Astronomy HW 11

pdf

School

University of California, Berkeley *

*We aren’t endorsed by this school

Course

Subject

Physics

Date

Jan 9, 2024

Type

pdf

Pages

Uploaded by DukeTigerPerson976

1. What is the cosmic microwave background radiation and how was it discovered? What is its origin and why does it now correspond to a very low temperature? The cosmic microwave background radiation (CMBR) is a faint, uniform glow of radiation that permeates the universe and was discovered in 1965 by Penzias and Wilson. It originated from the recombination era, around 380,000 years after the Big Bang when the universe cooled sufficiently for electrons and protons to combine, allowing photons to travel freely. The CMBR now corresponds to a very low temperature of approximately 2.7 Kelvin due to the expansion of the universe, causing the originally higher-temperature photons to redshift and cool over time. 2. Discuss the significance of tiny spatial variations (“ripples”) detected in the cosmic microwave background radiation. To what do they correspond, physically? The tiny spatial variations or "ripples" in the cosmic microwave background radiation (CMBR) are echoes of quantum fluctuations in the early universe, representing fluctuations in matter density. These variations serve as the seeds that grew into the vast cosmic structures we observe today, such as galaxies and galaxy clusters. Studying these anisotropies provides a direct window into the early universe's conditions, supporting the inflationary model and offering insights into the fundamental forces and processes at play during the first moments of cosmic evolution. Experiments like COBE and WMAP have mapped these variations, aiding our understanding of the universe's complex and dynamic history. 3. What has been deduced about the overall geometry of the Universe through measurements of the variations discussed in the previous question? (If you use the term “flat”, explain what it means). Measurements of cosmic microwave background radiation (CMBR) variations have consistently revealed a spatially flat geometry for the universe. In this context, "flat" signifies that the large-scale structure of the universe adheres to Euclidean geometry, as predicted by the inflationary model. The observations, notably from experiments like WMAP and Planck, support the idea that the density of matter and energy in the universe closely approaches a critical value, indicative of a geometrically flat universe. This consensus reinforces the ΛCDM model and underscores the impact of inflationary processes on the overall structure and geometry of the cosmos. 4. Discuss the significance of the matter-antimatter asymmetry in the Universe. The matter-antimatter asymmetry in the universe is a fundamental puzzle in cosmology because, according to the principles of symmetry, matter and antimatter should have been created in equal amounts during the early moments of the Big Bang. If this were the case, they would have annihilated each other, leaving behind only radiation. However, our universe is predominantly composed of matter, and the reason for this profound imbalance remains one of the most significant unresolved questions in physics. Understanding the mechanisms responsible for this asymmetry is crucial for unraveling the fundamental nature of the universe's origins and its subsequent evolution. 5. Which three elements existed shortly (about 10 minutes) after the Big Bang? Hydrogen, helium, small amount of lithium 6. What are two main observational problems with the original Big Bang theory of the Universe?

The horizon problem in the original Big Bang theory arises from the observed uniformity of the cosmic microwave background radiation (CMBR) over large distances. In a universe expanding at conventional rates, distant regions that we observe today should not have had enough time to exchange information and achieve a consistent temperature. This raises questions about how such uniformity emerged. The flatness problem, on the other hand, is concerned with the observed spatial flatness of the universe on large scales. For the universe to be geometrically flat, its density must be extremely close to a critical value. This precise tuning of density seems unlikely without a mechanism that can account for it. 7. Explain how the two main problems discussed in the previous answer can be resolved if, at very early times, the Universe was much smaller than we had thought and subsequently expanded exponentially (i.e. inflated) by an enormous factor? The inflationary model proposes that, at the universe's very early stages, it underwent a rapid and exponential expansion. This inflationary epoch resolves the horizon problem by allowing distant regions to achieve uniform temperatures before quickly moving out of causal contact. Additionally, inflation naturally leads to a nearly flat geometry, addressing the flatness problem by stretching the universe from a much smaller initial size. The introduction of inflationary expansion offers a comprehensive solution to the two main observational problems in the original Big Bang theory. 8. The theory of inflation suggests that the Universe expands faster than the speed of light. Does this violate Einstein’s theory of relativity, which is often taken to imply that nothing can travel faster than light? While it might seem counterintuitive, the theory of inflation does not violate Einstein's theory of relativity, which states that nothing with mass can travel at or faster than the speed of light within spacetime. The apparent contradiction is resolved by understanding that during inflation, it is the fabric of space itself that undergoes exponential expansion, rather than objects moving through space. Inflation does not involve matter or energy exceeding the speed of light. Instead, it results in the stretching of space itself faster than the speed of light. This concept remains consistent with the principles of Einstein's theory of relativity. 9. Describe the fundamental forces of nature and attempts to unify them. The fundamental forces of nature include gravity, electromagnetism, weak nuclear force, and strong nuclear force. Physicists aim to unify these forces into a comprehensive "Theory of Everything" (TOE). Grand Unified Theories (GUTs) seek to merge the strong nuclear force with the electroweak force, while String Theory proposes that tiny vibrating strings are the fundamental building blocks, aiming to unify gravity with the other forces. Despite progress, experimental validation for these unification theories is yet to be conclusively observed, and a complete TOE remains an ongoing challenge in theoretical physics.

