immediately. Surface tension, which we never notice, is to an ant a force strong enough to trap it. The world's ants may outweigh all its wild birds and mammals combined.
Limit: A generic worker ant; the family spans well over ten thousand species and a wide range of sizes.
Smithsonian — ants
https://www.si.edu/spotlight/buginfo/ants

20. A human being
1.7 m tall | height | typical
This is the only rung on the ladder you can check with your own body, and it sits remarkably close to the logarithmic middle of everything that exists. From here it is about thirty-five orders of magnitude down to the Planck length and about twenty-seven up to the edge of the observable universe. You are built from roughly 7 × 10²⁷ atoms, nearly all of them forged inside stars that died before the Sun was born.
Limit: A chosen reference height for comparison — not a claim about any individual or population.
CDC NCHS — US body measurements
https://www.cdc.gov/nchs/fastats/body-measurements.htm

21. A blue whale
≈30 m long | body length | typical
Nothing in the fossil record matches it. A blue whale's heart is the size of a small car, its tongue outweighs an elephant, and its call carries for hundreds of kilometres through the deep sound channel of the ocean. Water makes this possible: on land, the square–cube law would make such a body impossible to support, but buoyancy cancels the penalty. Hunted to near-extinction in the twentieth century, some populations are now slowly recovering.
Limit: Length and mass vary between populations; these are upper-typical figures for adults.
NOAA Fisheries — blue whale
https://www.fisheries.noaa.gov/species/blue-whale

22. Mount Everest
8 848.86 m tall | height above sea level | exact
Mountains cannot grow indefinitely: past a certain height the rock at the base begins to flow under its own weight and the crust beneath sags into the mantle. Everest is close to that ceiling for Earth's gravity and rock strength. It is still rising a few millimetres a year as India drives into Asia, and its summit limestone holds the fossils of sea creatures from an ocean that closed fifty million years ago.
Limit: The 2020 joint China–Nepal survey figure, measured to the snow cap. Mountains are measured several different ways.
USGS / NGS — the height of Everest
https://www.usgs.gov/news/national-news-release/new-elevation-mount-everest

23. The Moon
≈3 475 km | mean diameter | exact
No other rocky planet has a moon anything like this big in proportion to itself. It formed when something Mars-sized struck the young Earth, and the debris coalesced in orbit. Its mass stabilises Earth's axial tilt, so our seasons stay predictable over millions of years rather than lurching. It is drifting away from us by about 3.8 cm each year, which we know because Apollo astronauts left mirrors on it.
Limit: Distance from Earth is not shown to scale here; the Moon is about 30 Earth-diameters away.
NASA — Moon facts
https://science.nasa.gov/moon/facts/

24. Earth
≈12 742 km | mean diameter | exact
Liquid water on the surface, a magnetic field deflecting the solar wind, plate tectonics recycling the crust and regulating carbon over geological time, and an atmosphere whose oxygen is itself the waste product of life. Every human who has ever lived has lived here. Seen from the edge of the solar system it is less than a pixel across — the pale blue dot.
Limit: Cloud and surface imagery is a NASA composite from a particular date; Earth is not a perfect sphere but bulges at the equator by 43 km.
JPL — planetary physical parameters
https://ssd.jpl.nasa.gov/planets/phys_par.html

25. Jupiter
≈139 822 km | mean diameter | exact
Jupiter holds more than twice the mass of everything else orbiting the Sun combined, yet fusion needs about eighty times more. Instead of burning it merely glows, radiating more heat than it receives as it slowly contracts. Its gravity has shaped the whole solar system — clearing and stirring the asteroid belt, and deflecting or capturing comets that might otherwise have reached the inner planets.
Limit: Band structure and the Great Red Spot are rendered procedurally; cloud patterns change continuously and this is not a dated observation.
JPL — planetary physical parameters
https://ssd.jpl.nasa.gov/planets/phys_par.html

