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Earth Sciences
Course
Earth Sciences 1086F/G
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Prof
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Fall

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Chap 1  - Hypothesis: is an educated guess based upon observation o Can be supported or rejected, it can never be proven true - Theory: summarizes a hypothesis that has been supported by repeated testing and observation, considered valid as long as there is no firm evidence to dispute it - Atheory allows you to make predictions of the end-result of the process being examined - Law: generally accepted as the proper explanation of the whole process - Mily way galaxy shaped like a disc, look parallel we see so many stars, look perpendicular we can see out into space - Galaxies range from elliptical to spiral - Galaxies distributed more or less evenly through space - If stars in galaxies had been radiating heat and light energy for a long time they would have heated the universe up to their temperature - BIG BANG THEORY - Singularity: a point of infinite density and infinitesimal volume, at which space and time become infinitely distorted, according to BBT, a singularity existed at the beginning of the universe - =’s condition o So this is a condition where all known laws of physics break down o All mater is infinitely dense o Time has no meaning o Fabric of space = 4-D (includes time), in this spacetime is deformed in upon itself o Black holes are also singularities: regions around enormously massive stars that have run out of fuel and have collapses essentially to appoint because of their own gravity, on in center of Milky Way - Gigantic expansion: big bang created space and time, so think of a rly small balloon (the universe) which in the tiniest fraction of time expands and keeps expanding THREE PILLARS OF PROOF THAT SUPPORT BBT 1. Recession of stars/galaxies (as described by Hubble’s Law) 2. Characteristics of CMB radiation 3. Abundance of light elements - Edwin Hubble o Demonstrated that there were many galaxies in the universe o Proved that the universe is expanding o Showed us how to measure distance in space - Doppler effect: approaching train = wavelengths of sound are compressed and shortened by motion of object, train moving away = wavelengths of sound are stretched and lengthened - If light source is moving toward the observer the light wavelength appears to shorten (i.e. to move into the blue spectrum or ‘blueshifted’) - If light source is moving away from the observer the light wavelength appears to lengthen (i.e. to move into the red spectrum or ‘redshifted’) - The faster the light-emitting object was moving the greater the shift - Speed of light is fixed and cannot change - So when Hubble observed apparent changes in speed of light from a star, it meant the stars had to be moving away from Earth - The more distant a galaxy is from us the longer its light takes to arrive, thus the more redshifted when it finally arrives - Hubble Law: v=H d o o V= speed in km/s o D= distance of the star/galaxy away from Earth in parsecs ( 1 parsecs = 3.262 times the distance light travels in one year) o H o hubble constant (speed of expansion of the Universe) - First seconds of universe hugely hot, and as it expanded it cooled - Cosmic microwave background: hot light photons, produced in the early period have since lost energy and dropped from visible light energy range into the microwave energy range o Comes from all directions with nearly the same intensity o This CMB represents the very last remnants’of the light/heat energy of the Big Bang’s initial expansions o Temp of space should be 0 K, its actually 2.726 K - The observed abundance of hydrogen, helium, and lithium can only be explained if they originated from one single ratio of the first subatomic particles of matter that can be fromed from a super-hot env;t SHAPE OF THE UNIVERSE - Universe might have a positive curvature, like a sphere, closed universe - The universe would be finite in size but with a boundary that was expandable just like a balloon - Closed in time, and eventually stop expanding and then contract in a “big crunch” - Amodel depends greatly upon there being sufficient matter in the universe that gravity can eventually pull things back together - Production of universe likely to be a cyclical event, Bang- a universe – crunch collapse REPEAT - Universe could be “open” or have negative curvature aka saddle-shaped - Infinite and unbounded - Parallel lines eventually diverge - Open universes expand forever, expansion rate never approaching zero - Universe could also be flat - Infinite in spatial extent and have no boundaries - Parallel lines are always parallel - Also expand forever BUT the expansion rate approaches zero - To all three models, a density parameter is critical - If space has a negative curvature there is insufficient matter around to allow gravity to act and stop