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Aerospace Engineering
Aerospace Engineer







Table of contents.
Answers to relevant questions.
Annotation or Definition
Aeronautical Engineering
Aircraft Altitude
Aeronautics and Space
Astronomer
Atmosphere of Earth
Aerospace Engineer
Aerodynamics
Avionics
Aerospace Structure Computing
Aviation World
Chemistry- A Molecular Science
Chemistry- A Quantitative Science
Earth Science
Engineer Dynamics
Engineering Aerospace
Environment Physics
Flight Vehicle control
Glossary of Aerospace Terms and Concepts
Health & Fitness Space Flight
Intro Engineering
Landing
Manufacturing.
Materials science
Planet Earth
Physics for Engineers and Scientists II
Pressure
Propulsion
Radar
Structural analysis
Solid Mechanics Calculus
Statics Propulsion Calculus II
Transponder
Universe & Space
Vehicle Design

Answers to relevant questions.
What is Engineering?
What is Aerospace Engineering?
What skills and knowledge should an aerospace engineer have?
What is Aeronautical Engineering?
What do Aeronautical Engineers do?
What is flight?
Who is included in flight crew?
What should be ratio of flight attendants to passengers?
What are the duties of an airport station manager?
What are the duties of airport security?

Aircraft Manufacture

What tests will you do and what questions do you need answered before you clear an aircraft as fit for safe flight?
What do you understand by a large aircraft?
How many aerospace engineers are required to manufacture all parts of a large aircraft?
How many aerospace engineers are required to assemble all parts of a large aircraft?
If all parts of a large aircraft are ready, and all aerospace engineers are ready, how long will it take to assemble all parts, do a flight test, and put an aircraft in service?
If the pilot dies in flight, what will happen?
Where is the central command of all aircraft operations in world?
What are the duties of a pilot?
What are the duties of the first officer in flight?
What are the duties of a flight engineer during flight?
What are the duties of flight attendants?
What do aerospace engineers do?
What various roles do aerospace engineers have?
What is this job like?
How do you get ready?
What is the remuneration?
How many jobs are there?
What about the future?
Are there other jobs like this?
Where can you find more information?

Annotation or Definition
What is Engineering?
Engineering, the practical application of science and math to solve problems, is everywhere in the world around you.

Engineers develop new products and find applications for new technologies. In addition to design and development, many engineers work in production, testing, and operations.

From airplanes and satellites to medical devices and renewable energy technologies, engineering makes our modern life possible.

Engineering is a team activity:
Engineers work as part of a team, each with their own responsibilities. The individuals succeed when the whole team succeeds.
Engineers are problem solvers who make things work more efficiently, more quickly, and less expensively.

What is Aerospace Engineering?
Aerospace engineers design, develop, and test aircraft, spacecraft, and missiles, and supervise their manufacture. Those who work with aircraft are called aeronautical engineers, and those working specifically with spacecraft are called astronautical engineers.

Aerospace engineers develop new technologies for use in aviation, defense systems, and space exploration, often specializing in areas such as structures, propulsion systems, vehicle movement and control, communications, and overall vehicle design.

They also may specialize in a particular type of aerospace product, such as commercial aircraft, military fighter jets, helicopters, spacecraft, or missiles and rockets, and may become experts in aerodynamics, thermodynamics, celestial mechanics, propulsion, acoustics, or guidance and control systems. Aerospace Engineering, generally known as ‘Rocket Science’, is a Specialized Field of Engineering that involves the science & engineering of aircrafts and spacecrafts including aeroplanes, helicopters, rockets, missiles, space stations, space-shuttles and many more such flying vehicles operating within and outside the earth’s atmosphere. This special feature of Careers360 brings you the Top Engineering colleges offering Aerospace Engineering and the scope and opportunities in this Specialized Engineering Branch. We also bring you insights on job profiles and top recruiters for Aerospace Engineering.

Aerospace Engineering deals with the research, design, development, construction, testing, collaboration processes, science and technology of aircraft & spacecraft, and their products. It involves the study of science and engineering behind the physical properties of rockets, aircrafts and spacecrafts. This domain is a complex subject and essentially requires superior & sophisticated tools. Aerospace Engineers also deal with development of new technology in aviation, space exploration & defense system.

Aerospace Engineering comprises of 2 major disciplines- •Aeronautical Engineering: Deals with aircrafts operating in the atmosphere of Earth. •Astronautical Engineering: Deals with spacecrafts operating outside the atmosphere of Earth.

What skills and knowledge should an aerospace engineer have? An aerospace engineer is expected to know more than a pilot, first officer in flight, flight engineer, flight attendants, aircraft dispatcher, airport manager, and airport security officer. Core Subjects

Students of Aerospace Engineering learn about different specialized aspects of the domain. The Core Subjects of this engineering include the following elements below:
•Chemistry- A Molecular Science
•Intro Engineering
•Aerodynamics
•Chemistry- A Quantitative Science
•Aerospace Structure Computing
•Environment Physics
•Engineering Aerospace
•Vehicle Design
•Engineer Dynamics
•Physics for Engineers and Scientists II
•Statics Propulsion Calculus II
•Flight Vehicle control
•Solid Mechanics Calculus
•Health & Fitness Space Flight

Roles of Aerospace Engineer

An Aerospace Engineer is responsible for directing and coordinating the design, along with manufacturing & testing the aircrafts & aerospace products. He/she also needs to access the proposals to determine the technically and financially feasible ones. Let’s have a glance at some of the duties of Aerospace Engineers below-

Aerospace Engineers make sure that the project on which they are working shall result in safe aircrafts and their parts.
•Engineers evaluate the designs of the products so that they meet engineering principles, customer requirements and environmental challenges.
•They ensure that the projects meet acceptance criteria for design methods and required quality standards.
•Aerospace Engineers are involved in inspection of malfunctioning or damaged products in order to identify the sources of errors and suggest possible solutions.
•They develop new technologies to be used in aviation, defense systems, and spacecraft. Areas such as structural design, guidance, navigation, aerodynamic fluid flow, robotics, propulsion, combustion, etc. are taken care of by specialized Aerospace Engineers.
•Aerospace Engineers supervise the assembly of airframes, installation of engines, instruments, and other such equipment.
•They are required to participate in the flight test programmes in order to measure rate of climb, stall speeds, take-off distances and landing capacities.

How to pursue Aerospace Engineering?

Did you always wanted to know how things fly? Are you intrigued by air and space travel?

What is flight?
Entire air journey which may involve change of aircraft and several flight legs from the starting point to the final destination.

Who is included in flight crew?
1. Pilot (also called captain)
2. First officer (The second in command sits on the right side of the cockpit)
3. Flight engineer (also called second officer)
4. Flight attendants.

What should be ratio of flight attendants to passengers?
There must be one flight attendant for every 50 passengers.

Aeronautical Engineering
What is Aeronautical Engineering?
What do Aeronautical Engineers do?

Aeronautical engineers plan and supervise the design, development, manufacture, modification, and maintenance of all types of flight vehicles.

Astronomer
What is an astronomer?
Astronomers are scientists who study the Universe and the objects within it. There are so many interesting things to learn about within the Universe that astronomers often become specialists who focus on galaxies, stars, planets, star-forming regions, the Sun, the search for life, or the origin and evolution of the Universe as a whole. Many astronomers are also professors at universities or colleges and spend time teaching as well as doing research. Other astronomers help plan and support space missions.
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Aerospace Engineer
What should you know about this work?
Abilities
Additional information
    Where can you find more information?
    Would you like to add anything else?

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Duties
    What do aerospace engineers do?
    Aerospace engineers design aircraft, spacecraft, satellites, and missiles. In addition, they test prototypes to make sure that they function according to design.

    What various roles do aerospace engineers have? Here are further guidelines.
Education
Guide
Interests
Knowledge
Location of work
    What is the location of this work?
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Meetings
    How often are you expected to attend meetings?
    Why do we organize a meeting?
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Number of such professions/workers/jobs required in a state.

    How many of such professions/workers/jobs are required in a state?
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Profile questions
Related occupations
Remuneration
    What about remuneration?
    What is the remuneration?

    Remuneration depends on the quality of the economy in the state, surrounding states, and distant states.

    Every state needs to provide remuneration as per basic needs.
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Resources
    What resources are required for this work?
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Requirement for human resources
Skills
    What skills and knowledge are required for this work?

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Supervisor
Tools and machines
Tools and technology
    What tools and machines are required for this work?
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Travel
Tasks
Work activities
Work context
Work styles
Work values
Work specific questions
Work hours
    What are usual daily work hours?
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Earth Science
What is Earth Science?

Earth Science is the study of the Earth and its neighbors in space. It is an exciting science with many interesting and practical applications. Some Earth scientists use their knowledge of the Earth to locate and develop energy and mineral resources. Others study the impact of human activity on Earth's environment and design methods to protect the planet.

Many different sciences are used to learn about the earth, however, the four basic areas of Earth science study are: geology, meteorology, oceanography and astronomy.
Geology: Science of the Earth
Meteorology: Science of the Atmosphere
Oceanography: Science of the Oceans
Astronomy: Science of the Universe
World Records in Earth Science
Where is the deepest place in the ocean and how deep is it?
What is the biggest mountain and where is it located?

Biggest Wave
Coldest Place on Earth
Deepest Ocean
Driest Desert
Extreme Weather
Greatest River
Highest Elevation
Highest Waterfall
Hottest Place on Earth
Longest Mountain Range
Lowest Elevation
Wettest Place on Earth

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Altitude
Aircraft Altitude
What is the altitude above earth at which satellites can maintain orbits for a reasonable time without falling into the atmosphere?
100 miles (160 kilometers) above the surface approximately.

What is the altitude of an international flight?
The flight level of an aircraft is based on the purpose of the flight, weather, flight distance, and instructions from supervisors of the aircraft.

As a rule, the longer the flight, the higher the altitude.

