Fourmilab Earth and Moon
Fourmilab Earth and Moon is a model of the Earth and Moon system for the Second Life virtual world which combines high-resolution NASA imagery of the Earth (with ice, snow, and vegetation based upon the middle of each month) with calculation of the position of the Sun as observed from Earth to show the illuminated portion of a cloudless Earth.
The Moon is shown in its current relative position to the Earth, with a day and night mask showing the illuminated and dark portions of the Moon. The Moon is usually shown much closer to the Earth than its actual distance in order to fit in typical display spaces, but if you have a large property (say, 128 metres on a side), you can configure the Moon's distance to be at the correct scale. The Moon's near face is oriented with respect to the Earth accounting for optical librations due to the eccentricity and inclination of the Moon's orbit. Imagery of the Moon is derived from NASA high-resolution images from the Lunar Reconnaissance Orbiter spacecraft.
This repository contains all of the software and resources, including programs in Linden Scripting Language, texture images, notecards, and development documentation, tools, and resources used the model and its development. The actual model is built within Second Life and these components are installed within it. (The model is very simple: just five "prims", one cone and four spheres, linked together into one object.)
The complete model is available for free in the Second Life Marketplace. This repository contains everything in the model (except the prims, which are objects built within Second Life), plus additional resources for developers who may wish to extend or adapt the model as they wish. The model is delivered with "full permissions": those who obtain it are free to copy, modify, and transfer it to other users within Second Life.
All of this software is licensed under the Creative Commons Attribution-ShareAlike license. Please see LICENSE.md in this repository for details.