Презентация Астрономия Билингвальный урок

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  Origin of Modern Astronomy
  

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  Ancient Greeks
  Early Astronomy
   Astronomy is the science that studies the universe. It includes the observation and interpretation of celestial bodies and phenomena.
  . The Greeks used philosophical arguments to explain natural phenomena
   The Greeks also used some observational data.
  

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  Ancient Greeks
  Early Astronomy
   Geocentric Model = Ptolemy Greek Astronomer
  • In the ancient Greeks’ geocentric model, the moon, sun, and the known planets—Mercury, Venus, Mars, and Jupiter—orbit Earth.
   Heliocentric Model = Nicolaus Copernicus
  • In the heliocentric model, Earth and the other planets orbit the sun.
  

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  Ancient Greeks
  Early Astronomy
   Ptolemaic System
  • Ptolemy created a model of the universe that accounted for the movement of the planets.
  • Retrograde motion is the apparent westward motion of the planets with respect to the stars.
  Retrograde motion of Mars
  East
  West
  Sept.
  Aug.
  July
  June
  Dec.
  Jan.
  Feb.
  March
  April
  May
  

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  Retrograde Motion
  

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  99 Years of Astronomy
  

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  The Birth of Modern Astronomy
  Early Astronomy
   Nicolaus Copernicus
  • Copernicus concluded that Earth is a planet. He proposed a model of the solar system with the sun at the center. Heliocentric Model
  
  This model explained the retrograde motion of planets better than the geocentric model.
  
  

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  The Birth of Modern Astronomy
  Early Astronomy
   Tycho Brahe
  • Tycho Brahe designed and built instruments to measure the locations of the heavenly bodies. Brahe’s observations, especially of Mars, were far more precise than any made previously.
   Johannes Kepler
  • Kepler discovered three laws of planetary motion:
  1. Orbits of the planets are elliptical.
  2. Planets revolve around the sun at varying speed.
  3. There is a proportional relationship between a planet’s orbital period and its distance to the sun.
  
  
  
  

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  The Birth of Modern Astronomy
  Early Astronomy
  German astronomer
  Johannes Kepler
  (1571-1630) helped establish the era of modern astronomy by deriving three laws of planetary motion.
  

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  Johannes Kepler
  
  1599 – Kepler hired by Tycho Brahe
  Work on the orbit of Mars
  
  1609 – Kepler’s 1st and 2nd Laws
  Planets move on ellipses with the Sun at one focus
  The radius vector sweeps out equal areas in equal times
  
  1618 – Kepler’s 3rd Law
  The square of a planet’s orbital period P is proportional to the cube of its semi-major axis R.
  

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  Early Astronomy
  Johannes Kepler used Tycho Brahe’s data to develop three laws that explained the motions of the planets.
  June 15th
  July 15th
  January 15th
  December 15th
  (30 days)
  (30 days)
  Sun
  Equal areas
  Earth’s orbit
  KEPLER’S EQUAL AREA LAW states that a line connecting Earth to the sun will pass over equal areas of space in equal times. Because Earth’s orbit is elliptical, Earth moves faster when it is nearer to the sun.
  

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  Early Astronomy
  Faster
  Slower
  Equal areas law
  KEPLER’S EQUAL AREA LAW states that a line connecting Earth to the sun will pass over equal areas of space in equal times. Because Earth’s orbit is elliptical, Earth moves faster when it is nearer to the sun.
  

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  Early Astronomy
   Galileo Galilei
  Italian scientist
  Galileo Galilei (1564—1642) used a new invention, the telescope, to observe the Sun, Moon, and planets in more detail than ever before.
  

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  The Birth of Modern Astronomy
  Early Astronomy
   Galileo Galilei
  • Galileo’s most important contributions were his descriptions of the behavior of moving objects.
  • He developed his own telescope and made important discoveries:
  1. Four satellites, or moons, orbit Jupiter.
  2. Planets are circular disks, not just points of light.
  3. Venus has phases just like the moon.
  4. The moon’s surface is not smooth.
  5. The sun has sunspots, or dark regions.
  

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  Early Astronomy
   Sir Isaac Newton
  English scientist
  Sir Isaac Newton (1642—1727) explained gravity as the force that holds planets in orbit around the Sun.
  

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  The Birth of Modern Astronomy
  Early Astronomy
   Sir Isaac Newton
  • Although others had theorized the existence of gravitational force, Newton was the first to formulate and test the law of universal gravitation. The universal law of gravitation, helped explain the motions of planets in the solar system.
  
   Universal Gravitation
  • Gravitational force decreases with distance.
  • The greater the mass of an object, the greater is its gravitational force.
  

