Use of constellations (88) - PowerPoint Presentation

1. Use of constellations (88)Use of signs of zodiac (12)Stars have no significance to humansStates that stars predict fatePlanets have no significance to humansPlanets predict fate/behaviorMoon has no advice for human behaviorMoon predicts fate and behaviorNot used to advise farmers beyond use of calendarUsed to hatch chickens, butcher hogs, cure meet, or can foodNo prediction of human behaviorTries to predict human behavior but makes to attempt to verify resultsFollows other science disciplines; physicsMay advise to use of Ephemeral tables produced by astronomersDoesn’t advise to use astrologyDoesn’t require higher math. Uses simply geometry or astronomer calculationsRequires higher math; calculus and beyondNo scientific standard; is considered an “art”Can obtain college degree in itCannot obtain a college degree in itRequires equipment for measurement and verificationDoes not require equipment for measurement or verificationContinuous improvements to measuring instrumentsHave not made improvements to measuring instruments in modern times

2. Origin of Modern Astronomy

3. Ancient GreeksEarly 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.

4. Ancient GreeksEarly 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.

5. Ancient GreeksEarly 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 MarsEastWestSept.Aug.JulyJuneDec.Jan.Feb.MarchAprilMay

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7. Retrograde Motion

8. 99 Years of Astronomy

9. The Birth of Modern AstronomyEarly 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.

10. The Birth of Modern AstronomyEarly 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.

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

12. Johannes Kepler 1599 – Kepler hired by Tycho Brahe Work on the orbit of Mars1609 – Kepler’s 1st and 2nd LawsPlanets move on ellipses with the Sun at one focusThe radius vector sweeps out equal areas in equal times1618 – Kepler’s 3rd LawThe square of a planet’s orbital period P is proportional to the cube of its semi-major axis R.P2 = a3 where P is measured in years and a is measured in AU

13. Early AstronomyJohannes Kepler used Tycho Brahe’s data to develop three laws that explained the motions of the planets.June 15thJuly 15thJanuary 15thDecember 15th(30 days)(30 days)SunEqual areasEarth’s orbitKEPLER’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.

14. Early AstronomyFasterSlowerEqual areas lawKEPLER’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.

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

16. The Birth of Modern AstronomyEarly 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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18. Early Astronomy  Sir Isaac NewtonEnglish scientist Sir Isaac Newton (1642—1727) explained gravity as the force that holds planets in orbit around the Sun.

19. The Birth of Modern AstronomyEarly 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.

20. Gravity’s Influence on Orbits

21. Newton’s Laws of Motion1st LawA body at rest, or in uniform motion, will remain so unless acted upon by an unbalanced force.2nd LawThe change in motion (acceleration) is proportional to the unbalanced force3rd LawFor every action there is an equal and opposite reaction

22. GravityGravity is the force thatholds us to the Earthcauses a rock to fall towards the groundcauses the Earth to go around the Suncauses the Sun to be pulled towards the center of the Milky Way galaxyGravity acts between any two objects even if they are far apart. “action at a distance”

23. The Movements of Planets and StarsB. Ptolemy’s Geocentric ModelC. Copernicus’s Heliocentric ModelD. Tycho, Kepler, and Planetary MotionE. Isaac Newton and the Law of GravitationVOCABULARYObserving the Solar System: A Historygeocentricheliocentricgravitationretrograde

24. SummaryKepler’s and Galileo’s Laws provided Newton with important clues that helped him formulate his laws of motionNewton arrived at 3 laws that govern the motion of objectsThe law of inertiaThe law of forceThe law of action and reactionNewton also arrived at a law of gravityBut it seemed to require action at a distance!

25. Light and Astronomical ObservationsEarth Science

26. • An ellipse is an oval-shaped path.An astronomical unit (AU) is the average distance betweenEarth 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

27. Electromagnetic radiation Visible light is only one small part of an array of energyElectromagnetic radiation includesGamma raysX-raysUltraviolet lightVisible lightInfrared lightRadio 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.