expansion, the density parameter is less than 1 - If space has a positive curvature there is more than enough matter around to allow gravity to pull everything back together, density parameter is greater than 1 - Is space is flat we can say there is exactly the ‘critical’value of matter around that will prevent the universe from back together or from expanding indefinitely - So what affects gravity? - Conventional matter: stars, planets, asteroids, comets, etc o Less than 0.4% of the universe - Dark matter: matter we’ve never seen because it gives off now electromagnetic energy, but we know it’s there because we can detect that there’s a gravitational attraction between it and conventional matter, the effect which is visible o 23 % of the universe - Dark energy: acts opposite to gravity, it repels matter o 70-73 % of the universe o This is the force that seems to control the expansion of space o When it is exactly counterbalanced by the gravitation energy of matter, we’re at the critical value of 1 for a density parameter (i.e. a flat universe) - 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 - Nearly flat AGE OF THE UNIVERSE - Certain components are radioactive; they breakdown at fixed rates to form other components and give off energy in the process - Universe age between 11.5 and 17.5 billion years, estimated by.... o observing the compositions of gases around old stars o from knowing the exact radioactive processes required to produce these gas compositions from the very first elements created in the Big Bang o AND knowing all the time factors involved in breaking down one component to yield others - Galaxy found in 2010 that dates to just over 13 billion years, so the universe has to be older than that - Hubble telescope found white dwarf stars= remnants of stars that have consumed all their fuel and are sitting around cooling off o To have gone thru whole life cycle = very very old o Their ages ranged between 12-13 billion years old - Assuming it would have taken something less than 1 billion years for the cosmos to cool sufficiently to form a star, the age of the universe has to fall between 13-14 years - CMB signals offer the most accurate view to date of conditions in the early universe - Assuming the right model has been developed the universe is exactly 13.7 billion years - In april 2009, 10-second burst of gamma energy from space was detected o Indicated a star explosion (supernova) had taken place o Realized they had just witnessed the explosion of a star that took place 13 billion years ago o Took that much time for the energy waves to reach earth Chapter 2­ time and space  - Light year: distance that light travels in on year - Light travels at about 300,000 km/s - 9.4608 x 10 to the power of 12 - To gauge near distances (up to 500 lights years): - Trigonometric parallax relies on an object appearing to be @ a different place relative to the background, depending on your viewpoint - Distant stars appear to wobble against the starry background - Astronomers use the orbit of earth about sun as their measurement base - 500-500 million light years distant - The first technique for stars in this range deals with the brightness of stars - Use chart called Hertzprung-Russell Diagram relating luminosity (equivalent to brightness) of stars to their temperature (related to colour) - Sun falls into the class defined as “main Sequence” - Using a calibrated colour chart, we determine the exact colour of the star were studying - Next draw a vertical line from the colour-determined temperature to intersect our main sequence average best-fit line on the H-R diagram and measure using a horizontalon the brightness scale which the true brightness (called intrinsic brightness) of that sar must be - Astar’s brightness dims with distance so the brightness you see from earth (apparent brightness) is rather less than true - Apparent brightness = intrinsic brightness/distance squared - Good for distances up to 150,000 light years away - Second technique for determining distance in this middle range makes use of ‘marker stars’ o Have a special property: pulsing brightness that peaks with absolute regularity (called its period lol) that is complete related to the star’s brightness o Called cepheids o Measure the time between one brightness peak and the next, and that gives us the intrinsic brightness value o Cepheids are all over the pace so they tell us how far away galaxies are up to 500 million light years away - Fuzzy spiral shaped clump of stars known as M31 or andomeda, hubble discovered a Cepheid star in it which helped determine that it resided were a million light years away o Andromeda galaxy is our closest neighbouring galaxy, looks quite a bit like the Milky way galaxy and like a Frisbee - 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 - Galaxy = a collection of stars, gas and dust held together by gravitational attraction - In our immediate env’t is a group of about 40-50 galaxies called