About — Orrery

Why “Orrery”

An orrery is a clockwork model of the solar system. It doesn’t tell you that the planets move; it lets you turn the crank and see. That is the standard for everything we make. Each exhibit takes one idea — why summer is warm, how circles can draw any shape, what a positive test result really means — and gives you something to handle: a picture you can drag, a dial you can turn, and plain words around it.

Who it is for

Anyone curious: readers who like to see how things work, students meeting an idea for the first time, and teachers looking for something to put in front of a class. There is nothing to sign up for.

The standard

Turn the crank. Every exhibit lets you manipulate something and see the consequence. Words serve the model.
True, with simplifications stated. Every fact, number and formula comes from a named source, and every exhibit says plainly what its model leaves out. A claim found to be false is fixed or withdrawn.
Sources on every page. Each exhibit ends with the sources its numbers and claims come from, so you can check them yourself.
Self-contained. Nothing on these pages reaches out to the internet — no fonts, no analytics, no tracking, no remote images. Once a page has loaded it works offline, and it works the same whether it is served from the web or opened straight from the disk.
For everyone. Usable with a keyboard alone, readable contrast, calm for people who prefer reduced motion, a dark theme when your device asks for one, and comfortable on a phone.
Finished or not shown. Partial work never appears among the exhibits. Small and complete beats big and broken.

What every exhibit gives you

It works in your hands. Every control, figure and readout responds to a mouse, to touch and to the keyboard, on a wide screen and on a phone.
It shows its sources. Facts, numbers and formulas come from the sources listed at the end of the page, and the numbers on screen are computed by the page itself, in your browser.
It says what it leaves out. Every model simplifies; each exhibit has a section that names its simplifications, so you know where the picture stops being true.
It is easy to read and use. Readable contrast in the light and dark themes, text alternatives for the figures, and calm for people who prefer reduced motion.
It works offline. No requests to anywhere else: once loaded, a page keeps working without a connection.

Mistakes and corrections

If you find something wrong — a fact, a number, a control that doesn’t work, a page that is hard to use — please open an issue at github.com/itayco2/orrery/issues, with the page and what you saw. Corrections are made on the page itself, and its colophon notes the revision.

How it is paid for

The exhibits are free to read, and they stay free. To pay for itself, Orrery sells extras on top of them, such as an offline edition and classroom materials. They will be linked here when they exist.

Licences

Text and figures are licensed under CC BY-NC 4.0: you may share and adapt them for non-commercial use, with credit to Orrery. The code is under the MIT licence. Data and ideas from other sources are credited on the page where they are used.

The emblem

The little orrery on the front page shows the eight planets at their real directions from the Sun on today’s date, computed in your browser from the approximate orbital elements published by NASA’s Jet Propulsion Laboratory (E. M. Standish, Keplerian Elements for Approximate Positions of the Major Planets, valid 1800–2050). Their distances from the Sun and their sizes are not to scale — Neptune is about 78 times farther out than Mercury. Turn its crank, or drag around the Sun, to move up to two years either way.