The Earth in Space Main Idea The earth has life because of the sun. Seasons change because of the way the earth tilts and revolves around the sun. Terms to Know • revolution • axis • rotation • equinox • winter solstice • summer solstice • solar system • atmosphere Places to Locate • Earth • sun
Section Objectives • Identify what makes up the solar system. • Describe how Earth moves in space. • Explain why Earth’s seasons change.
The Solar System • The solar system is the sun, the Earth, the seven other planets (Pluto was demoted in August, 2006), and thousands of smaller bodies (dwarf planets, moons, comets, and asteroids). • The planets and other bodies revolve around the sun. • A planet follows an elliptical path around the sun. This is known as its orbit. • There are two types of planets:1. Solid and small like Earth2. Resemble balls of gas like Jupiter.
Comets Spheres covered with ice and dust that leave trails of vapor as they race through space. Asteroids Large chunks of rocky material found in space.
What is Earth’s location in our solar system? Earth is the third planet from the sun
Earth Age: 4.5 billion yearsDiameter: 7,926 miles Temperature on surface: -89 °C to 57.7 °C Distance from the Sun: 93 million milesSatellite(s): the Moon (also known as "Luna" or "Selene") The name of Earth comes from the Anglo-Saxon word Erda, which means ground, soil and earth. OriginsWhen it was formed 4.5 billion years ago, the Earth looked very different to how it does now. The surface was littered with active volcanoes and, with no ozone layer, the atmosphere gave no protection from the Sun. As the Earth grew in size, its increasing gravitational field pulled more material towards it. This caused more asteroids to hit the Earth with greater force, which meant its surface heated up and began to melt. This melting gave Earth its layered structure. StructureThe innermost layer, or core, is under such intense pressure that it has remained partly solid at the centre. It is made up of nickel and iron and has an estimated temperature of 4,000 Kelvin or 3,726 degrees Celsius. Beyond the core is the mantle, which is the largest single part of the planet. It is semi-solid and accounts for 82% of the Earth's volume and 67% of its mass. The mantle is divided into three separate regions - the lower mantle, which is 2,290 km thick, the transition zone and the upper mantle, which is 630 km thick. Above the mantle is the surface of the Earth, known as the crust. The crust varies in thickness, from as little as 7 km in some parts of the ocean, to 70 km under the mountain ranges. AtmosphereThe Earth is surrounded by a blanket of gases, known as the atmosphere. It provides us with the air we breathe and insulates us from drastic changes in temperature. It also protects us from harmful ultraviolet radiation from the Sun. The atmosphere extends for more than 300 miles above the Earth but is thickest in the 10 miles closest to its surface. As you travel further from the Earth it thins out and merges with space. The biosphereConsidering the size of the Earth, life is confined to only a very small area. Almost all living things are found in a zone called the "biosphere", which runs from 200 m below the surface of the oceans to 30 m above it. Of course, many humans live above this height, but even for us the options are limited. The higher you go, the more you will experience altitude sickness as the atmosphere thins and your body struggles to get enough oxygen from the air. Mountaineers start to use breathing apparatus when they go above about 7,000 m.
What is unique about earth? It is the only planet that supports life!
Can You? Describe the solar system and Earth’s location in it.
Earth's Tilt The Earth's polar axis tilts at an angle of 23 ½ ° with its orbital plane around the sun. This inclination is responsible for more of the Earth receiving direct rays from the Sun and thus, the climate changes and the seasons experienced on Earth. The tilt of the Earth on its axis affects the amount of solar energy that different places receive during the year.Because of this tilt more of the earth’s surface receives direct rays from the sun.
If the Earth had no tilt all places on earth would receive the same amount of solar energy year round… How different would our world be?
Rotation – The spinning of the Earth on it’s axis. This spinning helps to “even out” heat from the sun. Remember!!! • Earth rotates around its own axis once every 24 hours (1 day). • This is the cause of day and night. • If we divide 360° by 24, we get 15°. • In other words, it takes the Earth 1 hour to turn through 15°. • Earth rotates from West to East
What if the Earth did not rotate? One side of the Earth would receive no sunlight One side of the Earth would receive sunlight all the time How different would our world be?
