Where did CMB radiation originate?
(a) It is the radiation from the electroweak phase transition when the weak force was spon-
taneously broken by the Higgs mechanism.
(b) It is radiation from supernovas in the early Universe that produced the heavier elements.
(c) The radiation is the photons that were made at the very beginning of the Big Bang.
(d) It is radiation leftover from the time period where electrons combined with protons to
form neutral hydrogen and hence no longer were in equilibrium with light.
The correct answer is (c) The radiation is the photons that were made at the very beginning of the Big Bang.
The Cosmic Microwave Background (CMB) radiation originated from the photons that were created during the very early stages of the Big Bang. As the universe expanded and cooled down, the free electrons and protons combined to form neutral hydrogen, allowing the photons to freely travel through space. These photons, which were originally in the form of energetic gamma rays, were stretched and cooled over time, eventually becoming the CMB radiation we observe today.
The correct answer to the question is (c) The radiation is the photons that were made at the very beginning of the Big Bang.
To explain the reasoning behind this answer, let's break down the different options:
(a) The electroweak phase transition refers to a time in the early universe when the electromagnetic and weak forces separated. While this phase transition did produce radiation, it does not explain the origin of CMB radiation.
(b) Supernovas do produce radiation, but they do not account for the CMB radiation. The heavier elements produced by supernovas are unrelated to the cosmic microwave background radiation.
(c) The most widely accepted explanation is that the CMB radiation originated from the photons that were generated during the very early stages of the Big Bang. The universe was extremely hot and dense at that time, filled with high-energy photons. As the universe expanded and cooled, these photons gradually stretched out and became the microwave radiation we now observe as the Cosmic Microwave Background (CMB).
(d) This option refers to a different phenomenon known as recombination. After the Big Bang, the universe was initially too hot for electrons to combine with protons, resulting in a plasma of charged particles that were constantly interacting with light. However, as the universe continued to expand and cool, it reached a point where electrons could combine with protons to form neutral hydrogen. This process, known as recombination, led to a decoupling of matter and radiation, and the CMB radiation could freely travel through space. While this is a significant event in the early universe, it is not the origin of the CMB radiation itself.
Therefore, option (c) is the correct answer as it accurately describes the origin of the CMB radiation as photons generated at the very beginning of the Big Bang.