Ch 26-Studying Space Objectives Describe the characteristics of the universe in terms of time, distance, organization Visible and nonvisible parts of electromagentic spectrum Refracting and reflecting teloscopes Explain how telescopes for nonvisible electromagnetic radiation differ from light telescopes Evidence for Earth’s rotation Explain how the change in apparent positions of constellations provides evidence of Earth’s rotation and revolution around the sun Summarize how Earth’s rotation and revolution provide a basis for measuring time Explain how the tilt of Earth’s axis and Earth’s movement cause seasons

Characteristics of Universe How have people studied the sky in the past? What is astronomy? Scientific study of the universe Astronomers Why is astronomy important? Cosmology-study of origin, properties, processes, and evolution of universe Big bang-big explosion 14 billion yrs ago Universe-large and objects far apart What tools are used to see distant objects?

Organization of Universe What makes up the solar system? Sun, Earth, other planets, asteroids and comets Galaxy-collection of stars, dust, and gas bound together by gravity What galaxy do reside in? Milky Way Beyond are billions of other galaxies

Measuring Distances in Universe Approximately 150 million km between Earth and sun-this is known as astronomical unit Use speed of light to measure distance Travels at 300,000 km/s Light yr-light travels 9.46 x 10^12 km Closet star other than the sun to Earth=4.22 light yrs away

Observing Space Electromagnetic spectrum-all frequencies or wavelengths of electromagnetic radiation Light, radio waves, x rays Visible electromagnetic radiation-different colors result because each color of light has characteristic wavelength Shortest wavelengths-blue and violet, longest-red and orange Wavelengths not visible-infrared waves, microwaves, radio waves, ultraviolet rays, x rays, gamma rays

Models of Solar System Aristole-model in which Earth was center, everything revolved around Earth Ptolemy-planets moved in small circles-epicycles, revolved around in larger circles around Earth Copernicus-sun centered, planets revolved around sun in same direction but at different speeds and distances from sun

Kepler’s Laws Law of ellipses-Each planet orbits the sun in a path called a ellipse, not a circle Elliptical orbits can vary in shape Eccentricity-degree of elongation of an elliptical orbit Law of equal areas-objects travel at different speeds in their orbits, equal areas are covered in equal amounts of time as an object orbits the sun Mars travels fastest when closet to sun Law of periods-describes the relationship between average distance between planet and sun and orbital period of planet What is orbital period?

Newton Hypothesized moving objects will keep moving and resist change in speed until acted upon by outside force Inertia-tendency of an object to resist being moved or resist change in speed or direction until outside force acts on object Newton’s Model of Orbits-gravity causes the orbit to curve Gravity pulls object toward sun, inertia keeps object moving forward in straight line Weaker gravitational pull further away from sun Longer orbits=outer planets

Telescopes Who constructed the 1st telescope? Galileo, 1609, viewed craters on moon and Milky Way Instrument that collects electromagnetic radiation from the sky and concentrates it for better observation Optical telescopes-only collect visible light Refracting telescopes-uses a set of lenses to gather and focus light from distant objects Focuses different colors of light at different distances Reflecting-uses curved mirror to gather and focus light from distant objects Issac Newton Gather more light than refracting

Telescopes for Invisible Electromagnetic Radiation Telescopes that detect invisible radiation Earth’s atmosphere acts as shield against many forms of electromagnetic radiation Prevents short wavelengths from reaching Earth’s surface Only way to study many forms of radiation is from space

Space Based Astronomy Space telescopes-launched into space to collect electromagnetic radiation from objects in space Examples-Hubble Space Telescope, Chandra X-ray Observatory, Compton Gamma Ray Observatory, Spitzer Space, James Webb Space Telescope Voyager 1 and 2 investigated Jupiter, Saturn, Uranus, Neptune in 1977 Galileo investigated Jupiter and moons from 1995-2000 Robotic-are spacecraft that carry only instruments and computers Humans never went past moon 1969-1972, 12 people landed on moon by NASA Mars Welcome to Discovery Education Player Challenger and Columbia

Sec 2-Movements of Earth Rotation-spin of a body on its axis, complete rotation= 1 day How do scientists know Earth rotates? Foucault pendulum-evidence of Earth’s rotation by using pendulum Jean Bernard Leon Foucault Coriolis Effect-movement of ocean surface currents and wind belts by rotation of Earth Revolution-motion of a body that travels around another body in space

Ellipse-closed curve, shape is determined by 2 pts w/in ellipse Orbit-the path that a body follows as it travels around another body in space Ellipse-closed curve, shape is determined by 2 pts w/in ellipse Earth orbits the sun in a ellipse Perihelion-pt in orbit of a planet at which planet is closest to sun Aphelion-pt in orbit of a planet at which the planet is farthest from sun

Constellations and Earth’s Moon What is a constellation? Group of stars organized in recognizable pattern 88 constellations Greek names-2000 yrs ago Earth moves, constellations do not. Rotation of Earth on its axis causes change in position Earth’s revolution, causes positions to change over several weeks Different constellations will appear in night sky as seasons change

Measuring Time Day and yr are based on periods of Earth’s motion Rotation=1 day Revolution=365 ¼ days Formation of calendar-created for measuring long intervals of time by dividing time into periods of days, weeks, months, and yrs Who created calendar? Egyptians, Bablonians, Aztecs Extra ¼ day added to February, leap yr Modern calendar-keep calendar aligned w/ seasons-Pope Gregory XIII

Time zones- Earth divided into 24 time zones Earth’s time zones cover about 15 deg each International date line-runs N to S through P ocean. Friday west, Thursday east No islands or continents Day light saving time-clocks set 1 hr ahead of standard time in April, set back to standard time in october No daylight savings time in equatorial region-12 hrs of day

Seasons Axis tilted at 23.5 deg Sun rays change as Earth moves toward orbit Seasonal Weather-changes in angle at which the sun’s rays strike Earth’s surface cause the seasons N Pole tilted away from sun in winter Equinoxes-moment when sun appears to cross the celestial equator-line drawn on sky directly overhead from equator on Earth Autumnal equinox-Sept 22 or 23 Vernal equinox-Mar 21 or 22 Summer solstices-pt at which sun is as far N or as far S of equator as possible. June 21 or 22 24 hrs of daylight during summer solstice at Arctic Circle, opposite at Antarctica Winter solstices-N Pole is titled to farthest pt away from sun. Dec 21 or 22