Sun-Earth-Moon connections

Review Question

People once believed that all planets and stars orbited around ____.

a. Mercuryb. Earthc. Venusd. Mars

The Rotating Earth

is a sphere, a round 3-dimensional shape

bulges slightly at equator and flattens slightly at poles

Radius: same from all points on the surface

Axis/Tilt: imaginary vertical line through the north and south poles it spins on

What is Earth’s rotation?

Rotation: spinning of earth on its axis, causes days and nights

One complete rotation in 24 hours

completes 365 rotations in a one year journey around the Sun

rotates from west to east

What is a Foucault pendulum?

Weight on a string suspended from a support and swings freely.

Swings in a constant direct but as earth turns it appears the pendulum shifts orientation.

Earths Rotation

Compass always points north is evidence of earth’s magnetic field

Earth’s magnetic axis and rotational axis are not at the same points Thus, your compass would

take you to magnetic north not the north pole

Magnetic north changes and moves around rotational north

What is the Coriollis Effect? rotation of

Earth causes ocean currents and wind belts to curve to the left or right

What is Earths Revolution?Revolution- the motion of a

body that travels around another body in space; one complete trip along an orbit

a satellite of Sun Earth’s orbit around the

Sun is an Ellipse, an elongated closed curve

is traveling around the sun at an average speed of 29.8 km/s.

Aphelion: planet is farthest from the sun

Perihelion: planet is closest to the sun.

What causes the changes in seasons ?

is tilted 23.5° causes our change

in seasons makes daylight

longer in summer and shorter in winter

hemisphere tilted toward the Sun has longer hours of daylight and makes summer warmer

Reasons for Seasons

What is an Equinox?

Equinox: occurs when the Sun is directly over the equator; causing spring and fall

THINK EQUAL: Hours of daylight and nighttime Spring equinox is Mar 21 and Fall equinox Sep 22

What is a Solstice?

hemisphere tilted toward the Sun receives and absorbs more solar radiation; causing summer

Solstice: is the day when the Sun rays are at its greatest/least distance from the equator

June 21:longest daylight Dec 21: shortest daylight

Reasons for Seasons

Incoming solar radiation

The Moon: Properties, history, phases, eclipses, and tides

What is the moon?

A natural satellite Satellite: a natural

or artificial body that revolves around planet.

One of more than 96 moons in our Solar System

The only moon of the planet Earth

What is the moons Distance, Size, and Gravity?

About 384,000 km (240,000 miles) from Earth

3,468 km (2,155 miles) in diameter (about ¼ the size of Earth)

1/6 of Earths gravity

What is the moons internal structure?

3 major divisions of the Lunar interior

Crust - average thickness of about 70 kilometers

Mantle Core - radius is

between 300 and 425 kilometers

Determined via seismic data from “moonquakes”

What are some lunar features?

No atmosphere No liquid water Extreme

temperatures Daytime = 130C

(265°F) Nighttime = -190C (-

310 F)

Lunar Features – Highlands (Terrae)

Mountains up to 7500 m (25,000 ft) tall

Rilles (trenchlike valleys)

Anorthosite: light patches seen on the moon’s surface

Lunar Features - Craters

a bowl-shaped depression that forms on the surface of an object when a falling body strikes the object’s surface or when an explosion occurs]

Up to 2500 km (1,553 miles) across Most formed by meteorite impact on the Moon Some formed by volcanic action inside the Moon

Crater Formation

Crater formation

Lunar Features - Maria

Originally thought to be “seas” by early astronomers

Darkest parts of lunar landscape

Filled by lava after crash of huge meteorites on lunar surface 3-4 billion years ago

Mostly basalt rock

Prominent Maria

Craters vs Maria

What is the moons rotation and revolution?

Revolution – Moon orbits the Earth every 29.5days

The moon rises in the east and sets in the west

The moon rises and sets 50 minutes later each day

Rotation – Moon turns on its axis every 29 days

Same side of Moon always faces usarth

What shape is the moons orbit around the sun?

The orbit of the moon around Earth forms an ellipse, the distance between Earth and the moon varies over a month’s time

Apparent Size

The illustration, based on Galileo spacecraft images, shows the approximate difference in apparent size between a full moon at perigee (the closest point in the lunar orbit, pictured at left) and a full moon at apogee, the farthest point in the lunar orbit.

The near sideThe Moon rotates in 29.5

days.

The Moon orbits Earth in 29.5 days.

Because the Moon rotates and revolves at the same rate, we only see one side The NEAR side

There is NO DARK SIDE

There is a FAR side….

Far side

How was the moon formed?

3 major theories 1. Capture theory: large object

ventured too near the forming earth and got trapped by gravity

2. Simultaneous formation theory: Earth and moon formed at the same time.

3. Impact theory: Most widely accepted.

How was the moon formed?

The Giant Impact Hypothesis 3 stages 1. began when a large object collided

with Earth more than 4 billion years ago 2. collision ejected chunks of Earth’s

mantle into orbit around Earth 3. debris eventually clumped together to

form the moon.

