Survey of the Universe ASTR 2003

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Survey of the UniverseASTR 2003

• Dr. Julia Kennefick
• jkennef_at_uark.edu
• Office Hours MWR 10-11am
• PHYS 213
• Course material available on WebCT

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ASTR 2003 Course Syllabus Fall 2007 (last
revised March 13, 2006) Course ASTR 2003,
Survey of the Universe Classroom.. Ozark
025 Time.. TuTh 200 320 PM Text
The Essential Cosmic Perspective (4th Edition Web
Homework.. Mastering Astronomy
www.masteringastronomy.com Instructor Dr.
Julia Kennefick, 575-5916, jkennef_at_uark.edu Office
. Physics Bldg., Room 213 Office Hours..
MWR 1000-1100am, or by appointment WebCT........
........ Course syllabus, schedules,
etc. Welcome to Astronomy 2003. I hope you
enjoy the class. This course is designed for
non-science majors and contains only a little
math (there are a few equations!) Please ask
questions and introduce topics for discussion.
If you are having trouble with any of the
material, please come and see me during my office
hours or e-mail me to make an appointment. I
will be happy to speak with you. Grades Your
grade will be based on 4 tests/retests and
homework. The scale will be 90A, 80B, 70C,
60D. Each test/retest will be worth 150 points
and the homework/classwork will be worth 400
points for a total of 1000 points possible. The
minimum point totals needed to earn a specific
grade are as follows 900A, 800B, 700C,
600D.
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Tests There will be 4 in-class tests consisting
of 50 multiple choice questions each. Each
question will be worth 3 points for a total of
150 points per exam. 600 pts (60). Students will
not be allowed to hand in their exams for the
first 25 minutes of class time. Once students
begin handing in exams, no student entering class
late will be able to take the exam. Retests
After each test, you will be required to rework
the exam (the retest) outside of class using
whatever materials you can find and with the help
of classmates (please do not ask me or the TAs
for help.) This retest is due at the beginning
of the next class meeting (if you cannot attend
the next class meeting, then put the retest in my
mailbox in PHYS 226 or slip them under my door
before class). The retest score will improve
your grade on the test - you get one extra point
for each additional question you get correct on
the retest.) Your grade will not be affected if
you do worse on the retest. Make-up Exams No
make-up exams are given, but if you miss an exam,
do the retest anyway. You may be able to apply
it to the optional final (see below). Note
Photo IDs and 2 pencils are required for all
tests. You will need to purchase General
Purpose NCS Answer Sheet form no. 4521 (they are
blue) for each test and retest (9 total).
Final There is an optional final covering the
entire course. You can choose to take this exam
and substitute the score for your lowest test
score, if it is higher. Your grade will not
suffer if you choose to take the final. If you
miss an exam or choose not to take one, then you
can use the final exam as a makeup exam. There
is no retest for the final, but a retest from a
missed exam may be applied if there was a good,
documented reason for missing the exam, such as
illness, family emergencies, etc. Students
entering the exam hall more than 25 minutes late
will not be allowed to take the final.
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Homework I will give approximately 10 web-based
homework assignments over the reading material.
These will be due before class. See schedule
below. The homework will be done on the
Mastering Astronomy website associated with your
textbook. In order to gain access to the web
site, you can either buy the textbook new at the
bookstore and use the password that is included,
or you can purchase access at (http//session.mas
teringastronomy.com/myct?productIDbennett_e4).
The Course ID for our course is ASTR2003FA07.
400 pts (40) Bonus Points I will put a few
optional films that you can view in the library
for extra points. There will probably also be
extra points available for attending public
lectures given on topics in astronomy around
campus. I will explain this during class
throughout the semester. Classroom
Environment If you have a question about the
lecture or class material, I strongly encourage
you to ask me questions during the lecture.
There are probably others in class with the same
question who would appreciate you having the
courage to speak up. However, please keep
extraneous talking during class lectures to a
minimum. I do not have a loud voice, and talking
during class lectures prevents others from
hearing what they have paid money to hear. If
this becomes a problem, I will ask offending
students to leave the lecture hall. Likewise,
please wait until I have dismissed class to begin
leaving. I often make announcements in the last
few minutes of class that all students need to be
able to hear. Thank you.
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Weather Policy Classes will meet unless the
University is closed. Closure of the University
is announced on KUAF Radio, 91.3 FM, or you may
call 575-7000. You may also check the UArk
Daily Headlines page at http//pigtrail.uark.edu/p
ubs/university/theuniversity.nclk. If the
University remains open, no announcement will be
made. Also, check the class website. The lab
course, ASTR 2001L is not a co-requisite for this
course. It is a separate course and grades in
that course are independent of grades in this
course. No exceptions will be made to the
grading policy above. I will not assign projects
for extra credit to improve your grade under any
circumstances. Tests will not be given earlier
or later than scheduled. I do not give makeup
exams. As stated above, always do the retest and
come and see me about applying it to the optional
final.
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Grades
60 4 tests and retests (150 points each) 50
questions - 3 points each retest - 1 extra
point for each additional correct
question 40 homework (web based) and
classwork Optional final substitute for one exam
or use as makeup exam if you miss one Scale
90A, 80B, 70C, 60D

