Our measurements / reviewed 2026-09-08

Perspective starts
with honest numbers.

A useful comparison needs more than a number. It needs to say what was measured, which units were used and where the value came from. Each entry includes a source or an explanation of the example we have chosen.

Choosing a useful example

Many things vary in size. Our 1.75 m, 70 kg human is a fixed reference for comparison, not a health benchmark or a claim about the average person. Choosing a 25 m blue whale does not mean all blue whales are that length.

Rounded models of landmarks, places and astronomical objects are labelled. They help you compare sizes; they are not current surveys or precise predictions of where celestial bodies are.

Exact / definition / standard

An exact unit definition or a stated nominal format. A standard format does not mean every manufactured example has no tolerance.

Specified

A named object measured using a stated convention.

Representative / approximate

A useful selected value for something that varies or cannot be measured exactly.

Example / model

An explicitly chosen teaching example, not an independently measured claim or a population average.

Theoretical

A scale or concept from physics, not proof of a smallest or largest possible object.

How illustrations are scaled

The measurement comes from the record, not from counting pixels. We mark the feature being compared in each illustration and fit that span to the scale. This process is called calibration.

For an insect, the marked body length excludes antennae and wings. A planet's mean diameter excludes its rings and is separate from its distance from Earth. A4 paper stays 210 × 297 mm. Images resize evenly in both directions, so their proportions stay intact. Poses, patterns and details outside the measured span remain illustrative.

Rulers, grids and geometric diagrams show measurements that an object picture cannot explain accurately. Bars for mass, energy, power and data compare those quantities, not the physical sizes of the pictured objects.

Very different sizes

A true-scale view never quietly enlarges the smaller object. If it is too small to see, a ring marks its position and a separate enlarged view states the magnification.

A logarithmic scale makes large ranges easier to explore: equal steps represent equal ratios, such as ten times larger. The Scale of Everything labels these steps. Distance on the screen is not literal physical separation.

Area and volume

Known rectangular footprints keep both measured sides. When an outline is unknown, an equal-area square represents the area rather than pretending to be a map. Equal area alone does not tell you whether one shape will fit inside another.

Capacities use equal-volume cubes; spherical planets remain spheres. Cube edges and sphere diameters grow with the cube root of volume. Doubling a volume does not double its width.

Mass, weight and temperature

Mass stays the same when an object moves to another world. Weight is the force of gravity on that mass: F = m × g, measured in newtons. Any Earth-calibrated scale reading is labelled separately and does not mean the mass has changed. For gas giants, “surface” gravity refers to a stated atmospheric level.

Kelvin, Celsius and Fahrenheit conversions account for their different zero points. Values below 0 K are rejected. Temperature comparisons show differences; Celsius and Fahrenheit readings do not support a claim that one thing is “twice as hot”. The Planck temperature is theoretical.

The smallest and largest scales

The Planck length is a theoretical scale, not a proven smallest possible thing. The observable universe is approximately 92 billion light-years across using its present comoving diameter, which allows for cosmic expansion. That is different from its age of approximately 13.8 billion years. We do not claim to know the size of the whole universe.

Units and precision

Calculations retain precision until a result is displayed. Very large and very small values use scientific notation; diagrams use logarithmic normalisation where needed to handle extreme ranges.

Years mean Julian years of 365.25 days, and months are one twelfth of that interval. Mach uses dry air at 20 °C (343 m/s). Decimal data prefixes use 1,000; binary prefixes use 1,024. Gallons, pints and tons need an explicit measurement system.

How comparison references are chosen

Suggestions consider the measurement family, relative size, familiarity, source status, suitability of the illustration and variety of categories. Familiar pairs give you a starting point; the reference panel lets you explore further. All comparisons use the same calculation and drawing system.

Sources and uncertainty

A source supports only the measurements attributed to it. Derived and illustrative values are identified in the record. Each entry shows its selected measurement's source and assumptions, with a recorded range where one is available. A missing range does not imply an exact value.

• NIST — SI conversion factors

  International foot and mile; avoirdupois mass; liquid US and Imperial capacity.

• FIFA — pitch dimensions

  Recommended 105 × 68 m field of play. This is one reference size, not every football pitch.

• ITF — court dimensions

  Playing lines only, excluding run-off space.

• University of Cambridge — ISO paper sizes

  Nominal trimmed A-series dimensions. Area computed from millimetre-rounded sides.

• IFAB — the ball

  A 430 g ball is the midpoint of the permitted 410–450 g range; 69 cm circumference is the midpoint of 68–70 cm.

• Royal Mint — £1 coin specifications

  Twelve-sided format: 23.43 mm maximum span, 2.80 mm thickness, 8.75 g. Older round format: 22.5 mm diameter, 3.15 mm thickness, 9.50 g. Introduction and withdrawal dates are distinct.

