Astronomy Midterm #1 – Flashcards

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cosmology
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the study of the origin, evolution, and behavior of the universe as a whole
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universe
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that which contains and subsumes all the laws of nature, and everything subject to those laws; the sum of all that exists physically, including matter, energy, physical laws, space, and time
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astronomy
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the study of the contents of the universe beyond the Earth
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anthropomorphism
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the projection of human attributes onto nonhuman entities such as animals, the planets, or the universe as a whole
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myth
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a narrative intended to explain or justify the beliefs of a people. the term usually suggests a lack of historical and factual basis
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anthropocentrism
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the belief that humans are central to the universe
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experiment
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a controlled trial for the purpose of collecting data about a specific phenomenon
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scientific method
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an investigative approach in which data is gathered, a hypothesis is formulated to explain the data, and further experiments are performed to test the hypothesis
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data
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the outcome of a set of measurements from which inferences may be drawn, theories constructed, etc.
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hypothesis
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a proposed explanation for an observed phenomenon. in science, a valid hypothesis must be based upon data and must be subject to testing
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relevant
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of a scientific hypothesis: directly related to the phenomenon it seeks to explain
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falsifiable
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of a scientific hypothesis: leading to the possibility of performing an experiment that would disprove.falsify the hypothesis
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consistent
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of a scientific theory: containing and extending an earlier well-supported theory, ex. general relativity is consistent with Newtonian gravity
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crucial experiment
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an experiment that has the power to decide between two competing theories
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simplicity
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the property of a scientific hypothesis that its proposed explanation must not be unnecessarily complicated
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Occam's Razor
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the principle that when all other things are equal, the simplest explanation is preferred
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predictive power
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the ability of a hypothesis or model to predict unobserved effects. this provides an important means of testing a hypothesis.
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explanatory power
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the ability of a scientific hypothesis to account for known data
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theory
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in scientific usage, a hypothesis or related group of hypotheses that have become well established
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law
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in scientific usage, a theory that has become particularly well confirmed and well established
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model
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a hypothesis or group of related hypotheses that describes and clarifies a natural phenomenon, entity, etc.
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geocentric
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taking the Earth to be the center, for example, of the solar system
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mechanics
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the science of motion
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force
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that which produces an acceleration
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inertia
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that property of an object which resists changes in its state of motion
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heliocentric
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taking the sun to be the center (of the solar system)
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parallax
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the apparent shift in the position of a star due to the changing vantage point of the observer. can be caused by phenomena such as the orbital motion of the earth, or its daily rotation
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retrograde motion
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the apparent reversal in the motion of a planet across the sky relative to the background stars, caused by the Earth passing the planet or being passed by it
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Copernican revolution
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the revolution in thought resulting from the acceptance of the heliocentric model of the solar system
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Copernican principle
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the principle that the Earth is not the center of the universe
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ellipse
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a geometric figure generated by keeping the sum of the distance from two fixed points (the foci) constant
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Kepler's laws
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the three laws of planetary motion discovered by Johannes Kepler
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thought experiment
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an experiment that could be performed in principle but might be very difficult in practice, and whose outcome can be predicted by pure logic. often used to develop the consequences of a theory so that more practical phenomena can be predicted and put to actual experimental tests
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Newton's first laws
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the law of motion which states that an object in a state of uniform motion will remain in that state unless acted upon by an external force
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uniform motion
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motion at a constant velocity. the state of rest is a special case of uniform motion
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force
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that which produces an acceleration
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acceleration
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a change of velocity with respect to time
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Newton's second law
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the law of motion which states that the net applied force on an object produces an acceleration in proportion to the mass (F=ma)
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mass
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that property of an object which causes it to resist changes in its state of motion; also, that property which generates gravitational attraction
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conservation of momentum
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the principle that the linear momentum of a system (in Newtonian mechanics, mass times velocity) remains the same as long as no external force acts
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vector
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a mathematical entity that has direction as well as magnitude. important physical quantities represented by vectors include velocity, acceleration, and force. a vector changes whenever either its direction or its magnitude changes
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Newtons third law
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for every action, theres an equal and opposite reaction
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universal gravitation
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Newtons mathematical formulation of the law of attraction between two masses (Fg = (GMm)/(R^2))
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gravitational constant
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a fundemental constant of nature, G, which determines the strength of the gravitational attraction
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weight
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the gravitational force experienced by an object. usually refers to the gravitational attraction due to a large object, such as a planet, upon small objects at or near its surface
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radioactive dating
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the determining of the age of a sample by the measurement of the ratio of the decay products to the precursor, for one or more radioactive isotopes. radioactive dating is possible because each unstable isotope has a well-defined half-life.
