Environmental Science Physics Astronomy

							Environmental Science / Physics :
         Astronomy
                WARNING!
• “I thought this was going to be about
  astronomy. There was all this chemistry and
  physics!”
  – CCQ Comment
  Astronomy is Chemistry and Physics
• That’s why the course is cross-listed with
  Physics
• Physics is how we know what the stars are,
  and how they work
• Chemistry is about what everything –
  including you – is made of
• I will try to keep the pain manageable
• Cognitive dissonance will not hurt you, and it
  goes away
A Few Things You Really Need to
          Know First
        College is not High School
•   Less time in the classroom
•   Much more independent study needed
•   Less homework
•   More complex and labor intensive
•   Fewer quizzes
•   You have to monitor your progress
•   May look deceptively easy
        Astronomy Final Fall 2008
Score               Number of Students
90+                 3
80-89               10
70-79               20
60-69               19
59-                 30
What Do You Need to Build a
         House?
Materials – Plans - Methods
What Do You Need to Learn in
         College?
  • Facts (Materials)
  • Relationships (Plans)
  • Processes (Methods)
             Example: The Sun
• Facts:
  – Size, Mass, Distance, Layers, Composition
• Relationships:
  – Holds solar system together by gravity
  – Supplies energy to planets
• Processes:
  – Gets energy by nuclear fusion
  – How planets absorb and retain heat
  – How gravity and inertia result in orbits
  The Two Most Amazing Ideas in
            Science

• The Sun is a Star
• We Are Made of Star-Stuff
       About Learning Science
• It may be different than you expect
• Two questions you may not think to ask
  – How do we know?
  – What good is it?
• You have a lot of assimilated information
  about non-scientific subjects
• Much of what people think they know about
  science is wrong
               Essential Points
1.   Everything in Science is Metric
2.   Scientific Notation
3.   Temperature
4.   About Light
5.   Measuring size in the sky
6.   Astronomical Distances
7.   How Telescopes Work
Some symbols to know


 • > Greater Than
 • < Less than
 • ~ Approximately
    In Science, Everything is Metric
• 1 centimeter = 0.4 inches
• 1 meter = 39.4 inches = 1 yard +
• 1 kilometer = 5/8 mile: 5 mi = 8 km
• 1 kilogram = 2.2 pounds
• Unit of time = second
• All other quantities (energy, etc.) are
  combinations of kilograms, meters, and seconds
• U.S. is the only major country not using the
  metric system
• Your foreign customers use metric. Deal with it
                 1. Everything in Science is Metric
        Important Metric Prefixes
•   Nano = 1/1,000,000,000
•   Micro = 1/1,000,000
•   Milli = 1/1000
•   Centi = 1/100
•   Kilo = 1000
•   Mega = 1,000,000
•   Giga = 1,000,000,000
•   Tera = 1,000,000,000,000
                 1. Everything in Science is Metric
         Astronomical Numbers
• It’s no accident that large numbers are called
  “Astronomical.”
• Mass of Sun:
  2,000,000,000,000,000,000,000,000,000,000,000 kg
• Distance to Alpha Centauri:
  43,000,000,000,000 km
• Number of Stars in Milky Way Galaxy:
  400,000,000,000
• Age of Universe: 13,000,000,000 years

                    2. Scientific Notation
            Scientific Notation
• 1,2,3,4,5,6,7,8,9
• 10,20,30,40,50,60,70,80,90,99
• 100, 200,300 …… 900,999
• 10 x 10 x 10 = 103
• The small digit (the exponent) is the number of
  times we multiply 10 to get the number
• 500,000 = 5 x 100,000 = 5 x 105
• Exponent = Number of Digits – 1
• If it’s a round number, Exponent = Number of
  Zeros
                    2. Scientific Notation
         Astronomical Numbers
In Scientific Notation:
• Mass of Sun: 2 x 1030 kg
• Distance to Alpha Centauri:
   4.3 x 1010 km
• Number of Stars in Milky Way Galaxy:
   4 x 1011
• Age of Universe: 1.3 x 1010 years




                    2. Scientific Notation
    Working With Scientific Notation
• 100,000 x 10,000 = 1,000,000,000
• 105 x 104 = 109
• To Multiply, Add Exponents
• 100,000,000/1000 = 100,000
• 108 / 103 = 105
• To Multiply, Subtract Bottom Exponent from
  Top
• No Easy Rules for Addition and Subtraction

                  2. Scientific Notation
             Tiny Numbers
• 100 / 10,000 = 1/100 = .01
• 102 / 104 = 10-2
• Negative Exponents mean numbers less than
  1
• .01 = 1/100, so 10-2 = 1/102
• Exponent = - 1 x (Leading Zeros + 1)
• .00362 = 3.62 x 10-3

                 2. Scientific Notation
And Now The Most Confusing Part
•   10 = 101
•   .1 = 10-1
•   10 x .1 = 1
•   101 x 10-1 = 100 = 1
•   Therefore Anything to the Zero Power = 1
•   “But How Can it be 1 When It’s 0??!!”



