Every fact in the three magnetism lessons is listed here with where it comes from. The numbers in [brackets] on the lesson pages link to this list.
How we rate sources
High: space agencies (NASA), peer-reviewed open textbooks (OpenStax, Rice University) and professional scientific societies (American Physical Society).
Medium-high: reputable science news reporting directly on a primary document.
Medium: single-author essays and popular history sites. We only use these for history details, and never on their own: each one is paired with a second source.
Wikipedia was not used as a source. Numbers are rounded (for example 9.8 m/s² for Earth's gravity). The text was drafted with help from AI (Claude) and then checked against these sources. Corrections: hello@echoesof.science.
Simplifications to be aware of: the younger lessons say magnets attract 'iron'; everyday steel objects (paper clips, nails) are attracted because steel is mostly iron, but some stainless steels are hardly magnetic, so test objects first. The speed of the north magnetic pole (about 55 km per year) is from the latest NOAA survey and changes over time.
All sources
[1] College Physics 2e, 22.1 Magnets
OpenStax, Rice University · Reliability: High
Type: Peer-reviewed open textbook
Every magnet has a north and a south pole; like poles repel and unlike poles attract; cutting a magnet gives smaller magnets, each with two poles; Earth acts like a giant bar magnet whose pole near the geographic North Pole is magnetically a south pole.
[2] College Physics 2e, 22.2 Ferromagnets and Electromagnets
OpenStax, Rice University · Reliability: High
Type: Peer-reviewed open textbook
Iron, cobalt, nickel and gadolinium are ferromagnetic; domains act like tiny magnets and line up when magnetised; above the Curie temperature (1043 K for iron) a ferromagnet cannot be magnetised; electric current produces magnetic fields; a current-carrying coil is an electromagnet, much stronger with an iron core.
[3] Earth's Magnetosphere: Protecting Our Planet from Harmful Space Energy
NASA Science · Reliability: High
Type: Space agency
Most of Earth's magnetic field comes from the molten, mostly iron and nickel, outer core (the geodynamo); the magnetosphere shields the atmosphere from erosion by the solar wind; auroras are created by energetic electrons raining down from the magnetosphere.
NOAA National Centers for Environmental Information · Reliability: High
Type: Government science agency
The north magnetic pole moves (latest survey: about 55 km per year, north-northwest); declination is the angle between magnetic north and true north and varies by place; the field last reversed about 750,000–780,000 years ago.