Big Bang
closed universe
confinement
cosmic light horizon
cosmic microwave background
cosmological constant
cosmological redshift
cosmology
dark ages
dark energy
decoupling
era of recombination
expanding universe
Grand Unified Theory (GUT)
homogeneity
inflation
inflationary epoch
isotropy
isotropy problem (horizon problem)
matter-dominated universe
open universe
pair production
Planck era
Planck time
primordial fireball
primordial nucleosynthesis
quark
quintessence
radiation-dominated universe
strong nuclear force
superstring theories
Theories of Everything
universe
weak nuclear force
Review Questions
1. Which force in nature is believed to have formed second?
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2. Inflation most directly explains which of the following?
3. What does it mean when astronomers say that we live in an expanding universe?
4. Explain the difference between a Doppler redshift and a cosmological redshift.
5. In what ways are the fate of the universe, the shape of the universe, and the average density of the universe related?
6. Assuming that the universe will expand forever, what will eventually become of the microwave background radiation?
7. What does it mean to say that the universe is dark-energy–dominated? When was the universe radiation-dominated? When was it matter-dominated? How did radiation domination show itself?
8. Explain the difference between an electron and a positron.
9. Where do astronomers believe most of the photons in the cosmic microwave background originated?
10. Give examples of the actions or roles of each of the four basic physical forces in the universe.
11. What is the observational evidence for the (a) Big Bang, (b) inflationary epoch, and (c) confinement of quarks?
Advanced Questions
12. Explain why the detection of cosmic microwave background radiation was a major blow to the steady-state theory.
13. Some so-called “creation scientists” claim that the universe came into existence 6000 years ago. What is Hubble’s constant for such a cosmos? Is this a reasonable number? Explain your answers.
Discussion Questions
14. Discuss the implications of the fact that science cannot yet tell us what caused the Big Bang or what, if anything, existed before the Big Bang occurred.
15. Explain why gravitational attraction has dominated the behavior of the universe until recently and why the dark energy determines the fate of the universe.
What If…
16. The universe were destined to collapse and the collapse was underway? What would be different in space and on Earth under those conditions?
17. Our solar system formed very early in the evolution of our Galaxy, when the universe was just 2 billion years old? What would be different in space and on Earth?
18. Our solar system formed much later in the evolution of the universe than it actually did? How would observations of stars and galaxies be different than they are now?
19. Our solar system formed with the first generation of stars? What would be different about the solar system? Would Earth exist as an inhabitable world? Why or why not?
Web Question
20. Structure of the Early Universe. Search the Web for information about the Planck spacecraft, which was mapping the universe until October, 2003. In what ways was Planck an improvement over the WMAP mission? What new insights do scientists hope to gain about the cosmos from Planck? What have they already learned from it?
Got It?
21. Which of the following best describes the overall motion in the universe:
22. What is the weakest force in nature?
23. What do astronomers believe to be the fate of the universe?
24. Has the universe existed forever? If not, when did it come into existence?
Observing Project
25. In an attempt to explore the far reaches of the Universe, the Hubble Space Telescope (HST) took long-exposure images of very dark regions of space that appear to contain no bright stars or galaxies. These images, known as the Hubble Deep Field and Hubble Ultra Deep Field images, reveal very rich fields of faint and very distant galaxies. The light now arriving at Earth from some of these galaxies has traveled over 13 billion years and was collected by the HST at a rate of a few photons per minute! This light was emitted very early in the life of the universe, only a few 100 million years after the Big Bang. You can examine and measure these two images. (a) In Starry Night™, open the Options pane, and ensure that the Hubble Images option is checked in the Deep Space layer. Open the Find pane, ensure that the search edit box is empty, and click on the icon in this box to display a list of image sources. Click on Hubble Images, and double-click on Hubble Deep Field to center the view on this dark region of space. Note its position with respect to the Big Dipper. (Note: If you cannot identify this region of the northern sky, click on View > Constellations > Asterisms and View > Constellations > Labels. Remove these indicators after you have identified the region.) Zoom in to a field of view about 3° wide and note that the region still appears to be devoid of objects. Zoom in again until the Hubble Deep Field (HDF) fills the view. One-quarter of the full HDF, with dimensions of 1.15′ × 1.15′, is displayed in Starry Night™. The bright object with spikes radiating from it is a star in our own Galaxy (the spikes are caused by diffraction by the supports for Hubble’s secondary mirror), but all of the other objects that appear on this long-exposure image are galaxies containing millions of stars. Examine this image carefully and attempt to identify some examples of each kind of galaxy—spiral, barred spiral, elliptical, and irregular—in this field. Choose five or six of the larger galaxies in this field, record their shapes and galaxy types, and use the angular separation tool to measure carefully and record their angular dimensions. (b) Click the Zoom panel in the toolbar, and select 90° from the dropdown menu. Return to the Find pane and the list of Hubble Images, and double-click on Hubble Ultra Deep Field (HUDF) to center the view of this “dark” region of the sky. Zoom in on this region and note that, even at a field of view as small as 2°, no objects can be seen in the position of this long-exposure image. Zoom in further until the full HUDF, with dimensions of 3.3′ × 3.3′, fills the field of view to see this rich field of faint and very distant galaxies. Examine this image carefully and attempt to identify some examples of each kind of galaxy—spiral, barred spiral, elliptical, and irregular—in this field. Again, select five or six of the larger galaxies in this field, record their shapes and galaxy types, and use the angular separation tool to measure their dimensions. (c) Consider the mix of different kinds of galaxies and assess whether the proportions of different kinds are the same in these two images. Compare the angular sizes of the largest galaxies in these two images.
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