To record over an existing recording, the amorphous spots are reheated by the recording laser to a temperature that allows them to recrystallise.

ECONOMIST: Digital video discs

One of the ways scientists study the CMB is by subjecting the warm and cold spots in the radiation to a detailed statistical analysis, examining the deviations in temperature as a function of their size on the sky - their angular scale.

BBC: The first fractions of a second after the Big Bang