Negative mass using negative mass that requires no energy input and no reaction mass to achieve arbitrarily high acceleration. Forward also coined a term, "nullification", to describe what happens when ordinary matter and negative matter meet: they are expected to be able to cancel out or nullify each other's existence. An interaction between equal quantities of positive mass matter (hence of positive energy ) and negative mass matter (of negative energy ) would release no energy, but because the only configuration of such particles that has zero momentum (both particles moving with the same velocity in the same direction) does not produce
Velocity dispersion Velocity dispersion In astronomy, the velocity dispersion ("σ") is the statistical dispersion of velocities about the mean velocity for a group of objects, such as an open cluster, globular cluster, galaxy, galaxy cluster, or supercluster. By measuring the radial velocities of its members, the velocity dispersion of a cluster can be estimated and used to derive the cluster's mass from the virial theorem. Radial velocity is found by measuring the Doppler width of spectral lines of a collection of objects. The more radial velocities one measures, the more accurately one knows their dispersion. A central velocity dispersion refers to the