Scientists create negative-mass fluid that flows against the force

If you push an ordinary ball, it moves away from your hand. No surprise there. But if you pushed a ball with negative mass, it would actually accelerate backwards, moving towards you instead. It might be hard to picture how this could be possible, but according to Newtonian physics it should work in theory. Now, a team at Washington State University has demonstrated the phenomenon in practice, creating a fluid that has the properties of negative mass.