MCC PHS 142 M01 Astronomy Homework Ch.26-27      
Adj Prof Astronomy: Sam Wormley <>

Background Material

  Textbook - Read Chapters 26-27
  Textbook -
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      (take the Multiple Choice Quiz for for each chapter)

  Web - 
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Cosmology: The Modern Myth

Modern cosmology is taking us on the most exciting voyage in human
history. Far from diminishing our wonder at the Universe, this modern
story of Genesis surpasses even our wildest speculations. Consider the
simple words of Genesis: "Let there be light." A more succinct, more
cogent depiction of the Primeval Cosmic Fireball known as the Big Bang
cannot be envisioned. 

The evolution of the Universe is a "beautiful river of time" from the
earliest moments of the universe, to the formation of galaxies and
stars, then planets and finally life itself. In many ways the universe
is our mother who has nourished and produced us. Not only do we pursue
the science of cosmology, but we also ask the biggest of questions...
Why? What is Life? What is our part? 

Reflections on Observing

Much of the observing I have done in the last 22 years has been
unhurried and quiet with the companionship of my Golden Retriever,
Willow. When we do observations in this class, it is everything but
ideal. The building security lights blast into our eyes... interfering
with observations and preventing our eyes from becoming dark adapted. 

To make matters worse, you get your turn at the eye piece and get to
look for less than a minute. That's no way to observe! I do, however,
get some satisfaction from showing you some of the easier visual
delights, even if very briefly. 

The Friday night (day after Thanksgiving a couple of years ago) Jack
Troeger and I got together to observe. Jack was a science teacher at
Ames High School for many a year. He has an 8" Schmidt Cassegrain that
he sets up on a pillar in the middle of his back yard. I brought the
Astro Physics 5" refractor over and set it up a few feet from Jack's
telescope. We observed for a good five hours. By observing, I mean we
looked at specific celestial objects for a long time, studying their
detail, piecing together a composite picture. The atmospheric
turbulence is always present to some degree and is always changing. At
first the view may be so-so and then there may be a second or two of
better clarity. This changes second by second and can change quite
profoundly over an hour or so. 

The moon was fantastic at a low power (37x) where I could see the whole
lit portion. But at higher power (130x), trying to see crater-lets on
the smooth floor of the dark crater, Plato, the image squirmed and
danced around in the eye piece due to atmospheric turbulence. Turning
to Jupiter, there were hints of the Great Red Spot and at least one
other gigantic storm among the Jovian belts. At times I could see it
well, but most of the time the red spot danced in a blur of atmospheric
turbulence. Upon first looking at Saturn, that s all I saw--no wait--is
that a little moon just to the right of the rings--yes and another to
the left. And another just underneath! Once my eye-brain combination
knew where to look, I watched those three little pinpoints of moons
move slightly with respect to Saturn through the evening. It is so true
in observing that as the atmosphere permits, you see parts or glimpses
and then know where to look for detail. Observing is building up the
mental picture with glimpses awesome detail and structure. 

Later in the evening (about 10:30 p.m.) the Orion Nebula (M42) was high
enough to avoid trying to look through the lower atmosphere. It was
just beautiful--I could see the four trapezium stars well separated at
130x as bright pinpoints of light. The nebula itself becoming a
fascinating structure of light and dark areas--streaks. The more I
looked, the more I saw! And this beautiful piece of artwork is one of
the places that stellar birth is taking place. When I say artwork--I am
reminded of many fine charcoal sketches I've seen--but this is even
better, because there is subtle color. I know that you cannot
appreciate what I see in the Orion nebula until you have "lived with
it" for yourself, unhurried, and over a period of time. The more you
look, the more you see.

The Longest Night of the Year

Either Winter is long gone or coming soon and you are about to finish
this class, I hope you will all consider yourselves amateur astronomers
and pursue the night skies for the rest of your lives. I would like to
share this non-astronomy piece with you, although it does have imagery
from the longest night of the year near the Winter Solstice. Thoughts
you might think about at the next Winter Solstice or on Christmas eve.

