Acting as a subtopic of the General Chemistry Virtual Textbook's section on Atoms and the Periodic Table, this site seeks to answer the question, "Why doesn't the electron fall into the nucleus?"

Travel by land is the focus of these interactive vocabulary words. Learners will hear the correct Spanish pronunciation as the mouse is moved over each illustration.

Rhaetian Railway in the Albula / Bernina Landscapes, brings together two historic railway lines that cross the Swiss Alps through two passes. Opened in 1904, the Albula line in the north western part of the property is 67 km long. It...

A geo-political map of Switzerland that shows canton and country borders current to 1904, major cities, tunnels and railroad lines. Physical features such as mountain ranges with elevation measured in feet, glaciers, and major rivers....

Many civilizations have inhabited this small Aegean island, near Asia Minor, since the 3rd millennium B.C. The remains of Pythagoreion, an ancient fortified port with Greek and Roman monuments and a spectacular tunnel-aqueduct, as well...

The Upper Harz mining water management system, which lies south of the Rammelsberg mines and the town of Goslar, has been developed over a period of some 800 years to assist in the process of extracting ore for the production of...

East of the tombs of Ptah-hotep and Ti is the Serapeum, which consists of tunnels that were used for the funerary cult of the sacred Apis bulls. It dates back to the Saite period. The Serapeum was discovered as early as A.D. 1738 by...

Transformer house of the first large-scale, alternating current electric generating plant in the world; tapped power of Niagara Falls via a 7,500 foot (2,286 m) tail-race tunnel.

Photo image of a mole digging a tunnel.

An image of New Jersey State Monuments.