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Earth Sciences
Earth Sciences 2240F/G
Ron Podesta

Unit 1: Study Guide Chapter 1 1. The Scientific Method a. Learn how hypothesis- is an educated guess based upon observation – sometimes, only one observation. theory- A scientific theory summarizes a hypothesis (or group of hypotheses) that is supported by repeated testing and observation. (why something happens) law- A law explains a body of observations. At the time it is made, no exceptions will have been found to that law. Scientific laws explain things, but they do not describe them. (how something happens) law- the apple falls, theory- why the apple fell b. Review the scientific method and understand how scientists proceed from observation through hypothesis to theory (and maybe law) by continuous testing and revision 2. The Big Bang a. Learn the definition (section 3.1) - The Big Bang theory is an effort to explain exactly what happened at the very beginning of the universe b. Learn what observations and hypothesis support the theory – 3 Pillars of Proof i. Recession of the galaxies (be sure you thoroughly understand the cosmological redshift) - V=Ho x d where v is the speed expressed in kilometres per second; d is the distance of the star/galaxy away from Earth in parsecs (1 parsec = 3.26 times the distance light travels in one year), and Ho is the Hubble constant. That makes Ho the speed of expansion of the universe; Hubble assumed it was a constant (that has turned out to be somewhat wrong). If light source is moving toward observer, light wavelength appears to shorten= Blue Shift. If light source moving away from the observer, wavelength appears to lengthen= Red Shift. Amount of redshift used as measure of a star or galaxy’s distance form earth. ii. Significance of cosmic microwave background radiation - CMB represents the very last remnants of the light/heat energy of the Big Bang’s initial expansion. - The hot light photons, produced in the early period, have since lost energy and - dropped from the visible light energy range into the microwave energy range – and that - constitutes the cosmic microwave background (CMB) that we can still see today (Fig. 1.4). - Scientists figure that CMB can be seen from anywhere in the universe because it comes from all - directions, and with nearly the same intensity. iii. The abundance of light elements - hydrogen (75%), helium (25%) and lithium (trace) - The observed abundance of all the different atoms of those elements can be explained only if they originated from one single ratio of the first subatomic particles of matter that can be formed from a super- hot environment. The only way to get that one critical ratio is through a unique event like a Big Bang. Neat! 3. The Shape of the Universe a. Why is shape significant to the future of the universe- determines how the universe will end. - positive curvature= sphere shape. Like balloon. Closed, finite in size, but without a boundary. Fly in one direction, end up where you started - negative curvature= saddle-shaped, infinite and unbounded, parallel lines diverge, expansion rate never approaching zero. The ball you tossed keeps going up - flat- infinite in special extent, and have no boundaries, parallel lines are always parallel, expand forever, but expansion rate approaches zero, ball goes and goes but eventually appears to hang there, the movement outward is so slow. b. Why do we think the real shape is nearly flat - it repels matter. We call this dark energy. This is the force that seems to control the expansion of space; when it exactly counterbalances the kinetic energy of the Big Bang expansion, we are at the ‘critical’ value of 1 for a density parameter (i.e. a flat Universe). Right now, with an expansion rate apparently increasing, we seem to be accepting that the universe is almost perfectly flat – but has just the slightest negative curvature. For the purpose of this course, we will accept ‘flat’. 4. Age of the Universe a. The best evidence comes from cosmic microwave radiation - age of universe: 13.72 ± 0.12 billion years Chapter 2 1. Start by learning the definition of light year- A light-year is the distance that light travels in one year 2. Learn the very basic steps taken in the various methods to measure distance in space a. Use of trigonometric parallax- relies on an object appearing to be at a different place relative to the background, depending on your viewpoint. b. Use of the Hertzsprung-Russell diagram (be able to sketch the diagram, know what the horizontal and vertical axes are, where to find the Main Sequence, giants and dwarfs) - Apparent brightness (which you see and measure) = Intrinsic brightness (graph) / (distance)squared. This method of determining distance from colour is called main-sequence fitting and is good for 150,000 light years away. c. Use of Cepheid stars -e makes use of ‘marker stars’ that have a special property: they have a pulsing brightness that peaks with absolute regularity (its ‘period’), which is completely related to the star’s brightness. We call these Cepheids. We find a Cepheid and carefully measure the time between one brightness peak and the next (that is, we determine its period) – and that gives us the intrinsic brightness value (from a calibrated chart). From there on, we just use the same procedure as for the first technique. d. Use of Hubble’s Law - , according to the Hubble equation, you can tell how far away a galaxy (or a star) is by dividing its velocity (obtained from its degree of redshift) by the rate of expansion. That is what we use for really distant objects. 