Formation of the moon

What are phases?

Phase: in astronomy, the change in the illuminated area of one celestial body as seen from another celestial body; are caused by the changing positions of Earth, the sun, and the moon

Moon phases

Why are their phases of the moon?

Moonlight is reflected sunlight

Half the moon’s surface is always reflecting light

From Earth we see different amounts of the Moon’s lit surface

The amount seen is called a “phase”

Synchronous rotation: orbital and rotational periods are equal.

Waxing vs Waning

Waxing – lit side is getting bigger Waning – lit side is getting smaller

‘LEFT SIDE IS LIT, THE MOON IS LEAVING’ Left side, lit, leaving, waning

FOUR MAIN SHAPES

FULL

QUARTER

CRESCENT

GIBBOUS

For all phases: Note where the sunlight is coming from

Phases for the month

http://www.moonconnection.com/moon_phases_calendar.phtml

Review question

When only a small part of the moon is visible, the moon may be in its

A. first-quarter phaseB. waning-crescent phaseC. new moon phaseD. last-quarter phase

Why don’t we have eclipses every month?

MOON – SUN – EARTH: All do not travel in the same plane of orbit

What are eclipses?

an event in which the shadow of one celestial body falls on another

Bodies orbiting the sun cast long shadows into space

What is the shadow structure for an eclipse?

UMBRA (Latin for "shadow") is the darkest part of the shadow

PENUMBRA is a partial shadow, grayish outer part of a sunspot

Penumbra

Penumbra

Umbra

What is a solar eclipse?

A solar eclipse is when the moon comes between the sun and the Earth, so that a viewer is in the moon's shadow.

Total eclipses rare – only once every 360 years from one location!

How do I see a total solar eclipse?

Observers in the “umbra” shadow see a total eclipse (safe to view the Sun); can see the corona

Those in “penumbra” see a partial eclipse—not safe to look directly at Sun

Only lasts a few minutes Path of Totality about 10,000 miles long, only 100

miles wide

The diamond ring

Why not a solar eclipse every month then? Moon's orbit is tilted about 5o with respect to the

Earth's orbit (ecliptic), so the shadows usually miss!

Ecliptic

Moon

Moon’s Orbit

Earth

What is a lunar eclipse?

the passing of the moon through Earth’s shadow at full moon

occurs when Earth is positioned between the moon and the sun and when Earth’s shadow crosses the lighted half of the moon

Lunar eclipse

Sun EarthMoon’s

Path

Moon

Why is the Moon red during an eclipse?

The Earth’s atmosphere filters some sunlight and allows it to reach the Moon’s surface

The blue light is removed—scattered down to make a blue sky over those in daytime

Remaining light is red or orange Some of this remaining light is bent or

refracted so that a small fraction of it reaches the Moon

Exact appearance depends on dust and clouds in the Earth’s atmosphere

What causes the tides?

Tides: daily changes in the level of ocean water influenced by the sun and the moon occur in a variety of cycles The combination of gravity and inertia create two bulges of

water. High Tide and Low Tide: How often tides occur and the

difference in tidal levels depend on the position of the moon as it revolves around the Earth

What causes the tides?

The gravitational attraction between the Earth and the moon is strongest on the side of the Earth that happens to be facing the moon, simply because it is closer.

This attraction causes the water on this “near side” of Earth to be pulled toward the moon.

As gravitational force acts to draw the water closer to the moon, inertial force attempts to keep the water in place.

But the gravitational force exceeds it and the water is pulled toward the moon, causing a “bulge” of water on the near side toward the moon

On the opposite side of the Earth, or the “far side,” the gravitational attraction of the moon is less because it is farther away.

Here, the inertial force exceeds the gravitational force, and the water tries to keep going in a straight line, moving away from the Earth, also forming a bulge

Tides

Approximately how many days does it take the moon to go through a complete cycle? A. 7B. 11C. 26D. 29.5 ow many days does it take the moon to go through a complete cycle?

When the visible portion of the moon is increasing, the moon is A. waxingB. fullC. waningD. waning-crescent

A solar eclipse is most likely to occur when the

A. sun is located between the earth and moon

B. moon is located between the sun and the earth

C. earth is located between the sun and the moon

D. earth and moon are at right angles to each other

Earth has seasons because A. the temperature of the sun changesB. Earth rotates on its axisC. Earth's axis is tilted as it moves

around the sunD. the distance between Earth and the

sun changes

The sun appears larger than other stars because

A. it is the biggest star in the universe B. it is a double star C. it is the closest star to the earth

A lunar eclipse is most likely to occur when

A. sun is located between the earth and moon

B. moon is located between the sun and the earth

C. earth is located between the sun and the moon

D. earth and moon are at right angles to each other

From new moon to full moon phase you see

A. a decreasing amount of the lighted side of the moon

B. an increasing amount of the lighted side of the moon

C. more of the lighted side, then less of the lighted side of the moon

D. the same amount of the lighted side of the moon

During what moon phase can a lunar eclipse occur?

A. waxing gibbousB. first quarterC. new moonD. full moon