What is the altitude of most passenger or military jets?
Most passenger jets fly around only 30,000 feet (5.7 miles). Even the best military jets rarely climb above 100,000 feet (a little less than 19 miles).

How is the atmosphere of the earth classified?
Troposphere
Stratosphere
Mesosphere
Thermosphere
Exosphere

How high can a jet aircraft go?
The World record for both speed and height by an air-breathing aircraft (not a rocket) was 85,135 feet. It was set in an SR-71 Blackbird in 1976. The speed record is also held by an SR-71, at 2,193 mph. This is not as high or as fast as the airplane can fly, however, it's absolute speed and altitude limits are classified.

At higher speeds and altitudes, there isn't enough oxygen in the air to continuously burn the jet fuel required to stay up there. Engines designed to work very well that high, have serious limitations when they are operated closer to the surface. There are aircraft that have flown higher and faster (the X-15) but they really aren't aircraft, they are rockets, because they carry their own source of oxygen, instead of using the air.

Many military jet aircraft are able to fly considerably higher. Often, the plane itself is not pressurised and instead the pilot wears a pressure suit that provides him with a pressurised environment.

Feet to Miles
60000ft= 11mi 640.0000yd

Feet to Kilometers
60000ft= 18.28800km


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Glossary of Aerospace Terms and Concepts
Fluid mechanics Fluid mechanics – the study of fluid flow around objects. Specifically aerodynamics concerning the flow of air over bodies such as wings or through objects such as wind tunnels (see also lift and aeronautics).
Astrodynamics Astrodynamics – the study of orbital mechanics including prediction of orbital elements when given a select few variables. While few schools in the United States teach this at the undergraduate level, several have graduate programs covering this topic (usually in conjunction with the Physics department of said college or university).
Statics and Dynamics (engineering mechanics) Statics and Dynamics (engineering mechanics) – the study of movement, forces, moments in mechanical systems. Mathematics – in particular, calculus, differential equations, and linear algebra.
Electrotechnology Electrotechnology – the study of electronics within engineering.
Propulsion Propulsion – the energy to move a vehicle through the air (or in outer space) is provided by internal combustion engines, jet engines and turbomachinery, or rockets (see also propeller and spacecraft propulsion). A more recent addition to this module is electric propulsion and ion propulsion.
Control engineering Control engineering – the study of mathematical modeling of the dynamic behavior of systems and designing them, usually using feedback signals, so that their dynamic behavior is desirable (stable, without large excursions, with minimum error). This applies to the dynamic behavior of aircraft, spacecraft, propulsion systems, and subsystems that exist on aerospace vehicles.
Aircraft structures Aircraft structures – design of the physical configuration of the craft to withstand the forces encountered during flight. Aerospace engineering aims to keep structures lightweight.
Materials science Materials science – related to structures, aerospace engineering also studies the materials of which the aerospace structures are to be built. New materials with very specific properties are invented, or existing ones are modified to improve their performance.
Solid mechanics Solid mechanics – Closely related to material science is solid mechanics which deals with stress and strain analysis of the components of the vehicle. Nowadays there are several Finite Element programs such as MSC Patran/Nastran which aid engineers in the analytical process.
Aeroelasticity Aeroelasticity – the interaction of aerodynamic forces and structural flexibility, potentially causing flutter, divergence, etc. Engineers of ISRO working on Mars Orbiter Mission (MOM), Mars Orbiter Mission Spacecraft is being integrated to the 4th stage of PSLV-C25.Avionics – the design and programming of computer systems on board an aircraft or spacecraft and the simulation of systems.
Software Software – the specification, design, development, test, and implementation of computer software for aerospace applications, including flight software, ground control software, test & evaluation software, etc. Risk and reliability – the study of risk and reliability assessment techniques and the mathematics involved in the quantitative methods.
Noise control Noise control – the study of the mechanics of sound transfer.
Aeroacoustics Aeroacoustics – the study of noise generation via either turbulent fluid motion or aerodynamic forces interacting with surfaces.
Flight test Flight test – designing and executing flight test programs in order to gather and analyze performance and handling qualities data in order to determine if an aircraft meets its design and performance goals and certification requirements.

Pressure
What is Pressure?
What are various types of pressure?

Atmospheric pressure is the force per unit area that is always applied perpendicularly to a surface by the surrounding gas. It is determined by a planet's gravitational force in combination with the total mass of a column of gas above a location. On Earth, units of air pressure are based on the internationally recognized standard atmosphere (atm), which is defined as 101,325 Pa (760 Torr or 14.696 psi).

The pressure of an atmospheric gas decreases with altitude due to the diminishing mass of gas above each location
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Universe & Space
Constituents of Universe
Earth
What do humans know up to now about the universe?
What are galaxies?
What is a planet?
How big is the Universe?
What is the altitude above earth at which satellites can maintain orbits for a reasonable time without falling into the atmosphere?
What is the altitude of an international flight?
What is the altitude of most passenger or military jets?
How is the atmosphere of the earth classified?
What is Space?
Where does the atmosphere end and outer space begin?
Why don't we receive light from all the stars in the universe?
What is wavelength?
What are radio waves?
What is electromagnetic radiation?
What is the electromagnetic spectrum?
How do you make a radio wave?
How is data put on radio waves?
What is bandwidth?
What are uplink and downlink?
What is a satellite?
What are some different kinds of orbits?
How does a spacecraft get to where its going?
What are stars made of?
Is there gravity in space?
What is mass?
Why is mass important?
How does propulsion work?
What is in space?
How far away is Earth from the sun?
What is an orbit?
How do we put spacecraft into orbit?
How deep is the ocean?
How do we know a spacecraft's location?
What are planets made of?
What is interstellar dust?
Does heat travel differently in space than it does on Earth?
How can a spaceship leave orbit?
How does gravity work in space?
How do objects in space travel?
How do spacecraft use an orbit to move from planet to planet?
How and why do we control heat on a spacecraft?
What do humans know up to now about the universe?
Earth's location in the universe
Galaxies
Intergalactic Space
List of galaxies
Planets
Planet Earth
Solar System
Stars

Earth's location in the universe

Where is Earth Located?

The location of Earth in our solar system.

Since there is believed to be no "center" or "edge" of the universe, there is no particular reference point with which to plot the overall location of the Earth in the universe. Because the observable universe is defined as that region of the universe visible to terrestrial observers, Earth is, by definition, the center of the observable universe. Reference can be made to the Earth's position with respect to specific structures, which exist at various scales. It is still undetermined whether the universe is infinite.

How big is the universe?
100 billion galaxies in the observable Universe. 14 billion light-years in radius. As many stars as grains of sand on Earth’s beaches.

How long does it take our sun to orbit the Milky Way’s center?
The planets in our solar system orbit around the sun. One orbit of the Earth takes one year. Meanwhile, our entire solar system orbits the center of the Milky Way galaxy. Our sun and solar system move at about 800 thousand kilometers an hour – that’s about 500 thousand miles an hour – in this huge orbit. So in 90 seconds, for example, we all move some 20,000 kilometers – or 12,500 miles – in orbit around the galaxy’s center.

Our Milky Way galaxy is a big place. Even at this blazing speed, it takes the sun approximately 225-250 million years to complete one journey around the galaxy’s center. This amount of time – the time it takes us to orbit the center of the galaxy – is sometimes called a “cosmic year.”

Composition Of The Solar System

The Sun contains 99.85% of all the matter in the Solar System. The planets, which condensed out of the same disk of material that formed the Sun, contain only 0.135% of the mass of the solar system. Jupiter contains more than twice the matter of all the other planets combined. Satellites of the planets, comets, asteroids, meteoroids, and the interplanetary medium constitute the remaining 0.015%. The following table is a list of the mass distribution within our Solar System.

Sun: 99.85%
Planets: 0.135%
Comets: 0.01%
Satellites: 0.00005%
Minor Planets: 0.0000002%
Meteoroids: 0.0000001%
Interplanetary Medium: 0.0000001%

Interplanetary Space Nearly all the solar system by volume appears to be an empty void. Far from being nothingness, this vacuum of "space" comprises the interplanetary medium. It includes various forms of energy and at least two material components: interplanetary dust and interplanetary gas. Interplanetary dust consists of microscopic solid particles. Interplanetary gas is a tenuous flow of gas and charged particles, mostly protons and electrons -- plasma -- which stream from the Sun, called the solar wind.

How is Earth moving in our solar system?



Contrary to our perception, we are not “sitting still.”
We are moving with the Earth in several ways, and at surprisingly fast speeds…

Where is our galaxy in the universe?
Our solar system is made up of eight planets orbiting the sun. They are Venus, Mercury, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. The planets were formed as a by-product of the birth of the sun around 4.5 billion years ago. There are over 100 billion stars like our sun in our galaxy, so could there be other planets like Earth?

There were until recently nine planets, but Pluto, a small body on the edge of the solar system has been re-classified as a dwarf planet . Our sun is a very ordinary star, known as a G2 class main sequence star. There are about 100 billion similar stars in our galaxy, the Milky Way.

The Milky Way is like a spinning spiral disc with four arms. Our solar system is about two-thirds of the way from the centre along one of the arms, which is known as Pegasus . The galaxy's arms are where most of the dust and gases are concentrated and where most stars are born. The relatively flat arms spin at 250 kilometres a second around a bulging centre. This centre is thought to contain a supermassive black hole with a mass exceeding 50 times that of the sun that sucks in entire stars. The Milky Way is vast. It would take an object travelling at the speed of light (over 1 billion kilometres per hour), 51,000 years to travel from one side to the other.

The Milky Way is the second largest galaxy within a cluster of 17 galaxies. Beyond our cluster are more clusters forming a honeycomb structure of interconnected filaments around large empty bubbles. This structure was probably set out soon after the Big Bang, which created the universe. There are thought to be about 100 billion galaxies in the universe.

Our place within the universe is very small and insignificant, but it is interesting because it supports intelligent life that can observe the universe and ask how it came to be there and why.

