What is Cold?
{{for|the sickness|Common cold}} {{wikt}} [[Image:Wesselburenwinter.JPG|thumb|Cold winter weather]] '''Cold''' is a relative term used in comparison with the adjective [[warm]] (opposite of cold). Because it is relative, there is no range in coldness. The temperatures in the [[winter]] [[season]] are often categorized as being cold. Cold is the opposite of [[heat|hot]]. The coldest possible temperature is −273.15 °C, which can be expressed as −459.67 °F on the [[Fahrenheit]] scale. This is called [[absolute zero]]. Absolute zero is also 0 K on the [[Kelvin]] scale and 0 °R on the [[Rankine scale]] ==Cooling== Cooling is when an object gets cold, or lowers in [[temperature]]. This can happen by taking away heat, or by putting something in a place with a lower temperature. [[Fluid]]s used to cool objects are called [[coolant]]s. [[Air cooling]] is making the temperature of an object lower using [[air]]. This will only work if the air is at a lower [[temperature]] than the object. The process will work better if there is more [[surface area]] on the object or if the item's [[mass]] can be made smaller. Other ways to cool objects include using [[ice]], [[dry ice]], or liquid [[nitrogen]]. This works by [[convection]]; the [[heat]] is taken from the relatively warm object to the relatively cold [[coolant]]. ==Cold locations and objects== *The Boomerang [[Nebula]] is the coldest known place in the [[universe]]. Scientists believe the temperature is 1&nbsp;K ([[kelvin]]) (−272.15 °C/−457.87 °F).<ref>{{Cite web|url=http://www.jpl.nasa.gov/news/releases/97/coldspot.html|title=Boomerang Nebula boasts the coolest spot in the Universe|date=June 20, 1997|publisher=NASA's Jet Propulsion Laboratory|accessdate=July 8, 2009|archive-date=August 27, 2009|archive-url=https://web.archive.org/web/20090827115717/http://jpl.nasa.gov/news/releases/97/coldspot.html|url-status=dead}}</ref> * [[Herschel Space Observatory]] equipment is kept at temperatures below 2 K, using a large [[helium]] tank for cooling.<ref>{{cite news | au