• Royal Mint — UK coin designs and specifications

  Current circulation denomination dimensions, masses, compositions and design history.

• US Mint — circulating coin specifications

  Nominal format specifications. Direct retrieval returned HTTP 403 during the October 2026 review; additional references identify the thickness values used.

• US penny — composition and dimensions reference

  Secondary corroboration of copper-plated zinc cent dimensions: 19.05 mm diameter, 1.52 mm thickness and 2.5 g mass. Direct US Mint retrieval was blocked.

• CoinNews — US circulating coin specifications

  Secondary corroboration of nickel, dime and quarter thicknesses and format masses. Its older penny thickness differs; that value is not used.

• Royal Mint — 1p specifications

  20.3 mm diameter, 3.56 g; bronze 1.52 mm thick, copper-plated steel 1.65 mm.

• Royal Mint — 2p specifications

  25.9 mm diameter, 7.12 g; bronze 1.85 mm thick, copper-plated steel 2.03 mm. Both alloys were used in 1998.

• Royal Mint — 5p specifications and format history

  Smaller format introduced June 1990: 18 mm diameter, 3.25 g. Lists 1.7 mm thickness without a material-specific split; does not establish steel thickness here.

• Royal Mint — 10p specifications and format history

  Smaller format introduced September 1992, larger format demonetised 1993: 24.5 mm diameter, 6.5 g. Lists 1.85 mm thickness without a material-specific split.

• Royal Mint — 20p specifications

  Cupro-nickel format: 21.4 mm maximum span, 1.7 mm thickness and 5 g.

• Royal Mint — 50p specifications and format history

  Smaller format introduced 1 September 1997, larger format demonetised 1998: 27.3 mm maximum span, 1.78 mm thickness and 8 g.

• Royal Mint — bimetallic £2 specifications

  28.4 mm diameter, 2.50 mm thickness and 12 g; bimetallic circulation format.

• Royal Mint — cupro-nickel replacement programme (archived)

  Archived official statement: nickel-plated steel introduced in January 2012; cupro-nickel 5p and 10p coins remained legal tender during recovery. No thickness values.

• UK 5p — material-specific and historical dimensions reference

  Secondary reference: original diameter 23.59 mm; cupro-nickel thickness 1.7 mm, steel reported as 1.89 mm. The latter is not adopted as an official specification.

• UK 10p — material-specific and historical dimensions reference

  Secondary reference: original diameter 28.5 mm; cupro-nickel thickness 1.85 mm, steel reported as 2.05 mm. The latter is not adopted as an official specification.

• UK 50p — historical dimensions reference

  Secondary corroboration of the original 30 mm maximum span. Introduction and withdrawal dates use the Royal Mint.

• WA Government — table tennis dimensions

  Playing surface only.

• WA Government — badminton dimensions

  Doubles court, playing lines only.

• WA Government — volleyball dimensions

  Playing court excluding free zone.

• WA Government — squash dimensions

  Interior court length and width.

• NASA — Earth and Moon by the numbers

  Mean radius and average orbital distance; rounded values.

• Airbus — A380 facts and figures

  Overall length 72.7 m. Maximum takeoff mass example is the 575 t variant, not empty mass.

• Eiffel Tower — 330 metre antenna height

  Full height including antenna installed in 2022.

• US National Park Service — Statue of Liberty

  Total height including pedestal, rounded to 93 m.

• Cleveland Clinic — Heart anatomy

  The adult heart is about fist-sized and averages about 10 oz (283 g); dimensions vary by person.

• San Diego Zoo Wildlife Alliance — Capybara

  Adult length 100–130 cm and mass 27–79 kg depending on sex.

• NYC DOT — Brooklyn Bridge facts

  Main suspended span approximately 1,595.5 ft (486.3 m).

• British Airways — Celebrating Concorde

  Length 62.1 m, span 25.5 m, height 11.3 m, maximum takeoff mass 185 t and cruise 2,160 km/h.

• NASA — Phobos

  Irregular body approximately 27 × 22 × 18 km.

• World Squash — Squash ball specifications

  Competition balls are around 40 mm diameter and 24 g, subject to specification tolerances.

• Niagara Parks — Niagara Falls facts

  Horseshoe Falls has an approximately 51 m vertical drop; the three falls differ.

• NIST — Hydrogen hyperfine frequency reference

  Ground-state hydrogen hyperfine transition; wavelength and photon energy are derived from the frequency and exact c and h.

• NIST — ITS-90 fixed points

  Gallium melting-point fixed point near 302.9146 K.

• CERN — The Standard Model

  The top quark is the heaviest third-generation quark and decays extremely rapidly; its lifetime is inferred from the decay width.

• IAEA — Deuterium–tritium fusion

  A D–T reaction releases approximately 17.6 MeV.

• US FDA — Laser products and instruments

  Visible pointer output and class limits vary; 5 mW is used as a defined comparison ceiling.

