Transcript Astronomy
Ch 28-31 Earth’s Role as a Body in Space Earth’s Motion through Space How is Earth’s motion related to the origin of the galaxy and its solar system? The Origin of Our Expanding Universe The Big Bang Theory – universe began as a point & has been expanding ever since en.wikipedia.org The Origin of the Milky Way Astronomers hypothesize that the galaxy began as… A rotating, spherical cloud in space … Our solar system continues to orbit the center of the Milky Way because… it developed in the plane of the disk that orbited the central nuclear bulge of stars http://www.google.com/imgres?imgurl=http://casswww.ucsd.edu/archive/public/tutorial/images/mw.jpg&imgrefurl=http://casswww.ucsd.edu/archive/public/tutorial/MW.html&usg=__ The Origin of the Solar System Our solar system began when… …a rotating, interstellar cloud of gases (nebula) collapsed (due to gravity) & formed a sun & orbiting planets Earth orbits the Sun because … it was located outside the center of the spinning nebula Earth’s Position in Space What is Earth’s position within the hierarchy of the universe? A. Earth’s Position in the Universe Earth’s Position in the Universe… Earth Solar System (3rd planet from Sun) Milky Way Galaxy (the Orion Arm) Local Group (about 40 galaxies) Supercluster (Virgo) Universe! Focus Question How do Kepler’s laws describe Earth’s orbit? 1. Kepler’s First Law… The Law of Orbits: All planets move in elliptical orbits, with the sun at 1 focus. An ellipse is … oval shape centered on 2 points instead of 1 point. The orbital period of a planet is … how long it takes for it to travel a complete orbit around the Sun. We call this a year! 2. Kepler’s Second Law… The Law of Areas: A line that connects a planet to the Sun sweeps out equal (=) areas in equal (=) times. Earth sweeps out a longer path when it is closer to the Sun. Earth moves fastest when it is closest to the Sun. 3. Kepler’s Third Law… The Law of Periods: The square of the orbital period of any planet is proportional to the cube of the semi major axis of its orbit. P² = a³ (P = orbital period = unit of time in Earth yrs, a = length of the semi major axis) If you know the distance of a planet to the Sun, you would be able to figure out its… orbital period. Basically… The closer a planet is to the Sun, the shorter its orbital period is. Barycenter and Earth’s Orbit… Barycenter is …the center of mass between a planet and the Sun. The law of universal gravitation states that… every pair of bodies in the universe attracts each other with a force related to… …mass (the more mass they have, the stronger the pull) AND …distance (the farther apart they are, the weaker the pull) Focus Questions… What causes the day and night cycle? What motion and force causes Earth’s slightly squished shape? Earth’s Rotation Causes Day and Night Earth’s axis is… o … the imaginary line that goes through the N & S poles. Day and night are caused by… … the rotation of Earth on its axis spinning towards & away from the Sun. (23.9345 hrs) Earth’s Rotation Causes Its Slightly-squished Shape… What motion causes Earth to take the shape of an oblate spheroid? Earth’s rotation What force causes the Earth’s mass to move outward from its center at the equator as Earth rotates? centrifugal force Focus Question (and Answer!)… What causes the seasons? The tilt of the Earth on its axis as it revolves around (orbits) the Sun. Earth’s Orbit and the Seasons! What causes summer in the northern and southern hemispheres? when the hemisphere is tilted toward the Sun during Earth’s orbit Earth’s Orbit and thewhen Seasons! Fall occurs Fall occurs when a hemisphere is starting tilt away from the Sun. atohemisphere is starting to tilt away from the Sun. Earth’s Orbit and the Seasons! What causes winter in the northern and southern hemispheres? when the hemisphere is tilted away from the Sun during Earth’s orbit An Owl in Springtime! Spring occurs when the hemisphere is starting to tilt towards the Sun. Earth’s Orbit and Seasons… The seasons in the northern and southern hemispheres are opposite each other because… When 1 hemisphere is tilted towards the Sun, the other is tilted away from it Think About It… What would happen to the average temperatures during our winter if Earth was tilted MORE on its axis ? Focus Question… What circumstances can bring about a long term change in the seasons? Precession Precession is… the wobble in Earth’s rotational axis. One full cycle of precession takes… 26,000 years! The force that causes precession is… the sideways pull of the Moon & Sun on the Earth’s bulging equator. http://www.cgrer.uiowa.edu/people/carmichael/atmos_course/ATMOS_PROJ_99/bilskemp/natural_variability.html Nutation… Nutation is… … a change in the angle of tilt of Earth’s axis Present tilt of Earth’s axis is 23.5°. The tilt can vary from 22.1° to 24.5 °. http://www.cgrer.uiowa.edu/people/carmichael/atmos_course/ATMOS_PROJ_99/bilskemp/natural_variability.html Nutation… If the angle of tilt decreased to 22.1… there would be less of a temperature difference b/tw seasons. If the angle of the tilt of Earth’s axis increased to 24.5… there would be more of a temperature difference b/tw seasons. Focus Question… What forces and heavenly bodies cause the tides? Tides… Tides are caused by… the gravitational attraction among Earth, the Moon, and the Sun. What forces & heavenly bodies cause the tides? gravitational pull of Moon on oceans facing it causes high tide “centrifugal swish” oceans facing away from Moon experience less of a