3. Scale of Space a. In particular, learn the names of the three large galaxies in the Local Group - the Andromeda Galaxy (by far the largest - Milky Way Galaxy (home to our solar system) - Triangulum Galaxy (the smallest of the ‘big three’) b. Learn that the solar system developed on the Orion Arm of the Milky Way Galaxy - Sitting out a bit more than 2/3 from the core is our solar system, included as one of the many millions of star-planet systems on the Orion Arm of the Milky Way. Chapter 3 1. Definitions (sorry – but there is no alternative to memorization sometimes) a. Element - a substance that cannot be broken down to anything simpler by any chemical means. b. Atom- a particle of matter that has the unique properties of an element (i.e., atoms are the essential particles of elements). i. Nucleus with neutrons and protons - All atoms consist of a central nucleus that contains one or more particles called protons (positively charged) and may or may not contain particles called neutrons (neutral, or no charge); the nucleus as a whole, is thus positively charged ii. Electrons - The nucleus is surrounded by one or more electrons, which are negatively charged c. Ions - an atom with either a negative charge (i.e., it has extra electrons) or an atom with a positive charge (i.e. it has a deficiency of electrons) d. Isotopes- all atoms of a particular element have the same number of protons (by definition) but may contain different numbers of neutrons within their nuclei. e. Radioactivity- the spontaneous breakdown of unstable atoms (i.e., unstable isotopes) of an element, with the production of energy and other particles. f. Supernovae- the explosive death of a massive star 2. The Periodic Table of the Elements (no you do not have to memorize this) a. Understand the order of listed elements is from lightest to heaviest : RIGHT and DOWN b. H, He and Li are the three lightest (in that order) 3. Production of the Elements a. Only H, He and some Li were made from the energy of the Big Bang b. Up to and including Fe (iron- 26) are made by fusion within the cores of massive stars c. The elements after Fe (the heaviest elements) require the enormous energy of supernovae - we were made from the stuff of supernovae 4. The Nebular Hypothesis a. This is a long section but you will have to understand the general process in order to have any understanding of star-planet systems. Pay particular attention to Figures 3.4 and 3.5. - NEBULAR HYPOTHESIS: - 1. there is a slowly rotating cloud of gaseous molecules called a nebula. This nebula begins to collapse - 2. A Protostar forms out of gas, and planet elements or planetismals form out of dust, as the cloud continues to condense and flatten into a pancake shape - 3. The protostar ‘turns on’ and becomes a star. When this happens, dust close to the star is vaporized, and gas close to the star is blown away. - 4. The nebula clears away and only the star, and planets which formed out of the planet-elements are left. - ACCRETION MODEL: - 1.Orbiting dust grains accrete into planetesimals through non- gravitational forces - 2. Planetesimals grow, moving in near-coplanar orbits, to form ‘planetary embryos’. - 3. Gas-giant planets accrete gas envelopes before disk gas disappears - 4. Gas-giant planets scatter or accrete remaining planetesimals and embryos. - The nebular hypothesis suggests that the solar system formed over a relatively brief span of time and all as a unit (Sun, planets, and so on), from a nebula, or cloud, of interstellar gas (the Latin word ‘nebula’ means ‘cloud’) (Fig. 3.4). - Dark formless nebula floated within the graceful Orion Arm of the Milky Way Galaxy - Some disperse over time, or they are transformed like ours. - Theres a pronounced shrinkage and flattening of the original cloud - Happens due to cumulative gravitational effects, self-gravity of the cloud - Low density to begin, now extremely high density. - Collapses under self gravity - Eventually gets so hot, heat cant escape, get fusion reaction and a star is born - Particles become so densely packed that heat can no longer escape. Unit 2: Study Guide Introduction Pioneers and their Models Definitions • Geocentric- Earth is at the center of the solar system • Heliocentric- Sun is at the center of the solar system For each of the pioneers, learn what was most significant • Aristarchus- Appreciating the awkwardness of a solar system with Earth at the center, he experimented with placing Sun at the center instead. Has many scrolls in the great library of Alexandria. Never attempted to promote his model, but was on right track. • Ptolemy- he obediently put Earth back at the center of things and placed all the other objects he could see on various moving spheres. Catholic chuch’s bitch. Sucked up. His dum ass model of the solar system lasted 1400 years. • Copernicus- , had Earth rotate about Sun, and had Earth revolve on an axis once per day. His dickhead buddies inserted a preface that indicated that the contents were handy for calculating planetary position but should not be taken as anything representing reality • Kepler- applied math to astronomy. Kepler realized something magnetic must be the reason for orbit. Developed 3 laws that define the geometry of planets moving about stars. He also developed these 2 terms which must be learned: • Perihelion: The point of nearest approach of a planet to Sun. • Aphelion: The point of greatest separation. • Galileo- He (not Tycho) was the first to observe the planets through a telescope (hard to believe that most of the work we have talked about was based upon ‘naked-eye’ observations), and what he saw convinced him that Copernicus was right. Improved the telescope by polishing lenses himself. He improved it up to 33 fold and sold it to the venetian senate for military purposes. Declared himself a Copernican. Chapter 4: Sun • The photosphere (visible outer layer of a star) is the layer of Sun we see; the chromosphere (layer of gases that surrounds the photosphere) and the corona (the chromosphere merges into the outermost region of Sun’s atmosphere) are further out, but we cannot see them. • SUN Contains about 99.8 % of the solar system mass • Distance from Sun to Earth is defined as one astronomical unit (1 AU). • Age is over 4.6 billion years • Other properties: • Rotates, • is oblate- (an equatorial diameter greater than that between the poles of rotation) • is 98 % hydrogen + helium, • consumes (fuses) hydrogen atoms to make energy plus other elements (mostly helium) • has huge magnetic field and reverses its magnetic poles every 11 years • issues constant stream of charged particles (solar wind) • learn the life-death cycle (and times) from current state to a red giant and then a dwarf - Sun is about half way through its life cycle right now at about 4.6 billion years. - At 10 billion years it will expand into a red giant. When the last of the inner hydrogen fuel is consumed - Turns to a black dwarf at 13 billion years. • Be sure you can roughly sketch the H-R diagram • Understand how spectroscopy is used to identify chemical composition from light - wh
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