the CMB that we now ‘see’ is not really the ‘actual Big Bang’, however, as these photons come to us directly from what is called the ‘surface of last scattering’ which occurred some 379 000 years following the moment of the Big Bang (i.e. when the universe was about 1/36 000 of its present age). Earlier than this, the universe was opaque to electromagnetic radiation because it would have been inhabited by large numbers of separate charged particles—mainly protons and electrons—milling around separately from each other, constituting what is referred to as a ‘plasma’. Photons would have
...more