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  Gravity’s Influence on Orbits
  

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  Newton’s Laws of Motion
  1st Law
  A body at rest, or in uniform motion, will remain so unless acted upon by an unbalanced force.
  2nd Law
  The change in motion (acceleration) is proportional to the unbalanced force
  3rdLaw
  For every action there is an equal and opposite reaction
  
  

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  Gravity
  Gravity is the force that
  holds us to the Earth
  causes a rock to fall towards the ground
  causes the Earth to go around the Sun
  causes the Sun to be pulled towards the center of the Milky Way galaxy
  
  Gravity acts between any two objects even if they are far apart.
  “action at a distance”
  

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  The Movements of Planets and Stars
  B. Ptolemy’s Geocentric Model
  C. Copernicus’s Heliocentric Model
  D. Tycho, Kepler, and Planetary Motion
  E. Isaac Newton and the Law of Gravitation
  
  
  
  
  VOCABULARY
  Observing the Solar System: A History
  geocentric
  heliocentric
  gravitation
  retrograde
  

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  Summary
  Kepler’s and Galileo’s Laws provided Newton with important clues that helped him formulate his laws of motion
  
  Newton arrived at 3 laws that govern the motion of objects
  The law of inertia
  The law of force
  The law of action and reaction
  
  Newton also arrived at a law of gravity
  But it seemed to require action at a distance!
  

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  Light and Astronomical Observations
  Earth Science
  

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  • An ellipse is an oval-shaped path.
  An astronomical unit (AU) is the average distance between
  Earth and the sun; it is about 150 million kilometers.
  Light-year The distance that light travels in one year, about 9.5 trillion kilometers.
  
  Parsec: A unit of measurement used to describe distances between celestial objects, equal to 3.258 light-years.
  
  Important Astronomical Measurements
  

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  Electromagnetic radiation
  Visible light is only one small part of an array of energy
  Electromagnetic radiation includes
  Gamma rays
  X-rays
  Ultraviolet light
  Visible light
  Infrared light
  Radio waves
  The study of light
  *Energy radiated in the form of a wave, resulting from the motion of electric charges and the magnetic fields they produce.
  

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  The study of light
  Electromagnetic radiation
  All forms of radiation travel at 300,000 kilometers (186,000 miles) per second
  Light (electromagnetic radiation) can be described in two ways
  Wave model
  Wavelengths of radiation vary
  Radio waves measure up to several kilometers long
  Gamma ray waves are less than a billionth of a centimeter long
  White light consists of several wavelengths corresponding to the colors of the rainbow
  
  A continuum depicting the range of electromagnetic radiation, with the longest wavelength at one end and the shortest at the other.
  

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  Light (electromagnetic radiation) can be described in two ways
  Particle model
  Particles called photons
  Exert a pressure, called radiation pressure, on matter
  Shorter wavelengths correspond to more energetic photons
  

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  Spectroscopy
  The study of the properties of light that depend on wavelength
  The light pattern produced by passing light through a prism, which spreads out the various wavelengths, is called a spectrum (plural: spectra)
  
  The study of light
  

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  A spectrum is produced when white light passes through a prism
  The study of light
  

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  Spectroscopy
  
  The study of light
  Types of spectra
  Continuous spectrum: A spectrum that contains all colors or wavelengths.
  Produced by an incandescent solid, liquid, or high pressure gas
  Uninterrupted band of color
  Dark-line (absorption) spectrum
  Produced when white light is passed through a comparatively cool, low pressure gas
  Appears as a continuous spectrum but with dark lines running through it
  

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  Formation of the three types of spectra
  

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  A spectrum consisting of individual lines at characteristic wavelengths produced when light passes through an incandescent gas; a bright-line spectrum.
  Emission Spectrum
  A continuous spectrum crossed by dark lines produced when light passes through a nonincandescent gas.
  Absorption Spectrum
  Emission spectrum of hydrogen
  Absorption Spectrum of Hydrogen
  

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  Doppler effect
  The apparent change in wavelength of radiation caused by the relative motions of the source and observer
  Used to determine
  Direction of motion
  Increasing distance – wavelength is longer ("stretches")
  Decreasing distance – makes wavelength shorter ("compresses")
  Velocity – larger Doppler shifts indicate higher velocities
  
  The study of light
  

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  The Doppler effect
  Originally discovered by the Austrian mathematician and physicist, Christian Doppler (1803-53), this change in pitch results from a shift in the frequency of the sound waves.
  

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  Redshift, a phenomenon of electromagnetic waves such as light in which spectral lines are shifted to the red end of the spectrum.
  
  
  The electromagnetic radiation emitted by a moving object also exhibits the Doppler effect.
  
