Finish · Sources and licence

Sources, licence and attribution

Reading 10 min

Licence of the course text

The text of this course is licensed under Creative Commons Attribution 4.0 International (CC BY 4.0). You may copy, adapt and share it, for any purpose, if you give credit.

The simulation is a separate package under the MIT licence. It uses an Earth map from Solar System Scope (CC BY 4.0) and Three.js (MIT); its fonts are Inter and Roboto Mono (SIL Open Font License 1.1). The references below belong to their publishers.

How the facts were checked

Every number in the lessons was checked against the NASA, JPL or other reference named below. The orbital elements of the planets in the simulation follow the JPL tables of Standish and Williams. Where a figure in the simulation differs from the reference, the course uses the reference: the full list of checked claims is in the repository, in demo-content/gravity/FACTCHECK.md.

Sources by lesson

Start · Welcome

Approximate Positions of the Planets (Keplerian elements, Table 1, 1800-2050 AD) (NASA JPL Solar System Dynamics), https://ssd.jpl.nasa.gov/planets/approx_pos.html
Planetary Fact Sheet - Metric (comparison table) (NASA GSFC NSSDC), https://nssdc.gsfc.nasa.gov/planetary/factsheet/

4. Cosmic velocities

Kepler's 3rd Law - Lesson Plan #31 (first cosmic velocity) (NASA GSFC Stargazer), https://pwg.gsfc.nasa.gov/stargaze/Lkepl3rd.htm
Earth Fact Sheet (NASA GSFC NSSDC), https://nssdc.gsfc.nasa.gov/planetary/factsheet/earthfact.html
Astrodynamic Parameters (NASA JPL Solar System Dynamics), https://ssd.jpl.nasa.gov/astro_par.html

5. The Earth and the Moon

Moon Fact Sheet (NASA GSFC NSSDC), https://nssdc.gsfc.nasa.gov/planetary/factsheet/moonfact.html
What Causes Tides? (NOAA NESDIS), https://www.nesdis.noaa.gov/about/k-12-education/oceans-coasts/what-causes-tides
Geoid (GOCO06s model visualization) (NASA Scientific Visualization Studio), https://svs.gsfc.nasa.gov/5660/
Astrodynamic Parameters (NASA JPL Solar System Dynamics), https://ssd.jpl.nasa.gov/astro_par.html
First Close-up of the Far Side of Moon (Luna 3) (NASA Science), https://science.nasa.gov/resource/first-close-up-of-the-far-side-of-moon/

6. Orbits in 3D and a moving Sun

Moon Fact Sheet (NASA GSFC NSSDC), https://nssdc.gsfc.nasa.gov/planetary/factsheet/moonfact.html
Earth Fact Sheet (NASA GSFC NSSDC), https://nssdc.gsfc.nasa.gov/planetary/factsheet/earthfact.html
There's More to the North Star Than Meets the Eye (NASA Science (Hubble)), https://science.nasa.gov/missions/hubble/theres-more-to-the-north-star-than-meets-the-eye/
Solar System: Facts (NASA Science), https://science.nasa.gov/solar-system/solar-system-facts/
Approximate Positions of the Planets (Keplerian elements, Table 1, 1800-2050 AD) (NASA JPL Solar System Dynamics), https://ssd.jpl.nasa.gov/planets/approx_pos.html
Jupiter Fact Sheet (NASA GSFC NSSDC), https://nssdc.gsfc.nasa.gov/planetary/factsheet/jupiterfact.html
Venus Fact Sheet (NASA GSFC NSSDC), https://nssdc.gsfc.nasa.gov/planetary/factsheet/venusfact.html
Why is Polaris the North Star? (StarChild) (NASA GSFC), https://starchild.gsfc.nasa.gov/docs/StarChild/questions/question64.html