26. The Sun
≈1.39 million km | photospheric diameter | exact
Four million tonnes of the Sun becomes energy every second, through a fusion chain so slow that a single proton waits billions of years for its turn. Photons released in the core take tens of thousands of years to random-walk out to the surface, then eight minutes to reach you. It is an entirely ordinary star — and that ordinariness, repeated across hundreds of billions of stars per galaxy, is the point.
Limit: Surface granulation and prominences are procedural. The Sun has no solid surface; the photosphere is simply where it becomes transparent.
NASA NSSDC — Sun fact sheet
https://nssdc.gsfc.nasa.gov/planetary/factsheet/sunfact.html

27. Earth's orbit
≈299 million km across | orbital diameter | definition
Because Earth moves to the far side of this circle in six months, nearby stars appear to shift slightly against the background — and that shift, parallax, is the only direct way to measure stellar distance. Every rung further out on the cosmic distance ladder is ultimately calibrated against this one baseline. The astronomical unit is now defined exactly: 149 597 870 700 metres.
Limit: The orbit is drawn as a circle; it is a slight ellipse, and planet sizes here are not to scale against their orbits.
NASA NSSDC — planetary fact sheet
https://nssdc.gsfc.nasa.gov/planetary/factsheet/

28. The planetary system
≈60 AU across | span to Neptune's orbit | typical
If the Sun were a basketball in New York, Neptune would be a grain of rice near Philadelphia. Space probes cross this volume for a decade before passing the outermost planet, and the risk of hitting anything on the way is essentially zero. The planets occupy a thin disc, a fossil of the rotating cloud they condensed from — which is why the solar system is flat.
Limit: Orbits are compressed and bodies hugely enlarged for visibility; true planetary discs would be invisible at this scale.
NASA NSSDC — planetary fact sheet
https://nssdc.gsfc.nasa.gov/planetary/factsheet/

29. One light-year
9.46 × 10¹⁵ m | distance light travels in a year | definition
A light-year is a distance, not a duration — but it welds the two together. Because nothing outruns light, every object further away is also further into the past: see a galaxy ten million light-years off and you see it as it was ten million years ago. There is no way to know what any distant thing looks like "now". The night sky is a record of history, sorted by distance.
Limit: A unit of length, defined by the IAU as exactly 9 460 730 472 580 800 metres.
NASA — what is a light-year?
https://science.nasa.gov/exoplanets/what-is-a-light-year/

30. The Oort Cloud
up to ≈3 ly across | outer span (uncertain) | inferred
Long-period comet orbits motivate an extended, roughly spherical reservoir beyond the planets. Its inner region is often placed at a few thousand astronomical units and outer estimates extend to around 100,000 AU. Twice that outer reference gives a span of about 3.2 light-years. This is an uncertain model scale, not a directly photographed boundary. Objects on proposed inner-Oort orbits have been observed, but the distant reservoir has not been imaged as a whole.
Limit: The distant reservoir is inferred from comet dynamics. Its boundary, shape and extent are uncertain; the sphere is an illustration.
NASA — the Oort Cloud
https://science.nasa.gov/solar-system/oort-cloud/facts/

31. To Alpha Centauri
4.25 light-years | distance to the nearest star system | exact
Three stars: a near-twin of the Sun, a slightly cooler companion, and faint red Proxima, which is currently the closest of all and hosts a planet in its habitable zone. Voyager 1, the fastest object humans have ever launched outward, would need about seventy thousand years to cover this distance if it were aimed there. This is the shortest interstellar gap there is.
Limit: Distance to Proxima Centauri; the system's members vary in distance and Proxima is only currently the nearest.
NASA — Alpha Centauri
https://science.nasa.gov/universe/alpha-centauri-a-triple-star-system-about-4-light-years-away/

32. The Milky Way
≈100 000 ly across | stellar disc diameter | typical
We cannot photograph our own galaxy from outside, so its shape was reconstructed from within — a barred spiral, with the Sun in a minor arm about 26 000 light-years from a central black hole of four million solar masses. One orbit takes roughly 230 million years, meaning the Sun has completed about twenty circuits since it formed, and barely one since the dinosaurs appeared.
Limit: Arm structure is schematic. Our view from inside the disc leaves real uncertainty about the Milky Way's precise morphology.
NASA — the Milky Way
https://imagine.gsfc.nasa.gov/science/objects/milkyway1.html

