My Science School

In 1831 the Belgian physicist Joseph Plateau produced an apparatus which he called the phenakistoscope. This was followed by other devices such as the zoetrope or ‘wheel of life’ of the British inventor William Horner in 1834 and praxinoscope of the Frenchman Emile Reynaud in 1880. Despite their difficult names these apparatuses were all fairly simple and they all exploited a certain characteristic of the human eye.

If an object is placed before our eye its image is picked up by the retina, an extremely sensitive screen inside the eyeball. Every change of object outside causes a change in the image received by the retina and if the changes are rapid enough a whole line of images can blend into one. In the phenakistoscope and the other machines a series of image showing the various stages of a person in movements were shown on a revolving drum. All the images ran together and the viewer received the impression of continuous movement. Modern animated cartoons are also produced by rapid succession of drawings.

An important development in motion pictures took place in 1889 when the famous American inventor Thomas Edison, succeeded in using photographs instead of drawings. The photographs were taken one after the other on one roll of film. Edison then invented the Kinetoscope to show his moving pictures. This was kind of peep-show device which showed viewer about fifteen seconds of life-like movements.

The first truly modern cinematographic machine was produced in 1895. In that year the brothers Auguste and Louis Lumiere of France patented their famous and historic ‘cinematograph’.

 

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A camera is a fairly simple piece of equipment in its basic structure. One must not be put off by the numerous levers, buttons, scales and other gadgets on the outsides. These are all extremely useful aids but are not completely essential.

The essential part of the machine is what gives its name: the camera obscura. This is Latin for dark room. Photographs are produced when rays of lights penetrate into this dark chamber. The light must enter through a small opening and strike against a sensitive film. The surface of the film is covered in an emulsion of chemicals which capture the images being carried by light rays. The small opening, or aperture, must also be able to open the aperture to let the light in. this mechanism is called the shutter. In a simple camera this is about the only moving part.

In more expensive cameras the fitting includes mechanism which can vary the exposure time which determines how long the shutter will stay open. The can range from a thousandth of a second for fast-moving subjects to one second or more for still dimly-lit scenes. Other controls include an aperture selector to vary the amount of light passing through the lens, and a focusing mechanism to produce a sharp image.

The camera obscura has long been known to man and Leonardo da Vinci made accurate drawings of it in the fifteenth century. It was not until 1839, however, that the first commercially available cameras were made in Paris by Alphonse Giroux for Daguerre.

 

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When the first railway began to operate it was suggested that a messenger should ride on a horse ahead of the train to tell people of its approach and warn the engine driver of any obstacles along the track.

Soon the train was able to travel much faster than the horse. Men with flags stood beside the track and either signaled the train-driver to stop or waved him on.

The problem of travel safety grew as trains increased in speed and numbers and level crossing with gates were built as well as viaducts to take trains over dangerous or difficult places.

Eventually a comprehensive system of mechanical signaling was evolved. Semaphore signals that swung up or down on a tall pole beside the track were the most common. Nowadays the majority of large railway stations have colour-lights signals, with red meaning ‘stop’ , green ‘go’ and amber ‘caution’.

All these signals are now worked electrically. It is no longer necessary for a man with a watch to check the various times when trains pass, open gates or decides which track the train will go on to and make a note of trains which have been delayed. Today all these tasks are done by computers and the signal posts of large stations are completely automated.

 

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Sometimes films are shots or photographed without sound: the dialogue is added later together with sound effects and other noises. When these sounds are added the noise of a waterfall might be produced by merely shaking water about in a basin or the voice of a stage actor might replace that of the film actor in a process known as dubbing.

The major developments in cinematography were the introduction of sound in 1927 and the advent of colour photography.

The cinema really grew up as an art after the Second World War but it found an extremely dangerous rival in television. So the film industry began to think up counter attraction. These included the evolution of wide screens as in the processes known as Cinema Scope and Cinerama. In wide-screen presentations, a special lens may be used that spread out the image on the film to fill the screen. When the film is shot, a similar kind of lens is used to squeeze a wide field of view on to standard film. Modern cinemas in addition may also use stereophonic sound which is emitted by numerous loudspeakers. This gives the audience the impression that they are might in the middle of what is happening.

The story of the cinema is not yet finished. Scientists are studying a way of producing satisfactory three-dimensional films so that the images are no longer flat. Experimental have also been carried out with a circular screen that completely surrounds the audience.

 

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The first step towards making a film is the idea for the subject. The next requirement is money to pay for all the production costs. The producer is the man who raises this money and generally he chooses the director, the most important man in making a film. The director then appoints a writer to prepare a screenplay which is like a stage play but consists of hundreds of short scenes which finally make up the whole film.

A film studio seen for the first time is quite an overwhelming sight. You may see a straight road lined with marble columns representing a roman road of 2000 years ago. Near this scene there might be a ramshackle prairie town of the Wild West. In another part of the studio there may be a magnificent governor’s palace set in imperial India. The studio is therefore crowded with Roman soldiers or gladiators, cowboys or young English colonial ladies. Some part of the studio will probably be very strictly cordoned off because a film crew may be ‘shooting’ there.

