About

Cold Dark Matter is a collection of interactive astronomy: simulations you can turn and speed up, and games set in real places, from Tycho crater on the Moon to Jupiter’s moon Io. Each one is meant to be enjoyable, informative and scientifically accurate, and each has a page that tells you what is real in it and where its data comes from.

How accurate is this?

Everything stated as fact is true; anything stylised is labelled.

Every experience carries one of four tags, so you can tell at a glance how far to trust what you see:

REAL DATA: Built from actual mission measurements, such as a spacecraft's elevation data.
ACCURATE: Real physics and real figures, modelled. Any change of scale is stated and applied evenly.
STYLISED: Every fact is true, but some things are not to scale or not in real time, and the note says which.
ARCADE: A game first, with cartoon physics. The facts it teaches are true.

Sources & credits

DISCOVERY ONE

The Blue Danube (Johann Strauss II), excerpt · United States Marine Band, conducted by Albert F. Schoepper (recorded about 1972) · Public domain (the performance is a work of the US federal government; the composition is Strauss’s, who died in 1899) · The first 140 seconds, faded in and out and loudness-normalised
Also sprach Zarathustra (Richard Strauss) · Conducted by Philip Milman, www.classicals.de · CC BY 4.0
Engine rumble, thruster hiss and console tones · Generated with SoX by the site’s build scripts (tools/discovery-one, tools/tycho-audio) · The site author’s own work
Discovery One (3D model) · A fan model of the ship from 2001: A Space Odyssey (1968), built by the site’s author · The site author’s own work
Planet and Moon maps · Solar System Scope · CC BY 4.0
Jupiter colour map · Planet Pixel Emporium (James Hastings-Trew) · Copyright James Hastings-Trew. Free to use in renderings and real-time software; the maps may not be redistributed as is (Planet Pixel Emporium terms)
Saturn ring map · Solar System Scope · CC BY 4.0 · Reprojected from the 8K strip into a top-down picture with the rings at NASA’s radii, and brightened (tools/textures/ring_from_strip.py)
Approximate Positions of the Planets (orbital elements) · E. M. Standish, NASA/JPL Solar System Dynamics · Public domain (NASA/JPL)
Astronomical Algorithms, 2nd ed. (1998), ch. 47: lunar position, truncated series · J. Meeus · Cited (book)
Draco 3D compression decoder · The Draco Authors (Google) · Apache License 2.0 (notice in /draco/LICENSE)
Planetary satellite mean elements · NASA/JPL Solar System Dynamics · Public domain (NASA/JPL)
Planetary Fact Sheets · D. R. Williams, NASA Goddard Space Flight Center (NSSDCA) · Public domain (NASA)
Planet and moon pages (briefing facts) · NASA Science · Public domain (NASA)

TYCHO

LOLA gridded elevation, LDEM_128 (the regional heights) · NASA/GSFC, PDS Geosciences Node; downloaded from MIT’s imbrium archive · Public domain (NASA) · Cropped to 700 × 700 km and resampled to about 340 m per pixel
SLDEM2015, LOLA and SELENE Terrain Camera merged elevation (Barker et al. 2016), Tycho and Clavius · NASA/GSFC and JAXA, PDS Geosciences Node; downloaded from MIT’s imbrium archive · Public domain (NASA) · Cropped to 120 km round Tycho and 60 km round Clavius, at about 59 m per pixel
LROC WAC global mosaic · NASA/GSFC/Arizona State University, served by USGS Astrogeology · Public domain (NASA) · Cropped and resampled
CGI Moon Kit colour map (distant globe) · NASA Scientific Visualization Studio · Public domain (NASA)
Earth day map (Earth in the sky) · Solar System Scope · CC BY 4.0
Also sprach Zarathustra (Richard Strauss) · Conducted by Philip Milman, www.classicals.de · CC BY 4.0
In-flight music · Adobe Stock · Licensed (Adobe Stock)
Radio voices · Spoken by the eSpeak NG speech synthesiser · Generated with GPL-3.0 software
Sound effects · Generated with SoX · Generated with GPL-2.0 software
Moonbus (3D model) · A model of the Moonbus from 2001: A Space Odyssey (1968), built by the site’s author · The site author’s own work
TMA-1 camp and dig (3D model) · After the set of 2001: A Space Odyssey (1968), built by the site’s author · The site author’s own work
Clavius Base (3D model) · After the set of 2001: A Space Odyssey (1968), built by the site’s author · The site author’s own work

