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Newly created superfluid defies physics, accelerates backward when you push it

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Why it matters to you

Negative mass superfluid could help answer the secrets of the universe or, one day, make one heck of a cool desk toy.

It sounds impossible, but apparently it’s not: Scientists at Washington State University have created a superfluid that appears to move counter to the laws of physics.

That means that when you push it, it doesn’t accelerate in that direction, but rather accelerates backward instead.

“We have demonstrated that lasers can be used to design systems in which cold atoms behave as if they have a negative mass, [meaning that] if you push or pull them, they accelerate in the wrong direction,” Michael Forbes, assistant professor of physics and astronomy, told Digital Trends.

The fluid was created by reducing the temperature of rubidium atoms to almost absolute zero, at which molecules start to behave more like waves. This state was predicted by Satyendra Nath Bose and Albert Einstein in what is called the Bose-Einstein condensate. Washington State scientists then used lasers to interfere with the rubidium atoms to change the way they spin, which resulted in the effect of making them behave like they had a negative mass.

The work was described in a newly published article in the journal Physical Review Letters, where it is was given the recommendation of “Editor’s Suggestion.”

For now, the breakthrough remains unlikely to immediately affect your day to day life. You’re unlikely, for instance, to immediately get a superfluid desk toy that resists efforts to move in the direction you push it. As Forbes said, “These systems are [only] about 100 microns across. To realize the negative effective mass, one needs to embed the material in lasers, so at present, it is not obvious how to scale this up.”

That doesn’t mean there aren’t potential use cases, though.

“The field of cold atoms is advancing at an extremely rapid pace,” he continues. “Many of [these] cutting-edge experimental techniques quickly find practical application in quantum technologies such as high precision quantum sensing, quantum cryptography, and quantum computation. Having controllable access to a fluid that behaves as if it has negative mass may have some very interesting applications.”

One is that it provides a new tool for studying exotic material such as found in neutron stars, the early universe, and inside nuclei. These are systems which are extremely difficult to study experimentally, but could be simulated in a lab using cold atoms. The results may help refine theories related to nuclear physics — thereby shedding light on massive questions like the origin of the elements in our universe.

“Nuclear reactions have more terrestrial applications, but modelling nuclei is tricky,” Forbes said. “Unlike neutron stars, which are held together by gravity, nuclei hold themselves together. Cold atoms, however, need to have an external pressure to keep them together. With this negative mass effect, the cold atoms experience a form of self-trapping that we hope to use to study the behavior of self-bound systems.”