In Brief
  • A team of physicists has used principles of quantum mechanics to create a fluid with negative mass that accelerates backward when force is applied to it.
  • This breakthrough will allow scientists to study conditions found in space more easily.

Accelerating Backwards

A team of physicists from Washington State University (WSU) has created a fluid with negative mass. You read that right…negative mass. Now, this doesn’t mean that it weighs less than nothing. This means that, unlike other physical objects in the world, when force is applied to it, it accelerates backward, rather than in the direction it was pushed. Physicist Michael Forbes, a WSU assistant professor of physics and astronomy and University of Washington affiliate assistant professor, led the team.

In theory, just like electric charges can be positive or negative, matter can have positive or negative mass. This might seem impossible because we’re so accustomed to perceiving our world through the lens of Newtonian physics and positive mass. Under those terms, Newton’s Second Law of Motion is a basic ground rule, and F=ma (force equals the mass of an object times its acceleration). This means that when you push something, it moves in the same direction, and the harder and faster you push, the further and faster it goes.

Negative mass turns these basic rules that feel immutable on their heads—just like quantum mechanics and black holes do. “That’s what most things that we’re used to do,” said Forbes. “With negative mass, if you push something, it accelerates toward you.”

Via Pixabay
Image Credit: Pixabay

Negative Mass

The team created these negative mass conditions by creating a Bose-Einstein condensate. They did this by cooling rubidium atoms just slightly above absolute zero. Particles move very slowly in this state, and, as quantum mechanics predict, behave like waves. They also behave like a superfluid, moving in unison and flowing without losing energy.

“What’s a first here is the exquisite control we have over the nature of this negative mass, without any other complications,” said Forbes. This unusual phenomenon and the control that researchers have over it are rarely seen under laboratory conditions, but they provide researchers with a useful tool for engineering experiments that explore and study analogous conditions in the cosmos. This places the experimental study of phenomena such as black holes, dark energy, and neutron stars within reach.

“It provides another environment to study a fundamental phenomenon that is very peculiar,” Forbes confirmed. The research is featured as an “Editor’s Suggestion” in Physical Review Letters.