GALE CRATER

MSL Gale merged DEM and orthophoto mosaics (detail terrain and imagery) · Calef III, F. J., & Parker, T. (2016). MSL Gale Merged DEM and Orthophoto Mosaics. PDS Annex, U.S. Geological Survey. (NASA/JPL-Caltech, USGS Astrogeology Science Center.) · Public domain (USGS); the detail shade and colour, made with HRSC data, are CC BY-SA 3.0 IGO · Reprojected around Gale, resampled to about 4.9 m, heights relative to the crater floor, shadows baked; imagery toned to match the HRSC brightness
HRSC digital terrain model (regional terrain) · ESA/DLR/FU Berlin, CC BY-SA 3.0 IGO (HRSC DTM; Gwinner et al. 2009, 2010) · CC BY-SA 3.0 IGO · Reprojected to an orthographic plane, resampled to about 98 m, heights relative to the crater floor, 16-bit encoded, shadows baked; the derived height, shade and colour files carry the same licence
HRSC nadir images (regional brightness) · ESA/DLR/FU Berlin, CC BY-SA 3.0 IGO (HRSC nadir images, orbits 1916, 1927, 1938); colour from the Viking MDIM 2.1 colourised mosaic, NASA Ames / USGS · CC BY-SA 3.0 IGO (images); public domain (Viking MDIM 2.1) · Three strips mosaicked with their brightness matched, coloured from MDIM 2.1, resampled
Curiosity’s position and route waypoints · NASA/JPL-Caltech · Public domain (NASA) · Curiosity as of sol 5021 (21 September 2026); converted to metres around Gale
Place names · IAU / USGS Gazetteer of Planetary Nomenclature · Public domain (USGS)
Peace Vallis fan position · Palucis, M. C., et al. (2014). The origin and evolution of the Peace Vallis fan system that drains to the Curiosity landing area, Gale Crater, Mars. JGR Planets 119. · Cited (journal article); the position is our estimate from it
Mars colour map (distant globe) · Solar System Scope · CC BY 4.0
Radio voices · Spoken by the eSpeak speech synthesiser · Generated with GPL-3.0 software
Sound effects (all but the engine and the explosion) · Generated with SoX · Generated with GPL-2.0 software
Engine and explosion sounds · Reused from Dino Dodge on this site (source not recorded) · Not recorded

DODGER ON IO

Jupiter colour map (Cassini composite, retouched) · Planet Pixel Emporium (James Hastings-Trew) · Copyright James Hastings-Trew. Free to use in renderings and real-time software; the maps may not be redistributed as is (Planet Pixel Emporium terms)

SOLAR SYSTEM

Planet, Moon and Saturn maps · Solar System Scope · CC BY 4.0
Saturn ring map · Solar System Scope · CC BY 4.0 · Reprojected from the 8K strip into a top-down picture with the rings at NASA’s radii, and brightened (tools/textures/ring_from_strip.py)
Earth bump and specular maps, Jupiter colour map · Planet Pixel Emporium (James Hastings-Trew) · Copyright James Hastings-Trew. Free to use in renderings and real-time software; the maps may not be redistributed as is (Planet Pixel Emporium terms)
8 Low Poly Asteroids · Everios96 (Sketchfab) · CC BY 4.0