• Common Crawl — June 2025 crawl archive

  CC-MAIN-2025-26 reports 82.73 TiB compressed WARC files; other derivatives are separate.

• ESA — LISA Pathfinder overview

  Mission overview for drag-free proof masses and precision metrology; acceleration performance depends on frequency.

• Natural History Museum — Tyrannosaurus

  Large adults approached roughly 12 m; body-mass estimates depend on reconstruction.

• US National Park Service — Gateway Arch facts

  The monument is 630 ft (approximately 192 m) high and wide.

• NASA — Asteroid Bennu

  Bennu is roughly one-third of a mile wide; detailed mission solutions give a near-500 m rubble-pile body.

• UNESCO World Heritage Centre — Lake Baikal

  Approximately 3.15 million hectares and about 1,700 m deep.

• NCBI Bookshelf — Bacteriophage T4

  T4 morphology and characteristic head-tail scale; dimensions vary with preparation and measurement convention.

• Cleveland Clinic — Brain

  Adult brain anatomy and a mass around three pounds; the atlas uses a representative 1.4 kg specimen.

• San Diego Zoo Wildlife Alliance — Platypus

  Adult body dimensions and mass vary by sex; a 50 cm, 1.5 kg representative specimen is used.

• Opera della Primaziale Pisana — Leaning Tower

  The tower is roughly 56 m high; published side-specific heights differ because it leans.

• NASA Armstrong — SR-71 Blackbird

  Published aircraft dimensions and high-speed performance; mission conditions affect speed and mass.

• NASA — What was the Saturn V?

  Overall Apollo launch-vehicle height, fueled launch mass and liftoff thrust.

• Badminton World Federation — Statutes and equipment laws

  Shuttle dimensions and mass tolerances; a midpoint specimen is used.

• Geospatial Information Authority of Japan — Japan elevations

  Mount Fuji summit elevation is 3,776 m above mean sea level.

• BIPM — The International System of Units

  The second is defined by exactly 9,192,631,770 periods of the caesium-133 hyperfine transition.

• NASA — Earth facts

  Earth rotation and dimensions support a rounded equatorial surface-speed anchor.

• IAPWS — Fundamental physical constants of water

  Triple-point temperature and isotopic-composition convention.

• Particle Data Group — Muon properties

  Recommended mean lifetime for the positive muon.

• RFC 791 — Internet Protocol

  IPv4 addresses are 32-bit protocol fields.

• San Diego Zoo Wildlife Alliance — Meerkat

  Representative adult body size and mass; tail is excluded from the chosen body span.

• Tower Bridge — History

  The central opening span is approximately 61 m between the main towers.

• NASA — Deimos

  Mars’s smaller moon is an irregular body approximately 15 × 12 × 11 km.

• NASA History — Sputnik and the dawn of the Space Age

  Sputnik 1 sphere diameter, mass and four-antenna configuration.

• CDC — Influenza viruses

  Influenza virions are enveloped particles with variable morphology; 100 nm is a representative diameter.

• Cleveland Clinic — Liver

  Adult liver anatomy and representative mass.

• San Diego Zoo Wildlife Alliance — Axolotl

  Representative adult length and body mass.

• UK Parliament — Big Ben

  Elizabeth Tower is approximately 96 m high; Big Ben properly names the Great Bell.

• Antonov — AN-225 Mriya

  Published aircraft dimensions and maximum takeoff mass.

• NASA — Explorer 1 overview

  First US satellite dimensions, mass and mission context.

• Encyclopaedia Britannica — K2

  Summit elevation 8,611 m above sea level.

• NIST — Compact strontium optical clock

  Strontium-87 optical clock transition context and frequency scale.

• USGS — This Dynamic Earth

  Tectonic plates move at centimetres-per-year scales.

• NIST Chemistry WebBook — Carbon dioxide

  Carbon-dioxide phase data and sublimation temperature.

• Particle Data Group — Neutron properties

  Recommended free-neutron lifetime and experimental context.

• CERN — Large Hadron Collider

  Representative multi-TeV proton operating energy.

• China Three Gorges Corporation — Three Gorges Project

  Installed hydropower capacity 22.5 GW.

• NIST — Secure Hash Standard

  SHA-256 produces a 256-bit digest.

• ESA — Parabolic flights

  Reduced-gravity aircraft arcs last roughly twenty seconds.

• San Diego Zoo Wildlife Alliance — Emu

  Adult standing height and body mass ranges.

• Transport for NSW — Sydney Harbour Bridge

  Main steel arch span approximately 503 m.

• SpaceX — Dragon

  Crew Dragon vehicle dimensions and configuration.

• NIST — 2022 CODATA fundamental constants

  Recommended constants with uncertainties; exact SI definitions are distinguished from measured constants.

• NASA JPL — planetary physical parameters

  Mean radii and masses. Spherical area and volume here are derived from mean radius. This atlas rounds for scale comparison.

