Wind

Wind Air in motion. Winds are caused basically by temperature differences over the Earth's surface. A major circulation pattern is set up as air over the equator becomes hot and rises. This creates a low-pressure region, known to early sailors as the doldrums, where the air is still and waters calm for days on and.

As the hot air rises, cool air from polar regions moves in to take its place. The hot air in turn cools and sinks down near the poles. if the earth were not rotating, the winds would blow north-south. But the Earth is rotating, and the winds are deflected by the so-called Coriolis affect. This makes the winds blow towards the equator from the north-east in the northern hemisphere and from the south-east in the southern.

such winds, called the trade winds, blow towards the equator from about the 30th parallels north and south. Between about the 30-60th parallels, by contrast, the winds blow predominantly from the west-from the south-west in the northern hemisphere and from the north-west in the southern. These winds are called the prevailing westerlies.

Seasons

1 = 2004 Mar 20 9:00:00 pm UT
2 = 2003 Jun 21 9:00:00 pm UT
3 = 2004 Sept 22 9:00:00 pm UT
4 = 2003 Dec 22 9:00:00 pm UT


Seasons Natural divisions of the year, marked by regular changes in the weather and the lengths of the days and nights. The rhythm of the seasons is most evident in temperate regions,where the four seasons : spring - summer - autumn - winter , are most distinct.

The seasons are caused by the inclination (23½°) of the earth's axis to the plane of its orbit around the Sun. This allows a certain point on the earth to receive more solar radiation at some times than at others. It is summer in the northern hemisphere ( winter in the southern) when the north pole is tilted towards (south pole away from) the Sun ; and winter in the northern hemisphere (summer in the southern) when the north pole is tilted away (south pole towards) the Sun. At times in between, when the Earth's axis is tilted nether towards nor away from the Sun, the equinoxes occur. Then day and night are of equal length throughout the worlds.

Equinoxes The two tomes of the year when day and and night are of equal length throughout the worlds. They occur when the Sun lies exactly above the equator, in the spring (spring or vernal equinox) on about March 21 as the Sun is moving north; and in the autumn (autumnal equinox) on about September 23 as the Sun is moving south.

Solstices The times in the year when the Earth's axis is tilted most towards or away from the Sun; or from an observer's point of view, the times when the sun is highest and lowest in the sky at noon. In the northern hemisphere the Sun is highest in the moon sky on about June 21 each year (summer solstice); and lowest on about December 21 (winter solstice). On these dates occur, respectively, the longest and shortest periods of daylight.

Energy

Energy : The capacity for doing work. Head, electricity and radiation are forms of energy. Fuels release chemical energy when they burn. Kinetic energy is the energy possessed by moving objects. potential energy is energy that is stored in a system-an object that can fall has gravitational potential energy.

In a closed system, the overall energy content remains constant no matter what chemical or physical changes take place therein: this being termed the conservation of energy. Only in nuclear reactions does the conservation law not apply. Then energy is created by the destruction of matter, for the two are equivalent, related by Einstein's equation E = mc² .
The standard unit of energy is the joule.

Energy level or energy state; one of a number of states in which electrons or other atomic particles can exist. In each state a particle or atom possesses a certain energy. When it moves into another higher-energy state. In this state it is said to be excited.

Water

Water or Hydrogen oxide, H2O perhaps after oxygen the most important compound on Earth, without which life as we know it would be impossible. Over 70% of the Earth is covered with water and more is locked in the polar ice caps and glaciers. There is estimated to be some 1 · 5 million million million tonnes of water in the Earth's crust.

There is a constant exchange of water between the ground and the atmosphere, this being known as the water cycle. The presence of more or less water vapour in the atmosphere has a profound effect on the weather. Chemically, water is an excellent solvent. It has a pH when pure of 7, being neither acidic nor basic. It freezes at 0°C and boils at 100°C under normal pressure. It is chemically similar to hydrogen sulphide, H2S, and should theoretically also be a gas at room temperature. but it is less volatile due to hydrogen bonding.

Temperatures scale

Celsius scale The common scale of temperature, named after the Swedish astronomer Anders Celsius. On this scale the boiling point of water is 0° and the boiling point 100°. It is a Centigrade scale, the interval between 0° and 100° being split up into 100 divisions (centi-). Temperatures are expressed in degrees Celsius (°c)

Fahrenheit scale A scale of temperature, named after the German physicist Gabriel Fahrenheit. On this scale, once widely used in English-speaking countries, water freezes at 32° and boils at 212°.

Kelvin The unit of temperature of the absolute temperature scale, symbol K. The freezing point of water is 273 16K
Absolute temperature A temperature scale based on the absolute zero of temperature. The absolute Kelvin scale uses Celsius units.

X - rays

X-rays Also called Roentgen rays after their discoverer (1895) W.K. Roentgen invisible radiation of the electromagnetic spectrum of very short wavelengths, produced in commercial X-rays machines by bombarding a tungsten metal target with a beam of electrons from a heated cathode.