28. The study of light Electromagnetic radiation All forms of radiation travel at 300,000 kilometers (186,000 miles) per secondLight (electromagnetic radiation) can be described in two ways Wave modelWavelengths of radiation varyRadio waves measure up to several kilometers longGamma 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.

29. Light (electromagnetic radiation) can be described in two ways Particle model Particles called photonsExert a pressure, called radiation pressure, on matterShorter wavelengths correspond to more energetic photons

30. SpectroscopyThe study of the properties of light that depend on wavelengthThe 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

31. A spectrum is produced when white light passes through a prismThe study of light

32. SpectroscopyThe 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 gasUninterrupted band of color Dark-line (absorption) spectrum Produced when white light is passed through a comparatively cool, low pressure gasAppears as a continuous spectrum but with dark lines running through it

33. Formation of the three types of spectra

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

35. Doppler effectThe apparent change in wavelength of radiation caused by the relative motions of the source and observerUsed to determineDirection of motionIncreasing distance – wavelength is longer ("stretches")Decreasing distance – makes wavelength shorter ("compresses")Velocity – larger Doppler shifts indicate higher velocities The study of light

36. The Doppler effectOriginally 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.

37. 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

38. 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 effectRedshift: 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.

39. Optical (visible light) telescopes Two basic types (1) Refracting telescope Uses a lens (called the objective) to bend (refract) the light to produce an imageLight converges at an area called the focusDistance between the lens and the focus is called the focal lengthThe eyepiece is a second lens used to examine the image directlyHave an optical defect called chromatic aberration (color distortion) Astronomical tools

40. A simple refracting telescope

41. Optical (visible light) telescopes Two basic types (2) Reflecting telescope Uses a concave mirror to gather the lightNo color distortionNearly all large telescopes are of this type Astronomical tools

42. A prime focus reflecting telescope

43. Cassegrain focus reflecting telescope

44. Newtonian focus reflecting telescope

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

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

47. Optical (visible light) telescopes Properties of optical telescopes Magnifying powerThe ability to make an image largerCalculated by dividing the focal length of the objective by the focal length of the eyepieceCan be changed by changing the eyepieceLimited by atmospheric conditions and the resolving power of the telescopeEven with the largest telescopes, stars (other than the Sun) appear only as points of light Astronomical tools

48. Detecting invisible radiationRadio radiation Gathered by "big dishes" called radio telescopes Large because radio waves are about 100,000 times longer than visible radiationOften made of a wire meshHave rather poor resolutionCan be wired together into a network called a radio interferometer Astronomical tools

49. A steerable radio telescope at Green Bank, West VirginiaRadio Telescope

50. Detecting invisible radiationRadio radiation Gathered by "big dishes" called radio telescopes Advantages over optical telescopes Less affected by weatherLess expensiveCan be used 24 hours a dayDetects material that does not emit visible radiationCan "see" through interstellar dust clouds Astronomical tools

51. The 300-meter radio telescope at Arecibo, Puerto RicoRadio Telescope

52. 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

53. Photons converted into particle-antiparticle pairs and vice-versa E = mc2Early universe was full of particles and radiation because of its high temperature

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55. The Big Band TheoryEvidence for Big BangThis 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.

56. The Big Band TheoryThe 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.

57. Evidence for the Big BangThe 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.

58. The Cosmic Microwave Background

59. 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

60. The Cosmic Microwave BackgroundThe 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.

61. 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.

62. 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

63. Cosmic Background Explorer

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

65. 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

66. Evidence for the Big BangEdwin 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.

67. Hubble’s EvidenceDoppler shifting - wavelength emitted by something moving away from us is shifted to a lower frequencySound 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 spectrumThe 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.

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

69. Big Bang Theory - Evidence for the TheoryWhat are the major evidences which support the Big Bang theory? Evidence for the Big BangFirst 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.

70. Evidence for the Big BangThird, 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.

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

72. Synthesis of HeliumThe 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.

73. Energy is required to convert protons to neutrons.At T < 1010 K, only neutrons can be changed into protons. However, fusion continued to operateand 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

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

75. 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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77. Nebular Hypothesis of Solar System Formation.