Earth Screen Saver for Windows

by John Walker

The Earth screen saver displays an image of the Earth as currently illuminated by the Sun, from a variety of viewpoints. You can view the Earth from the Sun (day side), the night side, from the Moon, or from an arbitrary altitude above any point on the globe specified by latitude and longitude. Day and night regions of the globe are shown based on the current date and time. The image of the Earth shifts location on the screen every 10 minutes to avoid burning in the phosphor in one location.

The Earth Screen Saver is available exclusively for 32-bit Windows systems such as Windows 95/98/Me and Windows NT/2000/XP.

The Earth Screen Saver is in the public domain. You can do anything you like with it. The images are generated based on the cloudless Earth databases created by the NASA Goddard Space Flight Center from the MODIS instrument onboard the Terra satellite. The image of the Earth by night is based on nine months of observation by the Defense Meteorological Satellite Program. For further information and additional images, visit the NASA Earth Observatory site.

Downloading and Installation

After you've downloaded the program archive, extract the files in it with Info-ZIP or a compatible archive extract program, and follow the instructions in the included README.TXT file to install, configure, and activate the screen saver on your system.

Source Code

Experienced C programmers who wish to modify the screen saver or simply look under the hood to see how it works may download the source code. You're welcome to use this source code in any way you like, but absolutely no support is provided for it--you're entirely on your own. Note that the bitmaps included in the source code archive are reduced resolution and colour gamut images prepared expressly for this screen saver. If you're looking for cloudless Earth images for other applications, you're better off starting with the higher resolution, 24 bit per pixel images available from the aforementioned NASA site.

Release 2.0a Remains Available

The current 3.0 release of the Earth Screen Saver is a large (more than 4 Mb) program which consumes substantial CPU resources to render the image of the Earth. Users of older machines with modest memory and CPU capacity by present-day standards may prefer to install release 2.0a, which uses a lower resolution topographical map of the Earth from which it synthesises a subdued night side image, avoiding the need for a separate night side database. For further details, please visit the Release 2.0a page.

Related Software on this Site

Home Planet

The Earth Screen Saver was developed based on Home Planet, a comprehensive Earth and sky simulator for Windows which displays the Earth, tracks satellites, asteroids, and comets, includes an extensible multimedia object catalogue, a simulated telescope for viewing the sky at any magnification or location, a database of more than a quarter million stars, and a complete hypertext help file and introduction to astronomy linked to the components of the program. Displays include the illuminated portion of the Earth, the Sky, the Telescope, the Earth as viewed from a satellite, the Moon, or the Sun, an orrery, panels displaying current information about the Moon and planets, and more. Real-time astronomical information can be exported to other applications via DDE. There's even a cuckoo clock (you can turn it off).

Web Resources

Earth and Moon Viewer.
Your Sky: interactive planetarium.
Solar System Live: interactive orrery.
Terranova: a new terraformed planet every day.

For Windows:

Home Planet,
an Excel catalogue of the Palomar Observatory Sky Survey, and
Craters screen saver,
Sky screen saver,
Terranova screen saver,
Slide Show screen saver,
Bullets screen saver,
Millennium screen saver.

by John Walker
August, 2002