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Earth Sciences
Earth Sciences 1086F/G
Bob Larose

Introduction: The Solar System 1. Definitions a. Geocentric Model: Earth is at the center of the solar system b. Heliocentric Model: Sun is at the center of the solar system 2. Pioneers & their Models a. Pythagoras/Plato i. He pictured Earth as a stationary object in space, surrounded by a sphere which contained everything else (including Sun) b. Aristarchus: spent a lot of time at The Great Library of Alexandria (in Egypt) i. He was the first to experiment with placing Sun at the centre of Earth ii. He never attempted to promote his model and moved onto other interests c. Ptolemy i. Was extremely religious and „sucked up‟ to every authority in the Catholic Church at the time ii. He obediently put Earth back at the center of things and placed all the other objects he could see on various moving spheres iii. This was a complete throw-back to the Pythagoras/Plato models, with a few variations iv. This model of the solar system lasted form 1,400 years d. Copernicus i. He also put Sun (which he called Sol) at the center of the system, had Earth rotate about Sun, and had Earth revolve on an axis once per day ii. However, he was not able to publish his work because of the Church iii. His friends convinced him to let them write a book iv. In the preface of the book, they wrote that the contents “should not be taken as anything representing reality” thus permitting dissemination of the hypothesis by the Church e. Tycho Brahe i. He did not believe Copernicus ii. He insisted that Sun moves around Earth, dragging the rest of the planets with it iii. He built the world‟s first state-of-the-art observatory f. Kepler i. Thought that the planets were not siting upon a while series of celestial spheres but that they had somehow been pushed into their orbits by Sun ii. He figured that force was strongest near Sun and weakened with distance outward; he though this force had to be magnetic but he had no proof iii. Kepler‟s First Law defines the construction of an ellipse because he realized that planets did not move in perfectly circular paths iv. Earth-Sun distance is constantly changing as the planet goes around its orbit v. Perihelion: the point of nearest approach of a planet to Sun vi. Aphelion: the point of greatest separation g. Galileo i. Did not invent the telescope, but he greatly improved upon the existing version by modifying the lenses ii. He believed in the theories of Copernicus iii. However, when he presented this belief only to have himself declined by the Church iv. After gathering up the courage to present to the church (now that one of his friends is the new TA) v. Officials of the Inquisition immediately charged him again with the new Pope‟s permission vi. Church-held belief that everything (including Sun) rotated about Earth, Galileo was convinced that the plants rotated about Sun and the satellites of the planets rotation about them vii. It was in 1992, that the Roman Catholic Church finally absolved Galileo of his so-called crime Chapter 4: A Star Called Sun 1. The Anatomy of Sun a. The photosphere is the layer of Sun we see b. The chromosphere and the corona are further out, but we cannot see them c. Sun is the bunch of gas that becomes denser as you move rom space toward the solar core d. The photosphere (the visible outer layer of a star) would then represent the depth at which we can see no deeper toward the core e. Surrounding the photosphere is a layer of gases called the chromosphere i. Chromosphere is the irregular layer of gases that extends up and away from photosphere ii. This is a zone transparent to most visible radiation (we cannot see it) f. The chromosphere merges into the outermost region of Sun‟s atmosphere, the corona g. Usually, we cannot see the corona because of the brightness of the photosphere except during a total solar eclipse 2. Basic Sun Physical Facts a. The Sun‟s diameter is ~ 1.4 million km b. Mass is ~330,000 times that of Earth i. Sun contains 99.8% of the solar system‟s mass c. Sun‟s age is just over 4.6 billion year d. Sun rotates i. Because Sun‟s body is not rigid, as it rotates mass is transferred to its middle, giving the whole body a slightly oblate shape  Oblate: an equatorial diameter greater than that between the poles of rotation e. Its temperature is measure in Kelvins (K) 3. Distance Measurements Inside the Solar System a. The distance between Earth and Sun is about 150 million kilometres b. One astronomical unit (1AU) = the mean average distance between Sun and Earth i. 1AU is the distance from Sun to Earth 4. Chemical Composition a. NASA‟s Genesis was a mission to collect samples from Sun i. However, the mission was unsuccessful at the last step b. Scientists have been able to determine the composition from indirect samples using spectroscopy i. Spectroscopy: the measurement and analysis of energy of spectra to determine the composition of matter ii. A spectrometer or a spectrograph, which records the spectrum of light emitted (or absorbed) by a given material, where the light can be used to determine the chemical composition of a substance because particular elements emit unique and characteristic wavelengths of energy iii. A spectroscope splits up light. A beam of sunlight is made up of a mixture of colours, and a glass prism will bend or refract the various colours unequally; short wavelengths (blue and violet) are the most refracted, long wavelengths (orange and red) are the least refracted c. When a solar spectrum was obtained, it contained the order and colours of the rainbow, however, there were dark lines that crossed the rainbow band i. It was discovered that the dark lines were characteristic of particular elements (so, it you analyze the position and intensity of the lines you can identify the composition of the matter generating the spectrum – in this case, Sun) d. The most plentiful element in Sun is hydrogen (H), which accounts for 71% of the total mass i. Sun consumes (fuses) hydrogen atoms to make energy plus other elements (mostly helium) ii. The next most plentiful element is helium (He), with 27% e. Sun has essentially the same elements as found on/in Earth but the proportions differ i. The big difference between elements on Earth and in Sun is so hot that all the elements are in the gaseous state 5. Sun in Action a. Sun is never calm b. In the chromosphere there are prominences: arcs of gas that begin on the bright surface and soar to as much as 10,000 km into the corona c. Even more dramatic are the flares: short lived eruptions 6. Magnetic Fields a. Earth has a strong magnetic field, and it is produced by an interaction between an inner solid metal core inside a liquid metal layer b. Sun also has a huge magnetic field; we are not so sure of the “generator”, but it clearly has to do with the interaction of the unique properties of matter in the different layers inside Sun c. In both earth and Sun, we can express the magnetic fields as giant bar magnets: north at one end, south at the other, and a field surrounding them d. Both Earth and Sun are pretty dynamic systems – Sun more so than Earth – so the magnetic “generators” sometimes become “confused” and become unstable – and suddenly the poles of the magnet switch e. Sun reverses its magnetic poles every 11 years (the complete 22 year cycle is referred to as a “solar cycle”) f. The clearest manifestation of “switch-time” for Sun is development of a great number of sunspots i. Sunspot is a region of Sun‟s photosphere marked by lower than average temperature, thus appearing black g. If there are solar flares, there are corresponding magnetic storms that occur on Earth i. There is interference to complete breakdown of power grids and systems carrying telemetric signals ii. There are spectacular “northern lights” 7. The Solar Wind a. The solar wind is made up of charged particles sent out from Sun at all times and in all directions b. It is made up of a plasma i. Plasma is an ionized gas made up of a mixture of electrons and protons ii. Charged particles always react with a magnetic field c. Despite Sun‟s awesome gravity, these little particles escape because of their high kinetic energy d. The magnetic field volume around a body like Earth, (which generates a magnetic field) is called the magnetosphere e. The reaction essentially protects most of Earth‟s surface from devastating bombardment by the solar wind – but not the poles i. On their way to Earth‟s magnetic poles, the solar particles interact with the molecules of gas in the upper atmosphere; the result is emission of
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