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