Earth and Moon in Space

Earth Moves

Earth moves in space Earth spins around an imaginary line

called an axis The axis is an imaginary line passing

through the poles and the center of the Earth

Rotation

Rotation is the spinning of the Earth on its imaginary axis

Earth makes one complete rotation every 24 hours

Rotation of the Earth causes day and night as a point on the Earth rotates toward or away from the sun

Revolution

Earth moves around the sun in a regular, curved path called an orbit

Revolution is the movement of Earth in an orbit around the sun

Earth takes 365¼ days to make one revolution around the sun (one year)

Earth rotates on its axis and revolves around the sun at the same time

Seasons

Seasons are caused by the tilt of the Earth on its axis.

The hemisphere of the Earth that is tilted toward the sun receives more of the sun’s heat and light and its temperatures are warmer.

Summer happens in a hemisphere when the hemisphere is tilted toward the sun.

Seasons

Winter happens when a hemisphere is tilted away from the sun.

When a hemisphere is tilted away from the sun, it receives less heat and light and the Earth’s temperatures are cooler.

Seasons

Solstice

Solstice is point at which the sun reaches its greatest distance north or south of the equator.

In the northern hemisphere, the winter solstice happens around December 21 or 22.

The winter solstice has the fewest daytime hours.

Solstice

In the northern hemisphere, the summer solstice happens around June 21 or 22.

The summer solstice has the most daytime hours.

Equinox

When the sun reaches an equinox, it is directly above the Earth’s equator.

At the equinox, the number of daytime and nighttime hours equal each other all over the world.

In the northern hemisphere, the spring equinox is March 20 or 21 and the fall equinox is September 22 or 23.

The Moon

It's Just a Phase It's Going Through...

Moon

Our planet's large natural satellite, the Moon, is the easiest astronomical object to observe.

The only "scientific instrument" you'll need at first is a pair of eyes.

Picture from NASA

The Moon's Orbit

Rotation– Moon is spinning on its

axis, once every 27.3 days

Revolution– The moon orbits around

the Earth– Moon revolves around

the Earth once every 27.3 days

Why do we never see the DARK SIDE?

Synchronous Rotation is the reason we never see the dark side of the moon.

Over the millennia, the Moon has become "locked" into a special kind of motion around the Earth.

It rotates on its axis at the same pace as it revolves around the Earth

As a result, the Moon keeps the same face toward us throughout its orbit.

Phases

The lighted side of the moon always faces

the sun.

New Moon

New moon occurs when the moon is between the sun & the Earth.

The dark side of the moon is facing the Earth.

What we see

What is happening from above.

E

Sunlight

Full Moon

The full moon occurs when the Moon & the Sun are on opposite sides of the Earth.

The lighted side of the moon is facing Earth.

What we see

What is happening from above.

E

Sunlight

Blue Moon

When there is more than one full moon in a month, the second moon is called a blue moon.

A blue moon happens every two years on average.

The phrase, “Once in a blue moon” means very rarely or very seldom or almost never.

First QuarterMoon The First quarter

moon occurs when the moon is halfway between new and full.

As seen from the Earth, half the moon’s disk is illuminated.

What we see

What is happening from above.

E

Sunlight

Third QuarterMoon The Third or last

quarter moon occurs halfway between the full moon & the new moon.

As seen from the Earth, half the moon’s disk is illuminated.

What is happening from above.

E

Sunlight

What we see

Waxing

When the moon is between new & full, the visible part of the moon is increasing.

This is called waxing

E

Sunlight

Waning

When the moon is between full & new, the visible part of the moon is decreasing.

This is called waning.

E

Sunlight

Waning

Crescent

Crescent Moon When the moon

is between New & 1st Quarter it is called a waxing crescent.

E

Sunlight

New Moon

Full Moon

1st Quarter3rd Quarter

Waxing Crescent

When the moon is between 3rd & New it is called a waning crescent.