How do galaxies move within the universe?
Galaxies are carried along with the expansion of the Universe. But how did Hubble figure out that the universe is expanding

How is Earth moving in our solar system?
Earth rotates on its axis once each day and orbits around the Sun once each year at an average distance of 1 A.U. (˜150 million km).

How is our solar system moving in the Milky Way Galaxy?
Stars in the Local Neighborhood move randomly relative to each other.
Our Solar System orbits the center of the Milky Way Galaxy about every 230 million years: the entire Galaxy rotates.

How do galaxies move within the universe?
All galaxies beyond the Local Group are moving away from us with expansion of the Universe: the more distant they are, the faster they’re moving.

What are galaxies?
Galaxies are huge collections of stars, dust and gas. They usually contain several million to over a trillion stars and can range in size from a few thousand to several hundred thousand light-years across. There are hundreds of billions of galaxies in the Universe. Galaxies come in many different sizes, shapes and brightnesses and, like stars, are found alone, in pairs, or in larger groups called clusters. Galaxies are divided into three basic types: spirals, ellipticals and irregulars.

Why do the planets orbit the Sun?
The planets move like this because of the gravitational pull of the Sun. Without this force, the planets would move off into space.

Which way do the planets go around the Sun?
The answer to this question depends on where in space you are looking from. We normally imagine ourselves looking at our solar system from above the Earth's north pole. When viewed from this position, the planets move in an anticlockwise direction around the Sun. Our moon also orbits the Earth in an anticlockwise direction. If we viewed the planets from a position below the Earth's south pole, they would be seen moving around the Sun in a clockwise direction.

How long do the planets take to complete an orbit of the Sun?
The further away from the Sun a planet is, the longer it takes. The Earth takes one year to orbit the Sun, but Pluto (the furthest planet), takes about 250 times as long. Mercury (the closest planet), goes around the Sun about four times in the time it takes the Earth to go round once.

Does each planet spin on its axis?
Yes, but some spin much faster than others. All except Venus spin in an anticlockwise direction. The moons orbiting the planets spin too, most of them also in an anticlockwise direction.

How far away are the other planets?
Although most people think of the planets as moving in a circle around the Sun, they actually move in a slightly elongated orbit called an ellipse. Because of this, the distance from the Earth to the Sun varies between 147 and 152 million kilometres.

Pluto is about 40 times further from the Sun than we are. It has a highly elliptical orbit, which sometimes brings it closer to the Sun than Neptune. The Earth's distance from the other planets depends where they are in their orbits. For example, the closest that Earth gets to Mars is about 57 million kilometres. However, when Earth and Mars are on opposite sides of the Sun, the distance between them is about 400 million kilometres.

Has anyone ever been to another planet?
Although American astronauts landed on the moon in 1969 and again in the early 1970s, no one has ever visited any of the other planets. Robot spacecraft have flown past all the major planets, and probes have landed on Venus, Mars and Saturn's moon Titan.

Are there any more planets waiting to be discovered?
Within and outside of our solar system there are plenty of planets and planet-like objects still to be discovered. Since the late 1980s more than 1000 Trans-Neptunian Objects (TNOs) have been found beyond the orbit of Neptune. Some of these are large enough to qualify as 'dwarf planets'. In the same period more than 200 planets have been discovered in orbit around other stars.

What are asteroids?
They are rocky lumps of material, sometimes known as the minor planets. Most of the asteroids lie between Mars and Jupiter. The biggest known asteroid (Ceres – classified as a dwarf planet in 2006) has a diameter of about 1000 kilometres.

What are comets?
Comets are a bit like giant dirty snowballs with diameters between 5 and 50 kilometres. Most of them have highly elliptical orbits. On one side of their orbit they move in close to the Sun. On the opposite side, many move out far beyond the orbit of Pluto. As they get closer to the Sun, the icy layers start to melt and vaporize, leaving behind a trail of material which is seen as a tail.

The tail can be millions of kilometres long. One of the most famous comets is Halley's comet, which reappears every 76 years (the time it takes to orbit the Sun). The most recent spectacular comet was Hale-Bopp, which appeared in our skies in early 1997. Its orbit is so large that it won't be seen from the Earth again for more than 2000 years.

Solar System

A solar system is the collection of planets, asteroids, and moons (moons orbit the planets) that occupy a space around a sun and are held within the gravitational pull of the Sun. Our solar system consists of eight planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune) and a planetoid, Pluto.

What is a planet?
There are 8 planets, a small number of dwarf planets, and a large number of minor planets. The decisive criterion in the definition of a planet is based on dynamics (i.e. the science of forces and motions). This is an intelligent decision, and a decision that we can feel good about, for several reasons:
Planets have always been defined by their dynamics. The word "planets" comes from the Greek word for "wanderer", an object that moves across the background of the fixed stars.
Moons have always been defined by their dynamics. A moon is an object that moves around (orbits) a planet. There are moons that look round and there are moons that don't look round at all. Their shape is irrelevant to the classification.
A classification based on dynamics is far easier to implement than a classification based on physical properties. Newly discovered objects can be classified immediately, long before the details of their physical properties are known.

How big is the universe?
There are no words or numbers (figures) to describe the exact dimensions of universe.
Nobody really knows how big the Universe is because we cannot see to the edge of it. We don't even know if it has an edge. We can only see out to a distance of about 14 billion light years from Earth. This means that the size of the Universe that we can see is about 28 billion light years in diameter (across). Light has not reached us from beyond this distance. In addition, the size of the Universe is changing and gets larger with time.

What is the altitude above earth at which satellites can maintain orbits for a reasonable time without falling into the atmosphere?
100 miles (160 kilometers) above the surface approximately.

What is the altitude of an international flight?
The flight level of an aircraft is based on the purpose of the flight, weather, flight distance, and instructions from supervisors of the aircraft.

As a rule, the longer the flight, the higher the altitude.

What is the altitude of most passenger or military jets?
Most passenger jets fly around only 30,000 feet (5.7 miles). Even the best military jets rarely climb above 100,000 feet (a little less than 19 miles).

How is the atmosphere of the earth classified?
Troposphere
Stratosphere
Mesosphere
Thermosphere
Exosphere

What is Space?
Space is a term that can refer to various phenomena in science, mathematics, and communications.

In astronomy and cosmology, space is the vast 3-dimensional region that begins where the earth's atmosphere ends. Space is usually thought to begin at the lowest altitude at which satellites can maintain orbits for a reasonable time without falling into the atmosphere. This is approximately 160 kilometers (100 miles) above the surface. Astronomers may speak of interplanetary space (the space between planets in our solar system), interstellar space (the space between stars in our galaxy), or intergalactic space (the space between galaxies in the universe). Some scientists believe that space extends infinitely far in all directions, while others believe that space is finite but unbounded, just as the 2-space surface of the earth has finite area yet no beginning nor end.

In mathematics, space is an unbounded continuum (unbroken set of points) in which exactly three numerical coordinates are necessary to uniquely define the location of any particular point. It is sometimes called 3-space because it contains three distance dimensions. If a continuum requires fewer or more than three coordinates (dimensions) to uniquely define the location of a point, that continuum is sometimes called n-space or n-dimensional space, where n is the number of dimensions. Thus, for example, a line constitutes 1-space and a plane constitutes 2-space. When time is considered as a dimension along with the usual three in conventional space, the result is sometimes called 4-space, 4-dimensional space, time-space, or space-time.

In digital communications, the term space refers to an interval during which no signal is transmitted, or during which the signal represents logic 0. The term space may also be used in reference to the time interval separating two characters, bytes, octets, or words in a digital signal.

Where does the atmosphere end and outer space begin?
Very roughly, it starts about 100 kilometers above the Earth, but there is still part of the Earth's atmosphere even at this altitude.

As we said, space is the area above the Earth's atmosphere. However, there is no specific boundary because the atmosphere gradually thins as you move away from the Earth and you can find traces of the gasses we breathe over 100 miles above the earth. In contrast, most passenger jets fly around only 30,000 feet (5.7 miles). Even the best military jets rarely climb above 100,000 feet (a little less than 19 miles).

Why don't we receive light from all the stars in the universe?
There are about 6000 stars that are clearly visible to the naked eye above Earth. Yet we know that there are millions of stars in the universe. Since all stars are putting out light and other kinds of electromagnetic radiation and since light can travel for huge distances in space, why can't we see all the stars?

All stars, like our Sun, send out a huge amount of electromagnetic radiation, including light. However, that light spreads out with distance, making it so that only a tiny fraction reaches us. In addition, depending on the temperature of the star, the main color of light sent out by the star changes. Cooler stars put out redder light, hotter stars put out blue or white light. Generally, colors like white or blue are stronger colors (shorter wavelength, higher frequency) and can be seen more easily at far distances than reds, oranges or yellows. Also, some stars are simply larger than others and send out more light.

What is wavelength?
Forms of electromagnetic radiation like radio waves, light waves or infrared (heat) waves make characteristic patterns as they travel through space. Each wave has a certain shape and length. The distance between peaks (high points) is called wavelength.

What are radio waves?
Radio waves are part of a larger group of waves classified all together as electromagnetic radiation.


What is the electromagnetic spectrum?
What is electromagnetic radiation?

Abbreviated as EM, and also called just spectrum or electromagnetic radiation spectrum, electromagnetic spectrum refers to the complete range of wavelengths of electromagnetic radiation. The electromagnetic spectrum includes the following different types of of radiation (from lowest energy to highest): radio, microwaves, infrared, visible, ultraviolet, X-rays and gamma-rays.

