Sources & calculations
The iceberg collection
The four reading layers group investigations by the questions they examine: familiar observations, images and perception, physical structures, and the material record. Open any case for its calculation; its publications and constants are listed below.
The secrecy model
Give each person an independent annual probability p of disclosing a secret. The probability that n people remain silent for t years is (1 − p) raised to n × t.
The controls set the assumptions. The percentage shown is the probability of no disclosure at all. Its complement is the probability of at least one disclosure. This follows from multiplying probabilities for independent events.
Space & Flight: briefings
- Where are the stars?NASA Science
- Flag Day – Flying High: The Stars and Stripes in SpaceNASA Johnson Space Center
- What are the Van Allen Belts and why do they matter?NASA
- Spaceflight Radiation Health ProgramNASA Johnson Space Center
Sky & Sea: briefings
- Go Fast: Case Resolution and MethodologyAll-domain Anomaly Resolution Office
- Case Resolution of Southeast Asia TrianglesAll-domain Anomaly Resolution Office
- What is the Bermuda Triangle?NOAA National Ocean Service
Secret Power: briefings
- Embracing the Unbelievable: Denver International Airport Addresses Conspiracy Theories by Celebrating Them in OctoberDenver International Airport
- Architectural Design Standards Manual, Q4 2024Denver International Airport
- Exciting Things to Do at Denver International AirportDenver International Airport
- FAQs: Significance of the Great Seal on paper currencyBureau of Engraving and Printing
- Is the eye in the pyramid a Masonic symbol?Scottish Rite of Freemasonry, Southern Jurisdiction
- The Visual Mandela Effect as Evidence for Shared and Specific False Memories Across PeopleDeepasri Prasad and Wilma A. Bainbridge, Psychological Science
- New Research Shows Consistency in What We MisrememberUniversity of Chicago Division of the Social Sciences
Ancient World: briefings
- Fieldwork: Great Pyramid and its TempleAncient Egypt Research Associates
- Lines and Geoglyphs of Nasca and PalpaUNESCO World Heritage Centre
- From restoration to conservationEnglish Heritage
- Restoring Stonehenge 1881–1939Historic England
Deep Time: briefings
- Which Dinosaur Bones Are Real?Field Museum
- Street Grades, RaisingChicago History Museum / Encyclopedia of Chicago
- Street Raising on Lake Street between Clark and LaSalle Streets, 1850sChicago History Museum / Encyclopedia of Chicago
- Iron Preserves, Hides Ancient Tissues in Fossilized RemainsNorth Carolina State University
Verified: briefings
- Piltdown Man hoax findings: Charles Dawson the likely fraudsterNatural History Museum
- New genetic and morphological evidence suggests a single hoaxer created Piltdown manDe Groote and colleagues, Royal Society Open Science
- Explore: The Cardiff GiantFenimore Farm and Country Village
- Feejee Mermaid is unattractive attractionHarvard Gazette / Peabody Museum
Flat Earth: briefings
- What is the geoid?NOAA National Ocean Service
- Rise, Set, and Twilight DefinitionsU.S. Naval Observatory
- How are different map projections used?U.S. Geological Survey
- Map Projections: A Working Manual, plate 1U.S. Geological Survey
- Visual Appearance of Lunar EclipsesNASA Goddard Space Flight Center
Antarctica: briefings
- Glossary of Glacier Terminology: HornU.S. Geological Survey
- Diabase Sheets of the Taylor Glacier Region, Victoria Land, AntarcticaWarren Hamilton and colleagues, U.S. Geological Survey Professional Paper 456-B, 1965
- Southern Antarctic PeninsulaNASA Earth Observatory
- Floating fortressesAustralian Antarctic Division
- Getz Ice Shelf melt enhanced by freshwater discharge from beneath the West Antarctic Ice SheetWei Wei and colleagues, The Cryosphere, 2020
- Antarctica’s hidden lakesBritish Antarctic Survey
- International Antarctic Weather Forecasting Handbook: Vostok StationBritish Antarctic Survey
- Revised Release on the Pressure along the Melting and Sublimation Curves of Ordinary Water SubstanceInternational Association for the Properties of Water and Steam, 2011
Denver Airport: briefings
- Architectural Design Standards Manual, Q4 2024Denver International Airport
- New Train Cars at DEN Begin Carrying Passengers to the ConcoursesDenver International Airport
- Colorado AIP: Denver International, runway physical characteristicsFederal Aviation Administration
- AC 150/5300-13B Airport Design, Change 1 with errataFederal Aviation Administration
- Noise and Airspace FAQs: How is runway use determined at DEN?Denver International Airport
- New Denver Airport: Impact of the Delayed Baggage System, GAO/RCED-95-35BRU.S. Government Accountability Office; National Transportation Library archive
- Denver International Airport Announces Plans for Pedestrian Walkways Connecting ConcoursesDenver International Airport
Apollo black sky
Relative exposure from shutter time and aperture area.
