Transcript The Sun-Earth

WARM UP 3/21/2012

List 3 facts you know about the moon
HE SUN-EARTH-MOON SYSTEM
Chapter 28
TOOLS OF ASTRONOMY
Scientists use light from distant objects
Radiation = light (x-rays, gamma rays, UV, IR,
radio waves, and microwaves)
Electromagnetic spectrum includes all forms of
light. We see only a small portion of this light
Visible light has a frequency between 4.3 x 1014
to 7.5 x 1014 Hz

• Electromagnetic radiation consists of waves of
electrical and magnetic disturbances.
• Electromagnetic radiation travels at the same
speed and is classified by:
– Wavelengths—the distance between peaks on a wave.
– Frequency—the number of waves or oscillations occurring
per second.
TELESCOPES
Collects light from distant objects
 Brings light to a focus better than the eye
 Attach different detectors to observe what the
eye can’t see
 Used to take pictures of distant objects
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Reaching for the Moon
• Plans for a crewed lunar expedition began in
the late 1950s.
– In 1957 the Soviet Union launched the first satellite, Sputnik I.
– In 1961, Soviet cosmonaut Yuri A. Gagarin became the first
human in space.
– On May 5, 1961, Alan B. Shepard Jr. became the first
American in space
– Project Mercury was followed by Project Gemini.
– On July 20, 1969, the Apollo program landed Neil Armstrong
and Buzz Aldrin on the Moon, during Apollo 11.
Reaching for the Moon
Lunar Properties
– Earth’s moon is one of the largest moons in the solar system.
– The Moon is relatively farther from Earth than most moons are
from the planets they orbit.
– Earth’s moon is a solid, rocky body, in contrast to the icy
composition of the moons of the outer planets.
– Earth’s moon is the only large moon among the
inner planets.
Reaching for the Moon
The Lunar Surface
– The albedo of the Moon, the amount of sunlight that its
surface reflects, about 7% (Earth’s average 31%).
– Because the Moon has no atmosphere, surface temperatures
can range from 400 K (127°C) in sunlight to 100 K (–173°C)
where it is dark.
– There is no erosion on the Moon—except for wear caused by
recent impacts—because it has no atmosphere or flowing
water.
– Craters on the Moon are preserved until one impact covers
another.
Composition
• The Moon is made up of minerals similar to those of Earth—
mostly silicates.
History of the Moon
• Radiometric dating of lunar rocks from the highlands
indicates an age between 3.8 and 4.6 billion years.
Tectonics on the Moon?
– The Moon, like Earth, has a layered structure, which consists
of the crust, the upper mantle, the lower mantle, and the
core.
– The Moon experiences moonquakes approximately once a
year but scientists believe the Moon is not tectonically active.
– The Moon has no active volcanoes and no significant
magnetic field.
History of the Moon
Formation Theories
– The capture theory proposes that as the solar system was
forming, a large object ventured too near to the forming
Earth, became trapped in its gravitational pull, and formed
into what is now the Moon.
– The simultaneous formation theory states that the Moon and
Earth formed at the same time and in the same general area,
and thus the materials from which they formed were
essentially the same.
– The impact theory is the most commonly accepted theory
of how the Moon formed.
– This theory proposes that the Moon formed as the
result of a gigantic collision between Earth and a Marssized object about 4.5 billion years ago, when the solar
system was forming.
PASS OUT OF CLASS – USE COMPLETE
SENTENCES!
1.
2.
Why do scientists believe that tectonic activity
is not occurring on the Moon?
What is the most accepted theory of how the
Moon formed, and what are the problems with
the other theories?
The Sun-Earth-Moon System
• The relationships between the Sun, Moon, and Earth
are important to us in many ways.
– The Sun provides light and warmth, and it is the source of
most of the energy that fuels our society.
– The Moon raises tides in our oceans and illuminates our sky
with its monthly cycle of phases.
– Every society from ancient times to the present has based
its calendar and its timekeeping system on the apparent
motions of the Sun and Moon.
LUNAR SURFACE
Any object that orbits another object is called a
satellite.
 The moon rotates once every 27.3 days around
the Earth. We never see the other side of the
moon.
 Gravity on the moon is 1/6 that of Earth.
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MOVEMENTS OF THE MOON
Apogee – point the moon is farthest away
 Perigee – point moon is at closest
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 Earth
is at apogee in summer and perigee in winter.
Eclipse – one planetary body passes in front of
another creating a shadow.
 Umbra – darkest part of the shadow
 Penumbra - light is partially blocked

