GEOLOGY
Class_3_Earth_and_Space_B_Wu_Chen_new.pdf

Class_3_Earth_and_Space_B_Wu_Chen_new.pdf - LSGI1D03 Living...

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Unformatted text preview: LSGI1D03 Living on a Dynamic Earth Class 3 Earth and Space Part B Class 2 1 Earth and Space • Can we study Earth without consideration of the space immediately around it? • What about the bigger space that goes beyond the Solar System? • Some scientists go back to the origins of the universe in order to begin their study of Earth § Class 2 Is it necessary? 2 Earth and Space • Yes and no § Earth is made up of matter • Where does it come from? § Matter interacts with matter • Gravity, nuclear reactions, particle physics, chemical processes § What external forces and events make Earth a dynamic place? • Of course we could go all the way back to the start… Class 2 3 Earth and Space • Earth is a part of the Solar System • The Solar System is part of the Milky Way galaxy (the Galaxy) • The Milky Way is one of 10# galaxies in the universe § § Journey to the edge of the Universe (YouTube) How Big is the Universe (YouTube) • A glimpse of the Milky Way § § Class 2 Explore the Milky Way (YouTube) Beyond our Solar System (www) 4 Earth and Space • Of greater significance to how Earth works is the Solar System § § § § § You can get an appreciation for the distances between the planets from this web site and an Earth-­related appreciation here. Sun Planets Moons Asteroids Comets • Our Solar System (YouTube) Source Class 2 5 Planet X • Does the solar system has: “Planet Nine”? • The idea was proposed more than 100 years ago. • Try to detect it by observe its gravity effects • No directly evidence to prove it • Cause of 27 million year cycle of mass extinctions? Class 2 6 Kepler 22B • An earth-­like planet • 600 light year away from the earth • Discovered in 2011 Class 2 7 The Sun Dark Secrets of the Sun (YouTube) Class 2 8 The Sun • The Solar System is dominated by the Sun § A star • • • • Diameter: 1.410' Mass: 2.010+, (99.8% of Solar System mass) Composition: 92% 3, 8% Structure (GAS) § § § § § § Core Radiative zone Convective zone Photosphere Chromosphere Corona Source Class 2 9 The Sun • The Sun (pdf) is a nuclear fusion reactor • The source of (almost) all of Earth's energy Where does the rest come from? § § Energy received 53 : 1.410+ 58 (1.4 ) Defines the electromagnetic spectrum Source Class 2 10 The Sun • The Sun also is the source of Solar Energetic Particles (SEP) § § § Protons Electrons HZE ions also come from cosmic rays HZE ions (HZE = high charge and energy) • Produced by § § Solar flares Coronal mass ejections • Hazardous to life and technology Class 2 11 Sunspot • Sunspot: dark spot on the surface of the sun • Due to strong magnetic field • Reversal of magnetic poles (22 years) • Affect the earth climate? Class 2 12 Class 2 13 Earth's orbit Class 2 14 Earth's orbit • Earth travels around the Sun in a path called an orbit • Orbits are defined by § § Class 2 Inertia Gravity 15 Earth's orbit • Inertia is the property of a body to resist change in its state of motion (Newton's First Law of Motion) Not accelerate, = 0 F> § FG In the absence of external forces a body will tend to maintain it's motion with kinetic energy • ; = =.> ? 3 • Thus, in a perfectly empty universe Earth would forever travel in a straight line § ; = @.,#8,?A ∗ 3'.C#8,D 3 ? = 2.710++ • Changing the motion of a body requires the application of a force to counteract ; Class 2 16 Earth's orbit • Gravity is a force between bodies § I = . • • • • • =K .=? L? I = force between bodies ≈ 6.67410588 353 (gravitational constant) 8 = mass of body 1 3 = mass of body 2 = separation between bodies • For the Sun and Earth § Class 2 I ≈ DQ 588 3.,#8, ∗@.,#8, 6.710 8R,.,#8,S ? ?A ≈ 3.61033 17 Class 2 18 Earth's orbit • The net result is that the orbit of Earth is an ellipse with the Sun at one of the foci Focus Focus Minor semi-­axis, Major semi-­axis, Class 2 19 Earth's orbit • Ellipses are characterised by § § Major semi-­axis, And either • Minor semi-­axis, or • Flattening, = X5Y X • Eccentricity, = or Y? 1− ? X • The smaller is the closer the ellipse is to being circular Class 2 20 Earth's orbit • At one point in its orbit Earth will be closest to the Sun, the perihelion § ≈ 147,100,000 • The point where Earth is furthest from the Sun is the aphelion § ≈ 152,100,000 • Perihelion and aphelion are related to § § Class 2 Perihelion = . 