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photon
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a boson which is the particle of electromagnetic radiation (light). the photon is also the carrier particle of the electromagnetic force
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nucleon
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either of the two fermionic particles (proton and neutron) which form the nuclei of atoms
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isotope
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one of the forms in which an element occurs. one isotope differs from another by having a different number of neutrons in its nucleus. the number of protons determines the elemental identity of an atom, but the total number of nucleons affects properties such as radioactivity or stability, the types of nuclear reactions, if any, in which the isotope will participate, and so forth
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nuclear reaction
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a reaction that occurs in and may change the nucleus of at least one atom. ex. radioactivity, fission, and fusion
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neutrino
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any of three species of very weakly interacting lepton with an extremely small mass
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boson
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a class of elementary particles whose spin is an integer multiple of a fundamental quantized value. the major function is to mediate the fundamental forces. ex. photon
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fermion
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a class of elementary particles whose spin is a half-integer multiple of a fundamental quantized value. they make up matter. ex. protons, neutrons, electrons, neutrinos. they obey the exclusion principle
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exclusion principle
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the property that fermions of the same type that are able to interact with each other cannot simultaneously occupy the same quantum state
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antimatter
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particles with certain properties opposite to those of matter. each matter particle has a corresponding antiparticle. the antiparticle has exactly the same mass and electric charge as its partner. when these two particles combine both are annihilated and converted to photons
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strong nuclear force
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the fundamental force that binds quarks into hadrons and holds nucleons together in atomic nuclei
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weak nuclear force
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the fundamental force that accounts for some particle interactions, such as beta decay, the decay of free neutrons, neutrino interactions, and so forth.
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electromagnetic force
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the force between charged particles that accounts for electricity and magnetism. one of the four fundamental forces of nature, it is carried by photons and is responsible for all observed macroscopic forces except for gravitational forces
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gravity
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the weakest of the four fundamental forces; that force which creates the mutual attraction of masses
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energy
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the capacity to perform work
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work
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the exertion of a force to produce a displacement
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potential energy
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the energy possessed by something by virtue of its location in a potential field. ex. its position in a gravitational field
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kinetic energy
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the energy associated with macroscopic motion. in newtonian mechanics, the kinetic energy = ((1/2)m(v^2))
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thermodynamics
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the theory of heat and its relationship to other forms of energy
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heat
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a form of energy related to the random motions of particles that make up an object
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temperature
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a measure of the avg kinetic energy of random motion of the constituents (like molecules, atoms, or photons) of a system
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conservation of energy
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the principle that the total energy of a closed system never changes, but energy is only converted from one form to another
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conservation of matter
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the principle that matter is neither created or destroyed
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entropy
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a quantitative measure of the disorder of a system. the greater the disorder, the higher the entropy
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spectrum
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the components of emitted radiation, or a collection of waves separated and arranged in the order of some varying characteristic such as wavelength, frequency, mass, or energy
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interference
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the interaction of two waves in which their amplitudes are reinforced and/or cancelled
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Doppler effect
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the change in frequency of a wave (light, sound, etc.) due to the relative motion of source and reciever
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blueshift
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a shift in the frequency of a photon toward higher energy (star moving towards observer)
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redshift
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a shift in the frequency of a photon towards lower energy (star moving away from observer)
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lightyear (ly)
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a measure of distance equal to that travelled by light in one year
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blackbody
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a theoretical object that absorbs 100% of the radiation that hits it. Therefore it reflects no radiation and appears perfectly black.
