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Earth Science Chapter 27
Sections 1, 2, 3
Chapter 27Section 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 REFLECTING TELESCOPE
Use lenses to bring light into focus
First telescopes
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
New Horizons
Mars Reconnaissance Orbiter
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 27Section 2
First explored with telescopes
Most information was gained by probes and sending men to the moon
Clementine
Lunar Prospector
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 27Section 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