Fall 2005 ASTR 1120-001 Homepage
Fall 2005 ASTR 1120-001 Review for Final
4:30-7pm Mon Dec 12
The final will be mostly multiple-choice.
The intention is that all material on the final
(saving matters of logic and common sense)
is referred to somewhere here or on the
The final will test everything covered in class
cumulatively over the semester,
although there will be an emphasis on material covered
since the midterm.
Specifically, the final will test the material outlined in
Surely some of the
will be on the test.
We have covered
Ch 1, 4, 6, S2, S3, and 15-23 of Cosmic Perspective,
although not exhaustively.
Postulates of Special Relativity.
Special Relativity can be derived mathematically from a number of
The most important of these is that
"the speed of light c is the same for all observers".
How things look when you travel near the speed of light.
Describe how things look if you travel near the speed of light.
Name four ways in which a scene appears changed if you pass through it
at near the speed of light.
What is aberration?
How are colors changed?
How is the brightness of the scene changed?
How is the rate at which clocks tick change?
Faster than light.
One of the consequences of
special relativity is that nothing can move faster than light.
Does this mean that if you take, say a trip to the center of the Milky Way,
30,000 lightyears distant, it will take you at least 30,000 years?
If you go on a trip at near the speed of light and come back again,
how will your age have changed compared to those of the loved ones you left behind?
What is a black hole?
What is the horizon of a black hole?
What is the singularity?
What does the "no-hair" theorem of black holes state?
River model of Black Holes.
Explain the river model of black holes.
How does the river model explain what the horizon of a black hole is?
Friend falls into a Black Hole.
You watch a friend fall into a black hole.
Describe what you see.
Do you see the friend pass through the horizon?
What do you see happen to your friend at the horizon?
You fall into a Black Hole.
You fall into a black hole.
Describe what you see and experience.
What happens to you at the horizon?
Two kinds of Black Hole.
If black holes are black, how can you tell if one is there?
Astronomers see observational evidence for two kinds of black hole.
What are they?
If you wanted to search for black holes with a telescope,
what kind of telescope would you use
(radio, microwave, ...)?
What is an x-ray binary?
What is an accretion disk?
What produces the x-rays?
What heats the material to the point where it emits x-rays?
What is the main observational evidence used to distinguish
whether an x-ray binary contains a neutron star or black hole?
Quasars and Active Galactic Nuclei.
What is a quasar?
What observed property suggests that quasars are typically far away?
What is an Active Galactic Nucleus?
Name some of the observed characteristics of Active Galactic Nuclei.
See Cosmic Perspective p. 664.
Supermassive Black Holes.
What are supermassive black holes?
What is the main observational evidence for the existence of supermassive black holes?
What other observational evidence supports their existence?
See Cosmic Perspective p. 672.
Historical development of understanding of the Milky Way.
Give an account of the history of the historical development
of our understanding of the Milky Way.
Galileo, Herschel, Parsons, Leavitt, Slipher, Shapley, Hubble, Oort and Lindblad
How did the development of ever-better telescopes contribute?
What observation finally settled the issue of the nature of the spiral nebulae?
What observations finally settled the question of where was the center of
the Milky Way?
Sketch a diagram of the Milky Way,
indicating the bulge, the disk, and the halo.
Name some objects observed in each component.
See Cosmic Perspective p. 597.
What are globular clusters?
About how many are there in the Milky Way?
Whereabouts in the Milky Way are they?
What is it about their age and composition that
makes globular clusters particularly interesting?
What is the star-gas-star cycle?
How do observations of the Milky Way at different wavelengths
tell us about gas in the Milky Way?
"We are star stuff", said Carl Sagan.
What did he mean, and why is the star-gas-star cycle important to the process?
See Cosmic Perspective p. 598.
What has spiral structure got to do with star formation?
See Cosmic Perspective p. 617.
What is a redshift?
Most galaxies appear redshifted. What does this imply?
See Cosmic Perspective p. 636.
What are "standard candles" in astronomy?
What are they useful for?
What are the two most important standard candles in astronomy?
What is the Period-Luminosity law for Cepheid variables,
who discovered it, and how?
Why are Cepheid variables a particularly important rung
on the Cosmic Distance Ladder?
What makes thermonuclear supernovae good standard candles,
and what are they especially important?
See Cosmic Perspective p. 632.
Expansion of the Universe.
What observation, by whom,
led to the notion that the Universe is expanding?
What is a Hubble diagram?
What is Hubble's Law?
Why is Hubble's constant of fundamental interest in cosmology?
See Cosmic Perspective p. 636.
Age of the Universe.
How do we measure the age of the Universe?
Approximately what is the age of the Universe?
See Cosmic Perspective p. 643.
What is the Local Group of Galaxies?
The Local Group is the region of the Universe
that has turned around from the general Hubble expansion of the Universe,
and is collapsing for the first time.
About how many galaxies does it contain?
About what is its radius?
Who are its largest members?
Does our Galaxy have companion galaxies in orbit around it?
Does the Andromeda Galaxy (M31),
the largest member of the Local Group,
have companion galaxies in orbit around it?
Describe roughly what the Local Supercluster looks like.
In what constellation lies the center of the Local Supercluster?
Whereabouts is the Local Group in the Local Supercluster?
Is the Local Group moving towards or away from the Local Supercluster?
Are there other groups in the Local Supercluster?
Why does the Local Supercluster appear flattened?
Do galaxies collide?
Do stars collide?
What happens to galaxies when they collide?
When galaxies collide, what actually collides?
How do galaxy collisions affect spiral structure?
See Cosmic Perspective p. 658.
Dark Matter in Spiral Galaxies.