pull (high tide) The sides of Earth NOT directly facing toward or away from the Moon experience low tide. The Cause of Tides… The Cause of Tides… What motion causes tides at location to change every 6 hours? Earth’s rotation on it’s axis http://loneswimmer.com/2010/08/23/tides-for-swimmers-part-1-theory/#jp-carousel-535 Spring Tide… Twice a month, the Earth, Moon, & Sun align (line up) causes the Moon & Sun to pull together on Earth’s oceans. Higher high tides / lower low tides Neap Tide… Twice a month, the Earth, Moon, & Sun will form a right angle which causes the Moon & Sun to pull from different directions on Earth’s oceans. Evens the tides http://www.yourdictionary.com/neap-tide Fusion Fusion is… – the fusing of smaller, lighter hydrogen atoms to form a larger, heavier helium atom (which releases energy) Fusion… Fusion occurs in the stars! (our Sun) Or in Iron Man’s chest… http://scifi.stackexchange.com/questions/43005/did-starkalready-have-a-design-of-an-arc-reactor-in-mind Fission Fission is… – splitting of bigger, heavy atoms (like uranium or plutonium) into smaller, lighter atoms Fission Differs From Fusion… Fission differs from fusion in that… Fission is SPLITTING atoms, not FUSING atoms. The Radioactive Boy Scout is a warning about investigating fission in your backyard shed! http://www.dangerouslaboratories.org/radscout.html Fission Fission is used on Earth … – in nuclear power plants & submarines (to generate electricity) www.pollutionissues.com Fusion and Fission: Nuclear Reactions Fusion and fission are nuclear reactions because… …the nuclei of atoms are fusing (in fusion) OR splitting (in fission). (Remember… That’s the center part of the atom where protons and neutrons are located) New atoms are made in both types of reactions. http://en.wikipedia.org/wiki/Combustion Combustion Combustion is… burning of a fuel in presence of O2 (oxygen) to produce energy (heat & light) a. It is a chemical reaction which recombines atoms. (FUEL) Methane Combustion used in… Vehicles Fireplaces Power Plants (Belews Creek) http://www.news-record.com/news/article_73ce9953-637d-5c7c-bfdd-49fee0a35773.html http://en.wikipedia.org/wiki/Volkswagen_New_Beetle Think About It… How does the Sun harm living things? (What types of energy from the Sun are harmful?) Focus Question… How are the harmful forms of radiation from the Sun deflected away or filtered so that they don’t reach living things? The Sun’s Energy… 1. Electromagnetic radiation consists of … … electric & magnetic disturbances that travel through space as waves. 2. The electromagnetic spectrum… …organizes forms of EM energy by wavelength 3. The Sun produces electromagnetic radiation across the spectrum… radio waves, microwaves, infrared energy (heat), visible light, ultraviolet radiation, xrays, & gamma rays The Electromagnetic Spectrum… 4. The shorter the wavelength, the more harmful the energy! http://www.lbl.gov/MicroWorlds/ALSTool/EMSpec/EMSpec2.html The Ozone Layer… 5. Which gas blocks ultraviolet radiation from the Sun? Ozone (O3) a. It is found in the stratosphere. b. Chlorofluorocarbons (CFCs) damage O3. c. These are found in aerosols, coolants, & cleaners. http://mmedia.pl/ozone-layer-diagram-for-kids Solar Wind and Earth’s Magnetic Field 1. Solar wind is… …a supersonic plasma (Remember, that’s charged particles or ions) that flows outward from Sun at high speeds &… …bathes planets in a flood of highenergy particles. (Which isn’t very good for us!) Solar Wind and Earth’s Magnetic Field… 2. Earth’s magnetic field protects us from the solar wind by… deflecting these particles and trapping them in two huge rings (Van Allen belts) http://www.redorbit.com/education/reference_library/space_1/solar_system/2574610/van_allen_radiation_belt/ Focus Question… How does the Sun’s energy warm Earth’s surface and atmosphere? Energy For Earth… 1. Radiation is … transfer of energy through space by EM waves (visible light, ultraviolet radiation, & other) http://virtualskies.arc.nasa.gov/weather/images/2b1.png Energy For Earth… 1a. The Sun’s energy reaches Earth by the process of radiation. 1b. About 50 % of the Sun’s energy is absorbed by Earth’s surface. 1c. Remember – ozone blocks most of the UV radiation. http://ossfoundation.us/projects/environment/global-warming/earths-radiation-budget Differential Heating… 1d. Which heats up and cools down more slowly – water or land? This is called differential heating. This is what moderates the climate in coastal areas. In winter, the ocean acts like a giant heater and in summer, the ocean acts like a giant air conditioner. Differential Heating and North Carolina… Our moderate coast – The Outer Banks! 2. Conduction is… the transfer of energy that occurs when molecules collide a. Air molecules just above Earth’s surface are warmed by conduction. b. Energy moves from your hand to your desk. Why? Energy for Earth… Heat waves over hot sand! http://visualparadox.com/wallpapers/dryseason1600.htm Energy for Earth… 3. Convection is… a. b. c. the transfer of energy by the flow of a heated substance Warm air will rise. When the warm air gets high enough, it cools and sinks. This creates a convection current. http://avstop.com/ac/fig5-9.jpg Energy for Photosynthesis… 1. 2. 3. 4. 5. During photosynthesis, solar energy is transformed into chemical energy (food). This occurs in plants, algae & some bacteria. For this to occur, there must be water, CO2, Energy source: sunlight. In plants, this occurs in chloroplasts. http://abhsscience.wikispaces.com/Photosynthesis+TD