US, WASHINGTON (ORDO NEWS) — In July 2018, NASA announced an incredible achievement. The Agency created the coldest place in space – right there, on the International Space Station, in orbit around the Earth.
They took the atoms of the soft metal – rubidium, and cooled them to about 100 nano Kelvin – one tenth of a million degrees above absolute zero.
This led to the emergence of a very cold cloud called the Bose-Einstein condensate, an exotic “fifth” state of matter that can help us understand the strange quantum properties of ultracold atoms. But research did not stop there.
Using the Laboratory of the Cold Atom, scientists continued to produce Bose-Einstein condensates, cooled even more, using microgravity conditions at the space station to learn more about this condition than we could on Earth.
Bose-Einstein condensates are rather strange. They are formed from bosons cooled to a fraction above absolute zero (but not reaching absolute zero when atoms stop moving). This makes them sink to the lowest energy state, move very slowly and get close enough to overlap – creating a cloud of high density atoms that acts as a single “superat” or wave of matter.
Because quantum mechanics, in which each particle can be described as a wave, is easier to observe on an atomic scale, Bose-Einstein condensates allow scientists to study quantum behavior on a much larger scale, rather than trying to study individual atoms.
Bose-Einstein condensates can be created on Earth using a combination of laser cooling, magnetic fields and evaporative cooling. The last method – the last step – atoms are held in a magnetic trap, and radio-frequency radiation is used to “vaporize” the most energetic particles, leaving the cold particles forming a condensate.
Once this happens, the trap is turned off, and scientists can conduct experiments. But they must act quickly – the natural repulsive force between atoms will cause the cloud to expand and disperse. Gravity makes this process happen quite quickly – just a few tens of milliseconds.
Without gravity, you can create a Bose-Einstein condensate that can exist for more than a second.
This is what the researchers achieved with the Cold Atom Lab – but when they examined the created condensates, they discovered effects that could not occur with Earth’s gravity.
“We find that evaporative cooling caused by radio frequencies produces noticeably different results under microgravity conditions,” they write in their article.
“We are seeing an increase in the number of atoms in orbit by almost three times. Through the application of various magnetic field gradients, we confirm that approximately half of the atoms are in a magnetically insensitive state, forming a halo-like cloud around the location of the magnetic trap.”
On Earth, gravity is the dominant force acting on these atoms, removing them from the trap.
In space, if you look at the condensate closer, a halo of loose rubidium atoms has been discovered, soaring around the edges of the cloud. Thanks to the method of cooling the material, these atoms hardly pay attention to the magnetic trap. In free fall, they hung, providing a potentially useful ultracold resource for future research.
The possibility of producing colder, longer Bose-Einstein condensates also means that we can begin to think about other ways to study them. For example, trap shapes impossible on Earth can be created to observe various quantum behaviors.
The wave properties of condensates can be used for atomic interferometers measuring fundamental physical constants.
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