1 − Aphelion = . (1 + ) 21 Class 2 22 Earth's orbit Planet Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune Class 2 a (km) 57,909,227 108,209,475 149,598,262 227,943,824 778,340,821 1,426,666,422 2,870,658,186 4,498,396,441 b (km) 56,671,624 108,206,990 149,577,372 226,947,532 777,429,150 1,424,595,473 2,867,450,923 4,498,230,455 e 0.205636 0.006777 0.016711 0.093394 0.048386 0.053862 0.047257 0.008590 Perihelion (km) 46,001,009 107,476,170 147,098,291 206,655,216 740,679,835 1,349,823,615 2,734,998,229 4,459,753,056 Aphelion (km) 69,817,445 108,942,780 152,098,233 249,232,432 816,001,807 1,503,509,229 3,006,318,143 4,537,039,826 23 Earth's orbit • Seasons caused by inclination of Earth's axis to orbital (ecliptic) plane § § Inclination is 23.439° Vary from 22.1-­24.5 ° Source Class 2 24 Earth's orbit • The elliptical orbit is not responsible for the seasons • Earth's motion around the Sun (YouTube) Class 2 25 Time Class 3 26 Day and night • Earth rotates § Once in about 24 hours with respect to Sun (solar day) • Variations described by Equation of Time § Rotation is slowing so days are becoming longer • Due to tidal friction • About 1 second per 50,000 years Class 3 27 Day and night § § From West to East Noon at points directly opposite the Sun • Places to the East are morning • Place to West are evening • Midnight at points on other side of Earth Class 3 28 Day and night • A sidereal day is the time between instants when a particular star is overhead § Once every 23 hours, 56 minutes, 4.099 seconds • A year has one more sidereal day than solar days § Class 3 Sidereal days vs Solar days (YouTube) 29 Day and night Terminator or twilight zone Class 3 30 Time zones • Earth divided into time zones based on longitude § 1 hour of time = 15˚ longitude • Time zones adjusted for convenience • Origin of time is the Prime Meridian • Time standard is UTC (Coordinated Universal Time) § Class 3 Greenwich Mean Time (GMT) within 0.9 second of UTC Source 31 Time zones • UTC § Exactly 36 seconds behind International Atomic Time (TAI) on 30 June 2015 • Controlled by 400 atomic clocks • Correction of UTC by the application of leap Leap seconds added to UTC seconds • Does not take into account slowing of Earth’s rotation 40 35 30 25 20 15 10 Class 3 6/20/2012 6/23/2002 6/25/1992 6/28/1982 0 6/30/1972 5 32 Time zones Class 3 33 Time zones Source Class 3 34 Time zones • China § § Spans 5 time zones from UTC+5 to UTC+9 Uses UTC+8 • Internally known as Beijing Time • Externally known as China Standard Time § § Time regulated by National Time Service Centre, Chinese Academy of Sciences Xinjiang has unofficial Urumqi Time (UTC+6) • Hong Kong and Macao § Class 3 Have own time regulators (HKO and SMG) 35 Time zones • Daylight savings time (DST, summer time) § § § § Class 3 In order to maximise the sunlight available in summer Clocks advanced by one hour at start of daylight savings period Moves time zone one hour forward Not uniformly adopted 36 Time zones DST used DST never used DST was used Source Class 3 37 Seasons Class 3 38 Seasons • Due to Earth's axis being tilted at 23.439° from the normal to the ecliptic plane Source Class 3 39 Seasons Source Class 3 40 Seasons • At one point in Earth's orbit the South Pole pole will be pointing towards the Sun and the North Pole away from the Sun § 20 or 21 December • Northern winter § Winter Solstice • Southern summer § § Summer Solstice Sun opposite Tropic of Capricorn Source Class 3 41 Seasons • Six months later the situation is reversed § 21 or 22 June • Northern summer § Summer solstice • Southern winter § § § § Winter solstice Sun opposite Tropic of Cancer North Pole day South Pole night Source Class 3 42 Seasons Source See also this video Class 3 43 Seasons • Mid-­way between these two events the Sun is directly over the Equator § § 19, 20 or 21 March and 22 or 23 September Vernal (spring) and Autumnal equinoxes • Variation in dates due to § § § § Class 3 Calendar alignments Axis wobble (2.4° over 41 ky) } Variations in orbit eccentricity } Precession (26 ky) } Milankovitch cycles (YouTube) 44 Seasons Source Class 3 45 Space Weather • Concern time variations within solar system • More emphasis on space close to the earth: the magnetosphere, ionosphere and thermosphere • Affecting : satellite, communication, navigation, and