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What you need

• TextbookThe Essential Cosmic Perspective 4th
  Ed.
• Internet access for online Homework
• Account on the Mastering Astronomy site
• 8 (or 9) NCS Answer Sheets 4521
• 2 pencil
• Photo ID

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Parts I and II Chapters 1-5
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Chapter 1Our Place in the Universe
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Light!

• Astronomers use light to study the Universe.
• Light travels at a finite speed, c
• c 300000 kilometers/second (3x108m/s)
• 186000 miles/sec
• We see distant objects as they appeared in the
  past because it takes light some time to reach us
• Light from the Sun takes 8 minutes to reach us
  light from the nearest star takes over 4 years to
  reach us.

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d v t

• distance velocity x time
• If you drive v 60 miles/hour for t 1 hour,
  how far a distance, d, will you go?
• 60 miles
• If you drive for t 30 minutes 1/2 hour?
• 30 miles

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Definition Light-Year

• The distance light can travel in one year.
• About 10 trillion kilometers (6 trillion miles).

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Light-years - its a distance!

• d v t
• v speed of light c 300000 km/sec
• t 1 year 365 days/year x 24 hours/day x 3600
  sec/hour 31536000 sec
• d 1 ly c x 1 year
• 1 ly 300000 km/sec x 31536000sec
• 1 ly 9.460,800,000,000 km
• 9.5 trillion km
• WHEW!

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In order to make it easier to write these types
of large numbers, we use scientific
notation 9,460,800,000,000 km 9.4608 x 1012
km 1,000,000,000 LY 1.0 x 109 LY 109
LY 0.0000045 sec 4.5 x 10-6 sec
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Lets Do a Problem

• Please work these on your own paper and discuss
  it with your classmates

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Express the following numbers in scientific
notation

• 12345
• 2.5 million
• 5 percent
• A thousandth
• 0.0000345

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Express the following numbers in scientific
notation

• 12345 1.2345 x 104
• 2.5 million 2.5 x 106
• 5 percent 5.0 x 10-2
• A thousandth 1.0 x 10-3
• 0.0000345 3.45 x 10-5

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What is our place in the universe?

• Our Cosmic Address

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Universe

• The sum total of all matter and energy
• for now, this means everything within and between
  all galaxies

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What are we made of?
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How can we know what the universe was like in the
past?

• Light travels at a finite speed (300,000 km/s).
• Thus, we see objects as they were in the past
• The farther away we look in distance, the
  further back we look in time.

Destination Light travel time
Moon 1 second
Sun 8 minutes
Sirius 8 years
Andromeda Galaxy 2.5 million years
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At great distances, we see objects as they
were when the universe was much younger.

