The 9 Biggest Unsolved Mysteries in Physics

In theoretical physics, negative mass is a hypothetical concept of matter whose mass is of opposite sign to the mass of normal matter, e.g. −2 kg. Such matter would violate one or more energy conditions and show some strange properties, stemming from the ambiguity as to whether attraction should refer to force or the oppositely oriented acceleration for negative mass. It is used in certain speculative theories, such as on the construction of wormholes. The closest known real representative of such exotic matter is a region of pseudo-negative pressure density produced by the Casimir effect. Although general relativity well describes the laws of motion for both positive and negative energy particles, hence negative mass, it does not include the fundamental forces other than gravitation. Whereas the Standard Model which describes elementary particles does not encompass gravitation, which is yet intimately involved in the origin of mass and inertia. Thus a correct particle model should explicitly include gravity.