ground services Class 2 46 The Moon Universe Today Class 3 47 The Moon • Dimensions = 1,738.14 § = 1,735.97 § = 1 801 • Mass: 7.34771033 8 53 • Surface gravity: 1.622 ( of Earth) @ • Rotation period: 27 days § We can only see one side of the moon. • The rotation rate was much slower when it was born • Surface temperature § § Class 3 Minimum: −200° Maximum: +120° 48 The Moon • The Moon orbits Earth § § § Every 27.3 Average distance of 385,000 Average speed of 1.02 58 • Orbit parameters § § § § Class 3 : 384,748 : 0.026 to 0.077 Apogee: 404,00 to 406,700 Perigee: 356,400 to 370,400 49 The Moon Source Class 3 50 The Moon • The Moon rotates once every 27.3 • The Moon and Earth orbit around each other at a point called a barycentre § § Centre of mass of the two bodies about which both orbit Located 4,600 from Earth's centre • So we have Earth and Moon § § § Class 3 Rotating about their own axes Orbiting about their barycentre Orbiting the Sun 51 The Moon Source Source Class 3 52 The Moon • The combined effect of the orbits plus the lighting from the Sun produce periods of full and no illumination of the Moon's surface generating phases (NASA) § § § § § § Class 3 New Moon = no illumination Full Moon = full illumination Waxing = increasing Waning = decreasing Crescent = less than half Gibbous = more than half Source 53 The Moon • When Earth is directly between the Moon and the Sun (in syzygy) it's shadow causes a Lunar Eclipse § § Can be seen from anywhere on the night side of Earth The strength of the eclipse depends on the part of Earth's shadow it passes through • Umbral eclipse § Moon lies totally within Earth's shadow • Penumbral eclipse § Class 3 Moon lies in partial shadow 54 The Moon Source Class 3 55 The Moon • When the Moon passes between Earth and the Sun it's shadow causes a Solar Eclipse § Only occurs with a new moon • About 5 times per year § § Only seen from limited locations Currently the diameter of the Moon and it's distance from Earth allows for total eclipse • This will no longer happen in about 600 as the Moon is moving away from Earth by approximately 4 each year Class 3 56 The Moon Source Class 3 57 The Moon Source Total Solar Eclipse of 20 March, 2015. Moon was at perigee making it appear larger than usual and almost exactly cover the Sun's disc and allowing a clear view of the Solar flares. Class 3 Source 58 The Moon • Surface covered by craters and seas (mare) • Geography of the near side is much better known than the far side • First maps appeared in early 17th Century • Modern maps from orbiting imagery Gilbert's "naked eye" map of 1603 Class 3 Source 59 The Moon Source Far side Class 3 Near side Far side 60 The Moon Lunar mosaic produced from images of China's Chang'E-­1 (嫦娥一號) mission in 2008 Source Class 3 61 The Moon • Where did the Moon come from? § Giant Impact Hypothesis (GIH) • Formed from debris following impact with Earth by a Mars-­sized body (Theia) • Evidence mounting for this (Space.com) § Capture of a wandering planetoid • Still under debate with evidence for and against § Separate accretions of materials • Problems with differences in composition and structure • Birth of the Moon (YouTube) Class 3 62 The Moon • Study of the Moon called selenology • Main factors controlling structure are § § § Solar energy Meteor impacts Vulcanology • Structure consists of § § § Core Mantle Crust Source Class 3 63 The Moon • Composition similar to that of Earth § § § Oxygen, silicon, magnesium, iron, calcium… Titanium, uranium, potassium… Is it worth mining? Rare earths such as Yttrium and Lanthanum • Mares composed of basalt • Deep quakes caused by gravitational effect of Earth • Many geological features revealed from 3D modelling by recent exploration Class 3 64 The Moon Rift valleys revealed by gravity surveys Video from Japan's Selene (Kaguya) Lunar mission Photogrammetric far side surface model Class 3 65 The Moon • Tides § § § In an empty universe Earth’s oceans would lie on the geoid The gravitational forces of the Sun, planets and the Moon attract the oceans The Moon’s gravity has greatest effect • The Sun has the next largest effect § Class 3 As it orbits Earth its gravity attracts the water making it bulge towards the Moon 66 The Moon Ocean surface High tide Moon Earth Moon's gravitational attraction Low tide Class 3 67 The Moon • The Sun also attracts the oceans • The