Geissler Tube, an electron tube that is used to study the behavior of gases. It was invented in the 1860's by Heinrich Geissler, a German. The tube is made of glass, with an electrode at each end. Electricity is passed through a gas under low pressure within the tube; the color of the light produced depends on the kind of gas. Geissler tubes are used in physics demonstrations in high schools and colleges. They were forerunners of neon lights.
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Condensation, the formation of a liquid from a vapor or gas. It occurs in the formation of clouds and when cooled, water vapor turns into dew or rain.
Every November, the Leonid meteor shower fills the sky with "shooting stars." This year, the shower is expected to peak twice. Learn how Leonid and other meteor showers work.