AST251 - Finals Notes

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Department
Astronomy & Astrophysics
Course
AST251H1
Professor
H.Pfeiffer
Semester
Winter

Description
AST251 Final Exam NotesContinuation of Midterm NotesLecture 712Midterm AnswersIf life is eventually found in the solar system it would most likely be in the form of microbesAstronomy has shown us that the fundamental laws of physics are the same everywhere in the universeThe Ptolemaic model has planets moving in small circles the centers of which move in a larger circle about the EarthStellar parallax is the apparent shift in position of nearby stars as the Earth moves around the SunWhat is the relationship between Newtons three laws and Keplers three lawsoNewtons laws are general and apply to any motion while Keplers laws apply only to planetary motion in the solar systemTwo comets have identical masses However one comet is four times farther from the sun than the other According to Newtons Universal Law of Gravitation the force of gravity exerted by the Sun on the more distant planet is onesixteenth 116 the size of the force exerted on the closer cometWhich of the following places the structures on our own part of the universe in order of increasing smallest to largest scaleoSolar System Milky Way Galaxy Local Group Local SuperclusterIf we were to detect a signal from an advanced civilization in 2013 which is located at a distance of 7 lightyears from the Sun in what year was the signal actually transmittedo2006A star that is more massive than the Sun will have a shorter lifetime because its central core is hotterWhich planet lies between the planets Saturn and NeptuneoUranusThe most abundant materials in the solar nebula were hydrogen andhelium gasesThe larger moons of the Jovian planets were probably formed from spinning disks of gas that surrounded the planetsAn isotope of the element Manganese Mn has an atomic number of 25 and a mass number of 55 Assuming the atom is neutralthis means it has 25 protons 25 electrons and 30 neutronsHow does the speed in a vacuum of a highfrequency electromagnetic wave compare with a lowfrequency electromagnetic waveoThe two waves have the same speed because the speed of light is constantThe main way astronomers determine the physical and chemical properties of an object in the distant universe is through spectroscopyWhich of the following processes is believed to have been an important source of the Earths atmosphereoOutgassing by volcanoes on the Earths surfaceRocks are found on the surface of another planet which appear to have been formed at the bottom of an ancient ocean Given this they are most likely to be classified as sedimentaryIf originally there were X atoms of radioactive isotope present and now there are only X4 atoms how many halflives have elapsedoTwo Which type of rock is the easiest to date radiometricallyoIgneousIn which eon of Earths history did dinosaurs and mammals first appearoPhanerozoicThe composition of the early atmosphere was dominated by carbon dioxide CO2The center of the Earth consists of an inner core of solid iron and nickel and an outer core of liquid iron and nickelThe Himalayas were formed by two pieces of continental crust collidingIf you were to come back to Earth in 150 million years time what would a map of the planet look like compared to todayoQuite different because plate tectonics would have caused a shift in the position of the continentsWithout the greenhouse effect the global average temperature of the Earths surface would be well below the freezing point of waterMost of the Earths carbon dioxide has dissolved in the oceans and is locked up in sedimentary carbonate rocks like limestone Why cant the carbon dioxide cycle easily correct for the increasing amounts of carbon dioxide introduced into our atmosphere by industrializationoIt operates far too slowly to correct for any shortterm changesA mule is an example of an exception to which of the fundamental characteristics of lifeoReproductiona mule is sterile and cannot reproduce even though it is the product of reproduction between two closely related animals a horse and a donkeyThe different species of finches found on the Galapagos islands are evidence of Darwins theory of natural selection because they have all evolved adaptations from a common ancestor to suit the environmental conditions found on different islandsThe fact that all cells used in life on Earth are based on the same biochemistry suggests that all life on Earth shares a common ancestorThe bond between carbon atoms in the molecule ethane HCCH is referred to as a single bond33What is the MOST important role that lipids play in living organisms on EarthoLongterm energy storage and cell membranesCells that lack a nucleus are called prokaryotesThe basic requirement for metabolism inside cells is a source of carbon and a source of energyA chemoautotroph gets its energy from chemical reactions and its carbon from its environmentThe heavy bombardment period is an early phase of the solar system where asteroid impacts were very commonoCrater counts on Mercury and the Moon combined with radiometric dating of Moon rocksoMoons highlands heavily cratered and older than about 4 GyrsoMaria between 3 and 4 Gyrs old and much less crateredoTherefore heavy bombardment stopped around 4 Gyr and since then only comparatively few asteroid impactsSilicon based life is less likely because oSilicon cannot form double bondsoSilicon bonds weaker than Carbon bondsoSiO is solid and immobile in contrast to the gaseous CO22oSilicon is much more abundant than Carbon on Earth yet life is CarbonbasedH C N O are important elements for life Describe the origin of these elementsoH formed during the big bangoRest inside starsoVia nuclear fusion at end of lifeoSupernovae release oGases mix and spread out collapse to form new solar systems Lecture 7How did it startoThe essential organic materials CO CH water H N were there2422oComets and meteorites may have brought more complex organic molecules from outer space and wateroSteps neededFormation of organic molecules amino acids and nucleotidesJoining of large molecules into proteins and nucleic acidsAggregation into droplets with different chemical properties than the environmentReplication and heredityRNA and DNAThe early atmosphereoIt did not contain oxygen and was dominated by hydrogen compoundsoVolcanic gasescarbon dioxide about 351000x more than todays nitrogen hydrogen sulfide steam methaneoRed or orange in colour thick and opaquelike VenusoHeat deposited by frequent hits by comets and meteorsSome hits vaporized the oceans but some brought water ice from the outer solar systemoRapid changes of solar illuminationearly Sun more variable and 30 fainter than todayoRapid rotation of the globe812hand violent lightning stormsEartha water planetoOcean crust sinks back into mantleoContinental crust floats on top and grows over timeoThe total amount of water on Earth is 01 of its massCompare with outer solar system20oHeight variation of surface 8km above 5km below the sea levelAverage ocean depth 4kmWith twice the water 02 of mass oceans would cover all the landThe MillerUrey experimento1920s a realization that the early atmosphere was without any oxygen o50s Miller and Urey performed an experiment of electrical discharges in an atmosphere of water vapour methane ammonia and hydrogenoAfter 1 week it produced many amino acids among 18 produced 6 occur in living organismsEarly ideas about the origins of Life
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