Using the Web

Go to the Goddard Multimedia website and view the animation of a Cepheid variable star in a spiral galaxy ( Explain how astronomers use data like this to estimate the distance to the galaxy. What is actually observed, what is assumed, and what is calculated? (Review the discussion in Chapter 16 as needed.)
For more details on the history of the discovery of the expanding universe, go to the American Institute of Physics’ “Cosmic Journey: A History of Scientific Cosmology” website ( Read through the sections titled “Island Universes,” “The Expanding Universe,” and “Big Bang or Steady State?” Why was Albert Einstein “irritated” by the idea of an expanding universe? What was the contribution of Belgian astrophysicist (and Catholic priest) Georges Lemaître? What is the steady-state theory, and what was the main piece of evidence against it?
Go to the University of Washington Astronomy Department’s “Hubble’s Law: An Introductory Astronomy Lab” Web page (, and do the lab exercise, which uses real data from galaxies to calculate Hubble’s law. Your instructor will indicate whether you should use the regular or the shorter version.
Go to the “Astronomy” page of the Phys.Org website (, click on “Search,” and enter “Type Ia supernova” in the Search box. Find a recent story about one of these supernovae. What is its distance and brightness? What type of star produced the explosion?
Observations of the CMB from the Planck space telescope are expected to be released in 2013. Go to ESA’s Planck website ( and view the all-sky CMB map. Compare this with the WMAP data in Figure 19.18c; what is different? What has been learned from this mission?

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