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Astronomy

Chapter 25 Homework

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Homework

Scholars Online Astronomy - Chapter 25: Cosmology

Homework

Reading Preparation

Reading: Astronomy, Chapter 25: Cosmology

Study Guide

Key Formulae to Know

Cosmological Redshift z   =   λ λ 0 λ 0   or   λ λ 0   =   1   +   z z: redshift = v/c
λ: observed wavelength of photon
λ0: wavelength of emitted photon at source
Hubble's law v = H0dv: recessional velocity due to expansion of space
H0: constant rate of expansion
d: distance of object from observer

Web Lecture

Read the following weblecture before chat: Cosmology

Study Activity

Use the iCosmos to manipulate the omega values to generate flat, curved, and negatively curved spacetimes.

  • Examine the default values for the cosmological parameters, then click on Submit button without changing any. Note the shape of the curves and be sure that you understand what each of these factors means (Co-moving Distance, Angular Diameter Distance, Luminosity Distance, Co-moving Volume, Age of The Universe and Perturbation Growth Factor.)
  • Change the Hubble constant to 45 and click on the Reference check box, then click submit. How does each new plot compare with the accepted Hubble value of 70? How do the values compare?
  • Change the Hubble constant to 85 and click on the Reference check box, then click submit. How does each new plot compare with the accepted Hubble value of 70? How do the values compare?
  • Which change increased the age of the univers? the angular diameter at a redshift of 1.0?
  • Restore the values to their defaults by clicking on the iCosmos logo, then change ΩM from 0.3 to 0.7. What happens to the shape of the universe? Try making smaller changes in ΩM until you can keep the shape of the universe flat. How small a change is necessary for it to become "unflat"?
  • Restore the values to their defaults, then change ΩΛ from 0.7 to 0.5. What happens to the shape of the universe? What is the largest change you could make where the universe remains flat?
  • Restore the default values, then change the redshift value only. Which values change? Which stay the same?

UNL Tools Exercises

  • ClassAction:
    • Under Cosmology, work through General Questions 1-17.
    • On the Animations tab, explore the Balloon Universe and Galactic Redshift Simulator.
    • Under Outlines, Check out the Cosmic Distance Later Parts 1 and 2.

Website of the Week: The Big Bang Time Machine lets you explore the theory of the Big Bang and step through the process of the current model.

Chapter Quiz

Lab Work

Read through the lab for this week; bring questions to chat on any aspect of the lab, whether you intend not perform it or not. If you decide to perform the lab, be sure to submit your report by the posted due date.