Credits and sources

Data

• Planet and Moon figures: NASA NSSDCA planetary fact sheets.
• Physical constants: CODATA 2022, via NIST.
• Planet and Moon positions: astronomy-engine by Don Cross (MIT licence).
• Voyager positions: NASA JPL Horizons, geometric heliocentric vectors for 5 October 2026, extended forward at the probes' steady speeds.

1 · Falling

• Surface gravity, radius and GM for each world, and the Moon's orbit: NASA NSSDCA planetary fact sheets.
• Constants G, standard gravity and the speed of light: CODATA 2022 via NIST.
• Apollo 15 hammer and feather drop: NASA NSSDCA, "The Apollo 15 Hammer-Feather Drop", and the Apollo Lunar Surface Journal (eds. E. M. Jones and K. Glover), "EVA-3 Closeout". The Earth half of the display is a simulation.
• Newton's cannon: after Isaac Newton, De mundi systemate (1728). Our own drawing.
• International Space Station speed and orbit time: NASA, "Space Station Facts and Figures".
• Escape speed: HyperPhysics, Georgia State University.
• The rubber-sheet analogy and its limits: M. Kersting and R. Steier (2018); M. Kersting, Physics Education 54 (2019), CC BY 3.0; C. A. Middleton and M. Langston, Am. J. Phys.
• Light bending at the Sun and the 1919 eclipse: "Tests of general relativity", Wikipedia.
• Black holes, what forms them, and why they don't pull harder from far away: NASA Science, "Black Holes", "Black Hole Types" and "Black Hole Anatomy".
• John Michell's dark stars: APS News, "This Month in Physics History", January 2021.

2 · The Neighbourhood

• Planet sizes, distances and periods: NASA NSSDCA planetary, Sun, Moon, Earth and Jupiter fact sheets.
• Average planet distances: E. M. Standish and J. G. Williams, JPL Solar System Dynamics, "Approximate Positions of the Planets".
• Planet, Sun and Moon positions, new moons and eclipses: the astronomy-engine library (MIT licence), by Don Cross.
• Eclipse seasons, limits and the Moon’s orbit: NASA Eclipse Web Site (F. Espenak).
• Seasons dates: US Naval Observatory. Sunlight formulas: NOAA Global Monitoring Laboratory.
• Sphere packing: densest and random-pour packing fractions. Totality at one place about every 375 years: J. Meeus via NBC News.
• Browser height limits: Eric Meyer, "Infinite Pixels", and Mozilla Bugzilla bug 1205604.

3 · Light and Time

• Today's distances to the Moon, Sun and Mars: computed with astronomy-engine (Don Cross, MIT licence).
• Voyager 1 distance: JPL Horizons vectors, extrapolated; one light-day date from NASA Science, "Where are Voyager 1 and Voyager 2 now?".
• Moon, Earth and Mars distances: NASA NSSDCA fact sheets.
• Star distances: SIMBAD, CDS, Strasbourg (Hipparcos 2007 and Gaia parallaxes); Polaris (Evans et al. 2018), Betelgeuse (Joyce et al. 2020), Deneb (EarthSky).
• Muon lifetime: Particle Data Group. CERN muon storage ring: Bailey et al. 1977.
• GPS clock figures: R. Pogge (Ohio State University) and N. Ashby, Living Reviews in Relativity (2003).
• Sagittarius A* mass: ESO / EHT Collaboration (eso2208).
• Age of the universe: Planck Collaboration 2018. Event ages: International Commission on Stratigraphy chart v2024/12, Connelly et al. 2012, NASA, ESA Gaia, Max Planck Institute for Evolutionary Anthropology.
• The cosmic calendar idea: Carl Sagan, The Dragons of Eden (1977), which used 15 billion years.
• Teaching notes on time dilation: Alstein, Krijtenburg-Lewerissa and van Joolingen (2021); Scherr, Shaffer and Vokos (2001); Kersting et al. (2018).

