In 1963, Robert L. Forward described hypothetical experiments that could use degenerate matter to explore gravitational effects and the potential for antigravity. The experiments involved cooling neutrons to temperatures sufficiently low to allow them to condense into neutron matter, and then subjecting them to rotating magnetic fields to accelerate them. Neutron matter is required as ordinary matter would not be dense enough to explore these properties, with Forward describing ideal densities from 10 to 10 g/cm.