10. Why do we feel the effects of gravity, given that the gravitational force is so weak relative to the other fundamental forces? Despite being weaker than other fundamental forces, gravity's effects are noticeable due to its universal nature and the cumulative impact of large masses. The strength of gravity is determined by the masses of interacting objects and the distance between them. On a macroscopic scale, such as the Earth and a person, the considerable mass of the Earth and the relatively short distance to its surface result in a substantial gravitational force. Gravity's influence is pervasive, keeping us anchored to Earth and governing the movements of celestial bodies across vast distances in the universe. 11. Discuss what should have happened to the “grand unified force” as the Universe expanded and cooled at an age of about ten to the negative 37th power second. Around 10−3710 −37 seconds after the Big Bang, during the Grand Unification Era, the universe was incredibly hot and dense. At this point, Grand Unified Theories (GUTs) propose that the three non-gravitational forces—strong nuclear force, weak nuclear force, and electromagnetism—were unified into a single force due to the extremely high energy conditions. As the universe rapidly expanded and cooled, it underwent a process known as symmetry breaking, causing the unified force to separate into distinct forces. The strong nuclear force and the electroweak force (a combination of weak nuclear force and electromagnetism) became distinguishable. Further expansion and cooling led to a subsequent phase transition in the Electroweak Era, separating the electroweak force into the weak nuclear force and electromagnetism. These events marked the differentiation of the fundamental forces, shaping the universe into its current state with gravity, electromagnetism, weak nuclear force, and strong nuclear force as distinct entities. 12. Outline how the universe may have “supercooled”, leading to the inflationary expansion by an almost arbitrarily large factor when the Universe was only ten to the negative 35th second old. In the inflationary theory, the universe underwent a rapid and exponential expansion within its first 10−3510 −35 seconds, driven by a hypothetical field called the inflaton field. Initially in a high-energy state, the inflaton field caused the universe to supercool as it expanded, maintaining its high-energy condition. This supercooling led to a repulsive gravity that fueled the inflationary expansion, smoothing out irregularities and flattening the curvature of the universe on large scales. The inflationary epoch ended when the inflaton field underwent a phase transition, converting its energy into particles and initiating the hot Big Bang phase. This theory explains observed cosmic features, such as the uniformity of the cosmic microwave background radiation and the formation of large-scale structures, providing insights into the early moments of the universe's evolution. 13. Explain how the total energy of the Universe might be zero, or nearly zero. How does this relate to the idea that the Universe might be the ultimate “free lunch”? The concept that the total energy of the universe might be zero or nearly zero stems from the interplay between the positive energy associated with matter and radiation and the negative gravitational potential energy resulting from the universe's expansion. If the overall geometry of the universe is flat or very close to flat, and dark energy is considered, these energy terms may cancel each other out, resulting in a

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version

Access to all documents
Unlimited textbook solutions
24/7 expert homework help

universe with zero total energy. This idea aligns with the notion that the universe could be the ultimate "free lunch," as its existence wouldn't violate the conservation of energy.

Related Documents

Online-LAB-06_Simple-Pendulum.docx

Magnetic_Fields_and_Forces_VLab_2023 (1).docx

Electromagnetic_Induction_VLab_2020 w answers.docx

Ch 5.pdf

PHY 112 - Rio Salado Quizzes Flashcards _ Quizlet.pdf

Phys 1443 Review Guide (1).pdf

Untitled document (54).pdf

Lab 8 Report.docx

LAB_M9_Report.docx

phisics.pdf

1_4_Hookes_law_lab revised_2022.docx

phisics.docx

Recommended textbooks for you

Modern Physics

Physics

ISBN:9781111794378

Author:Raymond A. Serway, Clement J. Moses, Curt A. Moyer

Publisher:Cengage Learning

Principles of Physics: A Calculus-Based Text

Physics

ISBN:9781133104261

Author:Raymond A. Serway, John W. Jewett

Publisher:Cengage Learning

Physics for Scientists and Engineers: Foundations...

Physics

ISBN:9781133939146

Author:Katz, Debora M.

Publisher:Cengage Learning

Astronomy

Physics

ISBN:9781938168284

Author:Andrew Fraknoi; David Morrison; Sidney C. Wolff

Publisher:OpenStax

University Physics Volume 3

Physics

ISBN:9781938168185

Author:William Moebs, Jeff Sanny

Publisher:OpenStax

Horizons: Exploring the Universe (MindTap Course ...

Physics

ISBN:9781305960961

Author:Michael A. Seeds, Dana Backman

Publisher:Cengage Learning

SEE MORE TEXTBOOKS

Recommended textbooks for you

Modern Physics
Physics
ISBN:9781111794378
Author:Raymond A. Serway, Clement J. Moses, Curt A. Moyer
Publisher:Cengage Learning
Principles of Physics: A Calculus-Based Text
Physics
ISBN:9781133104261
Author:Raymond A. Serway, John W. Jewett
Publisher:Cengage Learning
Physics for Scientists and Engineers: Foundations...
Physics
ISBN:9781133939146
Author:Katz, Debora M.
Publisher:Cengage Learning
Astronomy
Physics
ISBN:9781938168284
Author:Andrew Fraknoi; David Morrison; Sidney C. Wolff
Publisher:OpenStax
University Physics Volume 3
Physics
ISBN:9781938168185
Author:William Moebs, Jeff Sanny
Publisher:OpenStax
Horizons: Exploring the Universe (MindTap Course ...
Physics
ISBN:9781305960961
Author:Michael A. Seeds, Dana Backman
Publisher:Cengage Learning