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Environmental Science/Physics 141: Astronomy

Environmental Science/Physics 141: Astronomy. Steve Dutch LS 463 465-2246 dutchs@uwgb.edu www.uwgb.edu/dutchs. WARNING!. “I thought this was going to be about astronomy. There was all this chemistry and physics!” CCQ Comment. Astronomy is Chemistry and Physics.

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Environmental Science/Physics 141: Astronomy

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  1. Environmental Science/Physics 141: Astronomy Steve Dutch LS 463 465-2246 dutchs@uwgb.edu www.uwgb.edu/dutchs

  2. WARNING! • “I thought this was going to be about astronomy. There was all this chemistry and physics!” • CCQ Comment

  3. 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

  4. A Few Things You Really Need to Know First

  5. 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

  6. Astronomy Final Fall 2008

  7. What Do You Need to Build a House?

  8. Materials – Plans - Methods

  9. What Do You Need to Learn in College? Facts (Materials) Relationships (Plans) Processes (Methods)

  10. 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

  11. The Two Most Amazing Ideas in Science The Sun is a Star We Are Made of Star-Stuff

  12. 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

  13. Essential Points • Everything in Science is Metric • Scientific Notation • Temperature • About Light • Measuring size in the sky • Astronomical Distances • How Telescopes Work

  14. Some symbols to know > Greater Than < Less than ~ Approximately

  15. 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

  16. 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

  17. 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

  18. 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

  19. Astronomical Numbers In Scientific Notation: Mass of Sun: 2 x 1030 kg Distance to Alpha Centauri:4.3 x 1013 km Number of Stars in Milky Way Galaxy: 4 x 1011 Age of Universe: 1.3 x 1010 years 2. Scientific Notation

  20. 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 Divide, Subtract Bottom Exponent from Top No Easy Rules for Addition and Subtraction 2. Scientific Notation

  21. 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

  22. 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

  23. 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

  24. 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

  25. 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

  26. 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

  27. 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

  28. 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

  29. Measuring in the Sky 5. Measuring size in the sky

  30. Size in the Sky 5. Measuring size in the sky

  31. 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

  32. 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

  33. Astronomical Distance Units • The Astronomical Unit is used for planetary distances • 150,000,000 km = Earth-Sun distance • Pluto is 40 A.U. from the Sun • Light year is used for stellar distances • Distance light travels in a year = 1013 km • Alpha Centauri is 4.3 light years away • Galaxy is 100,000 light years across • Parsec (3.26 light years) is also used 6. Astronomical Distances

  34. 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

  35. Telescopes Refractor Reflector Compound (many designs) 7. How Telescopes Work

  36. What Most People Think a Telescope is For 7. How Telescopes Work

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

  38. 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

  39. Telescope Mounts 7. How Telescopes Work

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

  41. 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

  42. 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

  43. Saturn From Spacecraft

  44. Saturn in Small Telescope

  45. Hubble View of Orion Nebula

  46. Orion Nebula in Small Telescope

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