• NASA — Planet Compare

  Conventional surface gravities; giant-planet values refer to an atmospheric reference level. Earth uses standard gravity, 9.80665 m/s².

• NASA — Sun facts

  Solar dimensions and temperatures. Nominal radius 695,700 km and nominal luminosity 3.828 × 10²⁶ W use IAU conversion constants.

• IAU — nominal solar and planetary conversion constants

  Resolution B3 defines nominal solar radius and luminosity; nominal constants are conversion anchors, not new measurements.

• NASA — How big is space? (2025)

  Approximately 92 billion light-years across today. This is the observable universe, not a measurement of the total universe.

• NASA — Cosmic history

  Approximately 13.8 billion years since the early hot universe in the standard cosmological model.

• NASA — Galaxies

  The Milky Way stellar disk spans more than 100,000 light-years; 100,000 ly is our deliberately rounded scale anchor.

• NASA — The galaxy next door

  Distance about 2.5 million ly; UV extent about 260,000 ly. A galaxy boundary depends on the observing method.

• NASA — Oort Cloud facts

  The inferred cloud extends as far as about 100,000 AU from the Sun; it is not a directly mapped hard shell.

• NASA — Neutron stars

  City-sized stellar remnants. Our 20 km, 1.4 solar-mass example is illustrative, not a named measured star.

• NASA — White dwarfs

  Earth-sized stellar remnants; the chosen 12,000 km, 0.6 solar-mass example is a model.

• University of Michigan — Apis mellifera

  Worker body length 10–15 mm. The atlas uses a 15 mm worker; antennae and wings do not count toward body length.

• University of Michigan — African bush elephant

  Adult male shoulder height 3.2–4 m and mass 4,500–6,100 kg. The selected 3.3 m and 5,000 kg are representative choices within those ranges.

• WWF — African elephant

  Listed length 19–24 feet. A 6 m example is selected for the length view.

• NOAA Fisheries — Blue whale

  Lengths and masses vary strongly with population and sex. The 25 m, 100 tonne example is not a maximum.

• San Diego Zoo — Giraffe

  Adult males can reach 5.5 m; the illustrated male is a chosen 5 m, 1,000 kg specimen.

• Lufthansa — Boeing 747-8 specifications

  Length 76.30 m, wingspan 68.40 m, cruising speed 920 km/h and maximum takeoff mass 442,300 kg for this operator configuration.

• Guinness World Records — Burj Khalifa

  828 m architectural height. Other buildings use their stated measurement convention.

• NASA — International Space Station

  Rounded orbital speed of 17,500 mph. Instantaneous speed and altitude vary.

• USGS — How much natural water is there?

  Estimated ocean volume 1.338 billion km³; total Earth water 1.386 billion km³.

• NOAA — How deep is the ocean?

  Challenger Deep about 10,935 m; different surveys and methods give slightly different depths.

• NASA — COBE science results

  Cosmic microwave background blackbody temperature about 2.725 K; this is radiation temperature, not the temperature of every object in space.

• NASA Glenn — Speed of sound

  Sound speed depends on medium and temperature. Mach comparisons here use dry air at 20 °C, approximately 343 m/s.

• University of Utah — Cell size and scale

  Approximate biological size regimes. Atlas specimens and geometric assumptions are individually labelled.

• NIST Chemistry WebBook — Nitrogen phase data

  Normal boiling point near 77.4 K; pressure affects phase changes.

• NIST Chemistry WebBook — Helium phase data

  Normal boiling point near 4.22 K.

• NIST — Binary prefixes

  Decimal storage units use powers of 1,000; IEC binary units use powers of 1,024. A byte is eight bits.

• NASA JPL — Planetary satellite physical parameters

  Published mean radii and gravitational parameters GM. Spherical areas, volumes, masses and local gravity are explicitly derived.

• NASA — Our nearest celestial neighbour

  Rounded distance of 4.25 light-years to Proxima Centauri.

• NASA — Apollo 11 mission report

  Apollo 11 command-and-service-module dimensions and launch configuration mass.

• NASA — Cassini spacecraft

  Spacecraft dimensions, launch mass and instrument configuration.

• Smithsonian National Zoo — American bison

  Adult body dimensions and mass vary strongly by sex and age; the atlas uses a defined bull within published ranges.

• San Diego Zoo Wildlife Alliance — Andean condor

  Adult wingspan and mass ranges; the atlas selects one explicit adult specimen.

• US Fish and Wildlife Service — Alligator snapping turtle

  Species anatomy and broad adult size variation; the atlas defines a straight-carapace specimen.

• Encyclopaedia Britannica — Femur

  Adult femur anatomy; the atlas uses an explicitly defined 45 cm dry-bone specimen.

• Encyclopaedia Britannica — Human eye

  The adult eye globe is approximately 24 mm in diameter; anatomy varies by person and axis.