the local group o 3 really big galaxies in the local group  Andromeda Galaxy (the largest)  Milky Way Galaxy  Triangulum Galaxy - Andromeda Galaxy moving towards the milky way and they are expected to crash in about 3 billion years - Sitting out a bit more than 2/3 from the core of the milky way is our solar system locatred on the orion spur (very short arm) of the milky way Chapter 3  - Big bang apparently created everything- time, space, energy and all matter - Nebular hypothesis: eventually pockets of matter/elements came together to form star- planet systems - One second after the big bang, the temperature was roughly 10 billion degrees and space was filled with neutrons, protons, electrons, anti-electrons, photons, and dark matter - As universe cooled, basic particles combined to mark elements - Element: a substance that cannot be broken down to anything simpler by any chemical means - Atom: a particle of matter that has the unique properties of an element (atomsa re the essential particles of elements) consist of o a central Nucleus that contains one or more particles called o protons (positively charged) o and may or may not contain particles called neutrons (no charge) o the nucleus as a whole is thus positively charged o the nucleus is surrounded by one or more electrons that are negatively charged, offsetting the positive charge of the nucleus - ion: an atom with either a negative charge (extra electrons) or an atom with a positive charge (deficiency of electrons) - isotope: atoms whose nuclei have the same number of protons but differing numbers of neutrons o isotopes area different atoms of a single element o identify each isotope by the number that’s the sum of the protons and neutrons in the nuclei (called the mass number) o any isotope that is not stable but breaks down naturally is said to be radioactive - radioactivity: the spontaneous breakdown of unstable atoms of an element with the production of energy and other particles o example: H o 0.5 of any amount of mass you collect will breakdown in exactly 12.32 years o Rate of breakdown is constant, so no matter what mass you start with ½ will be gone every 12.32 years o Every radioactive isotope has a defined half-life o Fission: a breakdown of the nucleus of a relatively heavy atom (i.e. isotope) into at least 2 other lighter particles plus energy o Another word for radioactivity and also can describe the nuclei breakdowns that ppl make happen o Fusion: the combination of two lighter atoms/isotopes to make one heavier atom/isotope plus energy  Not classed as a radioactive process, while the heavier atom produced may be radioactive it may also be stable  Vast amount of energy can be produced - Supernova: the explosive death of a massive star o Explosion is instantaneous, the bright effect can be seen for weeks both day and night - Periodic table of the elements: an arrangement of all the known chemical elements in a table according to some defined order o Atomic number: the number of protons in the nucleus of the atom o In typical periodic table arranged in order of increasing atomic number (lighter elements to heavier elements) - In first seconds + minutes after Big Bang hydrogen (H), Helium (He), and lithium (Li) were formed (lightest 3 elements) - Hydrogen has 3 isotopes 1 - H = most important and abundant - 2H (deuterium) = played an important role in those early moments of the Universe o Much of the early formed deuterium went through a reaction to form helium and a little bit of lithium - Bunch of elements were made by nuclei fusion reactions in stars - Really massive stars have enough energy to synthesis (by fusion) elements up to iron (Fe) atomic number 26 - In the explosion of a big star (supernova) so much temperature and pressure is involved that all the very heavy elements can be produced - THE NEBULAR HYPOTHESIS - Suggests that the solar system formed over a relatively brief span of time and all as a unit from a nebula (could of interstellar gas) - 5 billion years ago, a dark, formless nebular floated within the orion spur of the milky way galaxy - Enormous but very low density gas cloud, spread out over a very large volume of space, contracted under its self-gravity (i.e. all the particles were attracted together by the cumulative gravitational effects of all the other particles in the cloud) - Pronounced shrinkage of the cloud as well as flattening out - Solar system diameter now (all the way to Pluto) is about 10 light hours in diameter - Original cloud may have been about one light year across - COLLAPSE - the collapsed region increased in density when the contraction started - atoms once separated start to bang about vigorously generating heat - once this starts there is local collapse to that part of the cloud, once that starts the collapse tends to accelerate going faster and faster - Temperature increases ! but much of the heat get radiated out into space - Eventually particles get so densely packed that the heat can