7. The solar system as a machine

Astrodynamic Parameters (NASA JPL Solar System Dynamics), https://ssd.jpl.nasa.gov/astro_par.html
Ulysses Begins to Explore Sun's Northern Pole (NASA JPL), https://www.jpl.nasa.gov/news/ulysses-begins-to-explore-suns-northern-pole/
Magnetospheres (focus area) (NASA Science), https://science.nasa.gov/heliophysics/focus-areas/magnetosphere-ionosphere/
Webb Orbit (NASA Science), https://science.nasa.gov/mission/webb/orbit/
Euclid fact sheet (ESA), https://sci.esa.int/web/euclid/-/fact-sheet
Europa: Facts (NASA Science), https://science.nasa.gov/jupiter/jupiter-moons/europa/europa-facts/
Sun Fact Sheet (NASA GSFC NSSDC), https://nssdc.gsfc.nasa.gov/planetary/factsheet/sunfact.html
NASA's WISE Finds Earth's First Trojan Asteroid (NASA JPL), https://www.jpl.nasa.gov/news/nasas-wise-finds-earths-first-trojan-asteroid/
Newly discovered asteroid just second of its kind (2020 XL5) (ESA), https://www.esa.int/Space_Safety/Planetary_Defence/Newly_discovered_asteroid_just_second_of_its_kind
Vigil mission overview (ESA), https://www.esa.int/Space_Safety/Vigil/Vigil_mission_overview
WMAP overview (Sun-Earth Lagrange points diagram) (NASA Science), https://science.nasa.gov/mission/wmap/wmap-overview/
Venus Fact Sheet (NASA GSFC NSSDC), https://nssdc.gsfc.nasa.gov/planetary/factsheet/venusfact.html

8. Travelling by gravity, and beyond

Voyager 1 (NASA Science), https://science.nasa.gov/mission/voyager/voyager-1/
Voyager 2 (NASA Science), https://science.nasa.gov/mission/voyager/voyager-2/
Voyager mission overview (NASA Science), https://science.nasa.gov/mission/voyager/
Oort Cloud and Scale of the Solar System (infographic) (NASA Science), https://science.nasa.gov/resource/oort-cloud-and-scale-of-the-solar-system-infographic/
2025 Exoplanet Archive News (NASA Exoplanet Archive), https://exoplanetarchive.ipac.caltech.edu/docs/2025news.html
Solar System: Facts (NASA Science), https://science.nasa.gov/solar-system/solar-system-facts/
Astronomers reveal first image of the black hole at the heart of our galaxy (eso2208) (ESO), https://www.eso.org/public/news/eso2208/
Detection of the gravitational redshift in the orbit of the star S2 near the Galactic centre massive black hole (abstract) (GRAVITY Collaboration / arXiv), https://arxiv.org/abs/1807.09409
Planck 2018 results. VI. Cosmological parameters (abstract) (Planck Collaboration / arXiv), https://arxiv.org/abs/1807.06209
The Grand Tour (NASA Science), https://science.nasa.gov/image-detail/grand-tour/
What Is a Barycenter? (NASA Space Place), https://spaceplace.nasa.gov/barycenter/en/
Galaxies and the Expanding Universe (ESA), https://sci.esa.int/web/education/-/36827-galaxies-and-the-expanding-universe?fbodylongid=1732
Planck 2018 results. I. Overview (dipole, ar5iv HTML) (Planck Collaboration / ar5iv), https://ar5iv.labs.arxiv.org/html/1807.06205
Dark Matter (NASA Science), https://science.nasa.gov/dark-matter/

9. Einstein's gravity

Perihelion Precessions of Inner Planets in Einstein's Theory and Predicted Values for the Cosmological Constant (PubMed Central (peer-reviewed article)), https://pmc.ncbi.nlm.nih.gov/articles/PMC9635960/
Sun's Gravity Bends Starlight (Cosmic Times, 1919) (NASA Goddard Imagine the Universe), https://imagine.gsfc.nasa.gov/educators/programs/cosmictimes/educators/guide/1919/starlight.html
100 Years of General Relativity (Blueshift) (NASA Goddard), https://asd.gsfc.nasa.gov/blueshift/index.php/2015/11/25/100-years-of-general-relativity/
GW150914 (LIGO Scientific Collaboration), https://www.ligo.org/detections/gw150914/
Astronomers reveal first image of the black hole at the heart of our galaxy (eso2208) (ESO), https://www.eso.org/public/news/eso2208/
Gravitational-wave science (LIGO Scientific Collaboration), http://www.ligo.org/gravitational-wave-science/

Found a mistake?

Please tell us: open an issue at https://github.com/ulams-dev/ulams/issues with the lesson and the number.