section 1: earth in space - tracy unified school district 12 notes...chapter 12 earth, moon, and sun...

Chapter 12 Earth, Moon, and Sun

Section 1:Earth in Space

How does Earth move in space?

What causes the cycle of seasons on Earth?


How Earth Moves

Earth moves through space in two major ways: rotation and

revolution.

A revolution is the movement of one object around another.

How long does one complete revolution of Earth around the sun

take?

Answer:

365.25 days

(1 year)

Is the Earth’s orbit circular?

No, it is an ellipse.


How Earth Moves

The spinning of Earth on its axis is called rotation. As the

Earth spins eastward, only half of the planet is facing the sun

(day) while the other half is not (night).

How long does it take the

Earth to rotate once?

Answer: 24 hours (1 day)


Origin of Calendars

A calendar is a system of

organizing time that defines the

beginning, length, and divisions of a

year.

Over the last 4000 years, they have

been based on moon and star

cycles, season changes, and sun

position.

Stonehenge 1500 B.C.

Egyptian calendar

Mayan Calendar

What is a leap year?

An extra day added

every 4 years.


Sunlight Striking Earth’s Surface

Near the equator, sunlight strikes Earth’s surface more directly and is less spread out than near the poles.


Seasons on Earth

Earth has seasons because its axis is tilted as it revolves

around the sun. The axis is always tilted at what angle?

23.5 degrees


Common Misconception Alert!

Although the Earth can be at different distances from the sun

due to its ellipsoid orbit, this DOES NOT cause the

changes in season. In fact, the Earth is farthest from the

sun during our summer!


Seasons on Earth

The height of the sun above the horizon varies with the

season. It is at its lowest angle in winter and highest angle

(more direct) in summer.


Section 2:Gravity and Motion

What determines the strength of the force of

gravity between two objects?

What two factors combine to keep the moon

and Earth in orbit?


Gravity, Mass, and Distance

The strength of the force of gravity between two objects

depends on two factors: the masses of the objects and the

distance between them.


Gravity Versus Distance

Four million newtons

Reading Graphs:

What is the force of gravity on

the rocket at the planet’s

surface?



One million newtons

Reading Graphs:

What is the force of gravity on

the rocket at a distance of two

units (twice the planet’s

radius from its center)?



It decreases.

Drawing Conclusions:

In general, how does the

force of gravity pulling on the

rocket change as the distance

between it and the planet

increases?


Gravity and InertiaNewton concluded that two factors–inertia and gravity–

combine to keep Earth in orbit around the sun and the moon

in orbit around Earth.


Section 3:Phases, Eclipses,

and TidesWhat causes the phases of the moon?

What are solar and lunar eclipses?

What causes the tides?


Motions of the Moon

The changing relative positions of the moon, Earth, and sun

cause the phases of the moon, eclipses, and tides.

How long does

it take the moon

to orbit the Earth?

29.5 days


Phases of the Moon

The phase of the moon you see depends on how much of

the sunlit side of the moon faces Earth.


The Moon’s Orbit

The moon’s orbit is tilted about 5 degrees relative to Earth’s

orbit around the sun.


Solar Eclipse

A solar eclipse occurs when the moon passes directly between

Earth and the sun, blocking sunlight from Earth.


Lunar Eclipse

During a lunar eclipse, Earth blocks sunlight from

reaching the moon’s surface.


Tides

Tides occur mainly because of differences in the force of

gravity between the moon and different parts of Earth.


Spring and Neap Tides

When Earth, the sun, and the moon are in a straight line, a

spring tide occurs (twice a month at new & full moons).

When the moon is at a right angle to the sun, a neap tide

occurs (at 1st and 3rd quarter moons).


Section 4:Earth’s Moon

What features are found on the moon’s

surface?

What are some characteristics of the moon?

How did the moon form?


The Moon’s Surface

Features on the moon’s surface include maria, craters, and

highlands.


The Moon’s Surface

Maria (Latin for “seas”): Dark, flat areas

first thought to be oceans, but actually

huge ancient lava flows.

Craters: Large round pits caused by the

impacts of meteoroids (NOT volcanoes).

Highlands: These are the mountains and

crater rims that cover most of the

moon’s surface.

Why do the maria have fewer cratersthan the rest of the moon?

Most of the impacts occurred before the maria formed.


The Moon’s Size

The moon is 3,476 km in diameter, a little less than the

distance across the contiguous Untied States. It’s about ¼

the Earth’s diameter.


Characteristics of the Moon

The moon is very dry and airless. Since it has no atmosphere,

it has large variations in its surface temperature (from 130

degrees Celsius in direct sunlight to -180 degrees at night).

The moon is made out of much of the same elements that

make up the Earth such as oxygen, silicon, magnesium,

potassium, nickel, sulfur among many others.

Though it’s ¼ the diameter of Earth, it only has 1/80th of the

mass. This causes its gravity to be about 1/6 of what it is

here on Earth.

What would you weigh on Earth? Divide your weight by six.


The Origin of the Moon

Scientists theorize that a planet-sized object collided with

earth to form the moon.


The Origin of The Moon

Moon Mysteries Part One

section 1: earth in space - tracy unified school district 12 notes...chapter 12 earth, moon, and sun...

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