Robert Frost was at work on a new book. Poems from Derry were still
maturing, some from England were almost ready. He had never succeeded
in larruping a poem as one might a horse to make it go. Poems had to
come to him in their own ways: 

"A poem begins with a lump in the throat; a home-sickness or a
love-sickness. It is a reaching-out toward expression; an effort to
find fulfillment. A complete poem is where an emotion has found its
thought and the thought has found the words". 

Some poems took years to find their words. Among the slow-growers was
"Birches." The impulse for "Birches" had been with him from the
earliest memories in Lawrence, never changing, always nagging him with
the sensations of striving and balance, but always incomplete.
Throughout Derry the poem seemed to be waiting a revelation. In England
(where no boys swing birches) Frost found the physical act carried
through to a spiritual meaning, something to do with Earth and human
aspirations. Now, in Franconia, after three full decades, the poem
found its thought and the thought worked out its words. 

There were other times when words came bubbling like a spring runoff.
At such times Frost would often write straight through the night. One
spring night a few years later he found the cantankerous drafts of a
long satiric poem suddenly turned agreeable, almost doing the writing
for him. During five hours he hurried to keep up--images, stories,
history, snatches of conversation, phrases flowing together as though
following some unseen channel. The poem ran on page after page without
serious hindrance right to the concluding ironies. Only then did he
look up. Dawn's first graying had begun outside his window; across the
road the angular rooflines of a barn were emerging. He realized how
tired he was, let out completely. 

He got up to make coffee. Opening the door, he watched the light coming
and listened to the birds waking up in the trees... Suddenly he knew he
had company: in that tranquil moment a new troupe of words began to
play through his mind: 

        Whose woods these are I think I know.... 
Pine trees, dusk, December, a horse-drawn sleigh, falling snow--where
did these words come from, so unbidden, so self-assured? 

        His house is in the village, though; 
        He will not see me stopping here 
        To watch his woods fill up with snow. 

Derry again, never-to-be-forgotten Derry. The words drifted down out of
the dark memories: a Christmas Eve when, much too late to be selling
anything, he had driven into town to peddle milk and eggs in order to
buy presents--no one interested, all busy with their own family
celebrations--returning home empty-handed. And yet this poem seemed
bent on avoiding the personal reality in order to create a new reality
of its own. To make matters more difficult the lyric demanded a tighter
than usual bonding of rhyme: four rhymes instead of two, and a linking
of one stanza to the next: a-a-b-a, b-b-c-b, c-c-d-c ... 

This posed an enormous challenge: how to keep such a linkage going.
Dante could manage a rhyme-chain in Italian, but in English the weight
of crude links usually buried its poem. Frost felt the bind at once.
Four times he tried to get into his second stanza; four times the lines
collapsed. Going on to explore the third stanza, he had better luck. 

        He gives his harness bells a shake 
        To ask if there is some mistake.... 

Beginning with the right words, the third stanza not only moved freely
to completion but showed the poet how to go back and remake the second.

One other test remained: the ending; where and how to cut the
rhyme-chain. Leave it dangling? Stop the poem in a final three rhymes?
Jam the end with five rhymes? Try to hook the last link back into the
first stanza? All were unworthy of the symmetry the poem has promised

Frost tried one line, then another; both were wrong. But half-hidden in
the words of the second attempt--"that bid me on, and there are
miles"--he saw the shining ending he had been looking for. The
collaboration was done, the unexpected company satisfied. Groggy but
elated, Frost could now go to bed. The Sun was just coming up [again]. 

"Stopping by Woods on a Snowy Evening" is a work of pure sorcery.
Whatever there is about good poetry--a mystery beyond meter, rhymes,
images, metaphor--it throws a spell over the simple scene. An
experience of pain and humiliation is wholly transformed. Poet, reader,
light, dark, duty, life, love join in an instant of communion. No words
or rhythms interrupt the spell. They all move in a planetary harmony.
Form and energy become one within the poem, as elemental as the mystery
of an atom. The poem is a culminating display of why Frost trusted


        Whose woods these are I think I know 
        His house is in the village, though; 
        He will not see me stopping here 
        To watch his woods fill up with snow. 

        My little horse must think it queer 
        To stop without a farmhouse near 
        Between the woods and frozen lake 
        The darkest evening of the year. 

