Exam 21: The Expanding Universe

Employing Hubble's law, calculate the distance to the Andromeda Galaxy, which is approaching at 110 km/s.The directly measured distance to Andromeda is 2.5 million light-years.How do the two numbers agree or disagree? Explain.

If the Hubble constant had a value that was half of its current measured value of 70 km/s/Mpc, the age of the universe would be about

The current temperature of the cosmic background radiation of 2.73 K means that the peak of its spectrum occurs at a wavelength of

The Hubble Space Telescope can be used to study galaxies at a redshift equal to 2.How much has the universe expanded since that light was emitted from these galaxies?

The temperature of the CMB is hotter on one side of the sky than on the other by approximately 3 milliKelvin.What does this tell us?

Provide an example of something that is homogenous but not isotropic.You may use an imaginary (but clear) situation, if desired.

Explain how the two images in the figure below describe the confinement and eventual release of the cosmic microwave background.

Prior to detailed studies of the cosmic microwave background, the age of the universe was poorly known.The age of the universe was thought to be around 16 billion years.If the universe were 16 billion years old, what would be the value of the Hubble constant, assuming constant expansion? Note that 1 Mpc = 3.086 * 10¹⁹ km and 1 year= 3.154 *10⁷ s.

What do astronomers mean when they say that the universe is homogeneous?

Does the expansion of the universe make the Sun bigger? What about the Milky Way? Why or why not?

The CMB spectrum shown in the figure below is

The apparently "grainy" CMB distribution shown in the WMAP in the figure below represents temperature fluctuations of about

After the Big Bang, as the universe cooled and protons and electrons combined, what important consequence happened?

Explain the difference between the universe and the observable universe.

The CMB fluctuations seen in the WMAP temperature distribution measures are of crucial importance in that

Why is it not possible to look all the way back to the Big Bang itself?

Distant Galaxy A has a larger redshift than distant, but otherwise identical, Galaxy B.This means that Galaxy A

Two galaxies are currently separated by 55 Mpc.Roughly how long did it take for them to reach this separation?

What is the correct interpretation of a redshift larger than 1?

We see the universe around us expanding at 70 km/s/Mpc, a rate given by the Hubble constant.If you were an astronomer living today in a galaxy that was located 1 billion light-years from the Milky Way, what would you measure for your Hubble constant?