  The Doppler effect
  

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  The radiation emitted by an object moving toward an observer is squeezed; its frequency appears to increase and is therefore said to be blueshifted. In contrast, the radiation emitted by an object moving away is stretched or redshifted. Blueshifts and redshifts exhibited by stars, galaxies and gas clouds also indicate their motions with respect to the observer.
  
  The Doppler effect
  Redshift: This spectrum shows hydrogen shifted to the red end of the spectrum. This star is moving away from Earth.
  Blueshift: This spectrum shows hydrogen shifted to the blue end of the spectrum. This star is moving toward Earth.
  

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  Optical (visible light) telescopes
  Two basic types (1) Refracting telescope
  Uses a lens (called the objective) to bend (refract) the light to produce an image
  Light converges at an area called the focus
  Distance between the lens and the focus is called the focal length
  The eyepiece is a second lens used to examine the image directly
  Have an optical defect called chromatic aberration (color distortion)
  Astronomical tools
  

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  A simple refracting telescope
  

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  Optical (visible light) telescopes
  Two basic types (2) Reflecting telescope
  
  Uses a concave mirror to gather the light
  No color distortion
  Nearly all large telescopes are of this type
  Astronomical tools
  

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  A prime focus reflecting telescope
  

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  Cassegrain focus reflecting telescope
  

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  Newtonian focus reflecting telescope
  

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  The 200" (5m) Hale Reflector of Palomar Observatory is shown above. Until recently it was the world's largest optical/infrared telescope.
  
  

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  Optical (visible light) telescopes
  Properties of optical telescopes
  Light-gathering power
  Larger lens (or mirror) intercepts more light
  Determines the brightness
  Resolving power
  The ability to separate close objects
  Allows for a sharper image and finer detail
  Astronomical tools
  

• 46 слайд

  Optical (visible light) telescopes
  Properties of optical telescopes
  Magnifying power
  The ability to make an image larger
  Calculated by dividing the focal length of the objective by the focal length of the eyepiece
  Can be changed by changing the eyepiece
  Limited by atmospheric conditions and the resolving power of the telescope
  Even with the largest telescopes, stars (other than the Sun) appear only as points of light
  Astronomical tools
  

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  Detecting invisible radiation
  Radio radiation
  Gathered by "big dishes" called radio telescopes
  Large because radio waves are about 100,000 times longer than visible radiation
  Often made of a wire mesh
  Have rather poor resolution
  Can be wired together into a network called a radio interferometer
  Astronomical tools
  

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  A steerable radio telescope at Green Bank, West Virginia
  Radio Telescope
  

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  Detecting invisible radiation
  Radio radiation
  Gathered by "big dishes" called radio telescopes
  Advantages over optical telescopes
  Less affected by weather
  Less expensive
  Can be used 24 hours a day
  Detects material that does not emit visible radiation
  Can "see" through interstellar dust clouds
  Astronomical tools
  

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  The 300-meter radio telescope at Arecibo, Puerto Rico
  Radio Telescope
  

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  The theory holding that the universe originated from the instant expansion of an extremely small agglomeration of matter of extremely high density and temperature.
  The Big Bang Theory
  

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  Photons converted into particle-antiparticle pairs and vice-versa
  
  E = mc2
  
  Early universe was full of particles and radiation because of its high temperature
  
  

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  The Big Band Theory
  Evidence for Big Bang
  This is the theory of the universe’s earliest moments.
  It presumes that the universe began from a tiny, hot, and dense collection of matter and radiation.
  It describes how expansion and cooling of particles could have led to the present universe of stars and galaxies.
  It explains several aspects of today’s universe with a very good accuracy.
  
  
  
  

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  The Big Band Theory
  The Big Bang theory is a model, which explains some facts (observations).
  It should be able to make predictions that can be verified through observations or experiments.
  Two important predictions:
  
  Cosmic microwave background radiation.
  2. Fusion of original hydrogen into helium.
  

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  Evidence for the Big Bang
  The Cosmic Background Radiation (Microwaves)
  Penzias & Wilson (1962) discovered an isotropic background microwave signal during testing a microwave antenna at Bell Labs in 1965. The noise was found to be coming from every direction.
  At the same time, physicists from Princeton calculated the expected radiation from the initially hot universe.They suggested that this radiation could be detected with a microwave antenna.
  The result was a Nobel Prize in physics for 1978.
  

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  The Cosmic Microwave Background
  
  

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  The Cosmic Background Radiation (Microwaves)
  Background radiation from Big Bang has been freely streaming across universe since atoms formed at temperature ~ 3,000 K: visible/IR
  

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  The Cosmic Microwave Background
  The background consists of photons (radiation) arriving at Earth directly from the end of the era of nuclei (when the Universe was about 380,000 years old).
  Neutral atoms captured most of the electrons.
  Photons were released and have flown freely through the universe ever since.
  
