The Earth in SpaceThe Earth in Space

Chapter 2 Sections 2-3Chapter 2 Sections 2-3

2.2 Movements of the Earth2.2 Movements of the Earth

The movement of the earth around the sun The movement of the earth around the sun is called a is called a revolutionrevolution..

Each revolution takes 365.24 days, or 1 Each revolution takes 365.24 days, or 1 year.year.

The earth also spins on its axis, known as The earth also spins on its axis, known as rotationrotation..

Each rotation takes 24 hours or 1 day.Each rotation takes 24 hours or 1 day.

2.2 Movements of the Earth2.2 Movements of the Earth

The earth’s orbit is oval shaped.The earth’s orbit is oval shaped.At its closest point to the sun, the earth is At its closest point to the sun, the earth is

at at perihelionperihelion..At its farthest point to the sun, the earth is At its farthest point to the sun, the earth is

at at aphelionaphelion..Perihelion is on January 3Perihelion is on January 3rdrd

Aphelion is on July 4Aphelion is on July 4thth

2.2 Movements of the Earth2.2 Movements of the Earth

The earth’s axis is tilted 23.5The earth’s axis is tilted 23.5oo from the from the perpendicular plane of its orbit.perpendicular plane of its orbit.

During each revolution, the North Pole tilts During each revolution, the North Pole tilts at times toward the sun, and at other times at times toward the sun, and at other times away from it.away from it.

2.2 Movements of the Earth2.2 Movements of the Earth

On June 21 or 22, the North Pole tilts On June 21 or 22, the North Pole tilts toward the sun.toward the sun.

The sun’s rays strike the Tropic of Cancer The sun’s rays strike the Tropic of Cancer at 90at 90oo..

This is called the This is called the Summer SolsticeSummer Solstice..This is the beginning of summer in the This is the beginning of summer in the

Northern Hemisphere and winter in the Northern Hemisphere and winter in the Southern HemisphereSouthern Hemisphere

2.2 Movements of the Earth2.2 Movements of the Earth

On December 21 or 22, the South Pole On December 21 or 22, the South Pole tilts toward the sun.tilts toward the sun.

The sun’s rays strike the Tropic of The sun’s rays strike the Tropic of Capricorn at 90Capricorn at 90oo..

This is called the This is called the Winter SolsticeWinter Solstice..This is the beginning of winter in the This is the beginning of winter in the

Northern Hemisphere and summer in the Northern Hemisphere and summer in the Southern HemisphereSouthern Hemisphere

2.2 Movements of the Earth2.2 Movements of the Earth

During the summer solstice all areas north During the summer solstice all areas north of the Arctic circle have 24 hours of of the Arctic circle have 24 hours of daylight and south of the Antarctic circle daylight and south of the Antarctic circle have 24 hours of darknesshave 24 hours of darkness

During the winter solstice all areas north of During the winter solstice all areas north of the Arctic circle have 24 hours of darkness the Arctic circle have 24 hours of darkness and south of the Antarctic circle have 24 and south of the Antarctic circle have 24 hours of daylighthours of daylight

2.2 Movements of the Earth2.2 Movements of the Earth

On September 22 or 23 of each year, the On September 22 or 23 of each year, the sun’s rays strike the equator at 90sun’s rays strike the equator at 90oo..

This is called the This is called the Autumnal equinoxAutumnal equinox..This is the beginning of fall in the Northern This is the beginning of fall in the Northern

Hemisphere and spring in the Southern.Hemisphere and spring in the Southern.Equinox means “equal night”. There are Equinox means “equal night”. There are

12 hours of daylight and 12 of darkness12 hours of daylight and 12 of darkness

2.2 Movements of the Earth2.2 Movements of the Earth

On March 21 or 22 of each year, the sun’s On March 21 or 22 of each year, the sun’s rays also strike the equator at 90rays also strike the equator at 90oo..

This is called the This is called the Vernal equinoxVernal equinox..This is the beginning of spring in the This is the beginning of spring in the

Northern Hemisphere and fall in the Northern Hemisphere and fall in the Southern.Southern.

2.2 Movements of the Earth2.2 Movements of the Earth

PrecessionPrecession causes the earth’s axis to causes the earth’s axis to wobble, much like a top does as it spins.wobble, much like a top does as it spins.

The earth’s axis completes one full circle The earth’s axis completes one full circle every 26,000 years.every 26,000 years.

2.2 Movements of the Earth2.2 Movements of the Earth

The earth has been divided into 24 The earth has been divided into 24 standard time zonesstandard time zones..

In each zone, noon is set as the time when In each zone, noon is set as the time when the sun is highest over the center of that the sun is highest over the center of that zone.zone.

2.2 Movements of the Earth2.2 Movements of the Earth

The International Date LineThe International Date Line is a line is a line running from North to South through the running from North to South through the Pacific Ocean.Pacific Ocean.

When it is 8:00 am Friday on the west side When it is 8:00 am Friday on the west side of the line, it is 8:00 am Thursday on the of the line, it is 8:00 am Thursday on the east side of the line.east side of the line.

2.2 Movements of the Earth2.2 Movements of the Earth

During the summer, most of the United During the summer, most of the United States uses States uses Daylight Savings TimeDaylight Savings Time..

Clocks move ahead 1 hour in April and fall Clocks move ahead 1 hour in April and fall back 1 hour in October to provide an extra back 1 hour in October to provide an extra hour of daylight in the evening.hour of daylight in the evening.

2.3 Artificial Satellites2.3 Artificial Satellites

There are hundreds of satellites orbiting There are hundreds of satellites orbiting the earth.the earth.

Meteorological satellitesMeteorological satellites gather and gather and transmit weather informationtransmit weather information

2.3 Artificial Satellites2.3 Artificial Satellites

Communication satellitesCommunication satellites relay radio, relay radio, telephone, and tv signals around earthtelephone, and tv signals around earth

Navigation satellitesNavigation satellites send out radio send out radio signals to help ships and aircraft signals to help ships and aircraft determine their locations.determine their locations.

2.3 Artificial Satellites2.3 Artificial Satellites

At a height of 36,100 km, a satellite At a height of 36,100 km, a satellite completes one revolution in 24 hours.completes one revolution in 24 hours.

If a satellite is directly above the equator If a satellite is directly above the equator and moving in the direction of earth’s orbit, and moving in the direction of earth’s orbit, it is in it is in geosynchronous orbit.geosynchronous orbit.

Communication satellites are put in Communication satellites are put in geosynchronous orbit.geosynchronous orbit.

2.3 Artificial Satellites2.3 Artificial Satellites

The space shuttle is a temporary satellite The space shuttle is a temporary satellite that is designed to carry cargo, orbit the that is designed to carry cargo, orbit the earth, and then return to the earth’s earth, and then return to the earth’s surface.surface.