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black body radiation
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a body that doesn't reflect any radiation, but absorbs all light/radiation → can emit radiation for cooling.
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equilibrium
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a balance in the rates of opposing processes, such as emission and absorption of photons, creation and destruction of matter, etc.
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luminosity
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the total power output of an object in the form of light
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galaxy
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a large, gravitationally bound system of stars, star clusters, and interstellar matter
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galaxy cluster
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a group of galaxies that are mutually gravitationally bound
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supercluster
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a cluster of galaxy clusters
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Karl Popper
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author of The Logic of Scientific Discovery. held that science progresses only by falsifiability
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what the greeks knew
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that the earth was round, thought the earth was stationary, and believed that theory was more important than observation
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Aristotle
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student of plato, believed theres a separation between earthly and heavenly (earthly and heavenly elements), champion of Geocentric model of universe
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Ptolemy
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author of Almagest, explained retrograde motion of planets, his system made accurate predictions about the motions of the plantes
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Almagest
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Ptolemy's book that refined Aristotles geocentric system
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Ptolemy's model
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earth in center, with deferents and epicycles
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epicycle
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small circle within deferent that planet revolves in. part of Ptolemy's model
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deferent
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major circle of Ptolematic model
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what did ptolemy not believe?
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that planets are made of the same elements as the earth
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ptolemy believed...
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that planets move in combos of circles, planets move at a constant speed, and planets move around the earth
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Nicholas Copernicus
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author of De Revolutionibus Orbium Coelestrium (Revolutions), who proposed heliocentricism and uniform circular motions
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why didnt copernicus publish?
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he was afraid other scholars would laugh at him
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Revolutions
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written by Copernicus, banned by catholic church
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what did Copernicus not believe?
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that planets all travel at the same speed
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problems with Copernicus's model
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no one had observed parallax of stars, we dont feel the earth move or rotate, it still requires epicycles to accurately match observations of planets
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Platonic solids
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ether, fire, air, water, earth
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Kepler's First law
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planets travel in elliptical orbits, with the Sun at one focus
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Kepler's Second law
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a line from the Sun to a planet sweeps out equal areas in equal times (planets move faster when theyre closer to the sun)
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Kepler's Third law
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P^2 = a^3
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astronomical units (AU)
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1 AU = the avg distance from the earth to the sun
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Galileo
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author of Starry Messenger
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Pope Urban VIII
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early admirer of Galileo's works who first encourage Galileo to publish Dialogue, but then never aided Galileo when Dialogue went under fire by the church
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Dialogue Concerning Two Chief World Systems
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book by Galileo, with characters Salviati (represented Galileo), Simplicio (represented church/Aristotle's followers, also a fool), and Sagredo (represented impartial observer). Written in everyday italian. Was banned by church due to simplicios character, and Galileo stood trial and was forced to stop teaching copernicanism. Galileo had to recant his beliefs
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Isaac Newton
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went to Trinity College, and when he returned home he invented differential and integral calc, developed theory of light and optics, formulated modern dynamics (force, inertia, velocity, acceleration), and began to formulate universal law of gravity. Author of Principia, creater of 3 laws
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Edmund Halley
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prompted Newton to prove and publish that the inverse square law of gravity results in Keplers ellipses (Principia)
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Principia
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book by Newton published due to the urgings of Edmund Halley
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Newton's Universal Law of Gravity
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F = (GMm)/(R^2)
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William Herschel
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discovered Uranus in 1781
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Adams and Le Verrier
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men who predicted the existance of an unseen planet (Neptune) based on Uranus' orbit and Newton's law of gravity
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Joseph von Fraunhofer
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self-taught Bavarian mathematician and optician, discovered in 1814 that the spectrum of the sun contains hundreds of dark lines
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Gustav Kirchoff
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creater of Kirchoff's laws dealing with spectra
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Kirchoff's First Law
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hot opaque objects (solids or dense gases) produce continuous spectra (like a rainbow)
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Kirchoff's Second Law
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hot thin gases produce emission line spectra (neon signs)
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Kirchoff's Third Law