What is a rotation curve?
What can you deduce from the rotation curve of a galaxy?
In what sense are rotation curves evidence for Dark Matter?
Do rotation curves tell you what the Dark Matter is made of?
See Cosmic Perspective p. 680.
Dark Matter in Clusters of Galaxies.
How does x-ray emission from clusters of galaxies tell us about Dark Matter?
How does gravitational lensing by clusters of galaxies tell us about Dark Matter?
Do either of these tell you what the Dark Matter is made of?
See Cosmic Perspective p. 684, 685.
Why do galaxies cluster?
Were galaxies more or less clustered in the past?
See Cosmic Perspective p. 690.
What are the principal evidences favoring the standard hot Big Bang
theory of the Universe?
What shows that the Universe is expanding?
What shows that the Universe was once hot and dense?
What shows that the Universe was once much simpler than it is today?
What is the cosmological principle?
What observational evidence favors the cosmological principle?
Does the Universe have a center?
Does it have an edge?
What is the Universe expanding into?
Geometry of the Universe.
The cosmological principle restricts the spatial geometry of the Universe
to one of just three possibilities - closed, flat, and open.
What measurable differences do the three types have?
Is the Universe finite or infinite in a closed/flat/open Universe?
What is W?
What does it have to do with the geometry of the Universe?
What is the total value of W thought to be?
Cosmic Scale Factor.
What is the Cosmic Scale Factor?
How big is it (trick question)?
Sketch how the Cosmic Scale Factor varies with time
in matter-dominated closed/flat/open Universes,
and in a flat Universe containing matter and Dark Energy.
How does the wavelength, redshift, and temperature of photons
vary with Cosmic Scale Factor?
If we say that an object is at a redshift of z,
what does it imply about how much smaller the Universe was then than now?
What is meant by Dark Energy?
In January 1998 two separate teams reported that the Hubble
diagram of high redshift Supernovae showed that the Universe
What is the connection between this discovery and Dark Energy?
Non-baryonic Dark Matter.
What is meant by non-baryonic Dark Matter?
What is the evidence for its existence?
What does non-baryonic mean?
What is the main evidence that the Dark Matter is mostly non-baryonic?
Mass-Energy Content of the Universe.
What are the main contributors to the mass-energy content of the Universe?
The deeper we look in space,
the further back in time we see.
What, where, and why is our horizon?
What is meant by the edge of the observable Universe?
What lies beyond the edge of the observable Universe?
Does the Cosmic Background Radiation come from the horizon?
What happens to our horizon as time goes by?
See Cosmic Perspective p. 644.
Cosmic Microwave Background (CMB).
What is the CMB?
What kind of spectrum does the CMB have?
What is its temperature?
Has the CMB always been at the same temperature it is now?
Why can we see no further back than the CMB?
How does the Microwave Background vary around the sky?
Why does the CMB appear slightly hotter in one half of the
sky than the other half?
See Cosmic Perspective p. 707.
What is the Recombination Epoch?
Recombination happened at a temperature of 3,000 K.
What has this temperature got to do with the ionization of hydrogen?
What important things happened at Recombination?
Why is an ionized gas more opaque than a neutral gas?
What does it mean to say that the Cosmic Background Radiation
comes to us from the Epoch of Recombination?
Note that "Recombination Epoch" is the boundary between
what Cosmic Perspective p. 706 calls the "Era of Nuclei"
and the "Era of Atoms".
Fluctuations in the CMB.
What does the power spectrum of temperature fluctuations in the CMB mean?
What can we learn from the power spectrum of fluctuations in the CMB?
What is the connection between the horizon size at Recombination,
and the position (harmonic number) of the first acoustic peak?
How does this provide information about the geometry of the Universe?
What have measurements from the
Boomerang (2000) balloon,
and from the WMAP (2003) satellite,
revealed about the geometry?
Explain why regions of the CMB further apart than about 1°
were causally disconnected at the time of Recombination.
Why does the uniformity of the CMB then pose a problem?
This is the Horizon Problem.
How does inflation solve the problem?
If the Universe is decelerating,
does stuff appear or disappear over our horizon?
If on the other hand the Universe is accelerating,
does stuff appear or disappear over our horizon?
The Microwave Background is isotropic to a few parts in 105.
Why does this isotropy pose such a puzzle,
given that galaxies exist at the present time?
This is the Isotropy Problem.
How might non-baryonic Dark Matter solve this problem?
What is inflation?
What dominates the energy density of the Universe during inflation?
When is inflation thought to have happened?
How does the Universe expand during inflation?
What happens to the horizon during inflation?
See Cosmic Perspective page 712.
Problems of the Universe.
How does inflation solve the following problems:
Why is the Universe expanding?
Why is the Universe at large so smooth,
as indicated by the tiny (few × 10-5) fluctuations in the CMB?
Why is the Universe so flat, as indicated by Boomerang and WMAP
The Horizon Problem?
What caused ripples in the smoothness,
which later grew by gravity into galaxies, stars, and you?
Where did vacuum come from?
Unification of Forces.
The four forces of nature are:
What does the Unification of Forces mean?
Is there any evidence for it?
What is the electroweak force?
At what energy/temperature do the electromagnetic and weak forces unite?
What has the (de)unification got to do with vacuum energy?
the strong, or nuclear, or color force, which keeps atomic nuclei bound;
the electromagnetic force, which keeps electrons in orbit around nuclei;
the weak force,
which does not seem to have much direct effect on ordinary life,
but which allows protons and protons to transmute into each other,
and so allows all the different elements to exist;
the gravitational force,
which keeps planets in orbit around the Sun.
Fall 2005 ASTR 1120-001 Homepage