About Initial.The sky, from first principles.
What this is
Free simulators for the things people first learn about the sky: why the Moon changes, why seasons come, why the sky is blue. A student moves something, and the answer follows from what they see.
Who makes it
Initial is made by Neonsol, a small independent software company. We also make Sol, an app about the sun and sky.
How the numbers are worked out
The Sun and Moon come from the low-precision series in Jean Meeus's Astronomical Algorithms. Sizes and distances come from NASA's Planetary Fact Sheet. Bodies in a diagram are drawn larger than their true scale, and each simulator says so.
Pictures of Earth, the Moon and the planets
Earth is NASA's Blue Marble and Black Marble. Most planets are Solar System Scope's maps, under CC BY 4.0. Jupiter and Saturn come from NASA's Cassini images.
Write to us
hello@initial.app for anything about these pages. support@initial.app for help with Sol.