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Space Table of Contents Astronomy Solar System Inner Planets Outer Planets Earth Moon Other Space Objects Stars and Their Evolution Sun Galaxies and Universe Astronomy Who’s Who of Early Astronomy

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Table of Contents

  • Astronomy

  • Solar System

  • Inner Planets

  • Outer Planets

  • Earth

  • Moon

  • Other Space Objects

  • Stars and Their Evolution

  • Sun

  • Galaxies and Universe



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Who’s Who of Early Astronomy

  • Ptolemy: An Earth-Centered Universe Ptolemy thought that the Earth was at the center of the universe and that the other planets revolved around the Earth.

  • Copernicus: A Sun-Centered Universe Copernicus thought that sun was the center of the universe, and all of the planets orbit the sun.

  • Tycho Brahe: A Wealth of Data Brahe recorded precise observations about the movement of the planets and stars.

  • Johannes Kepler: Laws of Planetary Motion Kepler used collected data to form three laws of planetary motion that are still used today.

  • Galileo: Turning a Telescope to the Sky Galileo was one of the first people to use the telescope. He saw that the planets were large bodies of rock similar to Earth.

  • Isaac Newton: The Laws of Gravity Newton shows that all objects in the universe attract each other through gravitational force.


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Our Modern Calendar

  • A year is the time required for the Earth to orbit once around the sun.

  • A month is roughly the amount of time required for the moon to orbit once around the Earth.

  • A day is the time required for the Earth to rotate once on its axis.


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Optical Telescopes

  • The invention of the telescope and the description of gravity were two milestones in the development of modern astronomy.

  • A Refracting Telescopes use lenses to gather and focus light

  • A Reflecting Telescopes uses a curved mirror to gather and focus light

  • Edwin Hubble proved that other galaxies existed beyond the edge of the Milky Way.


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Optical Telecpoes

  • In some very large reflecting telescopes several mirrors work together to collect light and focus it in the same area.

  • Light pollution, humidity, and other atmospheric conditions decreases an optical telescope’s effectiveness.

  • To avoid atmospheric interference, scientists have put telescopes in space.



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Non-optical Telescopes

  • Because most electromagnetic waves are blocked by the atmosphere, scientists have placed many kinds of non-optical telescopes in space.

  • Radio Telescopes detect radio waves.

  • Astronomers can get more detailed images of the universe by linking radio telescopes together


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Electromagnetic Spectrum

  • The electromagnetic spectrum is made up of all of the wavelengths of electromagnetic radiation.

  • Most of the electromagnetic spectrum is invisible to the human eye.

  • The only part visible to humans is visible light

  • ROY G BIV



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The First Satellites

  • An artificial satellite is any human-made object placed in orbit around a body in space.

  • In 1957, the Soviets launched the first artificial satellite, Sputnik 1. It orbited for 57 days before it fell back to Earth and burned up in the atmosphere.

  • Two months later, Sputnik 2 carried the first living being into space—a dog named Laika.

  • The United States launched its first satellite, Explorer 1, in 1958.

  • The development of new satellites increased quickly. By 1964, communications satellite networks were able to send messages around the world.


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Choosing A Satellites Orbit

  • Satellites are placed in different types of orbits.

  • All of the early satellites were placed in low Earth orbit.

  • Low Earth orbit (LEO) is an orbit less than 1,500 km above the Earth’s surface.

  • A satellite in LEO moves around the Earth very quickly and can provide clear images of the Earth. However, this motion can place a satellite out of contact much of the time.


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Choosing A Satellites Orbit

  • Most communications and weather satellites circle the Earth in geostationary orbit.

  • Geostationary orbit (GEO) is an orbit that is about 36,000 km above the Earth’s surface and in which a satellite is above a fixed spot on the equator.

  • A satellite in GEO is always above the same spot on Earth.

  • Ground stations are in continuous contact with these satellites so that communications will not be interrupted.



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Satellites Today

  • Today, thousands of satellites orbit the Earth, and more are launched every year.

  • There are many kinds of artificial satellites including:

    • weather satellites

    • communications satellites

    • remote-sensing satellites


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LEO- Military Satellites

  • Some satellites placed in LEO are equipped with cameras that can photograph the Earth’s surface in amazing detail. It is possible to photograph objects as small as a book from LEO.

  • While satellite photographs are now used for everything from developing real estate to tracking movements of dolphins, the technology was first developed by the military.

  • Because satellites can take very detailed photos from hundreds of kilometers above the Earth’s surface, they are ideal for defense purposes.

  • The United States and the Soviet Union developed satellites to spy on each other right up to the end of the Cold War.

  • Even though the Cold War is over, spy satellites continue to play an important role in the military defense of many countries.


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LEO- Military Satellites

  • In the past, people invented very complicated ways to keep from getting lost.

  • Now, for less than $100, people can determine their exact location on Earth by using a Global Positioning System (GPS) receiver.

  • GPS is another example of military satellite technology that has become a part of everyday life.

  • The GPS consists of 27 solar-powered satellites that continuously send radio signals to Earth.

  • From the amount of time it takes the signals to reach Earth, the hand-held receiver can calculate its distance from the satellites.

  • Using the distance from three or four satellites, a GPS receiver can determine a person’s location with great accuracy.


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GEO and LEO- Weather Satellites

  • Every day, millions of people make decisions based on information provided by weather satellites.

  • Weather satellites in GEO provide a big-picture view of the Earth’s atmosphere.

  • These satellites constantly monitor the atmosphere for the “triggers” that lead to severe weather conditions.

  • Weather satellites in LEO are usually placed in polar orbits.

  • Satellites in polar orbits revolve around the Earth in a north or south direction as the Earth rotates beneath them.

