01 — 04 · Earth to Universe
From your doorstep to the
edge of everything.
Zoom out one step at a time. Each scale opens its own guides, tools and charts — from here, above us, out to the cosmos.
General educational information. Every figure cites its source. Free to read — no account needed.
Solar System
Planets, moons, asteroids and comets orbiting the Sun.
Stars
The life cycle, classification and physics of stars.
Galaxies
Structure, types and formation of galaxies.
Black Holes
Singularities, event horizons and how we detect them.
Exoplanets
Planets beyond our Solar System and the search for life.
Cosmology
The Big Bang, dark matter, dark energy and the fate of the universe.
02 — Tools
Calculators for work and study.
Every calculation runs in the browser. Nothing you type leaves this page.
All toolsTool
Weight on other worlds
Weight = Earth weight × surface gravity ratio. Gas giant values at cloud tops. Gravity ratios: NASA Planetary Fact Sheets.
Tool
Distance converter
1 AU = 149,597,870.7 km (IAU 2012) · 1 ly ≈ 9.4607 × 10¹² km · 1 pc ≈ 3.0857 × 10¹³ km. Light speed = 299,792.458 km/s. Straight-line path assumed.
03 — Data & Charts
See the scale of things.
The planets, side by side. Sphere sizes are proportional to diameter.
Planet explorerSphere sizes proportional to diameter. Distances not to scale.
Beginner
First Look Up
Start at Earth and zoom out, one step at a time. No maths required.
5 stages
Student
How It Works
The physics behind space: orbits, light, gravity and stellar evolution.
5 stages
Advanced
The Deep Universe
Cosmology, dark matter, dark energy and what we still do not know.
4 stages
06 — Events
New guides, as they land.
The next meteor shower, eclipse and community event — with date, time and where on Earth to look.
All eventsFrequently asked questions
- SpaceTheGuide is a free, browser-based guide to space organised by scale — Earth, Solar System, Milky Way and Universe. Every figure cites its source. It is built for curious readers, students and working professionals. There is no account required and nothing is tracked.
- Each guide starts from primary sources: NASA, ESA, the International Astronomical Union (IAU) and peer-reviewed journals. We rewrite in plain language, keep the numbers exact and list the source on every page.
- Yes. Every calculator — weight on other worlds, distance converter, age on other planets — runs entirely in your browser using JavaScript. Nothing you type is sent to any server.
- Astronomers use several units depending on scale. Within the Solar System they use the Astronomical Unit (AU) — the mean Earth–Sun distance of 149,597,870.7 km, as defined by the IAU 2012 Resolution B2. For stellar distances they use the light-year (≈ 9.461 × 10¹² km) and the parsec (≈ 3.086 × 10¹³ km). Our distance converter tool converts between all four units instantly.
- A meteoroid is a small rocky or metallic body in space. When it enters Earth's atmosphere and burns up, the visible streak of light is called a meteor. If any part survives and reaches the ground, it is called a meteorite. The American Meteor Society has a detailed FAQ on this distinction.
- Visit the News page for the latest additions, or sign up to The Weekly Signal — one short email summarising the week's space news and new content on SpaceTheGuide.