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Earth Science Chapter 27 Sections 1, 2, 3 Chapter 27 Section 1 Electromagnetic Radiation: • Consists of electric and magnetic disturbances traveling through space as waves. Electromagnetic Spectrum: • The wavelength and frequency of electromagnetic radiation. Electromagnetic Radiation is classified by wavelength. • Distance from crest to crest. It is also classified by frequency. • The number of waves or oscillations that pass through a point in one second. • See p. 764 Hz – Hertz • A unit equal to 1 cycle per second Scientists choose their tools based on the type of radiation they want to study in space. p. 765 Give us the ability to observe electromagnetic wavelengths beyond what a human can detect Aperture: the diameter of an opening where light is let in • Human eye- 7 mm • Telescope- 10 m Benefits: • Larger aperture than eye • Can collect object too dim for the eye to detect Eye only views objects for 1/10 of a second. Lenses can stay open for hours to collect more light Tools used with satellites • Photometer Intensity of visible light • Spectrophotometer Different wavelengths of radiation REFRACTING TELESCOPE Use lenses to bring light into focus First telescopes REFLECTING TELESCOPE Use mirrors to bring light into focus Used by most astronomers because mirrors can be made larger than lenses Infrared and ultraviolet radiation can be focused with mirrors- reflecting telescope X-Rays can’t be focused by normal mirrors Gamma rays can’t be focused at all Radio telescope: Collects longer wavelengths Uses a large dish antenna Reflects waves to a single point A receiver collects the signal and converts it to electric signals Interferometry • Uses images from several telescopes to produce a single image • Scientists get a detailed image with the same resolution as one large telescope with a dish as large as the distance between the telescopes Instruments in space collect data with our Earth’s atmosphere blurring the images. Orbits Earth every 97 minutes Obtains sharp visible light images James Webb Space Telescope (planned for 2013) • Observe the infrared range Sent directly to the bodies to collect data Robotic probes: • Spacecraft that can make close up observations or collect information • Cassini spacecraft Observed Saturn’s rings and moons • Mars Reconnaissance Orbiter Used high resolution cameras to search for signs of life • New Horizons Launched toward Pluto and beyond with visible, infrared and ultraviolet light cameras Cassini Mars Reconnaissance Orbiter New Horizons In order to pursue more advanced human spaceflight, scientists need to study: • The effects of weightlessness on humans, plants, and other phenomenon. • The effects of radiation The Space Shuttle program allows scientists to study short term effects Longer term effects need to be studied on space stations • International Space Station A multicountry space station Chapter 27 Section 2 First explored with telescopes Most information was gained by probes and sending men to the moon Lunar Prospector Clementine 1957 Soviet Sputnik • First satellite 1961 Yuri A. Gagarin • First human in space 1961 Alan B. Shepard, Jr. • First American in space during Project Mercury Project Gemini • First two person crew in space 1969 Apollo I1 • Neil Armstrong first human on the moon. Lunar surface is dark Albedo: the percentage of incoming sunlight that its surface reflects • About 7% • Earth’s Albedo is around 31% Moon has no atmosphere to absorb heat so its surface is hot (Varying temperatures • Light side: 127˚ C • Dark side: -173 ˚ C Lunar Highlands • Heavily cratered regions of the moon • Light colored Maria • Dark smooth plains with few craters Impact craters • Objects have crashed into the moon Ejecta • The material blasted out of the craters Rays • Trails of ejecta that radiate from the crater Rilles • Meandering valley- like structures • Might be collapsed lava tubes One of the largest moons Solid rocky body Composed of mostly silicates • Similar to Earth Highlands • Rocks formed by the fusion of smaller pieces of rock during impacts Maria • Predominately basalt (volcanic) but with no water Radiometric dating • 3.8-4.6 bya Heavily bombarded during the first 800 million years Breaking and heating of surface formed a layer of ground up rock Regolith- the fine layer of ground up rock Depth varies with location Crust • Varies in thickness • Thickest on the far side that faces away from Earth Upper Mantle- solid Lower Mantle- molten Core- solid iron During bombardment • Lava filled the impact basins • Left dark smooth plains • Fewer maria on the far side because the crust is thicker and the lava was too far under the surface Moon experiences about one moonquake per year Strong enough to shake plates from a cupboard Not much seismic activity Several theories Impact theory- widely accepted • Collision with a Mars shaped object and Earth 4.5 bya • Parts of the fractured Earth flew into space • Over time the orbiting objects came together to form the moon. • This explains the similarities to the composition of the moon and the Earth Chapter 27 Section 3 Daily rotation • Causes the Coriolis effect Day Length • 1 solar day is on revolution on Earth’s axis • 24 hours Earth revolves around the sun in a elliptical plane Earth’s tilt is approximately 23.5˚ relative to the ecliptic Earth’s axis remains fixed in space When Northern hemisphere is toward the sun the Southern hemisphere is away from the sun A solstice occurs when the sun is at its farthest distance from the equator Summer solstice brings the longest day of the year and winter solstice brings the shortest Summer solstice in North America• Note the rays are strongest in the Northern portion of the globe • Rays are weakest in the southern portion. This is their winter solstice. Earth’s axis is perpendicular to the sun. Days and nights are equal length Occur in spring and fall Waxing • The increasing visible light starting with the new moon Waxing crescent, first quarter and waxing gibbous Waning • The decreasing visible light starting at the full moon Waning gibbous, third quarter, waning crescent When the moon orbits Earth the same side faces it. The moon rotates exactly one time as it goes around the Earth This is synchronous rotation