Pendry, JBJBPendryGaliffi, EEGaliffiHuidobro, PAPAHuidobro2022-08-302022-08-302022-07-20Optica, 2022, 9 (7), pp.724-7302334-2536http://hdl.handle.net/10044/1/99281Structures that appear to move at or near the velocity of light contain singular points. Energy generated by motion accumulates at these points into ever-narrowing peaks. In this paper, we show that energy is generated by a curious process that conserves the number of photons, adding energy by forcing photons already present to climb a ladder of increasing frequency. We present both a classical proof based on conservation of lines of force, and a more formal quantum electrodynamics proof demonstrating the absence of unpaired creation and annihilation operators. Exceptions to this rule are found when negative frequencies make an appearance. Finally, we make a connection to laboratory-based models of black holes and Hawking radiation.© 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement (https://doi.org/10.1364/OA_License_v2#VOR-OA).Science & TechnologyPhysical SciencesOpticsTIMEVACUUMJournal Articlehttps://www.dx.doi.org/10.1364/OPTICA.462488https://opg.optica.org/optica/fulltext.cfm?uri=optica-9-7-724&id=477398