Revolution - The earth’s complete orbit around the sun. • This revolution takes 365¼ days, which is why we • have a leap year once every four years. What is the speed of earth’s revolution? 66,000 mph (1,100 miles per minute)
If the Earth did not revolve around the sun Can you imagine if it were always summer Or always winter No spring or fall Our earth would be a much different place
The shape of the Earth directly affects the amount of solar radiation received during certain segments of its revolution around the sun. Equatorial regions receive more direct rays of the sun, thus more solar radiation. Moving farther south or north of the equator will change the angle at which the rays strike the Earth, thus decreasing the amount of solar radiation received at that latitude.
Earth makes two motions in space. • It spins on an imaginary axis that runs through the center of Earth between the North and South Poles. • It takes 24 hours for Earth to complete one rotation on this axis. • What is our speed of rotation? About 775 mph • It revolves around the sun on its orbit • It takes 365 ¼ days (1 year) to complete 1 revolution
Can you? Assess the impact of tilt, rotation, and revolution on the amount of solar energy the earth receives.
The angle of Sun’s rays determine heat The amount of solar energy a place receives relates to the angle at which the Sun’s rays strike the earth. Sun angle diagram
Tropics (Red) – warm, low latitude areas near the equator Middle latitudes (Green) – areas of latitude between the tropics and polar regions High latitudes (White) – cold, high latitude areas near the poles Earth’s tilt ensures that more of the earth’s surface receives direct rays from the sun.
Earth’s Temperature Change • Which latitudes receive the most solar energy throughout the year?
SEASONS We refer to times of greater and lesser heat as the seasons. The four general seasons are: winter, spring, summer, and fall. The Sun’s energy is stronger during the summer. Daytime lasts longer. In the winter, daytime is shorter, and the Sun’s energy is weaker.
The tilt of the Earth’s axis causes the Northern and Southern Hemispheres to have opposite seasons at the same time of the year.
The Sun and the Seasons • The day on which the Northern Hemisphere receives the most hours of sunlight is the summer solstice. • On this day, the sun is directly over the Tropic of Cancer (23½ degrees north). • The summer solstice falls on June 21/22 Summer solstice
summer solstice Summer solstice diagram
Land of the Midnight Sun During the summer and winter our poles receive: 24 hours of daylight (Summer) or 24 hours of darkness (Winter) Midnight sun
The Sun and the Seasons • The day on which the Northern Hemisphere receives the least sunlight is the winter solstice. • On this day, the sun is directly over the Tropic of Capricorn (23½ degrees south). • The winter solstice falls on December 21/22 Winter solstice
winter solstice Winter solstice diagram
The Sun and the Seasons (cont.) • The two days each year on which the sun is directly over the Equator are known as the equinoxes. • Both hemispheres receive the same amount of sunlight on these days. • The autumnal equinox falls on September 22/23 • The vernal (spring) equinox falls on March 22/23 Equinoxes
equinox Equinox diagram
equinox Summary diagram
Can you? Discuss the impact of tilt and revolution on the seasons.
The Earth System Interaction of Earth’s different parts
We are in a continuous cycle if interactions with our planet.
Atmosphere • Earth is surrounded by a layer of air called the atmosphere. The atmosphere consists of a mixture of gases composed primarily of nitrogen, oxygen, carbon dioxide, and water vapor retained by the Earth's gravity.
It extends some 500 km above the surface of the Earth and the lower level (troposphere) constitutes the climate system that maintains the conditions suitable for life on the planet's surface. Our outer atmosphere, the stratosphere, contains the ozone layer that protects life on the planet by filtering harmful ultraviolet radiation from the Sun.
Hydrosphere All of Earth’s water Water covers about 70% of Earth’s surface.