GALAXY BUILDER

ApJ 543, 704 · Debattista, V. P. & Sellwood, J. A. 2000 · Cited (paper)
ApJ 586, 143 · Kranz, T., Slyz, A. & Rix, H.-W. 2003 · Cited (paper)
A&A 537, A146, Tables 2 and 3 · Ekström, S. et al. 2012 · Cited (paper)
A&A 436, 1049, Table 1 · Martins, F., Schaerer, D. & Hillier, D. J. 2005 · Cited (paper)
MNRAS 498, 235 · Haydon, D. T. et al. 2020 · Cited (paper)
JRASC 95, 32, "The Real Starry Sky", Table 2 · LeDrew, G. 2001 · Cited (paper)
"What color are the stars?" · Charity, M. 2001 (updated 2016) · Cited (web page)
ESO Picture of the Week potw2003a, "Caught 'Pink-Handed'", 20 January 2020 · ESO · Cited (web page)
"The Color of Nebulae and Interstellar Dust in the Night Sky" (updated 2025) · Clark, R. N. 2015 · Cited (web page)
A&A 641, A6, Table 2 · Planck Collaboration 2020 · Cited (paper)
ApJ 140, 646, "On the Spiral Structure of Disk Galaxies" · Lin, C. C. & Shu, F. H. 1964 · Cited (paper)
ApJ 238, 471, "Rotational properties of 21 Sc galaxies with a large range of luminosities and radii, from NGC 4605 (R = 4 kpc) to UGC 2885 (R = 122 kpc)" · Rubin, V. C., Ford, W. K. Jr. & Thonnard, N. 1980 · Cited (paper)
ApJ 356, 359, "An analytical model for spherical galaxies and bulges" · Hernquist, L. 1990 · Cited (paper)
ApJ 160, 811, "On the Disks of Spiral and S0 Galaxies" · Freeman, K. C. 1970 · Cited (paper)
A&A 625, L10 · GRAVITY Collaboration (Abuter, R. et al.) 2019 · Cited (paper)
ARA&A 54, 529 · Bland-Hawthorn, J. & Gerhard, O. 2016 · Cited (paper)
ApJ 871, 120, Table 1 · Eilers, A.-C., Hogg, D. W., Rix, H.-W. & Ness, M. K. 2019 · Cited (paper)
PASP 121, 213, "The Spitzer/GLIMPSE Surveys: A New View of the Milky Way" · Churchwell, E. et al. 2009 · Cited (paper)
MNRAS 450, 4277 · Vallée, J. P. 2015 · Cited (paper)
ApJ 574, 740, Appendix A · Tremaine, S. et al. 2002 · Cited (paper)
ApJ 806, 96 · Licquia, T. C. & Newman, J. A. 2015 · Cited (paper)
MNRAS 465, 1621 · Portail, M., Gerhard, O., Wegg, C. & Ness, M. 2017 · Cited (paper)
RC3, VizieR VII/155 · de Vaucouleurs et al. 1991 · Cited (catalogue)
MNRAS 501, 3621 · Anand, G. S. et al. 2021 · Cited (paper)
ApJ 897, 122, Table D1 · Lang, P. et al. 2020 · Cited (paper)
MNRAS 403, 83 · Kalapotharakos, C., Patsis, P. A. & Grosbøl, P. 2010 · Cited (paper)
A&A 631, A94 · Díaz-García, S. et al. 2019 · Cited (paper)
A&A 582, A86 · Herrera-Endoqui, M. et al. 2015 · Cited (paper)
ApJS 219, 4 (S⁴G P4) · Salo, H. et al. 2015 · Cited (paper)
ApJS 244, 24 (z0MGS) · Leroy, A. K. et al. 2019 · Cited (paper)
AJ 152, 144, "The Distance to M104" · McQuinn, K. B. W. et al. 2016 · Cited (paper)
ApJ 220, 98 · Schweizer, F. 1978 · Cited (paper)
ApJ 739, 21 · Jardel, J. R. et al. 2011 · Cited (paper)
ApJ 289, 81, Table 4 · Rubin, V. C. et al. 1985 · Cited (paper)
ApJ 338, 752 · Kormendy, J. & Westpfahl, D. J. 1989 · Cited (paper)
ApJ 773, 69 · Gieren, W. et al. 2013 · Cited (paper)
AJ 154, 41, Table 1 · Kam, S. Z. et al. 2017 · Cited (paper)
MNRAS 464, 2103 · Javadi, A. et al. 2017 · Cited (paper)
A&A 572, A23, Table 1 · Corbelli, E., Thilker, D., Zibetti, S., Giovanardi, C. & Salucci, P. 2014 · Cited (paper)
A&A 493, 453 · Verley, S., Corbelli, E., Giovanardi, C. & Hunt, L. K. 2009 · Cited (paper)
MNRAS 450, 4050, "The structure of the Milky Way's bar outside the bulge", Table 1 · Wegg, C., Gerhard, O. & Portail, M. 2015 · Cited (paper)
ApJ 645, 134, "Spitzer and JCMT Observations of the Active Galactic Nucleus in the Sombrero Galaxy (NGC 4594)", Table 3 · Bendo, G. J. et al. 2006 · Cited (paper)
New Astronomy 83, 101498, abstract and §4 · Rozwadowska, K., Vissani, F. & Cappellaro, E. 2021 · Cited (paper)
MNRAS, "Supernovae and their host galaxies - IV. The distribution of supernovae relative to spiral arms", abstract and §5 · Aramyan, L. S. et al. 2016 · Cited (paper)
MNRAS 412, 1473, "Nearby supernova rates from the Lick Observatory Supernova Search III", Table 11 · Li, W. et al. 2011 · Cited (paper)
ESA/Hubble opo0501a, "A poster-size image of the beautiful barred spiral galaxy NGC 1300" · NASA, ESA, and The Hubble Heritage Team (STScI/AURA) · CC BY 4.0 (ESA/Hubble) · Resized from 6637 × 3787 px (the Large JPEG) to 2400 px wide and converted to WebP.
ESA/Hubble opo0328a, "Hubble mosaic of the majestic Sombrero Galaxy" · NASA/ESA and The Hubble Heritage Team (STScI/AURA) · CC BY 4.0 (ESA/Hubble) · Resized from 11472 × 6429 px (the Large JPEG) to 2400 px wide and converted to WebP.
ESA/Hubble heic1901a, "The sharpest view ever of the Triangulum Galaxy" · NASA, ESA, and M. Durbin, J. Dalcanton, and B. F. Williams (University of Washington) · CC BY 4.0 (ESA/Hubble) · Resized from 4000 × 2251 px (the Publication JPEG, the full 34372 × 19345 px frame scaled down) to 2400 px wide and converted to WebP.