  This background radiation can be detected with a small TV antenna as part (1%) of static “snow”. The redshifted spectrum of the background radiation has now a temperature of 2.73 K.
  
  

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  Cosmic Background Explorer
  
  The first satellite built dedicated to cosmology. Its goals were to investigate the cosmic microwave background radiation (CMB) of the universe and provide measurements that would help shape our understanding of the cosmos.
  
  

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  This work helped cement the big-bang theory of the universe. According to the Nobel Prize committee, "the COBE-project can also be regarded as the starting point for cosmology as a precision science". Two of COBE's principal investigators, George Smoot and John Mather, received the Nobel Prize in Physics in 2006.
  
  Cosmic Background Explorer
  
  

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  Cosmic Background Explorer
  
  

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  The "famous" map of the CMB anisotropy formed from data taken by the COBE spacecraft.
  Cosmic Background Explorer
  
  

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  In 1927, the Belgian priest Georges Lemaître was the first to propose that the universe began with the explosion of a primeval atom.
  
  Evidence for the Big Bang
  

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  Evidence for the Big Bang
  Edwin Hubble found experimental evidence to help justify Lemaître's theory. He found that distant galaxies in every direction are going away from us with speeds proportional to their distance (the redshift).
  
  The big bang was initially suggested because it explains why distant galaxies are traveling away from us at great speeds. The theory also predicts the existence of cosmic background radiation (the glow left over from the explosion itself). The Big Bang Theory received its strongest confirmation when this radiation was discovered in 1964 by Arno Penzias and Robert Wilson, who later won the Nobel Prize for this discovery.
  
  

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  Hubble’s Evidence
  Doppler shifting - wavelength emitted by something moving away from us is shifted to a lower frequency
  Sound of a fire truck siren - pitch of the siren is higher as the fire truck moves towards you, and lower as it moves away from you
  Visible wavelengths emitted by objects moving away from us are shifted towards the red part of the visible spectrum
  The faster they move away from us, the more they are redshifted. Thus, redshift is a reasonable way to measure the speed of an object (this, by the way, is the principal by which radar guns measure the speed of a car or baseball)
  When we observe the redshift of galaxies outside our local group, every galaxy appears to be moving away from us - universe is expanding.
  
  
  

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  Expansion of universe has redshifted thermal radiation from that time to ~1000 times longer wavelength: microwaves
  

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  Big Bang Theory - Evidence for the Theory
  What are the major evidences which support the Big Bang theory?
  
  Evidence for the Big Bang
  
  First of all, we are reasonably certain that the universe had a beginning.
  Second, galaxies appear to be moving away from us at speeds proportional to their distance. This is called "Hubble's Law," named after Edwin Hubble (1889-1953) who discovered this phenomenon in 1929. This observation supports the expansion of the universe and suggests that the universe was once compacted.
  
  

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  Evidence for the Big Bang
  
  Third, if the universe was initially very, very hot as the Big Bang suggests, we should be able to find some remnant of this heat. In 1965, Radioastronomers Arno Penzias and Robert Wilson discovered a 2.725 degree Kelvin (-454.765 degree Fahrenheit, -270.425 degree Celsius) Cosmic Microwave Background radiation (CMB) which pervades the observable universe. This is thought to be the remnant which scientists were looking for. Penzias and Wilson shared in the 1978 Nobel Prize for Physics for their discovery.
  
  

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  Evidence for the Big Bang
  
  Finally, the abundance of the "light elements" Hydrogen and Helium found in the observable universe are thought to support the Big Bang model of origins.
  
  

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  Synthesis of Helium
  The current CMB temperature tells us precisely how hot the universe was when it appeared.
  
  It tells us how much helium was initially produced.
  
  A helium nucleus contains 2 protons and 2 neutrons.
  
  At T > 1011 K, nuclear reactions converted protons into neutrons and back, keeping their numbers nearly equal.
  Between 1010 and 1011 K, neutron – proton reactions favor protons, because neutrons are heavier than protons.
  
  

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  Energy is required to convert protons to neutrons.
  At T < 1010 K, only neutrons can be changed into protons.
  However, fusion continued to operate
  and protons and neutrons combined into deuterium.
  Then deuterium fused into helium.
  During the early era of nucleosynthesis, helium nuclei were being destroyed by gamma-rays.
  At ~1 minute, gamma-rays were gone and the proton – neutron ratio was set to 7:1.
  Synthesis of Helium
  

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  Big Bang theory prediction: 75% H, 25% He (by mass)
  
  Matches observations of nearly primordial gases
  Synthesis of Helium
  

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  Abundances of other light elements agree with Big Bang model having 4.4% normal matter – more evidence for WIMPS!
  Synthesis of Helium
  

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  Nebular Hypothesis of Solar System Formation.