Concept explainers
Suppose you measure the red shifts of all the images produced by gravitational lensing, such as in Figure 34.12. You find that the central image has a red shill less than the outer images, and those all have the same red shift. Discuss how this not only shows that the images are of the same object, but also implies than the red shift is not affected by taking different paths through space. Does it imply that cosmological red shifts are not caused by traveling through space (light getting tired, perhaps)?
Want to see the full answer?
Check out a sample textbook solutionChapter 34 Solutions
College Physics
Additional Science Textbook Solutions
Physics for Scientists and Engineers: A Strategic Approach, Vol. 1 (Chs 1-21) (4th Edition)
University Physics Volume 2
Essential University Physics: Volume 2 (3rd Edition)
Lecture- Tutorials for Introductory Astronomy
Physics: Principles with Applications
University Physics Volume 1
- In the Check Your Learning section of Example 27.1, you were told that several lines of hydrogen absorption in the visible spectrum have rest wavelengths of 410 nm, 434 nm, 486 nm, and 656 nm. In a spectrum of a distant galaxy, these same lines are observed to have wavelengths of 492 nm, 521 nm, 583 nm, and 787 nm, respectively. The example demonstrated that z=0.20 for the 410 nm line. Show that you will obtain the same redshift regardless of which absorption line you measure.arrow_forwardIt is possible to derive the age of the universe given the value of the Hubble constant and the distance to a galaxy, again with the assumption that the value of the Hubble constant has not changed since the Big Bang. Consider a galaxy at a distance of 400 million light-years receding from us at a velocity, v. If the Hubble constant is 20 km/s per million light-years, what is its velocity? How long ago was that galaxy right next door to our own Galaxy if it has always been receding at its present rate? Express your answer in years. Since the universe began when all galaxies were very close together, this number is a rough estimate for the age of the universe.arrow_forwardThe CMB contains roughly 400 million photons per m3. The energy of each photon depends on its wavelength. Calculate the typical wavelength of a CMB photon. Hint: The CMB is blackbody radiation at a temperature of 2.73 K. According to Wien’s law, the peak wave length in nanometers is given by max=3106T . Calculate the wavelength at which the CMB is a maximum and, to make the units consistent, convert this wavelength from nanometers to meters.arrow_forward
- This a question on Cosmology: Suppose that you have a flat universe that has matter and dark energy with wd = -2/3 & Ωd,0 =0.7 At the time when light with z = 1 was emitted from a distant galaxy what was the ratio Ɛd /Ɛm ?arrow_forwardQuestion A7 Consider the following line element, ds² = - dt² + a² (t) (da² + dy²) + b² (t) dz², where a(t) and b(t) are distinct functions. State whether or not this line element obeys the Cosmological Principle, if applied to describe the universe on large scales. Justify your answer.arrow_forwardPlease answer within 90 minutes.arrow_forward
- Suppose you measure the red shifts of all the images produced by gravitational lensing, .You findthat the central image has a red shift less than the outer images, and those all have the same red shift. Discuss how this not onlyshows that the images are of the same object, but also implies that the red shift is not affected by taking different paths throughspace. Does it imply that cosmological red shifts are not caused by traveling through space (light getting tired, perhaps)?arrow_forwardConsider the following line element, ds² = -dt² + a² (t) (dx² + dy²) + b²(t) dz², where a(t) and b(t) are distinct functions. State whether or not this line element obeys the Cosmological Principle, if applied to describe the universe on large scales. Justify your answer.arrow_forwardWhat is the role of symmetry in fundamental physics? Provide examples of symmetry principles in particle physics and cosmology.arrow_forward
- 8arrow_forwardChoose the correct statements from the following list. (Give ALL correct answers, i.e., B, AC, BCD...) A) The inflationary model of the universe solves both the flatness and the horizon problems. B) The critical density is the density needed to cause the Big Bang. C) The horizon problem in cosmology is that regions of the universe that should not have ever had thermal contact with one another have the same temperature. D) A major difference between dark matter and dark energy is that one causes the univserse's expansion to slow down, the other to make it expand faster. E) Observations show us that the geometry of our universe must be very close to flat. F) Assuming no dark energy, if the matter density of the universe is less than critical, the universe is closed. G) Assuming no dark energy, if the matter density of the universe is greater than critical, the universe is will expand forever.arrow_forwardPlease answer within 90 minutes.arrow_forward
- AstronomyPhysicsISBN:9781938168284Author:Andrew Fraknoi; David Morrison; Sidney C. WolffPublisher:OpenStaxModern PhysicsPhysicsISBN:9781111794378Author:Raymond A. Serway, Clement J. Moses, Curt A. MoyerPublisher:Cengage LearningFoundations of Astronomy (MindTap Course List)PhysicsISBN:9781337399920Author:Michael A. Seeds, Dana BackmanPublisher:Cengage Learning
- Principles of Physics: A Calculus-Based TextPhysicsISBN:9781133104261Author:Raymond A. Serway, John W. JewettPublisher:Cengage LearningStars and Galaxies (MindTap Course List)PhysicsISBN:9781337399944Author:Michael A. SeedsPublisher:Cengage Learning