• Encyclopaedia Britannica — Amoeba

  Amoebae change shape through pseudopodia; the atlas uses a defined 300 micrometre Amoeba proteus projection.

• RCSB Protein Data Bank — Antibody structure

  IgG has a flexible Y-shaped architecture; the atlas uses a representative maximum projected molecular span.

• United States Bowling Congress — Equipment specifications

  Ten-pin dimensions and permitted mass range.

• Evergreen Aviation & Space Museum — Spruce Goose

  Published dimensions for the sole Hughes H-4 Hercules.

• Stratolaunch — Roc carrier aircraft

  Published overall dimensions for the Roc carrier aircraft.

• Encyclopaedia Britannica — Aconcagua

  Summit elevation of 6,961 m above mean sea level.

• Encyclopaedia Britannica — Bali

  Approximate island area and east-west extent; coastline and administrative definitions affect values.

• NASA — Catalogue of Earth satellite orbits

  A geostationary orbit matches Earth’s sidereal rotation and requires circular equatorial prograde motion.

• IEEE 802.3 Ethernet working group

  Standard untagged Ethernet frame size convention; excludes physical-layer preamble and interpacket gap.

• RFC 6265 — HTTP State Management Mechanism

  General-purpose user agents should support at least 4,096 bytes per cookie, including name, value and attributes.

• NASA — Apollo 11 mission report

  Apollo 11 lunar-module dimensions and separation configuration mass.

• NASA — Hubble by the numbers

  Hubble overall length and in-orbit mass.

• NASA Technical Reports Server — Space Shuttle transportation system

  Orbiter and integrated Space Shuttle configuration, dimensions and propulsion data.

• NASA — Moon facts

  Mean lunar orbital speed and synodic phase-cycle context.

• NASA — Venus facts

  Venus solar-day duration and distinction from sidereal rotation.

• World Lacrosse — Equipment and ball standards

  Regulation ball circumference and mass ranges.

• MCC — Law 8, the wickets

  Regulation stump height and total wicket width.

• Encyclopaedia Britannica — Amazon River and rainforest

  Rounded river length and broad rainforest-area context; geographic definitions vary.

• Encyclopaedia Britannica — Sahara

  Approximate desert area under a broad geographic convention.

• NASA NSSDC — Vanguard 1

  Satellite body diameter, mass, antenna configuration and mission context.

• UNESCO World Heritage Centre — Great Barrier Reef

  World Heritage property extent and geographic context; mapped-area conventions differ.

• NASA — Saturn facts

  Rounded 10.7-hour rotation period; Saturn rotates differentially and has no solid surface.

• OpenStreetMap — Planet data

  Official weekly planet snapshots; the PBF listed on 10 September 2026 was 88 GB. File size changes with date and format.

• NASA NSSDC — Luna 2

  Mission identity, spacecraft mass and spherical-bus configuration.

• NASA NSSDCA — Vostok 1

  Vostok spacecraft cabin and service-module configuration with a recorded mission mass of 4,725 kg.

• Australian Antarctic Program — Antarctic krill

  Antarctic krill anatomy and adult length scale; the atlas selects an explicit adult specimen.

• US National Park Service — Grand Canyon facts

  Grand Canyon is approximately 277 miles (446 km) long.

• NASA Earth Observatory — Yarlung Tsangpo Grand Canyon

  Geographic context for the approximately 500 km canyon system; endpoint conventions vary.

• NASA — Gemini spacecraft

  Gemini programme spacecraft dimensions, configuration and mission context.

• Smithsonian Ocean — Pteropods

  Sea-angel identity, swimming anatomy and broad size variation.

• USGS — Yellowstone caldera

  Approximate 70 by 45 kilometre dimensions of the youngest Yellowstone caldera.

• MLB — Official rules hub

  Current Official Baseball Rules, including catcher-mitt construction constraints; no universal mitt length or mass is specified.

• Parco archeologico del Colosseo — The Colosseum

  Amphitheatre exterior axes and original facade-height context.

• NASA — The launch of Skylab

  Skylab orbital configuration and approximately 170,000 lb orbital mass.

• NASA — Webb fact sheet

  Deployed sunshield dimensions and observatory mass.

• Smithsonian Ocean — Nudibranchs

  Nudibranch anatomy, diversity and broad body-size variation.

• Australian Museum — Leafy seadragon

  Species identity, camouflage anatomy and adult length scale.

• FIE — Material rules

  Maximum foil dimensions and ready-to-use mass.

• World Curling — Rules and regulations

  Competition sweeping-device and approved-head requirements.

• Montana Fish, Wildlife & Parks — Giant Springs State Park

  Roe River location and commonly cited short surface course at Giant Springs.

• UNESCO — Ombla spring catchment

  Karst spring and short named surface-course context near Dubrovnik.