                    2. Scientific Notation
        Zero Power Is Just A Label
•   1000 = 10 x 10 x 10 = 103
•   100 = 10 x 10 = 102
•   10 = 10 = 101
•   1 = 10 no times = 100
•   .1 = 1/10 = 10-1
•   .01 = 1/(10 x 10) = 10-2
•   .001 = 1/(10 x 10 x 10) = 10-3

                      2. Scientific Notation
                  Temperature
• Scientists use the Celsius (Centigrade) scale
  •   32 F = 0 C (Water freezes)
  •   212 F = 100 C (Water boils)
  •   -40 F = -40C (Scales Equal)
  •   One C degree = 1.8 F degrees
  •   All atomic motion stops at -273 C (Absolute Zero)
• Kelvin Scale starts at Absolute Zero
  • K = C + 273
  • For Stellar temperatures, makes little difference
                        3. Temperature
                  About Light
• Light is made up of waves
  – Oscillating electrical and magnetic fields
  – Collectively called Electromagnetic Radiation
  – Speed = 298,000 km/sec (symbol: c)
  – Wavelength = distance between waves (λ)
  – Frequency = number of waves per second
  – One hertz = 1 wave per second
  – Wavelength x Frequency = c
  – Generally, radiation interacts with objects bigger
    than its wavelength
                       4. About Light
       Electromagnetic Spectrum
• Radio
   – AM = 1000 kHz: λ = 300 meters
   – FM = 100 MHz: λ = 3 meters
• Microwaves (a few cm)
• Infrared: λ = 1 cm – 7 x 10-7 m (700 nm)
• Visible light: 700 - 400 nm
• Ultraviolet: 400 – 1 nm
• X Rays: 1 - .01 nm (Atom = 0.1 nm)
• Gamma Rays: <.01 nm
                        4. About Light
                 Visible Light
•   Red = 700 nm (4 x 1014 Hz)
•   Orange
•   Yellow
•   Green = 550 nm
•   Blue
•   Indigo (we need a vowel for the mnemonic)
•   Violet = 400 nm (7 x 1014 Hz)
•   Roy G. Biv
                     4. About Light
       Visible Light and the Eye
• Infrared absorbed by molecular vibrations
• Ultraviolet absorbed by electrons around
  atoms
• Atmosphere is transparent to visible light
• That’s why we see in this range
• Maximum solar output is green light
• Maximum eye sensitivity is green light

                    4. About Light
Measuring in the Sky




    5. Measuring size in the sky
Size in the Sky




  5. Measuring size in the sky
                      Angles
• 1 degree = 60 minutes (60’)
• 1 minute = 60 seconds (60”)
• Size and Distance
  – A one degree object is 60 times its diameter away
    (57, to be exact). 1⁰ = a quarter 5 feet away
  – A one minute object is 3400 times its diameter
    away . 1’ = a quarter a football field away
  – A one second object is 200,000 times its diameter
    away 1” = a quarter 3 miles away
                  5. Measuring size in the sky
       Distances in Astronomy
• The Earth is 12,500 km in diameter
• The Moon is 400,000 km away
• The Sun is 150,000,000 km away
• Pluto is 6,000,000,000 km from the Sun
• Alpha Centauri is 43,000,000,000,000 km
  away
• The galaxy is 1,000,000,000,000,000,000 km in
  diameter
                 6. Astronomical Distances
     Astronomical Distance Units
• The Astronomical Unit is used for planetary
  distances
  o 150,000,000 km = Earth-Sun distance
  o Pluto is 40 A.U. from the Sun
• Light year is used for stellar distances
  o Distance light travels in a year = 1013 km
  o Alpha Centauri is 4.3 light years away
  o Galaxy is 100,000 light years across
  o Parsec (3.26 light years) is also used
                    6. Astronomical Distances
              Light Travel Times
•   Moon: 1.3 seconds
•   Sun: 8 minutes
•   Pluto: 6 hours
•   Nearest Star: 4.3 years
•   Center of Galaxy: 30,000 years
•   Andromeda Galaxy: 2.2 million years
•   Edge of visible universe: 13 billion years

                    6. Astronomical Distances
              Telescopes




A. Refractor
B. Reflector
C. Compound (many designs)
               7. How Telescopes Work
What Most People Think a
    Telescope is For




       7. How Telescopes Work
What Astronomers Think a
    Telescope is For




        7. How Telescopes Work
              Surprising Facts
• Astronomers rarely look through large
  telescopes visually
• Virtually all large telescopes are used solely
  for photography
• Telescope time is a fiercely competitive
  resource
• Modern large telescopes are $100 M +, built
  by consortiums of universities and
  governments
                   7. How Telescopes Work
Telescope Mounts




    7. How Telescopes Work
All Telescopes Are Limited By The
       Wave Nature of Light




            7. How Telescopes Work
      Bottom Line on Telescopes
• Magnification is vastly overrated
  – Magnification magnifies defects in the optics and
    unsteadiness in the mounting
• Images are inherently fuzzy because of the
  nature of light itself
  – This sets an absolute limit on magnification (rule
    of thumb: 20 x diameter in cm)
  – If we want detailed images of the planets, we have
    to go out there physically and get them

                   7. How Telescopes Work
          How to Use a Telescope
• The first planet you should observe is Earth
   – Learn to sight and focus on familiar objects – in the
     daytime – before trying to use the telescope at night
   – Learn how to use all the accessories
• Things will not look like published pictures
   – Objects will be small
   – Objects will be faint
   – Many things cannot be seen by eye even with large
     telescopes
   – Objects will have very subtle colors
   – Objects will have low contrast
• Never look at the Sun without eye protection
                        7. How Telescopes Work
Saturn From Spacecraft
Saturn in Small Telescope
Hubble View of Orion Nebula
Orion Nebula in Small Telescope