## LESSWRONGLW

A momentary note on why the conversation went the way it did:

what the hell are complex numbers doing in the Dirac equation?

Hopefully you can see why this looked like a rhetorical objection rather than a serious inquiry.

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So, what IS the i doing in Dirac's equation? Well, first let's look into what the i is doing in Schrödinger's equation, which is

$i\\hbar \\; \\partial\_\{t\}|\\psi> = H|\\psi>$

with H the 'Hamiltonian' operator: the operator that scales each component of psi by its energy (so, H has only real eigenvalues. Important!)

The time-propagation operator which gives the solutions to this e... (read more)