ASTRO 101

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ASTRO 101

• Principles of Astronomy

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Instructor Jerome A. Orosz
(rhymes with boris)Contact

• Telephone [phone]
• E-mail orosz_at_sciences.sdsu.edu
• WWW http//mintaka.sdsu.edu/faculty/orosz/web/
• Office Physics 241, hours T TH 330-500

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Text Perspectives on Astronomy First
Editionby Michael A. Seeds Dana Milbank.
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Course WWW Page

• http//mintaka.sdsu.edu/faculty/orosz/web/ast101_f
  all2009b.html
• Note the underline ast101_fall2009b.html
• Also check out Nick Strobels Astronomy Notes
• http//www.astronomynotes.com/

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Syllabus

• http//mintaka.sdsu.edu/faculty/orosz/web/ast101_f
  all2009/syllabus2/index.html
• Furloughs
• Safety
• Prerequisites
• Homework
• Grades
• Conduct in class

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Why Take this Class?
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We want to understand andappreciate everything
in the Universe!
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Since the earliest recorded times, people have
looked up at the sky and wondered about the
things they saw.Most early cultures had
extensive mythologies relating to the workings of
the Earth and things in the sky.
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We live in interesting times. We are in a
position to investigate and answer many basic and
profound questions about our world and
beyond.In this course we will survey such
topics as
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The Earth

• Why are there seasons on Earth?
• What causes the day/night cycle?
• How old is the Earth?

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The Sun

• What is it?
• How does it shine?
• How old is it?
• Will it go on forever, or will it die?

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The Moon

• What is it?
• Where did it come from?
• Is there life on it?

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The Solar System Planets

• What are they?
• What are they like?
• Where did they come from?
• Do they have life?

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The Stars

• What are they?
• Why are some stars red and other ones blue?
• Why do they twinkle?
• How old are they?
• Will they last forever, or will they die?

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Galaxies

• What are galaxies?
• How big are they?
• What is the Milky Way? Is it a typical galaxy?

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Strange Objects

• What is a White Dwarf?
• What is a Neutron Star?
• What is a Black Hole?
• What is a Quasar, and how do they work?
• What is a Nova explosion? What is a Supernova
  explosion?

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Deep Questions

• How big is the Universe?

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Deep Questions

• How big is the Universe?
• Does the Universe have a beginning and an end?
  If so, how old is it?

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Deep Questions

• How big is the Universe?
• Does the Universe have a beginning and an end?
  If so, how old is it?
• The meaning of infinity

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The Meaning of Infinity

• Suppose the universe is infinite in size and in
  age

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The Meaning of Infinity

• Suppose the universe is infinite in size and in
  age
• Then everything that is possible to happen has
  already happened, an infinite number of times.

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The Meaning of Infinity

• Suppose the universe is infinite in size and in
  age
• Then everything that is possible to happen has
  already happened, an infinite number of times.
• Therefore there are exact copies of you, me this
  classroom, this earth, etc. somewhere out there.

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The Meaning of Infinity

• Suppose the universe is infinite in size and in
  age
• Then everything that is possible to happen has
  already happened, an infinite number of times.
• Therefore there are exact copies of you, me this
  classroom, this earth, etc. somewhere out there.
• There are also an infinite number of near copies
  of you out there, e.g. someone like you but with
  different hair, more money, etc.

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Deep Questions

• How big is the Universe?
• Does the Universe have a beginning and an end?
  If so, how old is it?
• The meaning of infinity

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Deep Questions

• How big is the Universe?
• Does the Universe have a beginning and an end?
  If so, how old is it?
• The meaning of infinity
• Is there other life out there?

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Deep Questions

• How big is the Universe?
• Does the Universe have a beginning and an end?
  If so, how old is it?
• The meaning of infinity
• Is there other life out there?
• While your friends are thinking about what socks
  to wear, we will ponder these and other questions!

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Course Philosophy

• We will emphasize understanding concepts, not
  just memorizing jargon.
• We will spend a great deal of time discussing how
  we know what we know, e.g. the use of the
  Scientific Method.
• A good understanding of the Scientific Method
  will benefit you in situations beyond this class,
  so the effort is worthwhile.

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Math Review

• Powers of 10 and a sense of scale
• http//micro.magnet.fsu.edu/primer/java/scienceopt
  icsu/powersof10/
• http//www.wordwizz.com/pwrsof10.htm
• What is a googol?

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A googol is10,000,000,000,000,000,000,000,000,0
00,000,000,000,000,000,000,000,000,000,000,000,000
,000,000,000,000,000,000,000,000,000,000,000,000
(i.e. a 1 followed by 100 zeros)
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Scientific Notation

• In Astronomy, and elsewhere, large numbers are
  often needed.
• A more compact notation is needed, usually called
  Scientific Notation. It is based on powers of 10.

