The coldest place in the world is in Germany, but in a laboratory. According to research published in the scientific journal Physical Review LettersWhile investigating the wave properties of atoms, one of the “coldest places in the universe” was created for a few seconds at the Center for Applied Space Technology and Microgravity (ZARM) of the University of Bremen.
However, the temperature record close to absolute zero cannot be measured with a thermometer, but results from the extremely slow movement of atoms observed in an ultra-cold gas: a Bose-Einstein condensate (BEK), which is the state of matter at temperatures close to absolute zero.
What is absolute zero
The coldest a substance can get is when all molecular motion stops. This occurs at -273.15 ° C, also known as absolute zero, or 0 degrees in the Kelvin scale.
With the help of a newly developed matter wave lens system, the motion could be reduced in an unprecedented way and this could be demonstrated observing the BEK for up to two seconds in free fall at the Bremen Fall Tower.
The record for cold
With the matter wave lens system it was possible to reduce the internal kinetic energy of a BEK by 100,000 atoms more than ever. This means that the movement of atoms within the BEK could be slowed down so that an effective temperature of 38 picokelvin above absolute zero would be reached.
Those picokelvin are 38 billionths of a degree above -273 degrees Celsius, an absolute negative record. Furthermore, computer simulations indicate that the BEK theoretically can be held for 17 seconds in weightlessness with the help of the matter wave lens system, the prerequisite for future measurements of the highest precision in prolonged weightlessness, for example on a satellite.
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