Transcript Introduction to Astronomy

CJC Astronomy I
Some Course Basics
Instructor - Dr. Wayne Keith
 Contact info:
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Office Hours
 McM
Science 110C
 MWF: 9 – 11 am
 T: 9 – 10:30 am
 R: 2:30 – 5:30 pm
[email protected]
 http://www.mcm.edu/~keith.wayne
 (325) 793-3874
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Some Course Basics
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Textbook:
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Pathways to
Astronomy, by
Schneider and Arny
The textbook is
required!
I know it’s expensive,
but we’ll use it.
Some Course Basics
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Lecture:
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Monday & Wednesday
5:00 pm to 6:25 pm
Attendance is required!
No make-up work for
missed quizzes. Four
daily grades will be
dropped automatically.
Attendance will be taken
by roll sheets and/or inclass quizzes.
10% of your grade!
Some Course Basics
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Daily Grade
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Attend class
Bring astronomy-related
current events to discuss
at the beginning of class.
(Something you can turn
in as hard-copy, even if
it’s hand-written notes
about something you
saw on TV).
In-class quizzes based
on reading assignments
and lectures.
Some Course Basics
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Reading Assignments
I assign these in class, and they’re due by the next class
period.
RELAX! They’re usually pretty short.
They’re required! Consider them part of your homework!
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Not reading them WILL affect your grade because:
I assume you’ve read them when you come to class. You’ll likely
start feeling “lost” if you don’t read them!
I ask questions about them during in-class quizzes!
I ask questions about them on the exams!
Some questions on the online quizzes are related to the reading
assignments!
Some Course Basics
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Homework Questions/Problems
These are your main homeworks for the class!
Details:
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Will be announced in class and posted online
Due at the beginning of class on the date indicated
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Late work will loose 5% per class period
10% of your grade!
Some Course Basics
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TESTS!
Three Term Exams:
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Final Exam:
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Each is 15% of your grade.
Worth 15% of your grade.
Cumulative (some new material, mostly previous material).
Includes post-test
NO MAKE-UP FOR MISSED TESTS!
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Only exceptions: Severe personal illness, or death in immediate
family (official documentation required).
Must notify me BEFORE CLASS that you will not be present!
Extra Credit
There will be a few opportunities for “extra
credit” assignments over the semester.
 Most are announced near the end of the
semester.
 The amount and type of credit varies and
will be announced with the assignment.
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What Grade Will I Get?
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Based on past experience, if you miss
more than six classes, you’ll fail the
course.
If you don’t think you’ll be able to attend class
regularly, please drop the course!
 I expect everyone to make an effort to do well
in this class
 You don’t have to be a science major to do
well, grades will to a large extent reflect your
level of effort in the class.
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Other Common Questions
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Is there math in this class?
 Yes.
 I’m assuming you know how to add, subtract, multiply,
and divide.
 I’m assuming you know that in more “advanced”
math, letters are frequently used to stand for
numbers.
 I’m assuming you know how to “solve” a simple
equation.
 If you don’t know how to do this, please set aside
about 30 minutes to come by my office during
office hours and let me tutor you on what to do.
 We will use powers and logarithms, but I’m not
assuming you know or remember how to use these.
I’ll review them for you, in class, when we get to them.
Other Common Questions
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I freeze up when I see math, and I’m sure you
can’t help me with that! Can I still pass the
class?
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If you’re willing to put in the time, I can probably help
you more than you think, BUT…
If you study the conceptual (non-math) questions on
the test reviews, and learn that material very well,
attend classes, and do well on the quizzes, you’re
likely to get a B! With some help on the extra credit,
you can even still get an A.
Introduction: Why Study
Astronomy?
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For most of you, a
science course is a
“necessary evil” – you’re
required to take one.
Astronomy is one of the
coolest sciences to take,
because you study things
outside of everyday
experience!
It’s like taking a break
from the “real world” to
study the fantastic for a
while!
Introduction: Why Study
Astronomy?
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Here are some of the benefits
of studying a science:
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It improves your problem
solving skills.
It improves your critical
thinking skills.
