(Files in red–history)
 Index
2. Magnetic Field
2H. Oersted, 1820
3. Aurora
3H. Birkeland 1895
3a. Loomis & Aurora
3b. Fritz & Aurora
3c. The Terrella
4. Electrons
4H. Thomson, 1896
4a. Electric Fluid
|
 "Terrella" is Latin for "little Earth," the name given by William Gilbert to a magnetized sphere with which he demonstrated to Queen Elizabeth I his theory of the Earth's magnetism. By moving a small compass around the terrella and showing that it always pointed north-south, Gilbert argued that the same thing, on a vastly larger scale, was happening on Earth, and was the only reason why a compass pointed north-south. Later scientists such as Birkeland used the name "terrella" for magnetized spheres used inside vacuum chambers, together with electron beams, to study the motion of fast charged particles near the Earth. A sophisticated terrella experiment in a vacuum chamber is currently operated by Dr. Hafez u-Rahman at the University of California at Riverside.
|