Electromagnetic energy is a term used to describe all the different kinds of energies released into space by stars such as the Sun. These kinds of energies include some that you will recognize and some that will sound strange. They include:
Radio Waves
TV waves
Radar waves (Radio waves or microwaves or visible light)
Heat (infrared radiation)
Light
Ultraviolet Light (This is what causes Sunburns)
X-rays (Just like the kind you get at the doctor's office)
Short waves
Microwaves, like in a microwave oven
Gamma Rays

How do you make a radio wave?
When a direct electrical current is applied to a wire the current flow builds an electromagnetic field around the wire. This field sends a wave outward from the wire. When the current is removed, the field collapses which again sends a wave. If the current is applied and removed over and over for a period of time, a series of waves is propagated at a discrete frequency. If the current changes polarity, or direction repeatedly, that could make waves, too. This phenomenon is the basis of electromagnetivity and basically describes how radio waves are created within transmitters.

Other kinds of electromagnetic radiation, including radio waves, are made by natural processes such as the nuclear reactions in a star.

How is data put on radio waves?
There are two common ways to put information in a radio wave, and you've likely run into them yourself. They are called A.M. and F.M. just like the two choices you've always known are on a radio. To understand these two ways of sending information it is important to know that radio waves, by themselves, have very regular patterns. Generally they keep the same amplitude or frequency all the time. (Amplitude is the "height" of the radio wave, frequency is how close the waves are to each other.)

What is bandwidth?
Bandwidth is the total range of frequency required to pass a specific signal that has been modulated to carry data without distortion or loss of data. The ideal bandwidth allows the signal to pass under conditions of maximum AM or FM adjustment. (Too narrow a bandwidth will result in loss of data. Too wide a bandwidth will pass excessive noise.)

Transmitters and receivers have bandwidths. The "wider" the receiver's bandwidth is, the more information it can receive on different frequencies.

The term bandwidth is used metaphorically for the carrying ability of Internet carriers. For example, if you can receive information from the Internet over a slow modem, you get less information per second than if you were connected to a fast modem. Thus, you have "low bandwidth" and the Internet appears slower to you.

What are uplink and downlink?
The communication going from a satellite to ground is called downlink, and when it is going from ground to a satellite it is called uplink. When an uplink is being received by the spacecraft at the same time a downlink is being received by Earth, the communication is called two-way. If there is only an uplink happening, this communication is called upload. If there is only a downlink happening, the communication is called one-way.

What is a satellite?
An object in an orbit is called a satellite. A satellite can be natural, like the Moon, or human (or extraterrestrial?) -made. Satellites can travel around planets or around stars such as our Sun.

What are some different kinds of orbits?
Satellites put in space by people serve different purposes. Some use orbits to move from planet to planet. Others stay moving around one planet to do a specific job. The kinds of orbits they travel in help them to achieve this purpose. Some kinds of planetary orbits include:

Geosynchronous Orbits. A geosychronous orbit (GEO) is a circular, low orbit about Earth having a period of 23 hours 56 minutes 4 seconds--that is, the same amount of time it takes for the Earth to turn, so as the Earth spins, the satellite moves in time with it. Geosynchronous means "in time with the Earth." A spacecraft in geosynchronous stays over the same line of longitude. (A line of longitude marks one slice of the world from north to south pole.) Often a satellite in geosynchronous orbit stays above the same spot on Earth. When it does, it is called geostationary. This orbit is ideal for certain kinds of communication satellites, or meteorological (weather) satellites that have a job to do over one part of the world.

Polar Orbits. Polar orbits are useful for spacecraft that carry out mapping or surveillance operations. A satellite in polar orbit goes around the Earth from pole to pole. The planet spins underneath it as the satellite goes from north to south. This gives the spacecraft access to virtually every point on the surface. The Magellan spacecraft used a nearly-polar orbit at Venus. When the planet rotated once, all 360 degrees longitude had been exposed to Magellan's surveillance.

Walking Orbits. There are some things that interfere with making spacecraft follow perfect orbits easily. Planets are not perfectly spherical (ball shaped) and they do not have evenly distributed mass. Some parts of the planet might weigh a little more than others. For example a huge iron concentration could be in one part of the planet, making that side weigh a little more. Also, gravity can be uneven in space. Other bodies such as the Sun, the moon or other satellites, pull on spacecraft in orbit about a planet. Sometimes, scientists choose the path of a spacecraft's orbit to use this other gravity to slowly change the orbit over time. The result is called a walking orbit.

Suns-Synchronous Orbits. Sometimes a walking orbit can be designed so that the orbit changes slowly in time with the planet moving around the Sun, and in time with the planet's rotation so that the spacecraft is always at the same angle to the Sun. This is called a Sun-synchronous orbit. On Earth, this would work out so that the orbit always passes a low point at the same local time every day. This can be useful if instruments on board depend on a certain angle of solar illumination on the surface. Mars Global Surveyor's intended orbit at Mars is a 2-PM Mars local time Sun-synchronous orbit.

How does a spacecraft get to where its going?
Much of the work of getting a spacecraft to its destination is done before it is launched. All objects in the solar system are constantly moving. Scientists must know the clockwork of the solar system well enough to predict where a spacecraft's destination will be, when to launch and how fast to go to meet it in space. In addition to the movement of the objects in the solar system, scientists must take gravity in account. Gravity exerted by large bodies like planets and the Sun in the solar system will "bend" the flight of a spacecraft. If a flight is planned carefully, a spacecraft can use the gravity of planets and moons to do a swingby or be pulled into orbit.

Much of the "aiming" of spacecraft is done at or near launch, when the huge launch vehicle that puts it into space can push it onto a course that will take it to the right place. Once a spacecraft is in flight, small course corrections can be performed.

What are stars made of?
Basically, stars are big exploding balls of gas, mostly hydrogen and helium. Our nearest star, the Sun, is so hot that the huge amount of hydrogen is undergoing a constant star-wide nuclear reaction, like in a hydrogen bomb. Even though it is constantly exploding in a nuclear reaction, the Sun and other stars are so large and have so much matter in them that it will take billions of years for the explosion to use all the "fuel" in the star. The huge reactions taking place in stars are constantly releasing energy (called electromagnetic radiation) into the universe, which is why we can see them and find them on radio telescopes such as the ones in the Deep Space Network (DSN). Stars, including the Sun, also send out a solar wind and burst out occasional solar flares.

Scientists think that the core of the Sun is a 15 million degree Celsius plasma, a soup of electrons and protons that are stripped from hydrogen atoms. This "soup," called plasma, makes up 90 percent of the Sun. Every second, thousands of protons in the Sun's core collide with other protons to produce helium nuclei in a nuclear fusion reaction that releases energy. Just outside the core, energy moves outward by a process called radiation. Closer to the surface, the energy moves out by a process called convection - hot gases rise, cool, and sink back down again. As these masses of gas move, they push off of each other causing "Sun-quakes." These make the material in the Sun vibrate. These Sun-quakes help scientists determine the Sun's internal structure and the processes occurring at different locations underneath the Sun's surface.

Is there gravity in space?
There is gravity everywhere. It gives shape to the orbits of the planets, the solar system, and even galaxies. Gravity from the Sun reaches throughout the solar system and beyond, keeping the planets in their orbits. Gravity from Earth keeps the Moon and human-made satellites in orbit.

It is true that gravity decreases with distance, so it is possible to be far away from a planet or star and feel less gravity. But that doesn't account for the weightless feeling that astronauts experience in space. The reason that astronauts feel weightless actually has to do with their position compared to their spaceship. We feel weight on Earth because gravity is pulling us down, while the floor or ground stop us from falling. We are pressed against it. Any ship in orbit around the Earth is falling slowly to Earth. Since the ship and the astronauts are falling at the same speed, the astronauts don't press against anything, so they feel weightless.

What is mass?
We use the word mass to talk about how much matter there is in something. (Matter is anything you can touch physically.) On Earth, we weigh things to figure out how much mass there is. The more matter there is, the more something will weigh. Often, the amount of mass something has is related to its size, but not always. A balloon blown up bigger than your head will still have less matter inside it than your head (for most people, anyhow) and therefore less mass.

The difference between mass and weight is that weight is determined by how much something is pulled by gravity. If we are comparing two different things to each other on Earth, they are pulled the same by gravity and so the one with more mass weighs more. But in space, where the pull of gravity is very small, something can have almost no weight. It still has matter in it, though, so it still has mass.

Why is mass important?
Mass is important because of two major factors affecting how things move in space: inertia and gravity. The more mass something has, the more of both it experiences. That is why heavy things (things with a lot of mass) are hard to move. When an object is sitting still, it resists moving, and the more mass it has the more it resists. The amount of thrust needed to move something and how fast it ends up moving are both directly tied to its mass. On the other hand, once something massive starts moving, it is very hard to stop. This is also due to the relationship between mass and inertia.

Gravity is also proportional to how much mass each thing has. The bigger an object is, the larger the gravitational pull it exerts.

Because of gravity and inertia, the more massive something is, the harder it is to get into space, the harder it is to keep it there, and the harder it is to move it where you want it to go when it is there. For that reason, one of the goals of the New Millennium project is to make lightweight spacecraft.

How does propulsion work?
Propulsion moves things like spacecraft or jet planes forward by pushing something out of the back. Think of a balloon that you blow up and then release. The air rushing out of the back pushes the balloon forward.

What is in space?
The universe contains every substance and every kind of energy we know, and yet huge portions of it are completely empty. What is around you while you are in space depends on where you are in space. If you are on the surface of a planet, your experience is very different than if you are in a nebula, a meteoroid field or next to a star.

How far away is Earth from the sun?
The sun is at the heart of the solar system. All of the bodies in the solar system — planets, asteroids, comets, etc. — revolve around it. The distance from Earth to the sun is called an astronomical unit, or AU, which is used to measure distances throughout the solar system. The AU has been defined as 149,597,870,700 meters (92,955,807 miles).

Astronomers use the AU for measuring distances throughout the solar system. Jupiter, for example, is 5.2 AU from the sun. Neptune is 30.07 AU from the sun. On the outer edges of the solar system, the Oort Cloud, where comets are thought to originate, is 100,000 AU from the sun. The distance to the nearest star, Proxima Centauri, is about 250,000 AU. However, to measure longer distances, astronomers use light-years, or the distance that light travels in a single Earth year, which is equal to 63,239 AU. So Proxima Centauri is about 4.2 light-years away.

