The guide library
Pick a question.
We'll take it from there.
Every guide is sorted by scale — from Earth out to the whole universe — and by level, so you can start exactly where you are.
What is a black hole?
How they form, what the event horizon really is, and how we can see something that gives off no light.
Read the guide →Scale 01 · Earth
Why the Moon has phases
What changes each night, and why it is not Earth's shadow.
Scale 01 · Earth
How the seasons work
Tilt, not distance: the real reason summer is warm.
Scale 01 · Earth
Tides explained
How the Moon and Sun pull the oceans, with worked examples.
Scale 02 · Solar System
The eight planets at a glance
Size, distance and what makes each world different.
Scale 02 · Solar System
Asteroids, comets and meteors
Three words people mix up, sorted out for good.
Scale 02 · Solar System
How orbits work
Gravity, speed and Kepler's laws in plain steps.
Scale 03 · Milky Way
What is a black hole?
Event horizons, and how we see what gives off no light.
Scale 03 · Milky Way
The life cycle of a star
From gas cloud to white dwarf, neutron star or black hole.
Scale 03 · Milky Way
How we find exoplanets
Transits, wobbles and direct images of other worlds.
Scale 04 · Universe
The Big Bang in plain words
What it was, what it was not, and how we know.
Scale 04 · Universe
Dark matter and dark energy
The evidence for the parts of the universe we cannot see.
Scale 04 · Universe
Measuring cosmic distances
Parallax, standard candles and redshift, step by step.
Frequently asked questions
- Start at Beginner if you are new to the topic — no maths is required. Move to Student once you are comfortable with the concepts, then Advanced for university-level depth. The Learning Paths put guides in the right order for you.
- Every figure is sourced from a primary authority: NASA Science, ESA Science & Exploration, the International Astronomical Union or peer-reviewed journals. The source is listed at the bottom of each guide.
- Each guide carries a "last reviewed" date. When a major discovery changes the picture — such as a new moon count for Jupiter or a revised age for the universe — the affected page is updated. The News page notes when a guide changes.
- Yes. The content is written to be shared. Figures and definitions are sourced, so students can trace them back to the original paper or agency page. For classroom use, the Learning Paths provide a ready-made curriculum structure.