The conditions in the early universe, when the universe suddenly became transparent to radiation, in terms of age t, peak background wavelength λ, and equivalent temperature T, were: A)t = 3 minutes, λ = 0.3 μm, near UV, and T = 10⁷ K. B)t = 380,000 years, λ = 1 μm, infrared, and T = 3000 K. C)t = 3 × 10¹¹ years, λ = 1 mm, microwaves, and T = 3 K. D)The universe was never dominated by radiation, because matter has always dominated by generating the gravitational field into which the universe has expanded.

Question

Quizplus · Accepted Answer

This is known as the cosmic microwave background radiation (CMB) era, which occurred when the universe was about 380,000 years old. The peak background wavelength was around 1 μm, in the infrared part of the spectrum, with an equivalent temperature of about 3000 K. This is the background radiation that we can observe today and is often considered strong evidence for the Big Bang theory. Option A refers to the nucleosynthesis era, which occurred earlier at around 3 minutes after the Big Bang, while option C refers to the recombination era, which occurred later at around 300,000 years after the Big Bang. Option D is incorrect because radiation did dominate the early universe, particularly during the CMB era.

The Conditions in the Early Universe, When the Universe Suddenly