no longer escape - Heat energy emitted from the hot central regions gets blocked by the surrounding dense layers of matter - @ this stage particles near centre wind up moving with very high speeds (gas = very hot) and then can provide enough sustaining pressure to stop any further collapse - Fusion reactions can take place, this releases more energy and a star is born - Sun converts about 600,000,000 tonnes of hydrogen nuclei into helium nuclei - Fusion reactions release an enormous amt of heat + light energy into the solar system - Sun will run out of hydrogen fuel in about 5 billion years and then it will turn into a red giant and destroy most planets - CLOUD FLATTENING - Distended cloud with which we begin is a large amorphous blob in space with no particular shape to it - Conservation of angular momentum o Momentum: a measure of an object’s tendency to move at constant speed along a straight path o Angular momentum: a measure of the amount of spin of an object o Conservation of angular momentum: if no outside force acts on spinning object, the objects angular momentum will not change with time no matter how the object interacts with other objects - Probably some circulation or motion of gas inside the original cloud - When motions of atoms are added up, there is likely to be some slight cumulative motion in some direction (sense of rotation of the cloud and its angular momentum) - Given this slight original rotation, it is inevitable that the cloud will spin faster and faster - As it contracts, the increasingly rapid spin of orbiting material leads to its flattening out - CONDENSATIONAND PLANETARY DISK - The central blob of material (newly formed sun) was extremely hot - But would the whole nebula have become hot? The answer is no; the outer parts of it would have been fairly cool - Flattened nebular has a temperature gradient, hot @ the center, cool farther out - Clouds of interstellar gas and dust get all mixed up by random atomic motions, effects of magnetic fields, injections of energy from exploding stars etc - Nebula has the same composition everywhere (same mix of chemicals + elements)both before and after the slow collapse and flattening into a disk - Collapse itself would NOT have led to any compositional difference from region to region - The reason the planets do not form with similar compositions is a direct consequence of the temperature gradient - In the cooler outer parts, the temperature is low enough that essentially everything condenses o Even the light elements like hydrogen can condense into molecules, small particles and droplets - Closer to sun where it is much hotter, not everything can condense in the swirling nebula o Substances like hydrogen and water vapour (volatile elements) stay complete gaseous o Refractory elements (elements which do not readily respond to heat) can condense and freeze o Near the hot sun, small grains of refractory materials condense, consisting of things like metal oxides, alloys of nickel and iron etc  Quickly grow to the size of pebbles - Important point is that out where Jupiter is everything condenses, closer in where mercury is, only the heavier (refractory) elements do - ***** difference in composition is not caused by the fact that the heavy elements were more abundant near sun o Simply that the light gases don’t condense at the high temperatures which prevail in the inner parts of the solar system, never accumulate into planets - FROM PEBBLES TO PLANETS - Purely gaseous disk has now changed into a great number of small particles orbiting sun with a composition which depends on distance - b/c of original motion of the nebula, pebbles are now moving the same direction more or less - as a result when two pebbles collide they meet in gentle fashion at moderate speed and can end up sticking together (accretion) - small pebbles accumulate into planetismals (small planets) - go on to form protoplanets - eventually a few large planets result - what happened to leftover gas that inner planets are lacking (hydrogen and helium) - they were “swept out” of the solar system towards the end of the formation of the planetary system - some strong evidence that points towards it: o sun has what is known as “solar wind” a continuous outflow of charged particles (mostly electrons) which stream out thru the solar system at a velocity of several hundred km/s  where there is a flare or eruption on sun, the solar wind increases o T Tauri stars have very strong winds, such winds are amply strong enough to drive any remaining gas out of the solar system in pretty short order o Atmospheres we now find around the rocky inner planets are almost certainly not what they were when the planets first formed  Inference is that the atmospheres of the inner planets including that of earth, were completely swept off at some early stage in the history of the solar system  Atmosphere now is a result of the “outgassing” of the planets, in particular, the pumping out of volatile substance