magnitude of high and low tides controlled by the relative positions of the Moon and the Sun § Spring tides • Sun and Moon aligned (syzygy) • Occur at new and full moons § Neap tides • Sun and Moon perpendicular • Sun reduces effect of the Moon Class 3 68 The Moon Source Class 3 69 The Moon • Other factors affecting the height of tides § § § § § § Variations in orbits Location Depth of water Currents Weather : • Tidal patterns mathematically modelled to generate predicted heights Class 3 70 The Moon Source Source Class 3 71 The Moon Source Bay of Fundy, Nova Scotia, Canada Source Class 3 72 The Moon • Actual tides measured by tide gauges • Hong Kong has 11 gauges § § § 6 maintained by the Observatory 4 maintained by the Hydrographic Office 1 maintained by the Airport Authority • Tidal records used in quantifying sea level change Class 3 73 The Moon Source Class 3 74 The Moon Source Class 3 75 Meteors Class 3 76 Meteors • Meteors § Space debris that enters Earth's atmosphere • Asteroids/meteoroids • Fragments of comets § § Travel at up to 260,000 ℎ58 Friction causes them to burn and create fire trails • Meteorites § Class 3 Meteors that fall to Earth's surface 77 Meteors • Asteroids § § § Rocky objects in space smaller than a planet Up to 1,000 in diameter Main locations are • Asteroid Belt between Mars and Jupiter § § About 750,000 Mostly rocky • Kuiper Belt at edge of the Solar System § § § Class 3 Mostly frozen volatile gases Some wander through space A meteoroid is a small asteroid 78 Meteors Class 3 79 Meteors • Meteor showers § § Meteors may occur singularly or in showers Showers may occur regularly or sporadically • Regular showers belong to comets and their occurrence can be predicted § Next will be that of Draconid • The radiant point, where the shower appears to originate from, is in the constellation Draco, near the dragon’s eyes, the stars Draconis (Eltanin) and Draconis (Rastaban) • From comet 21P Giacobini-­Zinner Class 3 80 Meteorites Class 3 81 Meteorites • Meteorites can be dangerous § One explanation of the demise of the dinosaurs is Earth being struck by a large meteorite 65,000,000 years ago • Must be large enough to survive passing through the atmosphere • Sized from centimetres to kilometres § Large ones create craters • Composition either stone or metal Class 3 82 Meteorites Source Class 3 83 Meteorites Barringer crater, Arizona, USA 50,000 years old 1,180 m diameter 170 m deep Meteorite mass 10,000 t Source Class 3 84 Meteorites Wolf Creek, Western Australia < 300,000 years old 875 m diameter 60 m deep Meteorite mass 50,000 t Source Class 3 85 Meteorites • • • • Crater formation (YouTube) Discovery Channel (YouTube) 2013 event (YouTube) September 2015 event § § § Class 3 The Bizarre (www) Confirmed (YouTube) NASA (www) Source 86 Comets Class 3 87 Comets • "Dirty snowballs" § Gas • Ammonia, methane, carbon dioxide/monoxide § § § Dust Ice Rocks • Linked to providing Earth's water and organic material • The Comet's Tale (YouTube) Class 3 88 Comets • Elliptical orbit § Kuiper Belt (5,000,000,000 ) • Short period < 200 years § § Halley's Comet -­ 76 Oort Cloud (150,000,000,000,000 ) • Long period > 200 years § Comet McNaught -­ 92,600 • Parabolic or hyperbolic paths § § Class 3 Do not return Oort Cloud 89 Comets Source Source Class 3 90 Comets • Structure § Nucleus • Solid core 100 to 60 § Coma • Water and dust "atmosphere" • May be millions of kilometres wide § Tail • As the comet approaches the sun radiation vaporises coma and nucleus • Points away from the Sun Class 3 91 Comets Source Class 3 92 Universal abundance Class 3 93 Universal abundance • Not to be confused with the metaphysical kind • The relative amounts of chemical elements § § Periodic table Made from baryonic matter • Protons, electrons, neutrons • Earth § Class 3 31.2%, 30.1%, 15.1%, 13.9%, 2.9%, 1.8%, 1.5%, 1.2%, everything else 2.3% 94 Universal abundance Source Class 3 95 Universal abundance Source Class 3 96 Universal abundance • Milky Way § Mostly 71% and 23% • The Universe contains § Baryonic matter: 5% • Abundance decreases with atomic weight § § Average mass (protons + neutrons) of all isotopes of an element Dark matter: 27% • Invisible, seen only by gravitational effects § Class 3 Dark energy: 68% 97 Universal abundance Atomic mass Atomic mass Source Class 3 98 ...
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