* Astronomy

Physicists observe 'negative mass'

Physicists have created a fluid with "negative mass", which accelerates backwards when pushed.
In the everyday world, when an object is pushed, it accelerates in the same direction as the force applied to it; this relationship is described by Isaac Newton's Second Law of Motion.
But in theory, matter can have negative mass in the same sense that an electric charge can be positive or negative. 
Read more