What is an orbit?
An orbit is a regular, repeating path that an object in space takes around another one. An object in an orbit is called a satellite. A satellite can be natural, like the moon, or human (or extraterrestrial?) -made.

In our solar system, the Earth orbits the Sun, as do the other eight planets. They all travel on or near the orbital plane, an imaginary disk-shaped surface in space. All of the orbits are circular or elliptical in their shape. In addition to the planets' orbits, many planets have moons which are in orbit around them.

How do we put spacecraft into orbit?
Spacecraft like weather satellites and the Hubble Telescope need to be lifted most of the distance from the ground to their orbit. One way for them to get there is inside the nose cone of a rocket. Once the rocket reaches an altitude near the satellite's orbit height, the satellite is ejected from the rocket's nose cone and the rocket falls back to Earth, burning up upon reentering our atmosphere (so don't worry about getting hit on the head with bits and pieces of used rockets).

Spacecraft like the Hubble Telescope are lifted into orbit by the Space Shuttle. In that case, the space shuttle itself is lifted by rockets into orbit. The spacecraft to be deployed is riding snugly in the cargo bay. At a certain height, the spacecraft is ejected and small rockets on it move it to the proper orbit altitude.

How deep is the ocean?
The average ocean depth is 4.3 kilometers (2.65 miles)

The average depth of the ocean is about 4,267 meters (14,000 feet). The deepest part of the ocean is called the Challenger Deep and is located beneath the western Pacific Ocean in the southern end of the Mariana Trench. Challenger Deep is approximately 11,030 meters (36,200 feet) deep.

How do we know a spacecraft's location?
The distance between Earth and the ship is measured by sending up a radio signal from Earth with a time code on it. The spacecraft "bounces" back the signal, and people on the ground can see how long it took to travel from Earth to the ship and back. Since all radio waves travel at the speed of light, scientists can look at how long it took for the signal to make it to the ship and back and figure out the distance it traveled. The angle that the radiotelescope is pointing when it receives the signal tells the direction of the ship.
Astronomy
Earth
Space
Space station
Space Quiz
Space Medicine
Solar System
Here are further guidelines.
Stars and the Universe
Solar System - Time
What is the Solar System? Answer
What is the Sun? Answer
How many Planets are there? Answer
Which Force governs the Movement of Planets? Answer
Is there more than one Solar System? Answer
What is Space? Answer
What is one Day? Answer
What is one Year? Answer
What is a Leap Year? Answer
The Planets
What is a Planet? Answer
Do Planets give out Light? Answer
Is the Orbit of a Planet Circular? Answer
Give the names of all of the Planets from Mercury to Pluto. Answer
Which Planet is Closest to the Sun? Answer
What are the Inner Planets made from? Answer
Between which two Planets is there a Belt of Asteroids? Answer
What are the Outer Planets made from? Answer
What is an Orbit? Answer
In which Direction does Gravity Pull the Earth? Answer
Why does the Earth move in a Circle around the Sun? Answer
A Force which keeps an Object moving in a Circle is called what? Answer
Does a Planet with a Small Orbit move Faster than a Planet with a Large Orbit? Answer
What are the Minor Planets? Answer
What is a Meteor? Answer
What is a Shooting Star? Answer
What is a Meteorite? Answer
Planet

What is a Planet?
A planet is a natural satellite of a star.
There are eight planets (plus Pluto) in our solar system.
All of the planets in our solar system orbit the Sun.

The planets themselves do not give out light.
We can see some of the planets in the night sky because they reflect sunlight (like our moon does).
The planets are so far away that they appear to us like dots of light. They look to our eyes like stars.

The orbit of a planet is almost circular. All of the planets (except Mercury and Pluto) orbit in the same plane.
The Moon - Satellites - Comets
What is a Satellite? Answer
What is the Difference between a Natural and an Artificial Satellite? Answer
What is a Natural Satellite of a Planet called? Answer
What is the Moon? Answer
Does the Moon have Less Gravity than the Earth? Answer
What does Geostationary mean? Answer
What can a Geostationary Satellite be Used for? Answer
Why are all Geostationary Satellites at the Same Height above the Earth? Answer
Describe a Polar Orbit. Answer
What can a Satellite in a Polar Orbit be Used for? Answer
What does a Comet Orbit? Answer
What is the Shape of a Comet's Orbit? Answer
When is a Comet travelling at its Fastest? Answer
When is a Comet travelling at its Slowest? Answer
When does a Comet have its Maximum Gravitational Potential Energy? Answer
What is a Comet made from? Answer
Which way does a Comet's Tail Always Point? Answer
Stars - Life Cycle - Galaxies
What are Constellations? Answer
Is the Sun a Star? Answer
Is the Sun Bigger than the Earth? Answer
What is a Star made from? Answer
What is a Protostar? Answer
Why do Hydrogen Atoms Accelerate in a Protostar? Answer
What type of Reaction is Fusion? Answer
What Element is made in the main Fusion Reaction in Stars? Answer
Why must Protons be moving Very Fast for Fusion to happen? Answer
Does Fusion release Large Amounts of Energy? Answer
Where does the Energy released by Fusion come from? Answer
What is the Evidence that the Sun formed from a previous Supernova? Answer
What are the two Opposing Forces in a Main Sequence Star? Answer
What does the length of time a Star lasts as a Main Sequence Star depend on? Answer
Is a Red Giant Bigger than the Main Sequence Star it came from? Answer
Is a Red Giant Hotter than the Main Sequence Star it came from? Answer
Does a White Dwarf have Nuclear Reactions? Answer
What does a White Dwarf become after it Loses Energy? Answer
Can a Large Star become a Supernova? Answer
Is a Supernova Bright? Answer
What is a Neutron Star made from? Answer
What is a Black Hole? Answer
What is a Galaxy made from? Answer
What is the Galaxy which contains the Sun called? Answer
Are there more than a Thousand Galaxies in the Universe? Answer
The Universe - Big Bang - Red-Shift
What is the Universe? Answer
What did the Steady-State Theory say? Answer
What does the Big Bang Theory say? Answer
What is the Evidence for the Big Bang Theory? Answer
What is Red-Shift? Answer
How does the Red-Shift of a Galaxy depend on its Distance from the Earth? Answer
What does a Red-Shift mean? Answer
Do Galaxies move Very Fast or Very Slow? Answer
What Evidence is there that the Universe is Expanding? Answer
What has an Expanding Universe got to do with the Big Bang? Answer
What does the Final Fate of the Universe depend on? Answer
What does Extraterrestrial mean? Answer
Give one Method which Scientists use to look for Life on other Planets. Answer

The Solar System and Beyond
What is the Solar System?
How is Time Measured?
What is a Planet?
What is a Satellite?
What is a Star?
What is the Universe?
What is the Big Bang?
What is a Telescope?
Is there Life on Other Planets?
What is a Star?

When you look at the sky at night, all of the points of light which you see (except for a few planets) are stars.

Stars generate their own heat and light by a process of nuclear fusion. The nearest star to Earth is called the Sun.

Most of the stars are so very far away that they appear not to move.
In reality they might be hurtling through space at enormous speeds. The patterns of "fixed" stars are called constellations.

The planets of our solar system are so close to Earth that you can see them move against the fixed background of constellations. If you see Jupiter in one place in the sky at night, then the next night you can see that its position has changed.


Atmosphere of Earth
What is the Atmosphere?
How is the atmosphere of the earth classified?
How did Life Begin on the Earth?
What is the Origin of Life on the Earth?
What is the History of the Atmosphere?
What is Ozone?
What is the Ozone Layer?
What are the Gases of the Atmosphere Today?
What is the Amount of Oxygen in the Air?
What are the Useful Products from Air?
What are the Uses of Nitrogen?
What are the Uses of Oxygen?
What are the Uses of the Noble Gases?
What is the Amount of Oxygen in the Air?
What are the Useful Products from Air?
What are the Uses of Nitrogen?
What are the Uses of Oxygen?
What are the Uses of the Noble Gases?
What is the Atmosphere?
An atmosphere is a layer of gases surrounding a planet or other material body of sufficient mass[3] that is held in place by the gravity of the body. An atmosphere is more likely to be retained if the gravity is high and the atmosphere's temperature is low.

The atmosphere of Earth is mostly composed of nitrogen. It also contains oxygen used by most organisms for respiration and carbon dioxide used by plants, algae and cyanobacteria for photosynthesis. It protects living organisms from genetic damage by solar ultraviolet radiation, solar wind and cosmic rays. Its current composition is the product of billions of years of biochemical modification of the paleoatmosphere by living organisms.

The term stellar atmosphere describes the outer region of a star, and typically includes the portion starting from the opaque photosphere outwards. Stars with sufficiently low temperatures may form compound molecules in their outer atmosphere.

The atmosphere consists of 78% nitrogen, 21% oxygen, 1% water vapor, and a minute amount of other trace gases like argon, and carbon monoxide. All of these gases combine to absorb ultraviolet radiation from the Sun and warm the planet’s surface through heat retention. The mass of the atmosphere is around 5×1018kg. 75% of the atmospheric mass is within 11 km of the surface. While the atmosphere becomes thinner the higher you go, there is no clear line demarcating the atmosphere from space; however, the Karman line , at 100 km, is often regarded as the boundary between atmosphere and outer space. The effects of reentry can be felt at 120 km.