Waning

Gibbous

Waning

Crescent

Gibbous Moon When the moon

is between 1st Quarter & Full it is called a waxing gibbous.

E

Sunlight

New Moon

Full Moon

1st Quarter3rd Quarter

Waxing Crescent

When the moon is between Full & 3rd it is called a waning gibbous.

Waning Gibbous

Moon Movie

Link to current phase of the moon http://tycho.usno.navy.mil/vphase.html

Link to moon phases pictures and lunation movie

http://aa.usno.navy.mil/faq/docs/moon_phases.php

Forces governing planetary motion

Sun and planets or

Earth and moon

Force

A force is a push or pull one body exerts on another

A force causes an object to accelerate in the direction of the force

Tendency of an object to resist any change in motion

A moving object stays moving

Inertia

An object that is not moving will stay still, unless a force acts on it

An object at rest stays at rest

Inertia

A sliding hockey puck moves at the same speed and direction until it hits a wall or a stick

Velocity is constant, no acceleration

Inertia

If a force (a moving hockey stick or the wall) acts on the puck, then it will change direction

Velocity changes

Inertia

More mass an object has, the more inertia it has

More mass, harder to change the motion

Mass and Inertia

An object moving at a constant velocity keeps moving at that velocity unless a net force acts on it.

Newton’s First Law

An object at rest, stays at rest unless a net force acts on it.

Newton’s First Law

Newton’s first law is sometimes called the Law of inertia

Newton’s First Law

1st Law

Unless acted upon by an unbalanced force, this golf ball would sit on the tee forever.

1st Law Once airborne,

unless acted on by an unbalanced force (gravity and air – fluid friction), it would never stop!

Friction

Why then, do we observe every day objects in motion slowing down and becoming motionless seemingly without an outside force?

It’s a force we sometimes cannot see – friction.

Objects on earth, unlike the frictionless space the moon travels through, are under the influence of friction.

Newton’s 1st Law and You

Don’t let this be you. Wear seat belts.

Because of inertia, objects (including you) resist changes in their motion. When the car going 80 km/hour is stopped by the brick wall, your body keeps moving at 80 km/hour.

Gravity

Force exerted by every object in the universe on every other object in the universe.

Gravity

Gravity is affected by mass and distance

Closer things exert more gravity on each other

Object with more mass exerts more gravity on an object of less mass

Force of Gravity

Gravity is a pulling force

It pulls things down towards the earth

Things fall because of gravity

Things always fall down

Gravity was discovered by a scientist called Isaac Newton

Stories say he discovered Gravity when an apple fell on his head

Gravity holds everything and everyone on the earth

Even in Australia

In Space, Gravity keeps the planets moving around the sun

2nd Law

2nd Law

The net force of an object is equal to the product of its mass and acceleration, or F=ma.

Circular motion

Circular motion (planetary motion) occurs because of two things.

1. An object, like a planet or the moon, is already moving with a certain speed in a particular direction

2. A force (gravity) acts on the object.

Gravity causes Earth to speed up (accelerate) in a straight line towards the Sun

Newton’s second law explains this effect - a net force causes an object with mass to accelerate

If Earth was not moving to begin with, the force of gravity would cause the Earth to accelerate until it collided with the Sun

Combination of Earth’s linear motion and the acceleration toward the Sun (sideways to the linear motion) leads to a curved path, orbit, around the Sun

Earth travels in an orbit around the Sun because of two forces

Moon travels in an orbit around Earth for the same reasons

If gravity stopped working, then Earth would move in a straight line at a constant rate

If there was no linear motion, then the Earth would fall into the Sun

Projectiles

Projectiles – anything thrown or shot through the air

Projectiles have horizontal and vertical velocities and travel in a curved path

Projectiles

Horizontal velocity is constant due to inertia

Vertical velocity increases due to gravity

Gravity exerts an unbalanced force and pulls the object down

Artificial satellites If a projectile moves with enough linear

speed so that its fall towards the ground exactly matches the curvature of the Earth, then the projectile will orbit the Earth