by volcanoes  Early earth had sufficient gravity to hold onto some gases in its original atmosphere which was swept off, but then active geology led to outgassing and production of a secondary atmosphere - SOME PREDICTIONS - Bombardment rate (numbers of collisions) should have been very high early on, but fallen off fairly precipitously as time passed (true ) - There must have been occasionally really vigorous collisions between enormous fast- moving lumps of rock Unit 2 INTRODUCTION - Geocentric model: earth is at the center of the solar system - Heliocentric model: sun is at the center of the solar system - Our solar system consists of a central star called Sun surrounded by 8 major planets, 5 dwarf planets, too many comets to number, a lots of space debris - PIONEERSAND THEIR MODELS - Pythagorous/Plato - Pythagorous pictured earth as a stationary object in space, surrounded by a sphere which contained everything else, including the sun, the objects inside the sphere rotated slowly each at speeds depending upon how far they were from each - Plato produced nothing better than that of Pythagorus - Aristarchus: - He noted the awkwardness of a solar system with earth at the center and experimented with placing sun at the center instead - Satisfied that the geometry seemed to work and seemed able to predict events in the solar system - Never attempted to promote his model - Ptolemy: - Put earth back at the center of things and placed all the other objects he could see on various moving spheres - This model of the solar system lasted for 1400 years - Copernicus: - Played around with the Ptolemy model because he didn’t think it was predicting events well - Put sun at the center of the solar system, had earth rotate about the sun and had earth revolve on an axis once per day - Johannes Kepler: - He applied math to astronomy - It seemed to him that the planets were not sitting upon a whole series of celestial spheres but that they had somehow been pushed into their orbits by sun - Figured that force was strongest near sun and weakened with distance outward - This mysterious force had to be magnetic, but he had no proof - Developed three laws, laws define the geometry of planets moving about stars o First law defines construction of an ellipse, because he realized that planets did not move in perfectly circular paths o Earth-sun distance is constantly changing as the planet foes around its orbit  Perihelion: the point of nearest approach of a planet to sun  Aphelion: the point of greatest separation to sun - Galileo Galilei - He was the first to observe the planets through a telescope - Did not invent the telescope but greatly improved upon the existing version by polishing the lenses himself - Magnified his view 8-fold and then later 33 times - He observed moon and saw a mountains and seas - He observed sunspots - He saw Jupiter and 4 satellites orbiting around it, practically in the same place, close to the ecliptic (the ecliptic is the geometric plane that contains the orbit of the planet) - Observation of satellites orbiting Jupiter was inspirational, if satellites could orbit a planet, why not have planets orbiting a star? Death blow to the Ptolemaic model CHAPTER 4 - Sun is 85 % brighter than all stars in MWG - Sun is a bunch of gas which gets denser and denser as you move from space toward the solar core - Photosphere: the visible outer layer of a star, represents the depth at which we can see no deeper toward the core - Luminosity= total energy radiated per second from sun - size of sun, we usually mean the size of the region surrounded by the photosphere - surrounding the photosphere is a layer (2500km thick) of gases called the chromospheres, invisible to the eye but can be seen with special instruments o irregular layer of gases that extends up and away from photosphere - chromospheres merges into the outermost region of the sun’s atmosphere = the corona o extends for millions of kms into space o usually can’t see due to brightness of photosphere, can see during a total solar eclipse - PHYSICAL FACTS o Diameter = 1.4 million km (109 x earth) o Volume about 1.3 million times that of earth o Mass is about 330000 x earth (99.8% of solar systems mass) o Age is 4.6 billion years (earth = 4.54) o Rotation period (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)  @ equator: 25 earth days  @ poles: 35 earthdays o Interior: 15,000,000 K o Surface: 5800 K - Distance between earth and sun is about 150 million km - One astronomical unit (1AU) = the mean avg distance between sun and earth - CHEMICAL COMPOSITION - Sun is mostly made up of hydrogen and helium, small amts of all other elements as well - Sun contains over 99 percent of the matter that makes up our solar system - Scientists believe that samples of material streaming out from sun, caught from w/in solar win would be a direct sample of suns composition, but also would closely resemble the original dust, gas, and ice from which bodies of our solar