# What is negative energy as used by Dirac to explain pair production? [duplicate]

While reading about pair production, I came across the concept of negative energy. What is negative energy exactly? And can there be negative mass corresponding to this energy?

## marked as duplicate by John Rennie energy StackExchange.ready(function() { if (StackExchange.options.isMobile) return; $('.dupe-hammer-message-hover:not(.hover-bound)').each(function() { var$hover = $(this).addClass('hover-bound'),$msg = $hover.siblings('.dupe-hammer-message');$hover.hover( function() { $hover.showInfoMessage('', { messageElement:$msg.clone().show(), transient: false, position: { my: 'bottom left', at: 'top center', offsetTop: -7 }, dismissable: false, relativeToBody: true }); }, function() { StackExchange.helpers.removeMessages(); } ); }); }); Oct 20 '18 at 7:05

• Can you give a reference to where you were reading this? – my2cts Oct 20 '18 at 6:47
• Quantum Physics of Atoms, Molecules, Solids, Nuclei, and Particles Book by Robert Martin Eisberg and Robert Resnick – Mechanic7 Oct 20 '18 at 6:49
• Its a pretty lengthy explanation as how Dirac explained pair production by considering the negative possibility of energy combining quantum mechanics and relativity. Please read it. – Mechanic7 Oct 20 '18 at 6:59
• @my2cts Take a look at physics.stackexchange.com/questions/19378/… and related questions on the Dirac sea. – PM 2Ring Oct 20 '18 at 6:59
• @PM 2Ring Thanks, interesting discussion. In my opinion the answers there are an interesting record of how the physics community was and still is wrestling with this. Also in my opinion the concern remains that Dirac theory predicts negative energy, for either matter of for antimatter, and that the Dirac Hamiltonian commutation with position x does not produce p/m but the nonsensical result of c. – my2cts Oct 20 '18 at 7:29

Matter and antimatter have positive energy and mass. Both the electron and the positron have a positive rest energy of 511 keV and a positive mass of $$9.11\times 10^{-31}$$ kg.