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Chapter 22: Problem 6

The cosmic microwave background radiation indicates that the early universe a. was quite uniform. b. varied greatly in density from one place to another. c. varied greatly in temperature from one place to another. d. was shaped differently from the modern universe.

Short Answer

Expert verified
The early universe was quite uniform (a).

Step by step solution

01

Understanding the Cosmic Microwave Background Radiation

The cosmic microwave background (CMB) radiation is the thermal radiation left from the time of recombination in Big Bang cosmology. It provides a snapshot of the early universe.
02

Analyzing the Uniformity

The CMB radiation is highly uniform, with slight fluctuations. This uniformity indicates that the early universe was relatively homogeneous and isotropic.
03

Interpreting the Fluctuations

The slight fluctuations in the CMB data represent minor variations in temperature and density, but overall, they confirm the uniform nature of the CMB.
04

Eliminating Incorrect Options

Given the uniformity observed in the CMB radiation, the options indicating significant variations or different shapes can be eliminated.
05

Conclusion

By examining the CMB radiation, it is evident that the early universe was quite uniform, which aligns with option (a).

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Early Universe
The early universe sets the stage for everything we observe today. After the Big Bang, which occurred around 13.8 billion years ago, the universe was extremely hot and dense. Matter and energy were in an intense and chaotic state.
Over time, the universe expanded and cooled. This allowed the first atoms to form and phenomena like the Cosmic Microwave Background (CMB) radiation to emerge.
Understanding these early conditions helps scientists piece together the events that led to the formation of stars, galaxies, and everything in between.
CMB Uniformity
The Cosmic Microwave Background (CMB) is like a baby picture of the universe. It shows what the cosmos looked like when it was just around 380,000 years old. What makes the CMB special is its uniformity.
We see that the CMB radiation is almost the same in every direction. This smooth landscape tells us that the early universe was quite homogenous and isotropic, meaning it looked the same no matter where you were or which direction you looked.
But, there are slight variations—tiny fluctuations in temperature and density that we can detect. These small imperfections eventually led to the formation of galaxies and other cosmic structures.
Big Bang Cosmology
Big Bang cosmology is a model that explains the origin and evolution of the universe. According to this theory, the universe began from an incredibly hot and dense state and has been expanding ever since.
In the early moments after the Big Bang, the universe was filled with a hot 'soup' of particles. But as it expanded, it cooled down, allowing for the formation of atoms, stars, and galaxies.
The CMB radiation we observe today is a crucial piece of evidence supporting Big Bang cosmology. It is the thermal 'afterglow' from this early hot state, providing a view into the universe's infancy.
Thermal Radiation
Thermal radiation is energy emitted by matter in the form of electromagnetic waves due to its temperature. Think about how a pot of boiling water gives off steam—that's thermal radiation you can feel as heat.
The CMB is a type of thermal radiation created in the early universe, specifically around 380,000 years after the Big Bang. At this point, the universe had cooled down enough for protons and electrons to combine into neutral atoms in a process called recombination.
Because this radiation was emitted uniformly, it provides a thermal snapshot of the early universe, helping us understand its temperature and density at that time.
Recombination Era
The recombination era is a pivotal moment in cosmic history. It occurred approximately 380,000 years after the Big Bang. During this time, the universe cooled to about 3000 Kelvin, allowing protons and electrons to combine and form neutral hydrogen atoms.
Suddenly, the universe went from being opaque to transparent. This is because photons (light particles) could now travel freely without constantly interacting with charged particles.
The CMB radiation we observe today dates back to this era. It marks the moment when light could move through the universe unimpeded, giving us critical insight into the conditions of the early cosmos.

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Most popular questions from this chapter

Assume a planet's orbit is perfectly circular as it travels in the gravitational well of its star. If this were true, would the orbit's circumference be greater than, less than, or equal to \(2 \pi\) times the radius of the orbit?

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