X-rays are very penetrating and are used in medicine to human body. The rays are passed through the body into a photographic plate, on which bones and flesh can be distinguished. The latest computerized X-ray scanners can olso reveal details of soft body tissues. In crystallography, X-rays are used to investigate atomic structure. The ordered crystal lattice diffracts X-rays in a characteristic way, from which the crystal structure can be inferred.

Clock

Clock A device for indicating the passage of time. The mechanical clock has a power source, such as a falling weight or spring, whose energy is released slowly and at a measured rate by a regulator, such as a balance wheel or pendulum. The gradual mevement of the spring or fall of the weight is conveyed by a train of gears to hands that indicate the time. The first mechanical clocks appeared in Europe in the 13th century.
But clocks did not become reasonably accurate until the mid-1600s when Christian Huygens first used a pendulum as a regulator. In the 1670s the introduction of a balance wheel for regulation led to the development of compact portable clocks, or watches.

Atomic Clock The most accurate of all clock, which is regulated by the precise vibration of certain atoms or molecules. An atomic clock my gain or lose less than a second in 100,000 years.

Chronometer An accurate timepiece. The original chronometers were developed to aid navigation at sea. The first accurate instrument was invented by Yorkshireman John Harrison in 1759.

Clepsydra or water clock A device dating back at least to ancient Egyptian times which used the flow of water from a vessel to measure the passage of time.

Sundial An early device for telling the time by means of shadows. It consists of a pointer, or gnomon, which casts the shadow, set in the middle of a flat dial. The gnomon must slant upwards so that it makes an angle with the dial face equal to latitude of the location.

Quartz watch A Watch regulated by the vibrations of a wafer-thin quartz crystal. When a tiny current is applied to the crystal, it vibrates exactly 32,768 times a second. A microcircuit converts this 'time base' in the quartz digital watch to a digital dispaly, such as LCD or LED.
In the Quartz analog watch the time base drives a gear train to move the hands.

Doppler effect

The apparent change in frequency of sounds or light waves that accurs when the source of the waves and the observer are moving relative to one another. It is named after Christian Johann Doppler, who first described it in 1842. The effect is most commonly experienced with sound, as for example when an ambulance or police car passes by with siren blaring. The frequency, or pitch of the sound when the vehicle is approaching is noticeably higher than when it is receding.

The sound waves approaching are effectively bunched closer together, or shortened (higher frequency) , while those receding are effectively drawn out, or lengthened (lower frequency). The same effect occurs with starlight. The light from an approaching star has an apparently shorter wavelength, or looks bluer than it should. The light from a receding star has an apparently longer wavelength, or looks redder.

Source Image : Wikipedia

Barometer

Barometer An Intruments that measures atmospheric pressure. Italian physicist Evangelista Torricelli discovered the principle of the barometer in 1643 and made a mercury barometer. This is basically a glass tube full of mercury up-ended in a bowl of mercury.

The pressure of the atmosphere balances a column of mercury about 760 mm (30 in) high. Domestic barometers are of the aneroid ( without liquid) type. The pressure sensor in the aneroid barometer is a partly evacuated box, which expands or contracts as the pressure changes. This movement is magnified by levers and moves a pointer over a graduated scale.

Refrigerator

Refrigerator A device for keeping food and other substances cool. It works on a cycle of vaporization and compression of volatile fluid (refrigerant). The liquid refrigerant is made to expand through a valve and evaporate, extracting heat from the contents of the refrigerator. The vapour formed is then compressed by a compressor and passed through a condenser, whereupon it loses heat and liquefies. It is then recycled.

Refrigerant A substance, used as the working fluid in refrigerators, which will vaporize readily and condense readily when compressed. The commonest refrigerants are ammonia and the freons

Climate and Weather

Climate The average weather conditions of a region over along period. Broadly speaking the climate of a region is related to its latitude - its distance from the equator. it is also affected by its proximity to water - coastal regions tend to experience a different climate from inland regions at the same latitude.

Weather The prevailing atmospheric conditions - temperature, pressure, humidity, wind velocity and so on. The typical weather experienced by a region is the climate. The study of weather is Meteorology. Meteorologists take regular readings of atmospheric conditions and, guided by experience, try to forecast what the weather will be like in the future. They are now aided by data and pictures returned by weather satellites.

Rocks and Minerals

<---TRIGONAL, minimum symmetry one 3-fold axis.
Examples are calcite, rose quartz and tourmaline



<---TRICLINIC, minimum symmetry none. Examples are sunstone, turquoise and chalcanthite.



<---TETRAGONAL, minimum symmetry one 4-fold axis. Examples are zircon, calomel and wulfenite.