- Apollo nominal shutter time
- 0.004 s
- Apollo down-Sun f-number
- 11 f/
- Where are the stars?NASA Science
- Apollo 11 Mission ReportNASA Manned Spacecraft Center
- Nikon School: Working NotesNikon
Moon radio delay
Signal path divided by the speed of light.
- Mean lunar distance
- 384,400 km
- Speed of light in vacuum
- 299,792.458 km/s
- Astrodynamic ParametersNASA Jet Propulsion Laboratory, Solar System Dynamics
- Glossary: LD (Lunar Distance)NASA Jet Propulsion Laboratory, Center for Near Earth Object Studies
- Space Communications: 7 Things You Need to KnowNASA
- Read You Loud and Clear! The Story of NASA’s Spaceflight Tracking and Data NetworkNASA History Division
Gravity at ISS altitude
Inverse-square gravity for a spherical Earth.
- Earth mean radius
- 6,371.0084 km
- Earth gravitational parameter
- 398,600.435507 km³/s²
- Planetary Physical ParametersNASA Jet Propulsion Laboratory, Solar System Dynamics
- Astrodynamic ParametersNASA Jet Propulsion Laboratory, Solar System Dynamics
- What is Microgravity?NASA Glenn Research Center
- What is gravity?NASA Goddard Space Flight Center, StarChild
Horizon distance
Tangent geometry on a sphere, without atmospheric refraction.
- Earth mean radius
- 6,371,008.4 m
- What is the geoid?NOAA National Ocean Service
- Rise, Set, and Twilight DefinitionsU.S. Naval Observatory
- Planetary Physical ParametersNASA Jet Propulsion Laboratory, Solar System Dynamics
Flat Earth map distortion
Parallel-arc length compared with polar projection radius.
- Earth mean radius
- 6,371.0084 km
- π
- 3.14159265
- How are different map projections used?U.S. Geological Survey
- Planetary Physical ParametersNASA Jet Propulsion Laboratory, Solar System Dynamics
- Azimuthal equidistantEsri, ArcGIS cartographic documentation
- DLMF §4.14: Definitions and PeriodicityNational Institute of Standards and Technology
Flat disk eclipse shadow
Orthographic projection of an ideal circular disk.
- π
- 3.14159265
- Visual Appearance of Lunar EclipsesNASA Goddard Space Flight Center
- Eclipses and the MoonNASA Science
- Aristotle and the round EarthNASA Goddard Space Flight Center
- DLMF §4.14: Definitions and PeriodicityNational Institute of Standards and Technology
Great Pyramid build rate
Blocks divided by working hours and independent placement teams.
- Estimated total blocks
- 2,300,000 blocks
- Fieldwork: Great Pyramid and its TempleAncient Egypt Research Associates
- The Lost City of the Pyramid BuildersAncient Egypt Research Associates
- Les papyrus de la mer Rouge I: Le journal de MererPierre Tallet / Institut français d’archéologie orientale
- Construction of the Great Pyramid with pulley-like systems using counter-weights on sliding-rampsSimon Andreas Scheuring / npj Heritage Science
Nazca ground survey
Linear scaling of a documented reconstruction target.
- Reported condor reconstruction length
- 440 feet
- Lines and Geoglyphs of Nasca and PalpaUNESCO World Heritage Centre
- The Nazca Drawings Revisited: Creation of a Full-Sized DuplicateJoe Nickell / Skeptical Inquirer, Spring 1983, pp. 36–47
Stonehenge restoration dates
Conventional radiocarbon age from carbon mixing.