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Both are related to
competence on the job,
something employers value.
These skills improve your
leadership ability.
Improves your ability to
express yourself.
It helps guard against “being
taken” by a pseudoscientific
scam! (The world is filled with
these.)
Introduction: Why Study
Astronomy?
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You’d probably be
surprised just how many
people find astronomy
interesting in small doses.
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You’ll learn about the sky
and the constellations.
You’ll learn about LOTS of
other cool things, like:
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How the sun will KILL US
ALL!
Exploding stars!
Exploding galaxies!
Black Holes!
And much more!
First Quiz!
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Take the pretest (not graded)
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On the back page, write a short statement
about yourself. Suggested topics are
listed, but are not required.
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Your name (at least) must be legible for
you to receive credit.
The Scientific Method
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Astronomy is a
physical science.
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Astronomers use the
scientific method to
answer questions
about objects found in
outer space.
What is the scientific
method? How does it
work?
How Do We Gain Knowledge?
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Two basic methods:
Revelation
 Experimentation
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Revelation vs. Experimentation
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Revelation:
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Somebody gives us the
information.
Believe or disbelieve
information based on our
opinion of the validity of the
source.
Very common.
Examples:
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College Lecture Course
A Religious Text
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Experimentation:
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We gather the information
ourselves.
Believe or disbelieve based
on our opinion of the
validity of the data.
Examples:
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The Scientific Method
Comparative Shopping
Examples
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“Careful! Hot!”
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Revelation: warning from
parent.
Information gained: the
object is hot. Touching it
will hurt.
Possible conclusions:
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Mom/Dad is wrong (invalid
source); go ahead and
touch.
Mom/Dad is right; don’t
touch.
Examples
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“OUCH!”
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Experimentation: You
touch the hot object
yourself.
Information gained:
Object is hot.
Touching it hurt.
Conclusions:
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Data are valid – object
is hot.
Don’t touch again!
The Basic Idea…
When you find out something by learning it
from someone else, that’s revelation.
 When you find out something by figuring it
out for yourself, that’s experimentation.
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The Scientific Method
The Scientific Method is a way of
answering questions through
experimentation.
 First Step: Ask a question you want
answered (in science, it is typically a
question about nature.)
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The Scientific Method
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Step Two: Design and
conduct experiments
related to the
question. Collect the
resulting data.
The Scientific Method
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Step Three: Use the
data to formulate a
hypothesis.
Hypothesis: In
science, a statement
of how something is
believed to work.
The Scientific Method
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Hypothesis must be falsifiable!
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Step Four: Use hypothesis to make predictions, and
conduct experiments to test predictions.
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Must make a prediction that can actually be tested through
further experiments!
Experiments match predictions, hypothesis is upheld.
Experiments don’t match predictions, hypothesis must be
modified or discarded.
Modifying hypothesis based on data is a return to Step
Two. So process is ongoing.
Summary of Steps
1. Ask a Question
2. Gather Data About The Question
3. Formulate a Hypothesis using the
Data
4. See if predictions from Hypothesis
match results from further
experiments (i.e. collect more data).
The Scientific Method
Always possible future data could
contradict hypothesis – no hypothesis is
ever final.
 Science can’t prove what is true! It can
only prove what is false!
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Intelligent skepticism is very important.
Theories vs. Laws
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A hypothesis that can,
in principle, be
explained with a
mathematical relation
is a scientific law.
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A collection of
hypotheses that
attempt to explain a
natural phenomenon
is a scientific theory.
Laws Were Made To Be Broken!
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Hypothesis: The pressure
in a gas is proportional to
the temperature of the
gas divided by the
volume the gas takes up.
Called the Ideal Gas
Law, and is a law
because it can be
expressed
mathematically:
(Pressure) = (constant) x (temperature) / (volume)
or PV = nRT
Laws Were Made To Be Broken!
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Experiments show that if
you plug in temperatures
and volumes, the
pressures only match
reality for high
temperatures and low
densities (little gas in a
large volume)!
The Ideal Gas Law is not
accurate for gasses at
low temperatures or at
high densities.
Yet still referred to as a scientific law!