• NASA Technical Reports Server — Space Shuttle transportation system

  Solid Rocket Booster and main-engine sea-level thrust used to estimate total liftoff thrust.

• NASA — Kepler mission in depth

  Observatory configuration, telescope design and launch mass.

• Smithsonian Ocean — Mantis shrimp

  Stomatopod anatomy and broad adult size variation; the atlas uses a defined specimen.

• Natural Resources Canada — Nautley River

  Named river and endpoint context; the short channel length is approximate.

• English Heritage — Stonehenge

  Great trilithon arrangement, stone dimensions and reconstructed monument context.

• ESA — Gaia factsheet

  Observatory dimensions, deployed sunshield and launch mass.

• NASA — Voyager spacecraft

  Voyager configuration, spacecraft systems and 3.7 m high-gain antenna.

• Smithsonian Ocean — Cleaner shrimp

  Cleaner-shrimp anatomy and ecological context; the atlas uses a defined specimen.

• Monterey Bay Aquarium — California sea hare

  Sea-hare anatomy and broad size variation; the atlas uses a smaller defined Aplysia specimen.

• FIBA — Basketball equipment

  Regulation backboard width and height.

• FIVB — Official Volleyball Rules

  Net-post height and placement; post diameter is a defined specimen choice.

• Natural Resources Canada — Powell River

  Named British Columbia river and endpoint context; channel length is approximate.

• Texas State Historical Association — Comal River

  River source, course and approximate length at New Braunfels.

• Johns Hopkins APL — New Horizons spacecraft

  Official mission spacecraft configuration and launch mass.

• NASA — Juno spacecraft

  Deployed solar-array span, launch mass and instrument configuration.

• ESA — Rosetta factsheet

  Deployed spacecraft dimensions, launch mass and Philae mission configuration.

• Smithsonian Ocean — Basket stars

  Euryalid anatomy and branching-arm form; the atlas uses an explicitly defined projected specimen.

• Smithsonian Ocean — Crinoids

  Feather-star anatomy and posture; the atlas uses an explicitly defined arm-tip span.

• Smithsonian Ocean — Sea urchins and sand dollars

  Sand-dollar identity, rigid test and living spine covering; the atlas uses a defined specimen.

• US Antarctic Program — Onyx River

  McMurdo Dry Valleys geographic context; published river length and active course are approximate.

• Encyclopaedia Britannica — River Thames

  Approximately 346 km from source to the North Sea under the cited river convention.

• Encyclopaedia Britannica — Seine River

  Approximately 780 km from source to the English Channel; the atlas uses the commonly quoted 777 km scale.

• USDA FoodData Central — raw fruit portions

  Reference serving masses for raw fruits; dimensions remain explicit atlas specimen choices.

• ITF — Rules of Tennis

  Regulation tennis-ball mass range; kinetic energy is derived from a stated ball mass and launch speed.

• US FDA — Refrigerator and freezer storage

  Food refrigerators should be kept at or below 40 °F (4 °C); cabinet temperatures vary spatially and over the thermostat cycle.

• BWF — Laws of Badminton

  Court width and regulation net-post height used to define the complete net frame.

• USGA and R&A — Equipment rules

  Maximum regulation golf-ball mass; kinetic energy is derived from a stated mass and launch speed.

• NIST — DNA stretching measurements

  Single-molecule DNA stretching context; the atlas uses a representative 50 pN DNA stretching scale.

• NASA — Parker Solar Probe mission

  Spacecraft mission, launch mass and heat-shield context.

• NOAA Fisheries — White abalone

  Abalone shell anatomy and adult size variation; the atlas uses a defined multi-species comparison specimen.

• World Aquatics — Water polo competition regulations

  Senior goal inside width and crossbar height above the water surface.

• Encyclopaedia Britannica — Rhine River

  Approximately 1,230 km from Alpine headwaters to the North Sea; source and channel conventions affect length.

• NCBI — Human sperm motility assessment

  Progressive sperm motion is measured in micrometres per second and varies across cells, samples and methods.

• NASA Imagine the Universe — Neutron stars

  Young neutron stars have million-kelvin thermal surfaces and cool over time.

• NIST — Atomic spectra database ionization energies

  Recommended hydrogen ground-state ionization energy; joules are converted from electronvolts.

• SpaceX — Falcon 9

  Published overall height, diameter, mass and launch-vehicle configuration.

• NASA — Space Launch System

  Block 1 vehicle height, liftoff mass and launch configuration.

• NOAA Fisheries — Queen conch

  Adult shell anatomy, size and mass range; the atlas selects an explicit adult specimen.

• Washington Department of Fish and Wildlife — Geoduck

  Pacific geoduck shell, siphon anatomy and broad adult size variation; the atlas defines one specimen.

• MCC — The Laws of Cricket

  Sight-screen use and field context; no universal screen dimensions are prescribed, so the atlas dimensions are an explicit model.