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Powers of 10

• 102 10 x 10 100
• 103 10 x 10 x 10 1000
• 104 10 x 10 x 10 x 10 10,000
• etc

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Powers of 10

• 102 10 x 10 100
• 103 10 x 10 x 10 1000
• 104 10 x 10 x 10 x 10 10,000
• etc
• 100 102
• 1000 103
• 10,000 104

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10,000,000,000,000,000,000,000,000,000,000,000,000
,000,000,000,000,000,000,000,000,000,000,000,000
,000,000,000,000,000,000,000,000,000 10100a
googol 10100
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To write out a number given as a power of 10, the
number of zeros is the given by the
exponent.Example 104 10,000
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To write out a long number (consisting of a 1
followed by zeros) as a power of 10, the
exponent is the number of zeros.Example 100,000
105
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Some Rules for Powers of 10

• To multiply two different powers of 10, add the
  exponents
• 102 x 103 1023 105
• 103 x 103 106
• To divide two different powers of 10, subtract
  the exponents
• 104 102 104-2 102
• 105 103 105-3 102

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105 100,000104 10,000103 1000102
100101 10100 ?
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105 100,000104 10,000103 1000102
100101 10100 1
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105 100,000104 10,000103 1000102
100101 10100 110-1 ?
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105 100,000104 10,000103 1000102
100101 10100 110-1 1/10 0.1
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105 100,000104 10,000103 1000102
100101 10100 110-1 1/10 0.110-2 ?
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105 100,000104 10,000103 1000102
100101 10100 110-1 1/10 0.110-2
1/100 0.01
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What about other numbers, like 6,000,000?
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6,000,000 6 x 1,000,000
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6,000,000 6 x 1,000,000 6 x
106
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6,000,000 6 x 1,000,000 6 x
1061,200,000 1.2 x 1,000,000
1.2 x 106
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How do we say it?
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How do we say it?

• 103 1,000 one thousand

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How do we say it?

• 103 1,000 one thousand
• 106 1,000,000 one million

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How do we say it?

• 103 1,000 one thousand
• 106 1,000,000 one million
• 109 1,000,000,000 one billion

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How do we say it?

• 103 1,000 one thousand
• 106 1,000,000 one million
• 109 1,000,000,000 one billion
• 1012 1,000,000,000,000 one trillion

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How do we say it?

• 103 1,000 one thousand
• 106 1,000,000 one million
• 109 1,000,000,000 one billion
• 1012 1,000,000,000,000 one trillion
• 1015 1,000,000,000,000,000 one quadrillion

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How do we say it?

• 103 1,000 one thousand
• 106 1,000,000 one million
• 109 1,000,000,000 one billion
• 1012 1,000,000,000,000 one trillion
• 1015 1,000,000,000,000,000 one quadrillion
• Many numbers in Astronomy have no common names,
  and are written in scientific notation.

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How do we imagine it?
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How do we imagine it?

• Example what is my age, in seconds?

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How do we imagine it?

• Example what is my age, in seconds?
• (a) about 1 million seconds

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How do we imagine it?

• Example what is my age, in seconds?
• about 1 million seconds
• about 1 billion seconds

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How do we imagine it?

• Example what is my age, in seconds?
• about 1 million seconds
• about 1 billion seconds
• about 1 trillion seconds

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How do we imagine it?

• Example what is my age, in seconds?
• about 1 million seconds
• about 1 billion seconds
• about 1 trillion seconds
• about 1 quadrillion seconds

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How do we imagine it?

• Example what is my age, in seconds?
• about 1 million seconds
• about 1 billion seconds
• about 1 trillion seconds
• about 1 quadrillion seconds
• Hint I am 42.5 years old.

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Well, there are60 seconds in one minute,60
minutes in one hour,24 hours in one day,and
365.25 days in one year.
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Well, there are60 seconds in one minute,60
minutes in one hour,24 hours in one day,and
365.25 days in one year.So,age 42.5 x 60 x 60
x 24 x 365.25 1.341 x 109 seconds
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• Example what is my age, in seconds?
• about 1 million seconds
• about 1 billion seconds
• about 1 trillion seconds
• about 1 quadrillion seconds
• Hint I am 42.5 years old.

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• Example what is my age, in seconds?
• about 1 million seconds
• about 1 billion seconds
• about 1 trillion seconds
• about 1 quadrillion seconds
• Hint I am 42.5 years old.
• 1 billion sec 31 yr 251 d 7 hr 46 min

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Which makes more sense?
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Which makes more sense?I am 1.3 billion
seconds old.
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Which makes more sense?I am 1.3 billion
seconds old.I am 42 years old.
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Which makes more sense?I am 1.3 billion
seconds old.I am 42 years old.My neighbor
Francis was 3.13x109 seconds old.
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Which makes more sense?I am 1.3 billion
seconds old.I am 42 years old.My neighbor
Francis was 3.13x109 seconds old.Francis was
99 years old.
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Where possible, scale things to sensible units
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Where possible, scale things to sensible
unitsExample This black hole has a mass 7
times larger than the Suns mass.
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Where possible, scale things to sensible
unitsExample This black hole has a mass 7
times larger than the Suns mass.This black
hole has a mass of 1.39x1034 grams.
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Next The Scientific Method