How is the atmosphere of the earth classified?
Troposphere
Stratosphere
Mesosphere
Thermosphere
Exosphere

The Water Cycle
How does Water Vapour get into the Air? Give two sources.
What is Precipitation in the Water Cycle?
Why is the Sea Salty?
Give one process which removes Salt from the Sea.
The Carbon Cycle
Give two process which release Carbon Dioxide into the Atmosphere.
Give one process which removes Carbon Dioxide from the Atmosphere.
Does Carbon Dioxide dissolve in Rain Water?
How can Limestone release Carbon Dioxide into the Atmosphere?
The Nitrogen Cycle
What is Fixing?
Why do Plants need Nitrogen?
What type of bacteria turn Nitrite into Nitrate in the Soil?
What type of bacteria turn Nitrate in the Soil into Nitrogen in the Atmosphere?
The Early Atmosphere
Name two Gases which were present in the Earth's early Atmosphere?
Where did the Gases in the Earth's early Atmosphere come from?
Where did the Oceans come from?
What were the First Life Forms?
Which Gas do Green Plants add to the Atmosphere?
Where did Nitrogen in the Earth's Atmosphere come from?
The Atmosphere Today
How is Ozone Produced high up in the Atmosphere? How does the Ozone Layer Protect our planet?
Name one Chemical which can produce a hole in the Ozone Layer?
Give one risk of having a hole in the Ozone Layer.
What is the Proportion of Nitrogen in the Atmosphere Today?
What is the Proportion of Oxygen in the Atmosphere Today?
What is the Proportion of Argon in the Atmosphere Today?
Which Experiment can show the Proportion of Oxygen in the Air Today?
Give one Use of Nitrogen.
Give one Use of Oxygen.
Give one Use of Argon.
Here are further guidelines.


Planet Earth
Earth
Planet Earth
What do you know about Planet Earth?
What should you know about Planet Earth?
What is Earth?
What does Earth look like?
How does Earth move?
What is Earth made of?
How big is Earth?
How far is Earth from the Sun?
Why do we have day and night?
Why does Earth have seasons?
What are Earth's different parts?
What is Earth's orbit period?
What is the volume of Earth?
What is the mass of Earth?
What is Earth's density?
How is the atmosphere of the earth classified?
What is Earth Science?
What are various types of pressure?

What should you know about Planet Earth?
Atmosphere of Earth
Atmospheric pressure
Asteroids and artificial satellites
Axial tilt and seasons
Air
Biosphere
Composition and structure
Cultural and historical viewpoint
Chemical composition
Earth Science
Earth’s Components
Earth Materials
Earth’s Surface
Earth’s Layers
Earth’s Interior Layers
Earth’s Magnetic Field
Earth and the Solar System
Earth's internal heat
Habitability
Human geography
Hydrosphere
Life
Magnetic field
Moon

Though a satellite of Earth, the moon, with a diameter of about 2,159 miles (3,475 kilometers), is bigger than Pluto. (Four other moons in our solar system are even bigger.). The moon is a bit more than one-fourth (27 percent) the size of Earth, a much smaller ratio (1:4) than any other planets and their moons. This means the moon has a great effect on the planet and very possibly is what makes life on Earth possible.
Here are further guidelines.
Natural and environmental hazards
Natural resources and land use
Oceans
Orbit and rotation
Orbital characteristics
Physical characteristics
Shape
Seasons
Soil
Soil Size Classification
Tectonic plates
Upper atmosphere
Water
Weather and climate


Atmosphere of Earth

How is the atmosphere of the earth classified?
Troposphere
Stratosphere
Mesosphere
Thermosphere
Exosphere

Does the atmosphere of the Earth have an end-point boundary?
No.

How does the atmosphere of the Earth extend from its surface to outer space?
The Earth's atmosphere has no definite boundary; it slowly becomes thinner and fades into outer space. There are various objects in the solar system and universe. Up to now, 10000 km = 6213 mi 1252.9 yd above earth surface is included in the Earth’s atmosphere.

What is known about the atmosphere of Earth up to now?
Here are further guidelines.
http://www.qureshiuniversity.com/earthsatmosphere.html

10000km = 6213mi 1252.9yd
690km = 428mi 1313.2yd
85km = 52mi 1437.1yd
50km = 31mi 120.66yd
20km = 12mi 752.27yd
Km = Miles Yards


Earth Science

Atmosphere

Atmospheric chemistry
Climatology
Meteorology
Hydrometeorology
Paleoclimatology

Biosphere

Ecology
Biogeography
Paleontology
Palynology
Micropaleontology
Geomicrobiology
Geoarchaeology

Hydrosphere

Hydrology
Geohydrology
Limnology (freshwater science)
Oceanography (marine science)
Chemical oceanography
Physical oceanography
Biological oceanography (marine biology)
Geological oceanography (marine geology)
Paleoceanography

Hydrosphere

Hydrology
Geohydrology
Limnology (freshwater science)
Oceanography (marine science)
Chemical oceanography
Physical oceanography
Biological oceanography (marine biology)
Geological oceanography (marine geology)
Paleoceanography

Pedosphere

Soil science
Edaphology
Pedology

Geophysics
Geochronology
Geodynamics (see also Tectonics)
Geomagnetism
Gravimetry (also part of Geodesy)
Seismology
Glaciology
Hydrogeology
Mineralogy
Crystallography
Gemology
Petrology
Speleology
Volcanology

Systems

Environmental science
Geography
Human geography
Physical geography
Gaia hypothesis

Others

Cartography
Geoinformatics (GIS)
Geostatistics
Geodesy and Surveying

What is Earth Science?
Earth Science is the study of the Earth and its neighbors in space.

What is Earth?
Earth is our home planet. Scientists believe Earth and its moon formed around the same time as the rest of the solar system. They think that was about 4.5 billion years ago. Earth is the fifth-largest planet in the solar system. Its diameter is about 8,000 miles. And Earth is the third-closest planet to the sun. Its average distance from the sun is about 93 million miles. Only Mercury and Venus are closer.

Earth has been called the "Goldilocks planet." In the story of "Goldilocks and the Three Bears," a little girl named Goldilocks liked everything just right. Her porridge couldn't be too hot or too cold. And her bed couldn't be too hard or too soft. On Earth, everything is just right for life to exist. It's warm, but not too warm. And it has water, but not too much water.

Earth is the only planet known to have large amounts of liquid water. Liquid water is essential for life. Earth is the only planet where life is known to exist.

The Earth is divided into several layers which have distinct chemical and seismic properties (depths in km):

0- 40 Crust
40- 400 Upper mantle
400- 650 Transition region
650-2700 Lower mantle
2700-2890 D'' layer
2890-5150 Outer core
5150-6378 Inner core

Taken as a whole, the Earth's chemical composition (by mass) is:
34.6% Iron
29.5% Oxygen
15.2% Silicon
12.7% Magnesium
2.4% Nickel
1.9% Sulfur
0.05% Titanium

What does Earth look like?
From space, Earth looks like a blue marble with white swirls and areas of brown, yellow, green and white. The blue is water, which covers about 71 percent of Earth's surface. The white swirls are clouds. The areas of brown, yellow and green are land. And the areas of white are ice and snow.

The equator is an imaginary circle that divides Earth into two halves. The northern half is called the Northern Hemisphere. The southern half is called the Southern Hemisphere. The northernmost point on Earth is called the North Pole. The southernmost point on Earth is called the South Pole.

How does Earth move?
Earth orbits the sun once every 365 days, or one year. The shape of its orbit is not quite a perfect circle. It's more like an oval, which causes Earth's distance from the sun to vary during the year. Earth is nearest the sun, or at "perihelion," in January when it's about 91 million miles away. Earth is farthest from the sun, or at "aphelion," in July when it's about 95 million miles away.

What is Earth made of?
Earth is unique among the known planets: it has an abundance of water. Other worlds — including a few moons — have atmospheres, ice, and even oceans, but only Earth has the right combination to sustain life.

Earth's oceans cover about 70 percent of the planet's surface with an average depth of 2.5 miles (4 kilometers). Fresh water exists in liquid form in lakes and rivers and as water vapor in the atmosphere, which causes much of Earth's weather.

Earth has multiple layers. The ocean basins and the continents compose the crust, the outermost layer. Earth's crust is between three and 46 miles (five and 75 km) deep. The thickest parts are under the continents and the thinnest parts are under the oceans.

Crust

Earth's crust is made up of several elements: iron, 32 percent; oxygen, 30 percent; silicon, 15 percent; magnesium, 14 percent; sulfur, 3 percent; nickel, 2 percent; and trace amounts of calcium, aluminum and other elements.

The crust is divided into huge plates that float on the mantle, the next layer. The plates are constantly in motion; they move at about the same rate as fingernails grow. Earthquakes occur when these plates grind against each other. Mountains form when the plates collide and deep trenches form when one plate slides under another plate. Plate tectonics is the theory explaining the motion of these plates.

Mantle

The mantle under the crust is about 1,800 miles deep (2,890 km). It is composed mostly of silicate rocks rich in magnesium and iron. Intense heat causes the rocks to rise. They then cool and sink back down to the core. This convection — like a lava lamp — is believed to be what causes the tectonic plates to move. When the mantle pushes through the crust, volcanoes erupt.

Core

At the center of the Earth is the core, which has two parts. The solid, inner core of iron has a radius of about 760 miles (about 1,220 km). It is surrounded by a liquid, outer core composed of a nickel-iron alloy. It is about 1,355 miles (2,180 km) thick. The inner core spins at a different speed than the rest of the planet. This is thought to cause Earth's magnetic field. When charged particles from the solar wind collide with air molecules above Earth's magnetic poles, it causes the air molecules to glow, causing the auroras — the northern and southern lights.

How big is Earth?
Earth, the third planet from the sun, is the fifth largest planet in the solar system; only the gas giants Jupiter, Saturn, Uranus and Neptune are bigger. Earth is the largest of the terrestrial planets of the inner solar system, bigger than Mercury, Venus and Mars.

Radius, diameter and circumference

The mean radius of Earth is 3,959 miles (6,371 kilometers). However, Earth is not quite a sphere. The planet's rotation causes it to bulge at the equator. Earth's equatorial diameter is 7,926 miles (12,756 kilometers), but from pole to pole, the diameter is 7,900 miles (12,720 km) — a difference of only 40 miles (64 km).