        He gives his harness bells a shake 
        To ask if there is some mistake. 
        The only other sound's the sweep 
        of easy wind and downy flake. 

        The woods are lovely, dark and deep, 
        But I have promises to keep, 
        And miles to go before I sleep, 
        And miles to go before I sleep.

Adapted from:

Poems by Robert Frost
Photographs by Dewitt Jones
Text by David Bradley
Holt, Rinehart and Winston, New York  1979
PS3511.R94Z518  1979  811'.0'12  [B] 78-10444
ISBN 0-03-046326-2

Last Homework Problems

Note the answers to the odd (Conceptual Questions, Problems and
Figure-Based Questions) are in the back of your textbook. It is
strongly suggested that you do some of those in every chapter so you
have immediate feedback as how well you are understanding the material.
There are online multiple choice quizzes for each chapter of your
textbook. Goto then click on

  Your book
  Student Edition
  Choose a chapter
  Multiple Choice Quiz
You are expected to do all of your own homework. Statistical patterns
showing copying or collaboration will result in no credit for the
homework assignment for all participants involved. The Code of Academic
Conduct for Iowa Valley Community College District is found in the
Student Handbook.

Physical Science classes require the use of mathematics. If you don't
know algebra, you sould NOT be taking this class. If you need to review,
look at Introduction to Algebra
WolframAlpha is way faster than a scientific calculator.

There is little excuse for turning homework in late. You have a whole
week between classes to read the chapters and do the homework. Homework
one week late - half credit. Two or more weeks late - no credit. Do the
homework during the week, not in class! You got homework questions,
email me 24/7.  Even if you don't have a homework 
question, email me anyway!

Problem 1: 
Using you starwheel (planisphere) determine what Messier object is
located at 5h 35.4 Right Ascension and -5.5 degrees Declination.

Problem 2: 
Using you starwheel (planisphere) determine what constellation is
located at 16h 42m Right Ascension and +36.5 degrees Declination.

Problem 3: 
NGC 6720 looks like a cosmic smoke ring. It is the glowing outer layers
of gas that were "puffed off" of a star similar to our Sun during its
red giant phase. That "ring" of gas is ionized by the intense
ultraviolet light radiating from the extremely hot white dwarf star at
its center.

 The equatorial coordinates are:

  Right Ascension:  18:53.6  (hours:minutes)
  Declination:     +33.02 (degrees:minutes)
Using your starwheel (planisphere), determine what constellation NGC
6720 (M57) is found.

Problem 4: 
What evidence has led astronomers to reject the steady-state
cosmological theory?

Problem 5: 
What happened to all of the radiation that was produced during the
first few hundred thousand years after the Big Bang?

Problem 6: 
What is meant by the statement that the CBR (Cosmic Microwave
Background Radiation) has a temperature of 2.74 K?

Problem 7: 
What is the Hubble time if Hubble's constant is 71 km/s per Mpc?

Problem 8:
Set your planisphere (starwheel) so that all of the Summer Triangle
stars are up in the Western Sky and all of the Winter Hexagon stars are
up in the Easter Sky. What time does this happen on your birthday?

Problem 9: 
What properties of water are crucial to life on Earth? Discuss the
advantages and disadvantages of ammonia and methyl alcohol versus water
as a liquid on which life might be based.

Problem 10: 
Describe the observations of pulsar 1257+12 that lead to the
discovery that the pulsar is orbited by planets. Note: I cannot
find a reference to PSR 1257+12 made by the author, so I want you to
think in terms of what we can measure about pulsars, and what we would
detect in those measurements if a pulsar were orbited by one or more
planets at least the size of Jupiter.

Problem 11: 
The planet orbiting 16 Cyg B has an orbital distance of 1.7 AU. If
16 Cyg B has the same mass as the Sun, what is the orbital period of
the planet? Hint: Kepler's Third Law is helpful.

Problem 12: 
Use Figure 27.10 to find the age of the Sun when the Sun's habitable
zone moves beyond the Earth's orbit. Also, given the age of the Sun
(4.6 billion years), how long will it be before the Earth ceases to be
in the Sun's habitable zone?