Before revision: In the early twentieth century, these ideas led Kristian Birkeland to build a terella , or laboratory device which simulates the Earth's magnetic field in a vacuum chamber, and which uses a cathode ray tube to simulate the energetic particles which compose the solar wind.
After revision: In the early twentieth century, these ideas led Kristian Birkeland to build a terrella , or laboratory device which simulates the Earth's magnetic field in a vacuum chamber, and which uses a cathode ray tube to simulate the energetic particles which compose the solar wind.