4 · Leaving the Ground

• Rocket equation, specific impulse and thrust: NASA Glenn Research Center, Beginner’s Guide to Rockets.
• Saturn V stage masses and payloads: Wikipedia, “Saturn V”. J-2 performance: T. Byrd, NASA Marshall Space Flight Center (NTRS 20090009149). F-1 figures: NASA Saturn V News Reference via Wikipedia.
• Merlin engines and Falcon 9 data: SpaceX Falcon User’s Guide (2025) and Wikipedia, “SpaceX Merlin”. The Falcon 9-like stage masses are rounded and not yet checked against the guide.
• Speed budget to orbit and the Moon: Wikipedia, “Delta-v budget” (citing Farquhar 1972) and “Gravity drag” (citing Turner 2004).
• Apollo 11 ascent, burn and entry figures: Apollo Flight Journal (Woods, MacTaggart, O’Brien), used as a source only; no journal text or media is reproduced.
• Re-entry corridor: Foggatt and Carlisle, MSC Internal Note 68-FM-288 (NASA, 1968). Orion entry: NASA.
• Docking limits: International Docking System Standard, Revision E (2016). Crew Dragon Demo-1 approach: The Planetary Society.
• Edge of space: J. C. McDowell, “The edge of space: Revisiting the Karman Line”, Acta Astronautica 151 (2018). Layers of the atmosphere: NOAA JetStream.
• Earth’s mass, radius and air: NASA NSSDCA Earth Fact Sheet. Gravity at ISS height: NASA, “What Is Microgravity?”.

5 · To the Moon

• Apollo 11 timeline, Saturn V masses and burn times: R. W. Orloff, Apollo by the Numbers (NASA SP-2000-4029).
• Lunar module masses, fuel, touchdown speeds and the ascent: Apollo 11 Mission Report (NASA MSC-00171).
• Engine figures, the suit and the experiments package: Apollo 11 Press Kit (NASA, July 1969).
• Saturn V dimensions and engines: Saturn V Flight Manual SA-504 (NASA MSFC).
• The landing and the program alarms: Apollo Lunar Surface Journal, ed. E. M. Jones; P. Adler, "Apollo 11 Program Alarms"; D. Eyles, "Tales from the Lunar Module Guidance Computer". Figures only; no journal text is reproduced.
• The race: NASA mission pages and the NSSDCA Master Catalog and lunar chronology; Wikipedia summaries for Soviet missions.
• The Moon’s mass, distance and orbit: NASA NSSDCA Moon fact sheet.

6 · Robots on Mars

• Mars and Earth figures (sol, gravity, air density and pressure, distances, orbits): NASA NSSDCA Mars and Earth fact sheets.
• Entry, descent and landing figures: NASA/JPL Mars 2020 Perseverance landing press kit, and PIA13282 "Final Minutes of Curiosity’s Arrival at Mars" (NASA/JPL-Caltech).
• Rover operations: Gaines et al., "A Case Study of Productivity Challenges in Mars Science Laboratory Operations" (JPL, 2017); NASA Perseverance blog "A Day in the Life of a T-DOC"; NASA/JPL on AutoNav and the June 2025 driving record (PIA26645).
• Rover sizes, masses and status: NASA Science mission pages for Mars Pathfinder, Spirit, Opportunity, Curiosity and Perseverance; NASA NSSDCA; MER launch press kit (NASA/JPL, 2003). Zhurong and latest odometry: Wikipedia (secondary).
• Laser spectroscopy: Maurice et al. (2012) and Wiens et al. (2011) on ChemCam; Nachon et al. (2014), "Calcium sulfate veins characterized by ChemCam/Curiosity at Gale crater, Mars".
• Ingenuity: NASA/JPL Ingenuity landing press kit; NASA Science Ingenuity mission page; Dull et al., "Hover and Forward Flight Performance Modeling of the Ingenuity Mars Helicopter" (NASA Ames).
• Today’s Earth–Mars distance and positions: astronomy-engine (MIT licence).

7 · The Voyagers

• "Pale Blue Dot Revisited" (PIA23645), Voyager 1, 14 February 1990, reprocessed 2020 by Kevin M. Gill with Candy Hansen and William Kosmann. Courtesy NASA/JPL-Caltech. https://science.nasa.gov/photojournal/pale-blue-dot-revisited
• Voyager positions and speeds: JPL Horizons (Voyager_1_ST+refit2022_m), fetched at build time and extended at constant speed.
• Flyby dates and distances: NASA Voyager fact sheet and mission pages; John Uri, "Voyager's Grand Tour", NASA JSC History Office.
• Golden record greetings and music list: NASA Science, "Golden Record Contents". Sounds of Earth grouping: Wikipedia, "Contents of the Voyager Golden Record". Shown as text only; no recordings are played.
• Giant planet positions for the alignment: JPL "Approximate Positions of the Planets" mean elements.
• Mission status 2023–2026: NASA Science Voyager blog.

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