Physicists create fluid with 'negative mass'

April 17 (UPI) -- A team of physicists at Washington State University have created a fluid that ignores Isaac Newton's Second Law of Motion. The fluid has "negative mass." When it's pushed it accelerates backwards.

Almost all matter in the universe obey's Newton's second law -- matter accelerates in the direction of the force applied to it. The new fluid does the opposite.

"With negative mass, if you push something, it accelerates toward you," Michael Forbes, an assistant professor of physics and astronomy at Washington State, said in a news release.

The liquid consists of rubidium atoms cooled to a temperature barely greater than absolute zero. The cooled atoms formed a Bose-Einstein condensate, a phase of matter characterized by slow-moving particles that behave like waves. The matter behaves like a superfluid, meaning its particles move in unison without sacrificing energy.

Researchers used lasers to cool the liquid in a tiny bowl. When scientists broke the bowl, the rubidium atoms rushed outwards. Scientists applied a second set of lasers to alter the spin of the out-rushing atoms. As a result, the atoms took on negative mass.

"Once you push, it accelerates backwards," said Forbes. "It looks like the rubidium hits an invisible wall."

Researchers say their latest experiments -- detailed in the journal Physical Review Letters -- were simpler and offered greater control over negative mass than previous attempts.

"What's a first here is the exquisite control we have over the nature of this negative mass, without any other complications," said Forbes.

The success may allow for exploration of strange phenomena like black holes and neutron stars.