What phenomenon does cosmic microwave background radiation suggest about the early universe?

The presence of cosmic microwave background radiation provides significant evidence supporting the idea that the early universe was uniform and isotropic. This radiation is a remnant from the hot, dense state of the universe shortly after the Big Bang, around 380,000 years post-event when the universe became transparent to radiation as electrons and protons combined to form neutral hydrogen atoms.

The cosmic microwave background (CMB) is remarkably uniform in all directions, suggesting that the universe was in a very homogeneous state at that time. Any small fluctuations observed in the CMB are indicative of the seeds from which galaxies and large-scale structures later formed, but the overall uniformity of the radiation across the sky points to an isotropic universe at that early stage.

The other options do not accurately describe the implications of the cosmic microwave background radiation. For example, while the early universe was indeed extremely hot, it subsequently cooled as it expanded, rather than remaining cold. The CMB does not support the idea that the universe consisted solely of dark matter, as dark matter does not emit or interact with electromagnetic radiation in a way that would create such detectable background radiation. Lastly, claiming that the universe had only visible light contradicts the very nature of the CMB, which falls within the