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cool thin gases between a hot opaque object and the observer produce absorption line spectra (stars)
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continuous spectrum
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a series of colors formed when a beam of white light is dispersed so that the component light waves are arranged in the order of their wavelengths (without any black lines between colors)
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absorption line spectrum
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A spectrum that is continuous except for dark lines that appear due to material (usually cool gas) that absorbs specific wavelengths of light
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emission line spectrum
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the bands of color shown by a specific element when electric current is passed through it and then the emitted light is separated through a prism
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spectral lines
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unique to each element, and can be used to measure chemical composition, temp, density, magnetic fields, and motion towards or away from an observer
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temperature
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a measure of the speed of random internal motions of the molecules in a substance
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Max Planck
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solved the blackbody problem by accepting that energy came in discrete amounts called quanta. won nobel prize for this
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Plack's formula
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E = hv (Energy = Plancks constant x frequency)
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Stefan-Boltzmann Law
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Energy emitted is proportional to T^4. Hotter objects emit more total energy
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blackbody spectra
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aka continuous spectra aka thermal spectra. spectra cause by electrons in dense objects randomly vibrating due to hear.
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why don't I fall through the floor?
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because the electrons in my shoes repel the electrons in the floor
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absorption
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when electrons absorb energy, thus transferring to a higher energy level
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emission
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when electrons transfer to a lower energy level, giving off energy (photons) in the process
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inverse square law of light
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b = L/(4pi(R^2)). brightness = luminosity/(4pi)(distance^2). explains why light gets duller but more widespread as you move outward
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what makes one element different from another?
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the number of protons they have/their atomic number
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chemical reactions
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reactions between the electrons of atoms. the elements themselves remain unchanged
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fission
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type of nuclear reaction that occurs when large nuclei split into smaller ones, releasing energy. can happen spontaneously. ex. atomic bombs
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fusion
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type of nuclear reaction that occurs when small nuclei fuse into larger ones, releasing energy. requires high temps and densities. ex. hydrogen bombs
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age of the eart
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worked on by James Ussher, Darwin, Kelvin, Hans Bethe (whose work led to an age estimate of the sun for 5 billion years), and radioactive dating, which dated the earth at 4.6 billion years
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induction
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reasoning from detailed facts to general principles
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deduction
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reasoning from the general to the specific (or from cause to effect)
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earthly elements
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earth, water, air, fire
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heavenly elements
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quintessence, ether
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Aristotle's beliefs
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that objects move linearly with respect to the center of the universe, believed that force causes deviation in natural motion, believed in primacy of circular motion, believed that the heavens (not earth) moved, and described universe in terms of natural laws
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primacy of circular motion
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continuous circular motion of the heavens
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impetus
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travelling, generalized force
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Galileo
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famous because he was the first to use the telescope to see celestial things, discovered Jupiter's moons, and reasoned that all objects fall at the same rate in a vacuum, discovered the sun had spots
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Copernican beliefs
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believed each planet has their own unique velocity, believed earth was not center of universe
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atom models
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plum pudding model--> Rutherford experiment--> solar system nuclear model-->modern model of atom
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half-life
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the time required for half a sample of a radioactive element to decay. Its a means of dating radioactive samples
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cosmic rays
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high energy rays impinging upon earth from space
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quantum mechanics
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a system of physical laws that governs the behavior of the elementary particles, nuclei, and atoms
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speed of light
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c = wavelength x frequency
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radiation
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emission of energy from an object often in the form of a wave
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Balmer and Bunsen
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pointed an emission line spectra instrument at the stars to measure their composition, thereby discovering that stars are made of elements, not ether
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Planck's Distasteful Idea
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energy is not continuous, it comes in "packets"
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if something is 3 light years away...
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then the light left its source 3 years ago
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ion
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An atom that has gained or lost electrons, thus acquiring a charge.
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helium and hydrogen
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most abundant elements
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