GEL1 L01 Intro to Earth Science PDF

Lecture L01: Introduction to Earth Science Taken by NASA DISCVR satellite  Study Questions: Introduction to Earth Science What is Earth Science? Order the following layers of the Earth according to increasing density: crust, core, mantle What happens to density as substances...

Lecture L01: Introduction to Earth Science Taken by NASA DISCVR satellite  Study Questions: Introduction to Earth Science What is Earth Science? Order the following layers of the Earth according to increasing density: crust, core, mantle What happens to density as substances cool down or heat up? What is convection? Do all substances solidify at the same temperature? What are the sources of Earth’s heat? What are the strengths and limitations of science? Can hypotheses and theories be proven wrong? How do you know if you can trust what you read?  Earth Science Collective name for the sciences that study the Earth and surrounding space Made up of these interacting systems (‘spheres’): - Geosphere - Hydrosphere - Atmosphere - Biosphere - Solar system & beyond … -sphere Geosphere Hydrosphere Atmosphere Biosphere Solar System and Beyond  Recurring Concepts in Earth Science Heat Density Gravity  Why is the core at the center of the Earth? Crust Crust Mantle Mantle Core Core  Heat drives the Earth System 1 - Internal heat left over from formation of Earth and radioactive decay 2 - External heat from the sun  Different substance solidify at different temperatures Examples: - basalt from lava = solid at room temperature - Ice = liquid at room temperature - Methane = gas at room temperature water ice basalt methane ice in Pluto!  D=m/v Review of Density m: mass v: volume Equal mass, different volume Equal volume, different mass Less Dense More More Dense Less Dense MoreDense Dense 2 1 1 2  Geosphere layers have different densities Crust - Thin, low density rock layer  Granite = 2.7 g/cm3 (Continental Crust) Basalt → = 3.0 g/cm3 (Oceanic Crust) Mantle  Peridotite = 3.3 g/cm3 - Higher density rocks (Mantle) Core - Even higher density - Iron and nickel  Why is the densest layer at the center of the Earth? Crust - Thin, low density rock layer Mantle - Higher density rocks Core - Even higher density  Convection: Interaction of Density and Heat Differences Lava lamp analogy - cold wax is denser than liquid and sinks - wax expands as it is heated, rising as it becomes less dense than the liquid - wax cools as it reaches the top and sinks again colder hotter heat source Lava lamp convection video https://www.youtube.com/watch? v=wxEw1UbpRIg  Convection in the Mantle - Hot mantle rises, cooling as it reaches the surface - Cooled mantle is denser and sinks Stable mantle convection creates hotspots Cooler mantle Hot mantle Heat source  Convection in the Atmosphere - Hot air rises, cooling and condensing into clouds - Cooler air is denser and sinks Heat source = sun  The strengths of science Strength 1: It is based in facts - Physical objects - Observations - Measurements Strength 2: Hypotheses, theories, & laws must be testable - Data that disproves the hypothesis/theory/law must be obtainable Astronomy is a science - makes specific predictions about phenomena - tested by repeatable observations & measurements of physical objects - data = light, gravitational waves, etc. Photograph(!) of Stephen’s Quintet of 5 galaxies taken by the James Webb Space Telescope! Strength 2: Hypotheses, theories, & laws must be testable - Data that disproves the hypothesis/theory/law must be obtainable Astrology is not a science  Newton’s Theory of Gravity - Gravity is a force - Successfully predicted existence of Neptune based on motion of Uranus - Fails to account for orbit of Mercury (it’s too “wobbly”)  Newton’s Theory of Gravity replaced by Einstein’s Theory of General Relativity Einstein’s theory of general relativity (1916) - Gravity is a curve in space-time instead of force - Successfully accounts for the orbit of Mercury and other observations that Newton’s theory cannot - Predicts that light redshifts near massive objects and others  Einstein’s Theory of General Relativity - Can explain orbit of Mercury and other observations that Newton’s Theory cannot - Makes additional predictions: - expanding universe - light redshifts next to massive objects Strength 3: The scientific cycle is progressive - Hypotheses are based on a set of observations and measurements of physical objects (= data) - Every experiment provides new data - New data combined with previous data to form new hypotheses  The Scientific Cycle Initial Observations Hypothesis: - Testable explanation for a series of facts - Based on limited evidence Hypothesis - Starting point for further research - Can be proven wrong with new data Test Is hypothesis incorrect? New Observations  The Scientific Cycle Initial Observations NO YES Hypothesis New hypothesis Test Is hypothesis Test incorrect? New Observations New Observations  Hypotheses and Theories Hypothesis: - Testable explanation for a series of facts - Based on limited evidence - Starting point for further research - Could be proven wrong with new data Theories: - Well-supported hypotheses - Based on extensive evidence - Could still be proven wrong with new data  Limitations of Science The personal background of the scientist shapes the questions and interpretation of data Increasing diversity in science reduces these limitations! - More diversity = more questions are asked and studied What do you think this is? Real? Fiction? It’s me! ☺ Zuul from Ghostbusters? Cyclops skull? WSnyder from deviantart.com Medieval European interpretation of fossils as serpents and dragons  Limitations of Science The personal background of the scientist shapes the questions and interpretation of data The scientists that peer-review scientific work are subject to their own personal biases Increasing diversity in science reduces these limitations! - More diversity = more questions are asked and studied = data interpretations are richer due to more perspectives  Mary Anning (1799-1847) - Discovered first specimen of Ichthyosaurus - Discovered first plesiosaur - Many more discoveries and contributions but were not credited for most of them because of sexism bias  Limitations of Science The personal background of the scientist shapes the questions and interpretation of data The scientists that peer-review scientific work are subject to their own personal biases Funding agencies pick and choose which studies get funded Increasing diversity in science reduces these limitations! - More diversity = more questions are asked and studied = data interpretations are richer due to more perspectives = more potential sources of funding More fossils are discovered in some parts of the world than others. Why? Europe Number of Fossils Groups (Families) N. America Asia Africa S. & Central America Australasia  Limitations of Science The personal background of the scientist shapes the questions and interpretation of data The scientists that peer-review scientific work are subject to their own personal biases Funding agencies pick and choose which studies get funded Increasing diversity in science reduces these limitations! - More diversity = more questions are asked and studied = data interpretations are richer due to more perspectives = more potential sources of funding  Can you trust what you read? Does article have references to peer-reviewed sources?  Can you trust what you read? Does article have references to peer-reviewed sources?