Can we see the entire universe?
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Thought Question
Assume the universe is 14 billion years old. Why
cant we see a galaxy 15 billion light-years
away?

• Because no galaxies exist at such a great
  distance.
• Galaxies may exist at that distance, but their
  light would be too faint for our telescopes to
  see.
• Because looking 15 billion light-years away means
  looking to a time before the universe existed.

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Thought Question
Assume the universe is 14 billion years old. Why
cant we see a galaxy 15 billion light-years
away?

• Because no galaxies exist at such a great
  distance.
• Galaxies may exist at that distance, but their
  light would be too faint for our telescopes to
  see.
• Because looking 15 billion light-years away means
  looking to a time before the universe existed.

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The Cosmic Horizon
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The Scale of the Universe

• How big is the Earth compared to our solar
  system?
• On a scale of 1-to-10 billion, the Sun is about
  the size of a grapefruit. The Earth is the size
  of a tip of a ball point pen about 15 m away.
  The distances between planets are huge compared
  to their sizes.
• How far away are the stars?
• On the same scale, the stars are thousands of
  kilometers away.
• How big is the Milky Way Galaxy?
• It would take more than 3,000 years to count the
  stars in the Milky Way Galaxy at a rate of one
  per second. The Milky Way Galaxy is about 100,000
  light-years across.

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How big is the Universe?

• The Milky Way is one of about 100 billion
  galaxies.
• 1011 stars/galaxy ? 1011 galaxies 1022 stars

It has as many stars as grains of (dry) sand on
all Earths beaches.
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The Scale of the Universe

• How big is the universe?
• 100 billion galaxies in the observable universe
• 14 billion light-years in radius
• As many stars as grains of sand on Earths
  beaches
• How do our lifetimes compare to the age of the
  universe?
• On a cosmic calendar that compresses the history
  of the universe into one year, human civilization
  is just a few seconds old, and a human lifetime
  is a fraction of a second.

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Everything moves

• Contrary to our perception, we are not sitting
  still.
• We are moving with the Earth in several ways, and
  at surprisingly fast speeds.

The Earth rotates with respect to the Sun once
per DAY, or every 24 hours. Since the Earth is
6400 km in radius, this means people at the
equator travel 1650 km/hr (1000 miles/hr).
40000 km
6400 km
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Earth orbits the Sun (revolves) once every year

• at an average distance of 1 AU 150 million km.
• with Earths axis tilted by 23.5º (pointing to
  Polaris).
• and rotates in the same direction it orbits,
  counter- clockwise as viewed from above the
  North Pole.

Astronomical Unit 1 AU 1.496 x 108 km
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Our Sun moves randomly relative to the other
stars in the local Solar neighborhood

• at typical relative speeds of more than 70,000
  km/hr.
• but stars are so far away that we cannot easily
  notice their motion.

And it orbits the galaxy every 230 million
years.

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Hubble discovered that

• all galaxies outside our Local Group are moving
  away from us.
• the more distant the galaxy, the faster it is
  racing away.

Conclusion We live in an expanding universe.
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If we didnt move, gravity would pull objects
together
Earth rotates on axis gt 1,000 km/hr
Earth orbits Sun gt 100,000 km/hr
Solar system moves among stars 70,000 km/hr
Milky Way rotates 800,000 km/hr
Milky Way moves in Local Group
Universe expands
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Review of Concepts

• Astronomers use light to study the Universe
• Light travels at a finite speed c 3 x 105
  km/sec
• Light year 1 ly 9.5 trillion km
• Astronomical Unit 1AU 150 million km
• Rotation - spin (day)
• Revolution - orbit (year)
• We live on the planet Earth, in our Solar System
  dominated by the Sun, in our galaxy the Milky
  Way, in our Local Group of galaxies, in our Local
  Supercluster, in an expanding Universe.
• Distances in the Universe are vast we havent
  been around very long compared to the age of the
  Universe we move at enormous speeds.