How is cosmic background radiation related to the big bang?

Answer 1

Cosmic Background Radiation, also known as the **Cosmic Microwave Background (CMB)**, is directly related to the Big Bang as the afterglow of the universe’s formation. Here's how they are connected:

1. **The Big Bang Theory**

• The Big Bang theory suggests that the universe began about **13.8 billion years ago** from a hot, dense state and has been expanding ever since. In the early moments of the universe, it was extremely hot and filled with high-energy radiation.

2. **Cooling of the Universe**

• As the universe expanded, it cooled. About **380,000 years after the Big Bang**, the universe had cooled enough for protons and electrons to combine and form neutral hydrogen atoms in a process known as *recombination*. Before this, the universe was opaque because photons (light particles) scattered off free electrons. Once neutral atoms formed, the universe became transparent, allowing light to travel freely.

3. **Cosmic Microwave Background (CMB)**

• The light that was released at the moment the universe became transparent is what we now observe as the CMB. Initially, this radiation was very energetic, but as the universe expanded, the wavelength of this light stretched into the microwave part of the electromagnetic spectrum, lowering its energy and temperature.

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Answer 2

The cosmic background radiation is considered by science to be elegant proof of a model of the universe which was once dense and hot and filled with a uniform glow. Expansion of the universe would cause the wavelength of this light to increase (in other words, the energy of the photons to decrease) to the level seen today, which peaks in the microwave region of the spectrum. The fact that this detectable "afterglow" does not have a specific source and seems fairly uniform in all directions also supports this model. Since these observations seem consistent with the Big Bang, this tends to support its position as the leading scientific theory of the origin of the universe.