"What exotic matter has negative energy density?" I scratched my head, trying to remember the dense information that I had so recently studied through. "Is it dark matter? Antimatter? Negative matter?"
"Good guess," Papa said, "but it's actually matter with a negative mass. Quantum field theory allows the energy density in certain regions of space to be negative relative to the ordinary vacuum energy.
It also allows states where the energy can be arbitrarily negative at any assigned location. This means that if Simon and I can assign and maintain that negative density region and keep it stable for a predetermined amount of time, it might make it possible to stabilize a traversable wormhole long enough for the Destruction Team to get out safely."
"Is it safe?" I raised an eyebrow. "I remember when Simon was near the portal, he kept saying he could feel it and hear it."