system evolved - NASA’s genesis, robotic spacecraft, launched august 2001 - Traveled to an area in space between earth and sun where gravity of the two bodies is balanced, collected solar wind particles - Constructed collection tiles of materials such as gold, sapphire and even diamonds - Collector arrays with their samples were all retracted and stored - Aims of mission will in fact be achieved - How do we know sun’s composition from indirect samples? Spectroscopy! - Spectroscopy: the measurement and analysis of energy spectra to determine the composition of matter. Device used for analysis is a spectrometer or a spectrograph, which record 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 - Spectroscope splits light up - 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 refracted the most, long wavelengths (orange and red) the least - Analyze the position and intensity of the lines and you get the element composition of the matter generating the spectrum in this case, sun - Hydrogen = 71 % of mass - He = 27% - Oxygen = 0.97% (less than 1) - Carbon = 0.40 % (less than 1) - Essentially the same elements on/in earth but proportions differ - Sun is so hot all the elements are in the gaseous state - SUN INACTION - In chromosphere we have prominences = arcs of gas which begin on the bright surface and soar to as much as 10,000 km into the corona - Flares: short lived gas eruptions, last no more than 20 mins or so - MAGNETIC FIELDS - Sun has a magnetic field, not sure of the generator, has to do w/ the interaction of the unique properties of matter in the different layers inside sun - Can express magnetic fields as giant bar magnets, north @ one end, south @ teh other and field surrounding them that we express as lines of diff strength and orientation - Magnetic generators sometimes become confused and unstable and suddenly the poles of the magnet switch - Switch happens on sun every 11 years (complete 22 year cycle is referred to as a solar cycle) - The last time sun did a flip was feb 2001 - Clearest manifestation of “switch-time” for sun is development of a great number of sunspots, a region of sun’s photosphere marked by lower than avg temp, appears black - During intense flares, corresponding intense magnetic storms occur on earth o Interference to complete breakdown of power grids carrying telemetric signals o Northern lights o Both result of matter carried into earth’s upper atmosphere by the solar wind - SOLAR WIND - Solar wind made up of charged particles sent out from sun at all times and in all directions - Made up of a plasma (ionized gas, made up of mixture of electrons and protons) - Despite gravity, these little particles escape because of their high kinetic energy - During period of solar flares, streams of solar wind are devastating - The magnetic field volume around a body like earth (that also generates a magnetic field) is called the magnetosphere - Reaction essentially protects most of earth’s surface from bombardment by solar wind – but not the poles ! - On their way to earth’s magnetic poles, solar particles interact with molecules of gas in the upper atmosphere, result is emission of a light photon from each collision - Lots of collisions = lots of light photons so during solar flares there is lots of light - In the north called the aurora borealis - South = aurora australis - LIFEAND DEATH OF SUN YO - Sun supports photosynthesis and drives earth’s climate and weather - Ultraviolet radiation from sun is primary cause of skin cancer - Ozone in our atmosphere attenuates that radiation - Sun is half-way thru its life cycle - Sun has grown about 30% brighter than when it was first born - When hydrogen fuel is consumed (5 bill years from now) sun will expand into a red giant - Will bring sun’s radius past the present position of earth - This expansion accompanies the first use of helium as fuel (not H) and the helium fuses to form carbon and oxygen - In really big stars there can be a phase when all the helium is used that carbon replace it as fuel - Wont happen to sun - Instead it will end life as black dwarf - Of courseAndromeda galaxy and MWG due to merge in 3 billion years CHAP 5 YO - OPTICALTELESCOPES - An optical telescope gathers and focuses light from the visible part of the electromagnetic spectrum - Their purpose is to increase the apparent size and brightness of distant objects - 3 types - Refracting telescopes which use lenses to form an image o Earliest made o Have an optical lends, and eyepiece o Optical lens refracts (bends) the light from the object viewed such that they converge at a focal plane o Eyepiece then bends that arrangement further into parallel light rays that focus on your eyeball o Diameter of the lenses determines the magnification and brightness of the image* - Reflecting telescopes which use mirrors to form an image o Do same job as refracting ones, but use some combo of curved mirrors rather than
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