The circumference of Earth at the equator is about 24,902 miles (40,075 km), but from pole-to-pole — the meridional circumference — Earth is only 24,860 miles (40,008 km) around. This shape, caused by the flattening at the poles, is called an oblate spheroid.

Density, mass and volume

Earth's density is 5.52 grams per cubic centimeter. Earth is the densest planet in the solar system because of its metallic core and rocky mantle. Jupiter, which is 318 more massive than Earth, is less dense because it is made of gases, such as hydrogen.

Earth's mass is 6.6 sextillion ton (5.9722 x 1024 kilograms). It volume is 1.08321 x 1012 km.

The total surface area of Earth is about 197 million square miles (509 million square km). About 71 percent is covered by water and 29 percent by land.

Highest and lowest points

Mount Everest is the highest place on Earth above sea level, at 29,028 feet (8,848 meters), but it is not the highest point on Earth — that is, the place most distant from the center of the Earth. That distinction belongs to Mount Chimaborazo in the Andes Mountains in Ecuador. Although Chimaborazo is about 10,000 feet shorter (relative to sea level) than Everest, this mountain is about 1.5 miles (2.4 km) farther into space because of the equatorial bulge.

The lowest point on Earth is the Mariana Trench in the western Pacific Ocean. It reaches down about 36,200 feet (11,034 meters) below sea level.

How far is Earth from the Sun?
The sun is at the heart of the solar system. All of the bodies in the solar system — planets, asteroids, comets, etc. — revolve around it. The distance from Earth to the sun is called an astronomical unit, or AU, which is used to measure distances throughout the solar system. The AU has been defined as 149,597,870,700 meters (92,955,807 miles).

Astronomers use the AU for measuring distances throughout the solar system. Jupiter, for example, is 5.2 AU from the sun. Neptune is 30.07 AU from the sun. On the outer edges of the solar system, the Oort Cloud, where comets are thought to originate, is 100,000 AU from the sun. The distance to the nearest star, Proxima Centauri, is about 250,000 AU. However, to measure longer distances, astronomers use light-years, or the distance that light travels in a single Earth year, which is equal to 63,239 AU. So Proxima Centauri is about 4.2 light-years away.

The AU is the average distance from the Earth to the sun. Earth makes a complete revolution around the sun every 365.25 days ­— one year. However, Earth's orbit is not a perfect circle; it is shaped more like an oval, or an ellipse. Over the course of a year, Earth moves sometimes closer to the sun and sometimes farther away from the sun. Earth's closest approach to the sun, called perihelion, comes in early January and is about 91 million miles (146 million km). The farthest from the sun Earth gets is called aphelion. It comes in early July and is about 94.5 million miles (152 million km).

Finding the distance

Historically, the first person to measure the distance to the sun was Aristarchus around the year 250 BC. In more recent times, astronomer Christiaan Huygens calculated the distance from Earth to the sun in 1653. He used the phases of Venus to find the angles in a Venus-Earth-Sun triangle. For example, when Venus appears half illuminated by the sun, the three bodies form a right triangle from Earth's perspective. Guessing (correctly, by chance) the size of Venus, Huygens was able to determine the distance from Venus to Earth, and knowing that distance, plus the angles made by the triangle, he was able to measure the distance to the sun. However, because Huygens' method was partly guesswork and not completely scientifically grounded, he usually doesn't get the credit.

In 1672, Giovanni Cassini used a method involving parallax, or angular difference, to find the distance to Mars and at the same time figured out the distance to the sun. He sent a colleague, Jean Richer, to French Guiana while he stayed in Paris. They took measurements of the position of Mars relative to background stars, and triangulated those measurements with the known distance between Paris and French Guiana. Once they had the distance to Mars, they could also calculate the distance to the sun. Since his methods were more scientific, he usually gets the credit.

New equation

With the advent of spacecraft and radar, there were now methods for making a direct measure of the distance between the Earth and the sun. The definition of AU had been "the radius of an unperturbed circular Newtonian orbit about the sun of a particle having infinitesimal mass, moving with a mean motion of 0.01720209895 radians per day (known as the Gaussian constant)."

Along with making things unnecessarily difficult for astronomy professors, that definition actually didn't jibe with general relativity. Using the old definition, the value of AU would change depending on an observer's location in the solar system. If an observer on Jupiter used the old definition to calculate the distance between the Earth and the sun, the measurement would vary from one made on Earth by about 1,000 meters (3,280 feet).

Moreover, the Gaussian constant depends on the mass of the sun, and because the sun loses mass as it radiates energy, the value of AU was changing along with it.

The following table lists statistical information for the Sun and planets:

Distance
(AU)
Radius
(Earth's)
Mass
(Earth's)
Rotation
(Earth's)
# MoonsOrbital
Inclination
Orbital
Eccentricity
ObliquityDensity
(g/cm3)
Sun0109332,80025-36*9---------1.410
Mercury0.390.380.0558.8070.20560.1°5.43
Venus0.720.950.8924403.3940.0068177.4°5.25
Earth1.01.001.001.0010.0000.016723.45°5.52
Mars1.50.530.111.02921.8500.093425.19°3.95
Jupiter5.2113180.411161.3080.04833.12°1.33
Saturn9.59950.428182.4880.056026.73°0.69
Uranus19.24170.748150.7740.046197.86°1.29
Neptune30.14170.80281.7740.009729.56°1.64
Pluto39.50.180.0020.267117.150.2482119.6°2.03


At the equator, Earth spins at just over 1,000 miles per hour. Earth makes a full spin around its axis once every 24 hours, or one day. The axis is an imaginary line through the center of the planet from the North Pole to the South Pole. Rather than straight up and down, Earth's axis is tilted at an angle of 23.5 degrees.

Why do we have day and night?
At all times, half of Earth is lighted by the sun and half is in darkness. Areas facing toward the sun experience daytime. Areas facing away from the sun experience nighttime. As the planet spins, most places on Earth cycle through day and night once every 24 hours. The North Pole and South Pole have continuous daylight or darkness depending on the time of year.

Why does Earth have seasons?
Earth has seasons because its axis is tilted. Thus, the sun's rays hit different parts of the planet more directly depending on the time of year.

From June to August, the sun's rays hit the Northern Hemisphere more directly than the Southern Hemisphere. The result is warm (summer) weather in the Northern Hemisphere and cold (winter) weather in the Southern Hemisphere.

From December to February, the sun's rays hit the Northern Hemisphere less directly than the Southern Hemisphere. The result is cold (winter) weather in the Northern Hemisphere and warm (summer) weather in the Southern Hemisphere.

From September to November, the sun shines equally on both hemispheres. The result is fall in the Northern Hemisphere and spring in the Southern Hemisphere.

The sun also shines equally on both hemispheres from March to May. The result is spring in the Northern Hemisphere and fall in the Southern Hemisphere.

Soil

What on Earth is Soil?
Here are further guidelines.

Soil Size Classification
ParticleAmerican DiameterInternational Diameter
Clay< 0.00008" / < 0.002 mm< 0.002 mm
Fine Silt0.00008 - 0.00024" / 0.002 - 0.006 mm 
Medium Silt0.00024 - 0.0008" / 0.006 - 0.02 mm0.002 - 0.05 mm
Coarse Silt0.0008 - 0.002" / 0.02 - 0.05 mm 
Very Fine Sand0.002 - 0.004" / 0.05 - 0.1 mm 
Fine Sand0.004 - 0.01" / 0.1 - 0.25 mm0.05 - 0.2 mm
Medium Sand0.01 - 0.02" / 0.25 - 0.5 mm 
Coarse Sand0.02 - 0.04" / 0.5 - 1.0 mm 0.2 - 2.0 mm
Very Coarse Sand0.04 - 0.08" / 1 - 2 mm 
Gravel/Stones> 0.08" / > 2 mm> 2 mm


What are Earth's different parts?
Air/Clouds/Temperatures The air is made up of different gases, mainly nitrogen and oxygen.
Land (mountains, valleys, flat areas. Volcanoes(gas and dust)) The land contains mountains, valleys and flat areas.
Life (plants, animals. people) Life consists of people, animals and plants. There are millions of species, or kinds of life, on Earth. Their sizes range from very tiny to very large.
Rock and metal Below Earth's surface are layers of rock and metal. Temperatures increase with depth, all the way to about 12,000 degrees Fahrenheit at Earth's inner core.
Water The water includes oceans, lakes, rivers, streams, rain, snow and ice.

Earth consists of land, air, water and life. The land contains mountains, valleys and flat areas. The air is made up of different gases, mainly nitrogen and oxygen. The water includes oceans, lakes, rivers, streams, rain, snow and ice. Life consists of people, animals and plants. There are millions of species, or kinds of life, on Earth. Their sizes range from very tiny to very large.

Below Earth's surface are layers of rock and metal. Temperatures increase with depth, all the way to about 12,000 degrees Fahrenheit at Earth's inner core.

Earth's parts once were seen as largely separate from each other. But now they are viewed together as the "Earth system." Each part connects to and affects each of the other parts. For example:

Clouds in the air drop rain and snow on land.
Water gives life to plants and animals.
Volcanoes on land send gas and dust into the air.
People breathe air and drink water.
Earth system science is the study of interactions between and among Earth's different parts.

Aerospace
Air pollution
Atmospheric dynamics
Aviation
Earth Science
    Geology: Science of the Earth
    Meteorology: Science of the Atmosphere
    Oceanography: Science of the Oceans
    Astronomy: Science of the Universe
The Earth and Beyond
Atmosphere of Earth
Atmospheric pressure

What are various types of pressure?
Atmospheric pressure
Cabin pressure
Spray pressure (aerosol pressure)
Tire pressure
Water pressure
Here are further guidelines.
Air/Clouds/Temperatures
Land (mountains, valleys, flat areas. Volcanoes/gas and dust)
Life (plants, animals. people)
Rock and metal
Water

Earth’s Surface
What should you know about the surface of Earth?

