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Chapter 26: Problem 49

How can astronomers be certain that the cosmic microwave background fills the entire cosmos, not just the vicinity of the Earth?

Short Answer

Expert verified
Astronomers can be certain that the cosmic microwave background permeates the entire cosmos, not just the vicinity of Earth, because of acceptance of the cosmological principle of homogeneity, i.e., that the universe is the same in all directions and from any viewpoint. Moreover, observational evidence using telescopes supports this claim, as the CMB is detected consistently coming uniformly from all directions in the cosmos, reflecting a nearly perfect blackbody spectrum.

Step by step solution

01

Understand the Cosmic Microwave Background

First, it's important to comprehend what the cosmic microwave background (CMB) is. It is the afterglow of the Big Bang, which can be still detected today as a faint thermal radiation. The CMB fills the entire cosmos and can be observed from Earth in every direction.
02

Understand the Principle of Homogeneity

The cosmological principle states that the distribution of matter in the universe is homogeneous and isotropic when viewed on large scales. This means the universe looks the same in all directions (isotropic) and from all viewpoints (homogeneous). This principle suggests that the location in the universe where observers make measurements isn’t special or unique, hence the CMB observed is from the entire Universe and not just in the vicinity of Earth.
03

Understand Observational Evidence

Scientists use different types of telescopes to study the CMB. These telescopes provide supportive evidence as they detect microwave radiation coming uniformly from all directions in space, with a nearly perfect blackbody spectrum. This suggests it permeates the entire cosmos, and the observation is not merely unique to Earth's vantage point.

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