- Conventional radiocarbon mean life
- 8,033 radiocarbon years
- UB-3821 central radiocarbon age
- 4,023 BP
- UB-3821 quoted measurement error
- 21 radiocarbon years
- From restoration to conservationEnglish Heritage
- Stonehenge, Amesbury, Wiltshire: Chronological Modelling, Research Report 1/2012T. Darvill, P. Marshall, M. Parker Pearson and G. Wainwright / English Heritage
- Radiocarbon datingOxford Radiocarbon Accelerator Unit
T. rex fossil recovery
Standing population multiplied by generations; sample divided by total.
- Published rounded standing population
- 20,000 postjuvenile individuals
- Published rounded persistence
- 127,000 generations
- Defined curated fossil sample
- 32 postjuvenile individuals
- Which Dinosaur Bones Are Real?Field Museum
- Absolute abundance and preservation rate of Tyrannosaurus rexCharles R. Marshall and colleagues / Science 372, 284–287
- Vital statistics, absolute abundance and preservation rate of Tyrannosaurus rexEva M. Griebeler / Palaeontology 66, e12648
Chicago raised streets
Required screw revolutions over the reported lifting interval.
- Reported building rise
- 56 inches
- Reported screw count
- 6,000 screws
- Reported workforce
- 600 operators
- Reported lifting interval
- 5 days
- Street Grades, RaisingChicago History Museum / Encyclopedia of Chicago
- Street Raising on Lake Street between Clark and LaSalle Streets, 1850sChicago History Museum / Encyclopedia of Chicago
- The Great Building Raising, contemporary report reprinted in Our Whole Country, Volume IIChicago Press and Tribune / John Barber and Henry Howe, Library of Congress scan
Dinosaur bone carbon
Two-source carbon mixing and conventional apparent age.
- Measured bone-core organic activity
- 0.0149 fraction modern
- Measured adjacent mudstone activity
- 0.0573 fraction modern
- Conventional radiocarbon mean life
- 8,033 radiocarbon years
- Iron Preserves, Hides Ancient Tissues in Fossilized RemainsNorth Carolina State University
- Radiocarbon datingOxford Radiocarbon Accelerator Unit
- Cretaceous dinosaur bone contains recent organic material and provides an environment conducive to microbial communitiesEvan T. Saitta and colleagues / eLife 8:e46205
GoFast target altitude
Resolve the vertical component of the line of sight.
- Circle constant π
- 3.14159265
- Frame-one aircraft altitude
- 7,620 m
- Frame-one range
- 7,408 m
- Frame-one depression angle
- 29 °
- Go Fast: Case Resolution and MethodologyAll-domain Anomaly Resolution Office
- DLMF §4.14: Definitions and PeriodicityNational Institute of Standards and Technology
- UAP Independent Study Team Final Report: GoFast geometryNASA
Triangular UFO bokeh
Thin-lens geometry for a distant point source.
- Unidentified Aerial Phenomena: hearing transcript, 17 May 2022U.S. House of Representatives
- Bokeh for BeginnersNikon
- University Physics Volume 3: 2.4 Thin LensesOpenStax / Rice University
Bermuda Triangle rates
Compare counts after dividing by traffic exposure.
- What is the Bermuda Triangle?NOAA National Ocean Service
Denver Airport tunnels
Train size × usable load × departure frequency.
- Cars in the documented train configuration
- 4 cars
- Embracing the Unbelievable: Denver International Airport Addresses Conspiracy Theories by Celebrating Them in OctoberDenver International Airport
- Architectural Design Standards Manual, Q4 2024Denver International Airport
- New Train Cars at DEN Begin Carrying Passengers to the ConcoursesDenver International Airport
Dead Internet bot traffic
Divide request totals by requests per client.
- Automated request share in 2024 report data
- 0.51 fraction
- 2025 Bad Bot ReportImperva / Thales
Piltdown Man dating
Difference divided by combined quoted uncertainty.
- Published E590 determination
- 620 radiocarbon years
- Quoted E590 uncertainty
- 100 years
- Published E646 determination
- 970 radiocarbon years
- Quoted E646 uncertainty
- 140 years
- Piltdown Man hoax findings: Charles Dawson the likely fraudsterNatural History Museum
- New genetic and morphological evidence suggests a single hoaxer created Piltdown manDe Groote and colleagues, Royal Society Open Science
Cardiff Giant workshop
Mass balance for a carved block.