33. The Local Group
≈10 million ly across | span | typical
The Local Group includes the Milky Way, Andromeda, Triangulum and many dwarf galaxies. A span of roughly ten million light-years is a useful reference, while membership and boundary definitions vary. The future of the Milky Way–Andromeda encounter depends on uncertain masses, motions and the influence of companion galaxies. Recent models give different merger probabilities and times; a collision in four billion years is not a settled prediction.
Limit: Member positions and count are approximate; faint dwarf satellites are still being discovered.
NASA / Hubble — uncertain Milky Way–Andromeda collision
https://science.nasa.gov/missions/hubble/apocalypse-when-hubble-casts-doubt-on-certainty-of-galactic-collision/

34. The Virgo Supercluster
≈110 million ly across | span | typical
The historical Local, or Virgo, Supercluster describes the extended concentration of groups and clusters around Virgo, including our Local Group, over a representative span of about 110 million light-years. It is distinct from the much smaller Virgo Cluster and from the larger Laniakea region defined using galaxy flows. Such structures have survey-dependent boundaries and should not be treated as single rigid, gravitationally bound objects. Galaxy motions, gravitational lensing and other observations constrain the distribution of visible and dark matter.
Limit: A schematic supercluster, not a reconstruction of a galaxy catalogue. The Virgo Cluster, historical Virgo Supercluster and Laniakea are different structures. Neither the particle count nor the shell in the image is a measurement.
NASA — the Virgo cluster
https://science.nasa.gov/universe/galaxies/galaxy-clusters/

35. The cosmic web
≈1 billion ly across | span of filament structure | typical
Zoom out far enough and the universe reveals a structure like foam: galaxies gathered into sheets and filaments that meet at dense nodes, surrounding voids hundreds of millions of light-years wide and nearly empty. This pattern grew over billions of years from faint density ripples present in the first instants, amplified by gravity. Simulations starting from those ripples reproduce the observed web with remarkable fidelity.
Limit: A procedural impression of filament topology, not a rendering of any specific survey volume.
NASA — the cosmic web
https://science.nasa.gov/universe/the-universe-is-expanding-and-its-making-a-cosmic-web/

36. The cosmic microwave background
≈90.5 billion ly across | present comoving last-scattering diameter | inferred
The early universe was a hot, opaque plasma. As it cooled and neutral atoms became abundant, photons could travel much farther without scattering. The light reaching us from that epoch has been stretched into microwaves by cosmic expansion. Its near-perfect thermal spectrum has a mean temperature of about 2.725 K. After removing foregrounds and the large motion-induced dipole, intrinsic temperature anisotropies are typically of order one part in 100,000. These constrain the early density perturbations and cosmological models. The last-scattering surface is our observational description of this emission epoch, not a solid wall.
Limit: Approximately 90.5 billion light-years in a Planck-like flat ΛCDM cosmology; this is model dependent, not a directly measured physical shell. The mottled sphere is illustrative and is not the measured Planck sky map.
NASA — the cosmic microwave background
https://science.nasa.gov/mission/wmap/

37. The observable universe
≈93 billion ly across | comoving diameter | inferred
In standard cosmology, the observable universe has a present comoving diameter of roughly 93 billion light-years, although its age is about 13.8 billion years. Expansion changes the distance to the matter that emitted the ancient light. This particle horizon is not a physical edge and is not the same as the cosmic event horizon, which concerns future causal contact. The total universe may be finite or infinite; its full extent is not known. The galaxy census depends on observational sensitivity and extrapolation.
Limit: A model-inferred horizon, not a material shell or the largest possible object. Scroll beyond this reference for the unknown total extent; no finite size is assigned to it.
NASA — observable size and unknown total extent
https://www.nasa.gov/science-research/astrophysics/how-big-is-space-we-asked-a-nasa-expert-episode-61/