The Scientific Method At Work
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Step 1: Formulate A
Question
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Why does the sun
shine?
Step 2: Design and
Experiment / Make
Observations
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What else gives off
light and heat?
Fire!
The Scientific Method At Work
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Step 3: Formulate A
Hypothesis
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The sun is made from
wood. It shines
because it is on fire.
The Scientific Method At Work
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Step 4: Collect more data and compare to
hypothesis.
By observing the sun we can find out more
things about it.
 It puts out as much light as a
400,000,000,000,000,000,000,000,000 watt
light bulb.
 By observing fires we could find out that to put
out this much light, we would have to burn 73
million trillion pounds of wood each second.
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The Scientific Method At Work
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The sun “weighs” 6 million trillion trillion
pounds.
73 million trillion pounds of the sun would
have to “burn” each second to produce all the
sunlight we see…
 The sun will “burn out” in about 2,000 years.
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The Scientific Method At Work
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This creates a problem.
2,000 years ago was the
height of the Roman
Empire – we know the
sun was putting out light
then (observation based
on literature from back
then).
If our hypothesis is true,
the sun would have
burned out a long time
ago!
The hypothesis isn’t
correct!
What Do We Do Now?
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Now we need to make more observations to
come up with a new hypothesis.
And the process begins again. And keeps
going.
After hundreds of years of this process
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Here’s what we’ve eliminated:
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The sun is made mostly of: Oil, Coal, Methane, Calcium
The sun’s energy comes from: Chemical Reactions,
Gravitational Contraction.
And here’s where we are (the current hypothesis):
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The sun is made of hydrogen and helium.
It shines because of a nuclear fusion reaction happening at
its core.
Pseudoscience
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What if I’d “fixed” my failed hypothesis by
doing this:
New Hypothesis: The sun is made of a special
type of wood that burns 10,000 times brighter
and 10,000 times slower than “earth wood.”
 Now the sun will take billions of years to “burn
up” so everything is fine.
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Pseudoscience
Currently, that hypothesis is (nearly)
impossible to test – we can’t land a probe
on the sun and test it.
 Our hypothesis is now pseudoscience.
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We have forced the scientific method to give
us the answer we want.
 We have ignored any evidence that disagrees
with our idea.
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Occam’s Razor
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The principle of OCCAM’S RAZOR:
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When you have two competing theories that
both explain something equally well, the
simpler theory will usually be the correct one.
More on Pseudoscience
Modifying a hypothesis based on
new observations
= The Scientific Method
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Ignoring or manipulating
observations to fit a hypothesis
= Pseudoscience
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Common Examples of
Pseudoscience
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ASTROLOGY
Just some of the
evidence against it:
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Compatible-sign
marriages have the
same divorce rate as
the general population.
Astrologers didn’t
predict the dwarf planet
Eris.
Sun and moon given
same “weight” as
planets.
Common Examples of
Pseudoscience
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“Face on Mars”
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Later observations by
Mars Global Surveyor
show it’s just a
mountain range
“Moon hoax” hoax
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Uses a multitude of
easily-debunked
“evidence” to try to
show humans didn’t go
to the moon.
Common Examples of
Pseudoscience
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Read about these and many others in depth on
Phil Plait’s “Bad Astronomy” web site:
www.badastronomy.com
(don’t let its educational value fool you, it’s really quite
entertaining!)
The Ongoing Process
Most of what you’ll learn in this course
you’ll hear from me (Knowledge gained by
revelation)…
 BUT most of what I’m telling you has been
deduced using the process we’ve talked
about today (Knowledge gained by
experimentation).
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Announcements
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Please note that the lab WILL meet this
week, after class Wednesday.
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There is no lab manual, handouts will be
provided for the labs.
For Next time
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Read Units 1 and 2 (calm down, it’s only
15 pages).
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Homework 1 – Due Monday January 29
Unit 1: Review Questions 2 and 3, Test
yourself 1
 Unit 2: Problem 3, Test yourself 1
 Unit 5: Problem 1, Test yourself 1
 Unit 6: Problem 1, Test yourself 1 and 3
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