I read an article which states that some systems temperature can be expressed as negative quantity on the Kelvin scale. How is this possible? I think it is impossible to go below absolute zero on Kelvin scale. And it is also stated that a system with an absolute negative Kelvin temperature is actually hotter than any system with a positive temperature and if a negative-temperature system and a positive-temperature system come in contact, heat will flow from the negative- to the positive-temperature system. How is this possible? can someone explain this in layman terms
Source: http://functionspace.org/topic/1771