  • These satellites, which orbit between 830 km and 870 km above the Earth, provide a much closer look at weather patterns.


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Communications Satellites

  • Many types of modern communications use radio waves or microwaves to relay messages.

  • Radio waves and microwaves are ideal for communications because they can travel through the air.

  • The problem is that the Earth is round, but the waves travel in a straight line.

  • Communications satellites in GEO solve this problem by relaying information from one point on Earth’s surface to another.

  • The signals are transmitted to a satellite and then sent to receivers around the world.

  • Communications satellites relay computer data, and some television and radio broadcasts.


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Remote Sensing and Environmental Change

  • Satellites gather information by remote sensing. Remote sensing is the gathering of images and data from a distance.

  • Remote sensing satellites measure light and other forms of energy that are reflected from Earth.

  • Some satellites use radar, which bounces high-frequency radio waves off the Earth and measure the returned signal.

  • One of the most successful remote-sensing projects is the Landsat program, which began in 1972 and continues today.

  • Landsat satellites gather images in several different wavelengths—from visible light to infrared.


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Landsat Program

  • The Landsat program has produced millions of images that are used to identify and track environmental changes on Earth.

  • Satellite remote sensing allows scientists to perform large-scale mapping, look at changes in patterns of vegetation growth, map the spread of urban development, and study the effect of humans on the global environment.

  • In 1999, NASA launched Terra 1, the first satellite in NASA’s Earth Observing System (EOS) program.

  • Satellites in the EOS program are designed to work together so that they can gather integrated data on environmental change on the land, in the oceans, in the atmosphere, and on the icecaps.


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Landsat Images

  • One image was taken in 1973, and the other was taken in 2003.

  • The two images reveal a pattern of environmental change over a 30-year period.

  • The main change is a dramatic reduction in the amount of silt that is reaching the delta.

  • A comparison of the images also reveals a large-scale loss of wetlands in the bottom left of the delta in 2003.




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Discovery of the Solar System

  • Early Knowledge Up until the 17th century, the universe was thought to only contain Earth, Venus, Mercury, Venus, Mars, Jupiter, Saturn, the sun, and Earth’s moon.

  • Using a Telescope After the invention of the telescope, the moons of Jupiter and Saturn were discovered.

  • Modern Times By the 20th century, Uranus, Neptune, Pluto and many other bodies had been discovered.


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Solar System Theories

  • Earth Centered Model

    • Early Greek scientists thought the 5 planets (Earth did not count and no planets past Uranus), sun and moon rotated around the EARTH in a circle orbit

    • Many early Greek scientists thought the planets, the sun, and the moon were fixed in separate spheres that rotated around Earth.

    • The stars were thought to be in another sphere


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Sun Centered Model

In 1543, Nicholas Copernicus stated that the moon revolved around Earth and that Earth and the other planets revolved around the Sun.

He also stated that the daily movement of the planets and the stars was caused by Earth's rotation.

Proving the S.C.M.

Galileo Galilei observed that Venus went through a full cycle of phases like the Moon's.

This only could be explained if Venus were orbiting the Sun.

Galileo concluded the Sun is the center of the solar system.

Solar System Theories


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Solar System Theories

  • Modern View Model

    • Our solar system includes the sun, the planets, and many smaller objects.

    • Revolve around the sun located off center

    • The Sun's gravity holds objects in the solar system in their orbits.


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Solar System Formation

  • Scientists hypothesize that the solar system formed from part of a nebula of gas, ice, and dust.

  • The density in the cloud fragments becomes greater, gravity pulled in more gas and dust, it began to rotate faster, temperature increased

  • The matter that did not get pulled into the center collided and stuck together to form the planets and asteroids.




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Tour of the Solar System

  • The sun contains 99.86% of all the mass in the solar system

  • As with all the planets, much of what is known comes from spacecraft that send data back to Earth.

  • The inner planets are mostly solid, with minerals similar to those on Earth.

  • The outer planets are Jupiter, Saturn, Uranus, and Neptune.

  • All of the outer planets, except Pluto, are huge balls of gas called gas giants. Each might have a solid core, but none of them has a solid surface.

  • The only outer “planet” that doesn’t have rings is Pluto.


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Planet Information

  • In the forming of the planets the inner planets were so close to the sun that the lighter elements were vaporized leaving the rocky planets.

  • The inner planets— Mercury, Venus, Earth, and Mars—are small, rocky planets with iron cores.

  • The outer planets— Jupiter, Saturn, Uranus, and Neptune— are much larger and are made mostly of lighter substances such as hydrogen, helium, methane, and ammonia.

  • Pluto was the only rocky outer planet until 2006 when it was demoted. It is made mostly of rock and ice.



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Planet Information

  • Each planet spins on its axis.

  • The spinning of a body, such as a planet, on its axis (around itself) is called rotation.

  • The path that a body follows as it travels around another body in space is called the orbit.

  • One complete trip along an orbit is called a revolution.



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Planet Motion

  • In the early 1600s, German mathematician Johannes Kepler began studying the orbits of the planets.

  • He discovered the sun is off center

  • He discovered the shapes of orbits of ALL bodies are oval, or elliptical not circular.

  • He discovered objects orbit at varying speeds


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Kepler’s Laws

  • Kepler’s First Law of Motion The planets move around the sun in an ellipse.

  • Kepler’s Second Law of Motion The planets seemed to move faster when they are close to the sun and slower when they are farther away.

  • Kepler’s Third Law of Motion Planets further from the sun take longer to orbit the sun.


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Planet Motion

  • Kepler discovered the planets travel at different speeds in their orbits around the Sun.

  • Planets closer to the Sun travel faster than planets farther away from the Sun.


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