The trick to reaching the lowest temperature ever created (38 picoKelvin) has been to launch the experiment from a 120-meter tower
Motion, energy, and temperature are three closely related concepts. Scientists at the Center for Applied Space Technology and Microgravity (ZARM) at the University of Bremen know that well, and they have managed to create one of the “coldest places in the universe” for a few seconds taking advantage of precisely the effect that the fall had on the gas atoms used.
It is not the first work to reach temperatures close to absolute zero (-273.15ºC or directly 0 Kelvin). Experiments like those of the Cold Atom Lab on the International Space Station have succeeded in reducing the energy of the atoms with lasers enough to have 100 nanoKelvin and produce what is known as a Bose-Einstein condensate.
Now these German scientists have gone beyond what has ever been seen, setting a new record: 38 picoKelvin.,000,000,000 038 Kelvin or 38 billionths of a degree above absolute zero.
A tower that has been conducting fall experiments since 2007
The ‘Drop Tower’ is a well-known tower in Bremen where this type of experiment has been carried out since 2007. Although the capsule where it is launched travels 120 meters, the tower itself reaches 146 meters in height and includes areas set up for laboratories, workshops and control rooms.
The temperature reached cannot be measured with a thermometer, since it results from the extremely slow movement of the atoms observed in an ultra-cold gas. It is with the help of a recently developed interferometer that they have been able to measure this unprecedented temperature, reached “only” for about two seconds of the fall.
For this experiment, a gas cloud of 100,000 rubidium atoms was trapped in a magnetic field in a vacuum chamber. Later it was cooled until it became a Bose-Einstein condensate, this gas acting uniformly as if it were a single large atom. To keep going and reach such a low temperature, the ZARM scientists They threw this vacuum chamber through the Drop Tower and turned the magnetic field off and on several times to allow the gas to expand and contract. This switching slows the expansion of the gas and further reduces the molecular speed (and therefore the temperature of the gas), explain those responsible for the experiment.
While the two seconds may seem few, simulations carried out by the same team indicate that if an equivalent experiment is carried out in weightless conditions this state could be maintained for about 17 seconds. Conditions that cannot be replicated in the Bremen tower but we could see it on the ISS or a satellite.
Image | ZARM
More information | Physical Review Letters