<---ORTHORHOMBIC, minimum symmetry three 2-fold axes. Examples are barytes, alexandrite and olivine



<---MONOCLINIC, minimum symmetry one 2-fold axis. Examples are malachite, orthoclase and moonstone



<---HEXAGONAL, minimum symmetry one 6-fold axis. Examples are emerald, zincite and apatite



<---CUBIC, minimum symmetry four 3-fold axes. Examples are fluorite, garnet and diamond




Rocks The materials that make up the Earth's crust. They are composed of one or more minerals, but unlike minerals rocks do not usually have a uniform composition. They are usually, but not always, hard. Clay and gravel are classed as rocks, but they are not solid in the way, say, granite is.
For the three main types of rock, igneous rock, sedimentary rocks and metamorphic rocks.
The study of rocks is petrology

ATOM

Atom the smallest part of an element that retains its chemical identity and can take part in a chemical reaction.
Atoms are very, very tiny being typically about one ten-millionth of a millimetre (10 -7 mm) in radius. Each of the 100 or so chemical elements contains a different kind of atom. Atoms differ in the number of particles they contain.
Atom means that which cannot be divided for it was long thought that atoms were indivisible. The Greek democritos first suggested that substances were made up of atoms in about 400BC. But the idea was forgotten until John Dalton suggested it again in 1801. Experiments by J. J. Thomson and others near the turn of the century indicated that the atom contains smaller particles. In 1911 Ernest Rutherford build up a new theory of atomic structure which saw the atom as a positively charged nucleus (sun) around which circle negatively charged electrons (planets) and like the solar system, most of the atom consists of space. By the 1930s the modern concept of the atom was established, though it has since been much modified and extended.

In essence the atom consists of a nucleus containing two main particles - Positively charged protons and neutral neutrons - with negatively charged electrons orbiting around it.
There are as many electrons as protons, making the atom electrically neutral. Many other atomic particles are known to exist, baryons, hadrons, leptons, mesons, neutrinos, antiparticles.
And all atomic particles could be made up of different kinds of particles called quarks.
Nevertheless the structure of matter and the chemistry of the elements can still be best explained in terms of the three main particles - protons, neutrons and electrons. Different atoms have different numbers of these particles
Most atoms are stable. Others are unstable - they break down and give off particles and radiation. This phenomenon is called Radioactivity

Laser

An electronic device that produces an intense and very pure, parallel beam of light known as coherent light. Laser light can be focused to form a powerful cutting and welding tool. it can be used in telecommunications to carry signals along optical fibres. Surgeons and eye specialists also sometimes use laser instruments. The main types of lasers are Ruby crystal lasers, Gas laser and Semiconductor lasers. The ruby laser ca produces only pulses of laser light, The other two types can produce continuous beams . A widely used gas laser uses carbon dioxide. A common semiconductor laser uses gallium arsenide crystals. the word laser stands for light amplification by stimulated emission of radiation.

Gas laser

Source : wikipedia

Nuclear reactor

Nuclear reactor once called atomic pile a device designed to produce, sustain and control a nuclear fission reaction. The first successful reactor was built in a squash court at the university of Chicago in December 1942 under the direction of Enrico Fermi. Nuclear reactors used experimentally for the manufacture of radioisotopes and for producing power. Over 200 commercial power reactors producing electricity are in use worldwide. Other reactors power submarines in a typical power reactor heat is produced in a core by the fission of Uranium atoms. A gas or liquid coolant circulates through the core and extracts the heat it transfer this heat to water in a heat exchanger causing it to boil into steam. The steam then drives conventional steam turbo generating machinery to produce electricity. Most reactors are known as thermal reactors because they require slow or thermal neutrons to cause fission of the uranium. They incorporate a moderator graphite or water in the core to slow the neutrons down reactors are usually classified according to the type of coolant they use. Magnox gas-cooled reactors
Advanced gas-cooled reactor (AGR)
Pressurized-water reactor (PWR)
Boiling-water reactor (BWR)
Steam-generating heavy-water reactor (SGHWR)
Another type of reactor now coming into limited use is the fast or breeder reactor which uses fast neutrons and thus requires no moderator it is cooled by liquid sodium. Control over all types of reactor is exercised by means of control rods made of neutron-absorbing material when they are pushed further into the reactor core, they slow down the nuclear reaction.
Nuclear power plant picture
1. Reactor block
2. Cooling tower
3. Reactor
4. Control rod
5. Support for pressure
6. Steam generator
7. Fuel element
8. Turbine
9. Generator
10. Transformer
11. Condenser
12. Gaseous
13. Liquid
14. Air
15. Air (humid)
16. River
17. Cooling water Circulation
18. Primary Circuit
19. Secondary Circuit
20. Water Vapor
21. Pump

Water Cycle

Picture Process
Water on the earth in Evaporated by the head from the sun, Water collects as water vapor in the sky this makes clouds, The water in the Clouds gets cold this makes it become liquid again then the water falls from the sky as rain or snow, The water then collects into lakes or oceans from there it can be evaporated again and the cycle can happen again

Water Cycle : The never ending exchange of water between the ground and the atmosphere, also called the hydrological cycle. Water evaporates into the atmosphere from surface waters and growing plants. It returns to the ground mainly as rain