Gold can be used for many other things other than just jewelry and world currency. Gold is a good conductor of heat and electricity and does not tarnish when it is exposed to the air, so it can be used to make electrical connectors and printed circuit boards. Gold is also a good reflector of infrared radiation and can be used to help shield spacecraft and skyscrapers from the sun's heat. Gold coated mirrors can be used to make telescopes that are sensitive to infrared light. A radioactive isotope of gold, gold-198 is used for treating cancer. Gold sodium thiosulfate is used as a treatment for arthritis. Because Gold is such a malleable and ductile element, it is very useful for a very wide variety of tools, gifts, and useful products. Gold is one of the world’s most prized, useful, beautiful, and sought after elements.