  It is assumed, in general, that the electromagnetic spectrum in the
Primordial Universe was a blackbody spectrum in vacuum. We derive the
electromagnetic spectrum, based on the Fluctuation-Dissipation Theorem that
describes the electromagnetic fluctuations in a plasma. Our description
includes thermal and collisional effects in a plasma. The electromagnetic
spectrum obtained differs from the blackbody spectrum in vacuum at low
frequencies. In particular, concentrating on the primordial nucleosynthesis
era, it has more energy for frequencies less than 3 to $6\omega_{pe}$, where
$\omega_{pe}$ is the electron plasma frequency.
