In theoretical physics, negative mass is a type of exotic matter whose mass is of opposite sign to the mass of normal matter, e.g. −1 kg. ... Currently, the closest known real representative of such exotic matter is a region of negative pressure density produced by the Casimir effect.

Is a negative mass possible?

Washington State University physicists have created a fluid with negative mass, which is exactly what it sounds like. ... Hypothetically, matter can have negative mass in the same sense that an electric charge can be either negative or positive.

Why mass is always positive?

Answer: As, mass is a scalar quantity. so it is always a positive quantity.