For teachers
The solar system in your classroom
A live map of where the planets actually are, accurate to within an arcminute, free to use and free to embed. No account, no adverts inside the simulation, and nothing installed.
What it is
Most classroom orreries are animations on a timer: the planets go round at whatever speed looked good to the person who drew it. This one is computed. Every position comes from VSOP87 and an ELP-derived lunar theory — the same models professional ephemerides use — so what a class sees on the board is where those bodies actually are, to within about an arcminute.
That matters more than it sounds. A pupil who checks tonight and finds Jupiter exactly where the screen said it would be has learned something an animation cannot teach.
Six things you can teach with it
Each of these takes a few minutes at the board and needs nothing but the simulation. Ages are a guide, not a rule.
Why Mars appears to move backwards
Ages 14–18
Retrograde motion is the hardest idea in school astronomy and the easiest to show here. Set the rate to one week per second and watch Earth overtake Mars on the inside. The apparent reversal stops being a mystery the moment you can see both orbits at once — and it is the observation that took astronomy two thousand years to explain.
How long is a year somewhere else
Ages 8–12
Follow one planet for exactly one Earth orbit. Mercury completes four laps; Neptune has barely moved. Ask the class to work out their own age on Mars before you tell them the number.
Why the planets never line up
Ages 10–14
Scrub forward a few centuries and let the class watch for an alignment. It never comes. Every "planetary alignment" headline they will ever read gets quietly dismantled in about ninety seconds.
How empty space actually is
Ages 10–16
The simulation draws distances compressed by default, because otherwise the inner planets are a single pixel. Switch to true scale and the whole inner solar system vanishes into the middle of the screen. That switch, made live, teaches the scale of the thing better than any number on a worksheet.
Where the planets were on the day you were born
Ages 8–16
Jump to any date between 3000 BC and AD 3000. Every pupil gets their own sky. It is a hook rather than a lesson, and it works on every class that has ever been shown it.
Why the Moon has phases
Ages 8–14
Follow the Moon around Earth for one month and watch the lit side turn away from you. Pair it with the phase page for tonight, and set the class to check the real sky against it.
Putting it on your own site
The simulation can live on your school site, your department page or inside your VLE. It is one line of HTML, there is no account and no signup, and it costs nothing.
You can set the size, the starting body, the theme and the interface language — the widget itself speaks English, Dutch and French, so a Dutch-language lesson page gets Dutch controls.
The rest of the site, for lesson prep
The simulation is the centrepiece, but the pages around it answer the questions that come up after.
- What is visible tonightFrom 86 cities, in local time — so a class can be told exactly what to look for and when.
- Today's moon phaseTonight’s phase, the age of the Moon, and which craters are worth a telescope this week.
- Planet dataDistance, speed, size and orbital period for every planet, computed rather than copied.
- EclipsesEvery solar eclipse to 2040, with a map of where on Earth it is visible.
- Mars close approachesWhy Mars missions launch three months before Mars is nearest — with the transfer orbit drawn.
- The ISS overheadWhen the station passes over your town, bright enough to see. Reliably the most popular one with a class.
Accuracy, and its limits
Planet positions come from VSOP87 and the Moon from an ELP-derived series, both validated against NOVAS and JPL Horizons to within one arcminute. Eclipse and phase times are exact to the minute.
It is not suitable for navigation or spacecraft operations, and it is not an astrology tool. If a pupil asks whether it is "real", the honest answer is that it is the same class of model an observatory would use for planning, at lower precision than an observatory would need.
The practical questions
- Does it cost anything, ever?
- No. There is no paid tier, no trial, and no account. The site carries advertising around the edges; the embedded widget carries none.
- Do pupils have to log in or give any data?
- No. Nothing is required and nothing is collected from the simulation. The embedded widget sets no cookies at all.
- Will it run on our equipment?
- It runs in any current browser, on a smartboard, a laptop or a tablet. It needs JavaScript for the simulation itself; every other page on the site works without it.
- Can I use screenshots in worksheets?
- Yes — in teaching materials, freely and without asking. A credit is appreciated but not required.
- Can I use it offline?
- Not currently. It needs a connection to load, though not to keep running once open.
Something missing?
If there is a lesson you want to teach and the tool does not quite do it, say so. This page exists because teachers asked for things the site did not have yet, and that is a good reason to build them.