- Surviving Cardiff Giant mass
- 2,990 lb
- Starting block size in museum account
- 5 tons, convention unspecified
- Explore: The Cardiff GiantFenimore Farm and Country Village
- The Cardiff Giant, in Five of the Greatest Natural History Hoaxes of All TimeDaniel T. Ksepka, Bruce Museum curator, in Scientific American
Feejee mermaid resolution
Physical feature width divided by millimetres per pixel.
- Longest catalogued dimension
- 378 mm
- Mermaid, object 97-39-70/72853Peabody Museum of Archaeology and Ethnology, Harvard University
- The Merman: natural history specimen or composite cultural artefact?Paolo Viscardi and colleagues, Journal of Museum Ethnography, author manuscript
Antarctic pyramid peaks
Right triangles through a square-based peak.
- Degrees per radian
- 57.29577951 °/rad
- DLMF §4.14: Definitions and PeriodicityNational Institute of Standards and Technology
- Glossary of Glacier Terminology: HornU.S. Geological Survey
- Diabase Sheets of the Taylor Glacier Region, Victoria Land, AntarcticaWarren Hamilton and colleagues, U.S. Geological Survey Professional Paper 456-B, 1965
- Southern Antarctic PeninsulaNASA Earth Observatory
Antarctic ice cliff draft
Hydrostatic balance with an air-content correction.
- Dense glacier-ice density
- 917 kg/m³
- Seawater density
- 1,028 kg/m³
- Floating fortressesAustralian Antarctic Division
- Getz Ice Shelf melt enhanced by freshwater discharge from beneath the West Antarctic Ice SheetWei Wei and colleagues, The Cryosphere, 2020
Lake Vostok liquid water
Overburden pressure and the IAPWS melting curve.
- Dense glacier-ice density
- 917 kg/m³
- Rounded gravitational acceleration
- 9.81 m/s²
- Reference triple-point temperature
- 273.16 K
- Reference triple-point pressure
- 611.657 Pa
- Melting-curve coefficient 1
- 1,195,393.37 dimensionless
- Melting-curve exponent 1
- 3 dimensionless
- Melting-curve coefficient 2
- 80,818.3159 dimensionless
- Melting-curve exponent 2
- 25.75 dimensionless
- Melting-curve coefficient 3
- 3,338.2686 dimensionless
- Melting-curve exponent 3
- 103.75 dimensionless
- Getz Ice Shelf melt enhanced by freshwater discharge from beneath the West Antarctic Ice SheetWei Wei and colleagues, The Cryosphere, 2020
- Antarctica’s hidden lakesBritish Antarctic Survey
- International Antarctic Weather Forecasting Handbook: Vostok StationBritish Antarctic Survey
- Revised Release on the Pressure along the Melting and Sublimation Curves of Ordinary Water SubstanceInternational Association for the Properties of Water and Steam, 2011
- Report of the Third EISMINT Workshop on Model IntercomparisonEuropean Ice Sheet Modelling Initiative; Alfred Wegener Institute repository
Denver runway crosswinds
Wind speed × sine of the angle to each runway.
- Runway 34R published true bearing
- 1 ° true
- Runway 08 published true bearing
- 91 ° true
- Pi
- 3.14159265
- DLMF §4.14: Definitions and PeriodicityNational Institute of Standards and Technology
- Colorado AIP: Denver International, runway physical characteristicsFederal Aviation Administration
- AC 150/5300-13B Airport Design, Change 1 with errataFederal Aviation Administration
- Noise and Airspace FAQs: How is runway use determined at DEN?Denver International Airport
Denver baggage timing
Travel speed × timing error; compare with usable placement space.
- Original baggage-system design maximum
- 24 mph
- Embracing the Unbelievable: Denver International Airport Addresses Conspiracy Theories by Celebrating Them in OctoberDenver International Airport
- New Denver Airport: Impact of the Delayed Baggage System, GAO/RCED-95-35BRU.S. Government Accountability Office; National Transportation Library archive
- Denver International Airport Announces Plans for Pedestrian Walkways Connecting ConcoursesDenver International Airport