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1. Astronomy and the Universe

1. Astronomy and the Universe. The scientific method Birth, life & death of the Solar System Birth, life & death of the stars Birth, life & death of the Universe Angular measure in astronomy Basics of powers-of-ten notation Astronomical measures of distance An adventure of the human mind.

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1. Astronomy and the Universe

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  1. 1. Astronomy and the Universe • The scientific method • Birth, life & death of the Solar System • Birth, life & death of the stars • Birth, life & death of the Universe • Angular measure in astronomy • Basics of powers-of-ten notation • Astronomical measures of distance • An adventure of the human mind

  2. The Laws of Physics • A cause-and-effect Universe • Everything in the Universe follows clear patterns • There are physical “natural laws” • Uniform in both space & time • The common laws of physics in astronomy • Gravity • Pressure • Electromagnetic radiation (EMR) • Spectroscopy • The Doppler effect • E = m .c2 • Strong & weak nuclear forces

  3. The Scientific Method • Definition • Systematically ask & answer questions • Important aspects • Observation / experiment • Replication • Skepticism • One common strategy • Design the experimental procedure • Design the experimental apparatus • Execute the experimental procedure • Analyze the experimental results

  4. Hypotheses, Theories & Laws • Hypotheses 1,000’s • Educated guesses that will be modified many times • Hypothesis testing loop • Check your predictions against experimental results • Theories 100’s • Well-tested & generally-accepted hypotheses • Einstein’s Theory of Relativity • “Hypotheses” are usually misnamed “theories” • When you hear “theory,” think “hypothesis” instead • Laws 10’s • Proven & completely-accepted theories • Newton’s Law of Universal Gravitation

  5. Scientific Evidence, Support, Proof • Evidence • Single line of evidence • Often relatively weak affirmation of an hypothesis • Multiple lines of evidence • Often relatively strong affirmation of an hypothesis • Support • The evidence equivocally affirms the hypothesis • This is very common in science • Proof • The evidence unequivocally affirms the hypothesis • This is very unusual in science • ± 5.0 sigma statistical confidence

  6. Solar System’s Birth, Life & Death • Earth: Our home planet • Geocentric model of planetary motion • Philosophical& theological bases • Heliocentric model of planetary motion • Observational & theoretical bases • Our planetary system • Terrestrial & Jovian planets • Natural & artificial satellites • Asteroids & comets • Rocky & icy • Amazing diversity in processes & results • Range from “solid objects” to “rubble piles”

  7. Diameters are to scale Distances are not to scale Relative Sizes of the Sun & Planets

  8. The Birth, Life & Death of Stars • Stellar birth • Some compression mechanism begins a collapse • Gravity exceeds pressure • Stellar life • Produce 1 helium nucleus from 4 hydrogen nuclei • Gravity & pressure in dynamic equilibrium • Length of lifetime depends completely on mass • Stellar death • Gravity & pressure again compete for dominance • Death processes & products depend only on mass • White dwarf Degenerate electron pressure • Neutron star Degenerate neutron pressure • Black hole No kind of pressure

  9. Sunspots: 13 January 2013

  10. The Birth & Life of the Universe • Birth of the Universe • Evidence for a rapidly expanding Universe • Origins of the Universe in a Big Bang • Origin / Creation of all matter • Origin / Creation of all energy • Origin / Creation of space-time • Life of the Universe • Formation of atoms • Initial conditions were so hot that everything was plasma • Formation of stars • Gravitational collapse on a small scale • Formation of galaxies • Gravitational collapse on a large scale • Destiny of the Universe • Accelerating expansion => Universe torn apart

  11. The Crab Nebula A Nebula Inside Our Milky Way

  12. The galaxy M100 A Galaxy Outside Our Milky Way

  13. Angular Measure in Astronomy • Possible origins of 360° in a circle • ~ 365.25 days in a year • 360 = 23. 32. 5 • One degree of Sun motion equals about one day • Relative to the fixed background of stars • Only ~1.5% difference from “exact” time over one year • Variations on a theme • Degrees, minutes & seconds of arc 17° 15’ 00” • Decimal degrees of arc 17.25° • Some practical implications for astronomy • 24 hours = 360° of sky rotation • 1,440 minutes = 360° of sky rotation • 1 hour = 15° of sky rotation • 4 minutes = 1° of sky rotation

  14. Angular Measure & the Sky

  15. Angular Size In Astronomy • Angular distance • Distance measured in degrees, not meters or feet • Usually measured between two points • The position of two stars • The center of two planets • Relatively independent of distance • Points or objects are too far away to make a difference • Angular diameter • Diameter measured in degrees, not meters or feet • Usually measured between edges of large objects • The left & right edges of the Moon • The left & right ends of a comet’s tail • Extremely dependent on distance • The farther the object, the smaller its angular diameter

  16. Angular Distance in the Big Dipper

  17. Angular Measure & Human Hands

  18. Powers-of-Ten Notation • Representing very small & very large numbers • Counting a large number of zeros can be difficult • 0.0000000000000000000000000000000006625Js • 300 000 000 m / s • The pattern • A number; a power of 10; unit(s) • 6.625 . 10–34 J s • 3.0 . 10 8 m / s • The rules Scientific notation • 1.000 < Number < 10.000 • The exponent may be either positive or negative • Positive: The powers of ten are in the numerator • Negative: The powers of ten are in the denominator • Appropriate units for the quantity represented

  19. Examples of Powers of Ten Sizes Are Shown In Meters

  20. Astronomical Measures of Distance • Small distances within solar systems • Astronomical units AU Quite close • 1.00 AU = 9.296 . 107 mi • 1.00 AU = 1.496 . 108 km • Medium distances within galaxies • Parsecs pc Rather close • The distance of an object with a parallax of 1.0 arcsecond • 1.00 pc = 3.09 . 1013 km • 1.00 pc = 3.26 ly • Large distances between galaxies • Light years ly Quite far • The distance light travels in one year • 1.00 ly = 6.324 . 10 4 AU • 1.00 ly = 9.46 . 1012 km

  21. Parallax & the Parsec (pc)

  22. An Adventure of the Human Mind • The scientific method • Overwhelmingly observational • Occasionally experimental • Discovery • Materials & processes related to Earth • Extrasolar planets • Materials & processes related to stars • The range of stars • Materials & processes related to galaxies • The range of galaxies • Pursuit of knowledge for its own sake • New & improved tools • New & improved techniques

  23. Scientific method Hypothesis Well-educated guess Theory Very often misused Law Planetary motion Geocentric model Heliocentric model Angular measure Degrees, minutes & seconds Decimal degrees Angular distance & angular diameter Powers-of-ten notation Astronomical measures of distance Astronomical unit AU Within solar systems Parsecs pc Relatively close to our Solar System Light years ly Very far from our Solar System Important Concepts

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