Which evidence supports the idea that Cosmic Microwave Background radiation is a remnant of the Big Bang? *
a. Its mass is uniform.
b. Its temperature is uniform.
c. Its mass fluctuates greatly.
d. Its temperature fluctuates greatly.
b. Its temperature is uniform.
The evidence that supports the idea that Cosmic Microwave Background (CMB) radiation is a remnant of the Big Bang is option (b): its temperature is uniform.
This discovery was made in the mid-1960s by researchers Arno Penzias and Robert Wilson, who detected a faint microwave signal coming from all directions in the sky. They initially thought it was due to interference, but after consulting with physicists Robert Dicke and James Peebles, they realized that what they had discovered was the Cosmic Microwave Background radiation.
Here's how scientists reached the conclusion that the CMB radiation is a remnant of the Big Bang:
1. Big Bang Theory: The Big Bang theory states that the universe began with a tremendous explosion, where matter and energy were rapidly expanding from an extremely hot and dense state. This explosion filled the universe with photons (particles of light) that eventually cooled down.
2. Cooling and Expansion: As the universe expanded, it also cooled down. Around 380,000 years after the Big Bang, the universe had cooled enough for protons and electrons to combine and form neutral hydrogen atoms. This event, known as recombination, allowed light to travel freely through space.
3. Formation of CMB Radiation: Before recombination, the universe was filled with an intense plasma of ionized particles that strongly scattered light. However, after recombination, the universe became transparent to photons, and these photons started traveling through space mostly undisturbed.
4. Microwave Background: Over time, due to the expansion of the universe, the wavelengths of these photons stretched, resulting in a shift towards longer wavelengths. Today, these photons, originally emitted as visible light, have been stretched to microwaves. Hence, they are called Cosmic Microwave Background radiation.
5. Temperature Uniformity: One of the key pieces of evidence supporting the Big Bang theory and the CMB radiation is the uniform temperature of this radiation in all directions of the sky. In other words, no matter where we look, the temperature of the CMB radiation is approximately the same. This uniformity can be seen as a "fingerprint" of the early universe when it was much smaller and more uniform.
Therefore, the uniform temperature of the CMB radiation across the sky strongly supports the idea that it originated from the hot, dense, and early stages of the universe, providing evidence for the Big Bang theory.
b. Its temperature is uniform.
The evidence that supports the idea that Cosmic Microwave Background (CMB) radiation is a remnant of the Big Bang is the uniformity of its temperature. The CMB radiation is observed to have a nearly uniform temperature of approximately 2.7 Kelvin (-270.45 degrees Celsius), regardless of the direction of observation in the sky. This uniformity of temperature is consistent with the predictions of the Big Bang theory, which suggests that the radiation was evenly distributed throughout the early universe and has since cooled down over time as the universe expanded.