Marble is a Virtual Globe and World Atlas that you can use to learn more about Earth: You can pan and zoom around and you can look up places and roads. A mouse click on a place label will provide the respective Wikipedia article.
Of course it's also possible to measure distances between locations or watch the current cloud cover. Marble offers different thematic maps: A classroom-style topographic map, a satellite view, street map, earth at night and temperature and precipitation maps. All maps include a custom map key, so it can also be used as an educational tool for use in class-rooms. For educational purposes you can also change date and time and watch how the starry sky and the twilight zone on the map change.
I know it's on KDE's site, but it does not require KDE.