Cold

From Wikipedia, the free encyclopedia
Jump to: navigation, search

Cold refers to the condition or subjective perception of having low temperature, the opposite of hot.[note 1]

A lower bound to temperature is the absolute zero, defined as 0 K on the Kelvin scale, an absolute thermodynamic temperature scale. This corresponds to −273.15 °C on the Celsius scale, −459.67 °F on the Fahrenheit scale, and 0 °R on the Rankine scale.

Since temperature relates to the thermal energy held by an object or a sample of matter, which is the kinetic energy of the random motion of the particle constituents of matter, an object will have less thermal energy when it is colder and more when it is hotter. If it were possible to cool a system to absolute zero, all motion of the particles in a sample of matter would cease and they would be at complete rest in this classical sense. The object would be described as having zero thermal energy. Microscopically in the description of quantum mechanics, however, matter still has zero-point energy even at absolute zero, because of the uncertainty principle.

Cooling[edit]

Cooling refers to the process of becoming cold, or lowering in temperature. This could be accomplished by removing heat from a system, or exposing the system to an environment with a lower temperature.

Fluids used to cool objects are commonly called coolants.

Air cooling is the process of cooling an object by exposing it to air. This will only work if the air is at a lower temperature than the object, and the process can be enhanced by increasing the surface area or decreasing the mass of the object.

Another common method of cooling is exposing an object to ice, dry ice, or liquid nitrogen. This works by convection; the heat is transferred from the relatively warm object to the relatively cold coolant.

Laser cooling and Magnetic evaporative cooling are techniques used to reach very low temperatures.

Notable cold locations and objects[edit]

See also[edit]

Notes[edit]

  1. ^ A cold body is often described as having less heat, although this use of "heat" would be incorrect in the context of physics, as heat refers to the transfer of energy between bodies, which do not "have" heat themselves.

References[edit]

  1. ^ "Boomerang Nebula boasts the coolest spot in the Universe". NASA's Jet Propulsion Laboratory. June 20, 1997. Retrieved July 8, 2009. 
  2. ^ Staff (July 7, 2009). "Coldest Known Object in Space Is Very Unnatural". Space.com. Retrieved July 3, 2013. 
  3. ^ Hinshaw, Gary (December 15, 2005). "Tests of the Big Bang: The CMB". NASA WMAP. Retrieved 2007-01-09. 
  4. ^ Uranus Fact Sheet
  5. ^ Saturn Fact Sheet
  6. ^ http://www.nasa.gov/worldbook/mercury_worldbook.html[dead link]
  7. ^ Jupiter Fact Sheet
  8. ^ Mars Fact Sheet
  9. ^ Melting Ice in Antarctica : Image of the Day
  10. ^ Bignell, Paul (2007-01-21). "Polar explorers reach coldest place on Earth". The Independent (London). Retrieved 2010-04-30. 
  11. ^ Budretsky, A.B. (1984). "New absolute minimum of air temperature". Bulletin of the Soviet Antarctic Expedition (in Russian) (Leningrad: Gidrometeoizdat) (105).