EARTH

Earth day, night and cloud maps · Solar System Scope · CC BY 4.0
Earth bump and specular maps · Planet Pixel Emporium (James Hastings-Trew) · Copyright James Hastings-Trew. Free to use in renderings and real-time software; the maps may not be redistributed as is (Planet Pixel Emporium terms)
CGI Moon Kit (colour and elevation maps) · NASA Scientific Visualization Studio · Public domain (NASA)

MOON

CGI Moon Kit (colour and elevation maps) · NASA Scientific Visualization Studio · Public domain (NASA)
Also sprach Zarathustra (Richard Strauss) · Conducted by Philip Milman, www.classicals.de · CC BY 4.0

MARS

Mars colour map · Solar System Scope · CC BY 4.0
Mars bump and normal maps · Planet Pixel Emporium (James Hastings-Trew) · Copyright James Hastings-Trew. Free to use in renderings and real-time software; the maps may not be redistributed as is (Planet Pixel Emporium terms)

JUPITER

Jupiter colour map (Cassini composite, retouched) · Planet Pixel Emporium (James Hastings-Trew) · Copyright James Hastings-Trew. Free to use in renderings and real-time software; the maps may not be redistributed as is (Planet Pixel Emporium terms)
Astronomical Algorithms, 2nd ed. (1998): ch. 44, the Galilean satellites (Lieske’s theory E5), and the sidereal time, precession and rise and set methods · J. Meeus · Cited (book)
astronomia (jupitermoons.js): the E5 terms, transcribed · Sonia Keys and commenthol · MIT (notice in src/experiences/jupiter/engine/galilean.ts)
VSOP87B planetary theory (Earth and Jupiter, truncated) · P. Bretagnon and G. Francou (1988), Astron. Astrophys. 202, 309; CDS catalogue VI/81 · Cited (published theory)
Horizons ephemeris system: the positions and events the tests check against · NASA/JPL Solar System Dynamics · Public domain (NASA/JPL)
Polynomial expressions for ΔT · F. Espenak and J. Meeus (NASA) · Public domain (NASA)
Jupiter’s pole and rotation (IAU WGCCRE 2015 report) · B. A. Archinal et al. (2018), Celest. Mech. Dyn. Astron. 130, 22 · Cited (published report)

SATURN

Saturn colour map · Solar System Scope · CC BY 4.0
Saturn ring map · Solar System Scope · CC BY 4.0 · Reprojected from the 8K strip into a top-down picture with the rings at NASA’s radii, and brightened (tools/textures/ring_from_strip.py)
Astronomical Algorithms, 2nd ed. (1998): ch. 46, the satellites of Saturn (Harper and Taylor’s and Taylor’s theories), and the precession, sidereal time and rise and set methods · J. Meeus · Cited (book)
astronomia (saturnmoons.js): the chapter 46 terms, transcribed · Sonia Keys and commenthol · MIT (notice in src/experiences/saturn/engine/saturnian.ts)
VSOP87B planetary theory (Earth and Saturn, truncated) · P. Bretagnon and G. Francou (1988), Astron. Astrophys. 202, 309; CDS catalogue VI/81 · Cited (published theory)
Horizons ephemeris system: the positions and events the tests check against · NASA/JPL Solar System Dynamics · Public domain (NASA/JPL)
Polynomial expressions for ΔT · F. Espenak and J. Meeus (NASA) · Public domain (NASA)
Saturn’s pole (IAU WGCCRE 2015 report) · B. A. Archinal et al. (2018), Celest. Mech. Dyn. Astron. 130, 22 · Cited (published report)
Saturn’s rotation period from ring seismology · C. Mankovich et al. (2019), ApJ 871, 1 · Cited (published paper)
Saturn Fact Sheet, Saturnian Rings Fact Sheet and Saturnian Satellite Fact Sheet: the radii and the rings · NASA Goddard Space Flight Center (NSSDCA) · Public domain (NASA)

ASTEROID BELT

Asteroid 1a Game Model · Mykhailo Ohorodnichuk (Sketchfab) · CC BY 4.0

THE WHOLE SITE

Jost · Owen Earl (indestructible type*) · SIL Open Font License 1.1
IBM Plex Mono · IBM · SIL Open Font License 1.1

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Contact

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