• Encyclopaedia Britannica — Danube River

  Approximately 2,850 km from the Black Forest to the Black Sea under the cited river convention.

• Encyclopaedia Britannica — Volga River

  Approximately 3,530 km from the Valdai Hills to the Caspian Sea under the cited river convention.

• NCBI Bookshelf — Microcirculation

  Red cells deform and move through capillaries at tissue- and vessel-dependent millimetre-per-second scales.

• Energizer — CR2032 product datasheet

  Nominal 3 V lithium coin cell and representative 225 mAh capacity; stored energy is explicitly derived.

• Canal & River Trust — Boats and boating

  Waterway craft context and dimensional constraints; the atlas uses an explicitly defined cruising narrowboat specimen.

• Smithsonian Ocean — Sponges

  Sponge anatomy and colony growth; the atlas uses a defined adult giant-barrel specimen.

• Encyclopaedia Britannica — Mekong River

  Approximately 4,350 km under the cited source and channel convention.

• NIST — Firefighter protective equipment

  Structural-firefighting PPE and breathing-apparatus context; the atlas uses an explicit person-and-gear mass model.

• NASA — Andromeda galaxy overview

  M31 stellar-population and galaxy context; total stellar luminosity depends on wavelength, dust correction and boundary model.

• Human Cell Atlas — Data portal

  Single-cell transcriptomic datasets vary widely in cell count, processing level and representation; 100 GB is an explicit storage specimen.

• International Dragon Boat Federation — Rules and regulations

  Standard racing-boat dimensions, dry mass and removable decorative fittings.

• World Rowing — Rules of racing

  Racing-shell classes and equipment context; the non-standard six-person shell is an explicitly defined specimen.

• NOAA Fisheries — Elkhorn coral

  Branching anatomy, habitat and colony-scale growth of Acropora palmata.

• Smithsonian Ocean — Corals and coral reefs

  Massive coral colony anatomy and growth; the atlas uses a defined grooved dome specimen.

• FIFA — Futsal laws of the game

  Regulation 3 m by 2 m goal opening and frame requirements.

• FIVB — Official beach volleyball rules

  Referee position and equipment context; overall stand height is a defined approved-equipment specimen.

• Encyclopaedia Britannica — Murray River

  Approximately 1,570 miles, or 2,530 km, from the Snowy Mountains to the ocean.

• Encyclopaedia Britannica — Orange River

  Approximately 1,300 miles, rounded to 2,100 km, from the Lesotho Highlands to the Atlantic Ocean.

• PADI — Scuba gear

  Recreational scuba-equipment configuration and component context; the atlas uses an explicit dry person-and-gear mass.

• NASA — Spacesuits

  Extravehicular suit anatomy and life-support configuration; the atlas uses an explicit suited comparison specimen.

• Encyclopaedia Britannica — Gondola

  Traditional Venetian gondola construction and characteristic dimensions; handmade hulls vary slightly.

• Smithsonian Ocean — Corals and coral reefs

  Gorgonian colony anatomy and branching growth; the atlas uses an explicitly defined mature sea-fan specimen.

• Encyclopaedia Britannica — Lena River

  Approximately 4,400 km from headwaters near Lake Baikal to the Laptev Sea.

• International Orienteering Federation — Control descriptions

  Standard orange-and-white control-flag form and approximately 30 cm square faces.

• NASA Kennedy — Vehicle Assembly Building

  Kennedy Space Center VAB exterior dimensions and launch-vehicle assembly function.

• Harvard Wyss Institute — DNA data storage

  DNA information-density context; 215 PB/g is an idealised theoretical scale rather than delivered system capacity.

• NASA Imagine the Universe — Neutron stars

  Representative neutron-star mass and radius scales; the one-kilogram force is an explicit Newtonian GMm/r² model.

• Smithsonian Ocean — Polynesian voyaging

  Polynesian voyaging-canoe form and cultural context; dimensions and speed are explicit atlas specimen choices.

• International Formula 18 — Class rules

  Formula 18 maximum hull dimensions and minimum ready-to-sail boat mass.

• NOAA Ocean Service — Kelp forests

  Giant-kelp biology and tens-of-metres growth scale; the atlas uses a representative mature thallus.

• Schmidt Ocean Institute — Giant siphonophore

  Extended giant-colony observations and colonial zooid anatomy; length is posture- and observation-dependent.

• Encyclopaedia Britannica — Yenisey River

  Yenisei system and headwater context; the atlas uses the commonly listed 5,539 km system length.

• Encyclopaedia Britannica — Ob River

  Ob–Irtysh system and headwater context; the atlas uses an approximate 5,410 km system length.

• Professional Disc Golf Association — Technical standards

  Approved-disc diameter and diameter-dependent maximum mass; the atlas selects one driver specimen.

• NCBI Bookshelf — Sperm transport and capacitation

  Human sperm-cell anatomy and characteristic head-to-tail scale.

