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Chapter 17: Problem 11

Briefly describe how the cosmic microwave background was discovered. How does the existence and nature of this radiation support the Big Bang theory?

Short Answer

Expert verified
The Cosmic Microwave Background was discovered by Penzias and Wilson in 1965 as a uniform radiation that aligned with the Big Bang theory's predictions of primordial heat. It supports the theory by confirming the uniform hot and dense early universe.

Step by step solution

01

Understanding Cosmic Microwave Background

The Cosmic Microwave Background (CMB) is a faint glow of light that fills the universe, falling within the microwave region of the spectrum. It is considered the residual heat from the Big Bang, permeating throughout space.
02

Discovery of the CMB

The CMB was discovered accidentally in 1965 by Arno Penzias and Robert Wilson while they were working at Bell Labs. They were trying to eliminate background noise from their radio antenna but detected an inexplicable persistent hiss that came from every direction in the sky.
03

Realization and Interpretation

Upon consultation with astronomers and cosmologists, Penzias and Wilson learned that the noise was consistent with the predictions of the Big Bang theory, which anticipated the existence of remnant radiation.
04

CMB's Support for the Big Bang

The uniformity and spectrum of the CMB confirmed that the early universe was hot and dense, precisely as the Big Bang theory predicted. This provided a pivotal piece of evidence supporting the Big Bang theory over other competing theories, such as the Steady State theory.
05

Conclusion

The discovery of the CMB cemented the Big Bang theory as the leading explanation for the origin of the universe, as it matched the theory's predictions about the afterglow left from the initial explosion.

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Key Concepts

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

Big Bang Theory
The Big Bang Theory is a scientific explanation for the origin and evolution of the universe.
It suggests that around 13.8 billion years ago, the universe began from a singular, incredibly hot and dense point.
From this initial state, the universe rapidly expanded and continues to expand today. Over time, the initial concentration of energy cooled and formed the subatomic particles and atoms.
This eventually led to the formation of stars, galaxies, and larger cosmic structures that we observe today.
  • This theory provides a comprehensive understanding of the universe's beginnings and has become the most supported cosmological model.
  • Predictions from the Big Bang Theory include the existence of the Cosmic Microwave Background (CMB), a residual radiation from the early stages of the universe.
  • Other key pieces of evidence include the abundance of light elements and the redshift of galaxies, indicating their movement away from us.
Arno Penzias and Robert Wilson
Arno Penzias and Robert Wilson were two radio astronomers working at Bell Labs in 1965.
While attempting to detect microwave signals for telecommunications, they stumbled upon a persistent noise that seemed inescapable.
No matter where they pointed their telescope, the noise persisted. They investigated extensively to rule out possible sources of interference, including technical failures and even pigeons nesting in their equipment.
After these attempts failed, they consulted with physicists and astronomers in the community.
  • The scientists learned that the noise they detected was, in fact, the Cosmic Microwave Background (CMB).
  • This discovery was pivotal as it aligned perfectly with a prior prediction made by the Big Bang Theory.
  • Penzias and Wilson's findings became a cornerstone evidence for the Big Bang, leading to further explorations in cosmology.
For their monumental discovery, they received the Nobel Prize in Physics in 1978.
Microwave Spectrum
Microwave spectrum refers to a range of electromagnetic radiation with wavelengths between one meter and one millimeter.
This spectrum is situated between radio waves and infrared on the electromagnetic scale.
Microwaves are utilized in various technologies, from cooking food in a microwave oven to enabling wireless communication. The Cosmic Microwave Background (CMB) occupies a specific segment of the microwave spectrum.
It appears as a faint glow that is remarkably uniform throughout the universe.
  • When Penzias and Wilson discovered the CMB, it was found to have a temperature of about 2.7 Kelvin, or -270.45掳C.
  • The CMB's uniformity suggests that the universe has expanded uniformly since the Big Bang.
  • The spectrum of the CMB follows a nearly perfect black-body curve, which supports the theory that it is the thermal remnant of the early universe.
Steady State Theory
The Steady State Theory was once a major competitor to the Big Bang Theory.
Formulated in the mid-20th century, this theory proposed that the universe is eternal and unchanging on a large scale. The theory suggests that as the universe expands, new matter is continuously created to keep the overall density stable.
This contrasts with the Big Bang Theory, which proposes a dynamic and evolving universe from a singular origin.
  • The Steady State Theory does not account for the observed Cosmic Microwave Background.
  • The discovery of the CMB by Penzias and Wilson provided evidence that contradicted the Steady State Theory.
  • Due to the uniformity and spectral characteristics of the CMB, the Steady State Theory gradually fell out of favor.
As more observational evidence supported the Big Bang Theory, the scientific community largely moved away from the Steady State model.

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Most popular questions from this chapter

Decide whether the statement makes sense (or is clearly true) or does not make sense (or is clearly false). Explain clearly; not all of these have definitive answers, so your explanation is more important than your chosen answer. According to the Big Bang theory, most of the helium in the universe was created by nuclear fusion in the cores of stars.

Re-Creating the Big Bang. Particle accelerators on Earth can push particles to extremely large speeds. When these particles collide, the amount of energy associated with the colliding particles is much greater than the mass-energy these particles have when at rest. As a result, these collisions can produce many other particles out of pure energy. Explain in your own words how the conditions that occur in these accelerators are similar to the conditions that prevailed shortly after the Big Bang. Also, point out some of the differences between what happens in particle accelerators and what happened in the early universe.

Choose the best answer to each of the following. Explain your reasoning with one or more complete sentences. Which of the following does inflation help to explain? (a) the uniformity of the cosmic microwave background (b) the amount of helium in the universe (c) the temperature of the cosmic microwave background

The Big Bang. How convincing do you find the evidence for the Big Bang model of the universe's origin? What are the strengths of the theory? What does it fail to explain? Overall, do you think the Big Bang really happened? Defend your opinion.

New Ideas About Inflation. The idea of inflation solves many of the puzzles associated with the standard Big Bang theory, but we are still a long way from finding evidence confirming that inflation really occurred. Read a few recent articles that discuss some of the latest ideas about inflation and how we might test these ideas. Write a two- to three-page summary of your findings.
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