Continents (in alphabetical order):
Africa
Antarctica
Asia
Australia
North America
South America

Canyons
Caves
Coastlines
Mountains
Oceans
Plateaus
Plains
Valleys

What is the highest point on Earth?
Mt. Everest (Himalayas), 8848 m or 29,028 ft

What is the lowest point on Earth?
Mariana Trench -11,033 m or -36,198 ft

Canyons
Caves
Coastlines
Mountains
Oceans
Plateaus
Plains
Valleys

Weather and climate

What is the difference between weather and climate?
Here are further guidelines.

Here are further guidelines.

 

The Planets of the Solar System

Mercury

The planet closest to the Sun, Mercury, has no atmosphere. Always in the region of the Sun, Mercury is not easy to locate as it rises and sets during the twilight hours. The innermost planet takes 88 days to complete an orbit of the Sun. Maximum brightness magnitude -1.9.

Venus

Venus is nearly the same size as Earth. Venus is covered by thick clouds of carbon dioxide that reflect the Sun to be the brightest planet in the sky. Venus, also referred to as the 'evening star', can rise up to 3 hours before sunrise, or set 3 hours after sunset. The period Venus takes to circle orbit the Sun is 225 days. Venus has phases, like the moon, which affects its brightness. Maximum brightness magnitude -4.4

Earth

Earth, the third planet from the Sun, is the largest of the inner planets, with a surface area of 29% land and 71% water. Deep beneath the Earth's rock crust is a thick molten mantle. At the centre of the Earth is a metal core that generates a magnetic field. Earth is the only place in the Universe known to have life that exists in an atmosphere of 78% nitrogen and 21 % oxygen. The Earth takes 365 days, a year, to complete a circuit across the Zodiac and a rotation of the Sun. The Moon orbits Earth.

Mars

Mars has a reddish colour caused by iron oxide, rust, on its rocky surface. Another feature is the ice caps at its poles. Half the size of Earth, Mars is the last of the inner planets. Mars has two relatively small, irregular shaped moons, Phobos and Deimos, which are thought to be captured asteroids. A circuit of Mars around the Sun takes 687 days. On average, Mars move across a constellation every two month. Mars has a maximum magnitude of -2.8

Jupiter

Jupiter is the largest planet in the solar system, being 2.5 times more massive than all the planets combined. The planet has swirling clouds of ammonia crystals and a great red spot which is an eternal storm. Jupiter is composed of 10% helium and 90% hydrogen, with compressed metallic hydrogen at its centre, surrounded by liquid and a gas atmosphere. Jupiter has 16 moons, of which 4 (Ganyymede, Callisto, Io, Europa) are large enough to see with binoculars as they orbit.

Jupiter is currently in Leo. Jupiter takes 11.9 years to complete a circuit around the Sun and across the Zodiac constellations. Jupiter takes about a year to move across a Zodiac constellation to the next. The brightest magnitude of Jupiter is -2.6.

Saturn

Saturn has prominent ring formations made of ice, dust and rocks. The helium and hydrogen composition of Saturn is similar to Jupiter. Saturn has a many comparatively small Moons (satellites) among its rings, with 7 Moons large enough to be spheres, the largest Moon is Titan. Saturn takes 29 and half years to complete a circuit of the Zodiac.

Saturn crosses Libra to enter Scorpio. The maximum magnitude of Saturn is -0.3.

Uranus

Uranus has a frozen hydrogen and helium centre, with an outer atmosphere of methane which absorbs red light, so the planet has a cyan colour. Uranus has 27 satellites, with its 5 main Moons in order from largest are: Titania, Oberon, Umbriel , Ariel, Miranda.

Currently Uranus is in Pisces, with a 84 year path to complete an orbit of the Sun. Uranus is dim at +5.6 magnitude, so it is observed using binoculars or a telescope.

Neptune

Neptune is slightly more massive than Uranus. The composition of the two planets is similar, however Neptune's vivid blue colour and wind clouds are attributed to more methane in its atmosphere. Neptune has 13 satellites, with only one, Triton, larger enough to be a sphere.

Neptune is in Aquarius, moving towards Aquarius. Neptune takes 165 years to complete a circuit across the Zodiac during its orbit of the Sun. Look through a telescope to see the planet with a brightness magnitude of +7.7.

Pluto

Pluto was classified with Eris and Ceres as dwarf planets. The difference between these bodies and planets are their comparatively small size. Also, they have not cleared the 'neighbourhood' of their orbit. Each dwarf planet is found in the 'neighbourhood' of a belt of orbiting particle. Pluto, with its moon Charon, and another dwarf planet Eris, are the largest bodies in the Kuiper belt. Ceres is located in the asteroid belt between Mars and Jupiter. Pluto is in the constellation of Sagittarius.

Radar
Radio Detection and Ranging
What do you know about radar systems?
What is radar?
How does radar work?
What is the maximum altitude an aircraft can ascend?
What is the mechanism involved in radar systems?
How does an aircraft radar system determine distance from specific destination, speed, direction, and altitude while in flight or space?
What are the uses of radar?


What is radar?
The word "radar" is an acronym derived from the words RAdio Detection And Ranging..

Radar is an object-detection system that uses radio waves to determine the range, altitude, direction, or speed of objects.

It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish (or antenna) transmits pulses of radio waves or microwaves that bounce off any object in their path. The object returns a tiny part of the wave's energy to a dish or antenna that is usually located at the same site as the transmitter.
A radar system usually operates in the ultra-high-frequency (UHF) or microwave part of the radio-frequency (RF) spectrum, and is used to detect the position and/or movement of objects. Radar can track storm systems, because precipitation reflects electromagnetic fields at certain frequencies. Radar can also render precise maps. Radar systems are widely used in air-traffic control, aircraft navigation, and marine navigation.

High-power radar, using large dish antennas, has been used to measure distances to the moon, other planets, asteroids, and artificial satellites. From unmanned spaceprobes, radar has been used to map Venus, whose surface is obscured at visible wave lengths by a thick layer of clouds.

How does radar work?

Here's a summary of how radar works:
1.Magnetron generates high-frequency radio waves.
2.Duplexer switches magnetron through to antenna.
3.Antenna acts as transmitter, sending narrow beam of radio waves through the air.
4.Radio waves hit airplane and reflect back.
5.Antenna picks up reflected waves during a break between transmissions. Note that the same antenna acts as both transmitter and receiver, alternately sending out radio waves and receiving them.
6.Duplexer switches antenna through to receiver unit.
7.Computer in receiver unit processes reflected waves and draws them on a TV screen.
8.Plane shows up on TV radar display with any other nearby targets.

What are the uses of radar?

The modern uses of radar are highly diverse, including air and terrestrial traffic control, radar astronomy, air-defense systems, antimissile systems; marine radars to locate landmarks and other ships; aircraft anticollision systems; ocean surveillance systems, outer space surveillance and rendezvous systems; meteorological precipitation monitoring; altimetry and flight control systems; guided missile target locating systems; and ground-penetrating radar for geological observations. High tech radar systems are associated with digital signal processing and are capable of extracting useful information from very high noise levels.


A long-range radar antenna, known as ALTAIR, used to detect and track space objects in conjunction with ABM testing at the Ronald Reagan Test Site on Kwajalein Atoll.
Long-range radar antenna, used to track space objects and ballistic missiles.

Radar of the type used for detection of aircraft. It rotates steadily, sweeping the airspace with a narrow beam.


Radar frequency bands
Band name Frequency range Wavelength range Notes
HF 3–30 MHz 10–100 m Coastal radar systems, over-the-horizon radar (OTH) radars; 'high frequency'
VHF 30–300 MHz 1–10 m Very long range, ground penetrating; 'very high frequency'
P < 300 MHz > 1 m 'P' for 'previous', applied retrospectively to early radar systems; essentially HF + VHF
UHF 300–1000 MHz 0.3–1 m Very long range (e.g. ballistic missile early warning), ground penetrating, foliage penetrating; 'ultra high frequency'
L 1–2 GHz 15–30 cm Long range air traffic control and surveillance; 'L' for 'long'
S 2–4 GHz 7.5–15 cm Moderate range surveillance, Terminal air traffic control, long-range weather, marine radar; 'S' for 'short'
C 4–8 GHz 3.75–7.5 cm Satellite transponders; a compromise (hence 'C') between X and S bands; weather; long range tracking
X 8–12 GHz 2.5–3.75 cm Missile guidance, marine radar, weather, medium-resolution mapping and ground surveillance; in the USA the narrow range 10.525 GHz ±25 MHz is used for airport radar; short range tracking. Named X band because the frequency was a secret during WW2.
Ku 12–18 GHz 1.67–2.5 cm High-resolution, also used for satellite transponders, frequency under K band (hence 'u')
K 18–24 GHz 1.11–1.67 cm From German kurz, meaning 'short'; limited use due to absorption by water vapour, so Ku and Ka were used instead for surveillance. K-band is used for detecting clouds by meteorologists, and by police for detecting speeding motorists. K-band radar guns operate at 24.150 ± 0.100 GHz.
Ka 24–40 GHz 0.75–1.11 cm Mapping, short range, airport surveillance; frequency just above K band (hence 'a') Photo radar, used to trigger cameras which take pictures of license plates of cars running red lights, operates at 34.300 ± 0.100 GHz.
mm 40–300 GHz 1.0–7.5 mm Millimetre band, subdivided as below. The frequency ranges depend on waveguide size. Multiple letters are assigned to these bands by different groups. These are from Baytron, a now defunct company that made test equipment.
V 40–75 GHz 4.0–7.5 mm Very strongly absorbed by atmospheric oxygen, which resonates at 60 GHz.
W 75–110 GHz 2.7–4.0 mm Used as a visual sensor for experimental autonomous vehicles, high-resolution meteorological observation, and imaging.

Here are further guidelines.