MOVEMENTS OF THE MOON
Lunar eclipses don’t occur every month.
 Moon is at a 5° tilt from Earth’s orbit
 Phases – varying shapes of the moon’s
reflected light
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 New
moon – moon is unlit from sun
 Waxing – increasing in light
 Waxing
crescent
 Waxing gibbous
MOVEMENTS OF THE MOON
 First
Quarter – half full
 Full moon – the whole moon is visible
 Waning – decreasing in light
 Waning
crescent
 Waning gibbous
 Last
quarter – moon is half full
Earthshine – sunlight reflected off the surface
of the moon
 Know the phases on page 763
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Earth Rise: View of Earth rising over Moon's horizon taken
from Apollo 11 spacecraft. NASA picture
DAY AND NIGHT AND SEASONS
Earth’s axis – imaginary line going through
center on which the Earth rotates.
 What causes day and night and the seasons?

 Rotation
and revolution
DAY AND NIGHT
Earth rotates at 1600km/hr
 Takes 24 hours to rotate once
 Rotates counterclockwise (West to East)
 Length of day and night change due to tilt

 Earth
is tilted at 23 ½°
 Toward Sun = long days, short nights
 Away from Sun = short days, long nights
SEASONS

Year on Earth = 365.25 days
 Once
every 4 years we add extra day called leap
day
4 seasons – Winter, Spring, Summer & Autumn
 5 other planets have seasons

 Mars,
Saturn, Uranus, Neptune, Pluto
 All are tilted on their axis
WINTER
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Begins on December 21 or 22

Winter solstice
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Solstice means “Sun stop”
South pole is tilted a full 23 ½° toward Sun
Shortest daylight hours in Northern Hemisphere
Sun’s rays are at 90° at the Tropic of Capricorn
SPRING
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Begins on March 20 or 21
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Vernal Equinox
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Equinox means “equal night”
Neither pole is tilted toward the Sun
Day and night are equal lengths
SUMMER
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Begins on June 21 or 22
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Summer solstice
North pole is tilted a full 23 ½° toward Sun
Longest daylight hours in Northern Hemisphere
Sun’s rays are at 90° at the Tropic of Cancer
AUTUMN (FALL)
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Begins on September 22 or 23
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Autumnal equinox
Neither pole is tilted toward the Sun
Day and night are equal lengths
WARM UP – COMPLETE SENTENCES
USE NOTES FROM MONDAY (OR CHAPTER 28)
1.
2.
3.
4.
What are the causes of the seasons on Earth?
What would our seasons be like if Earth’s axis
were not tilted?
Explain why the Moon goes through phases as
seen from Earth.
If Earth’s axis were tilted 45°, at what
latitudes would the Sun be directly overhead
on the summer and winter solstices, and on
the vernal and autumnal equinoxes?
MAGNET IN SPACE

Magnetosphere – earth’s magnetic field
 Sphere
means around or surrounding
Geographic north is magnetic south
 Geographic south is magnetic north
 Earth’s magnetosphere comes from movement
of Fe (Iron) and Ni (Nickel) in the core
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MOVEMENTS OF THE EARTH
Rotation – one turn on its axis
 Revolution – one trip around the Sun
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 Perihelion
– closest point to Sun
 Aphelion – farthest point from Sun
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Time Zones – there are 24 standard time zones
 Ben
Franklin invented Daylight Savings Time move
clocks ahead one hour in April, back to normal in
October