• NCBI Bookshelf — Red blood cell physiology

  Human erythrocyte circulation and approximately 120-day lifespan; circulation time varies with physiology.

• Rail Explorers — Rail bikes

  Commercial pedal rail-bike configuration and operating context; dimensions, mass and speed are explicit atlas specimen choices.

• Smithsonian Ocean — Pyrosomes

  Hollow colonial-tunicate anatomy and variable colony size; the atlas uses a defined two-metre specimen.

• Encyclopaedia Britannica — Yellow River

  Published length 5,464 km from the Bayan Har Mountains to the Bohai Sea.

• Encyclopaedia Britannica — Boomerang

  Returning-boomerang form and flight context; dimensions and mass are an explicit sporting specimen.

• de Leva — Adjustments to Zatsiorsky-Seluyanov segment inertia parameters

  Adult body-segment mass fractions; atlas segment masses are derived for a defined 70 kg adult model.

• NASA JPL — Planetary satellite physical parameters

  Earth and Moon gravitational parameters support the stated circular restricted three-body L1 gradient calculation.

• NCBI Bookshelf — Neuroanatomy, Neurons

  Neuron soma, axon and dendrite anatomy; soma size varies by neuron type and the atlas uses a defined 20 micrometre body.

• Liebherr — Ship-to-shore container cranes

  STS trolley and hoist configuration; the atlas selects a representative loaded horizontal trolley speed.

• NASA — Gossamer Albatross

  NASA quotes a 94 ft span and describes the low-speed, lightweight human-powered aircraft programme.

• FISLY — International land and sand yachting

  Three-wheel racing classes and sailing context; dimensions, mass and speed are an explicit atlas specimen.

• Smithsonian Ocean — Salps

  Barrel-shaped tunicate anatomy and aggregate chains; the atlas uses a defined extended colony.

• MBARI — Dumbo octopus

  Deep-sea cirrate-octopus anatomy, including paired fins and webbed arms; the atlas uses a defined specimen.

• Encyclopaedia Britannica — Congo River

  Approximately 4,700 km using the Chambeshi as the remotest source.

• Encyclopaedia Britannica — Nile River

  Commonly published 6,650 km river-system length; the Nile has several headstream conventions.

• World Archery — Rulebook

  Outdoor target-face and equipment context; the 1.3 m round boss is a defined specimen accommodating a 122 cm face.

• Encyclopaedia Britannica — Snowshoe

  Traditional frame, webbing and binding form; dimensions and mass are an explicit one-shoe specimen.

• RP Photonics Encyclopedia — Radiation Pressure

  For normal incidence, perfect reflection transfers twice the incident photon momentum (F = 2P/c); complete absorption gives F = P/c.

• Itaipu Binacional — Hydroelectric power

  Itaipu reports full capacity with 20 generating units rated at 700 MW each, totalling 14,000 MW installed capacity.

• Monash University — Astrophysics I: Stars and Stellar Evolution, Lecture 25

  Derives the Eddington limit from radiation force balance. The canonical one-solar-mass value assumes pure ionized hydrogen, with electron-scattering opacity about 0.4 cm²/g; other composition changes it.

• Fermi-LAT Collaboration — Fermi-LAT observations of the Crab nebula and pulsar

  Reports Crab pulsar spin-down power of 4.6 × 10^38 erg s−1; this rotational energy-loss rate is inferred from pulsar timing and depends on the assumed neutron-star moment of inertia.

• NIST Technical Note 1334 — Thermodynamic Properties of Helium-4

  Reference thermodynamic properties for helium-4, including the lambda transition; transition conditions depend on pressure.

• NIST Chemistry WebBook — Hydrogen phase change data

  Phase-change reference data for hydrogen, including its normal boiling point.

• NIST Chemistry WebBook — Neon phase change data

  Phase-change reference data for neon, including its normal boiling point.

• NIST Technical Note 1265 — The International Temperature Scale of 1990 (ITS-90)

  Defines ITS-90 fixed points, including the assigned nitrogen triple-point temperature of 63.151 K.

• NIST CSRC Glossary — 0xab

  Defines a byte as eight bits and each hexadecimal digit as four bits.

• RFC 4291 — IP Version 6 Addressing Architecture

  Internet standards-track specification for IPv6 addressing; IPv6 addresses are 128-bit identifiers.

• RFC 9562 — Universally Unique IDentifiers (UUIDs)

  IETF standards-track specification stating that a UUID is 128 bits long.

Explore all measured things

How AI-assisted artwork is checked

Some illustrations are made with an AI image-generation tool, then reviewed for identity, anatomy, perspective, unwanted cropping and transparent backgrounds. We check the marked measurement against the recorded value. Generating or changing an image never changes that value.

Rulers, grids, orbits and geometric diagrams are drawn from the data when they explain a measurement more accurately than an object illustration.