Today film directors prefer to work on location which means they film their scenes in real places outsides instead of creating them from plaster and wood inside a studio. Other film crews with their actors and actresses travel from one continent to another. But when a film is historical or period piece it is usually shot inside a studio. Films employ armies of technicians. Skilful carpenters and scene painters build intricate structures known as sets which can be of medieval castles, or of ultramodern apartments.

 

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Modern science and technology have made it possible, among other wonderful things, to make a permanent record of sounds and human speech. The tape in a tape recorder is made of an insulation material on which a thin magnetic layer has been placed. The tape is normally 3 millimeters wide in cassettes and 6 millimeters in reels. How does a tape recorder work?

There is a motor which turns a reel of tape from the supply wheel to the take-up reel. The tape passes across the recording head. When we speak into the microphone the voice is turned into a series of electrical impulses. These impulses are caught on the tape in various patterns. In video tape recordings the light signals are turned into electrical impulses recorded on the tape.

When the tape is played back it runs past an electromagnet. The magnetic patterns that have been recorded along the magnetized tape set up a variable magnetic field with the electromagnet.

The impulses of this magnetic field are the converted into sounds which are amplified and played through a loudspeaker to re-emerge as the original speech or music that was first fed into the tape recorder.

Today tape recorders are very popular. Besides being easy to operate they have the added advantage that recordings can be erased and the tape used many times. A new compact type of tape recorder is the cassette recorder. The works on the same principle but use narrower tape in its own self-contained cassette.

 

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 Even air has weight and, like any solid object, it presses down on the surface of the Earth. Scientists decided to measure the amount of his pressure and the Italian Galileo was the first to succeed. He used a very long tube, closed at one end, which he filled with water and then placed the open end in a receptacle full of water. The water in the tube fell, stopping at a height of 10 meters. A few years later, in 1643, a pupil of Galileo named Evangelista Torricelli carried out further experiments using a heavier liquid than water; mercury. The mercury rose inside its tube, closed at one end, which he filled with water and then placed the open end in a receptacle full of water. The water in the tube fell, stopping at a height of 10 metres. A few years later, in 1643, a pupil of Galileo named Evangelista Torricelli carried out further experiments using a heavier liquid than water: mercury. The apparatus was given the name barometer from, the Greek baros meaning ‘weight’ and metron meaning ‘measure’. Torricelli soon noticed that the height of the mercury column varied with changes in air pressure. About 1647 Blaise Pascal’s experiments finally convinced people of the correctness of Torricelli’s ideas.

The most modern form of this instrument is the aneroid barometer, from Greek a meaning ‘without’ and neros meaning ‘liquid’. The aneroid barometer consists of a small steel box which contains a vacuum. The pressure of the air outside the box can cause the surface of the box to move in or out. A needle on the dial records the movements of the box along a graduated scale to show the changes in air pressure.

This type of barometer is smaller and more portable than a mercury barometer but it is not quite as accurate. It has first to be calibrated or set to a mercury barometer before it can be used.

 

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A roofer repairs, replaces, and installs roofs on residential homes or commercial buildings. They use a variety of materials such a metal, aluminum, wood, shingles, tiles, slate, and steel. Roofers scale the tops of a property to repair leaky roofs, replace broken tiles, or seal areas to make them watertight. Roofing is physically demanding and requires the stamina to stand, climb, and carefully walk in hot, cold, windy, snowy, or rainy weather. The work that roofers do ensures that buildings are structurally sound and safe for those who enter. Roofers can work on a full- or part-time basis, and many receive weekly salary payments.

Roofing systems may also incorporate plants and landscape materials. A vegetative roof, for example, is typically a waterproof low-slope roof covered by a root barrier and harboring soil, plants, and landscaping materials.

It is becoming increasingly popular to take advantage of solar energy on rooftops. Roofs may incorporate solar reflective systems, which prevent the absorption of energy; solar thermal systems, which absorb energy to heat water; and solar photovoltaic systems, which convert sunlight into electricity. Roofers install some photovoltaic products, such as solar shingles and solar tiles, but solar photovoltaic (PV) installers typically install PV panels. Plumbers and heating, air conditioning, and refrigeration mechanics also may install solar thermal systems.

 

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A house painter’s primary responsibility is to paint the interior and exterior surfaces of residential buildings using paint, varnishes, lacquers, sealers, or stains.

Their job description entails executing several pre-painting tasks, including utilizing sandpaper/scraping to strip old paint; performing preparation work for the surfaces and applying filler to cracks and holes using material such as plaster to prepare walls and surfaces before the actual painting tasks is executed.

House painters are also responsible for using power and hand tools to sand surfaces for further finishing and painting to accentuate the work done.

House Painters do not only apply paints but may also be required to apply various wallpaper, vinyl wall fabrics, and all types of coverings or coatings, drywall installation, tape and texture work.

They also ensure that the paint and other materials to be used are of the right color or texture following the specification of the client, and they may also take responsibility for blending paints before carrying out the assigned tasks using various tools.

 

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Plumbers install and repair pipes that supply water and gas to, as well as carry waste away from, homes and businesses. They also install plumbing fixtures such as bathtubs, sinks, and toilets, and appliances, including dishwashers and washing machines. Experienced plumbers train apprentices and supervise helpers. They work alongside other construction workers.

Most plumbers receive their training by doing an apprenticeship, which combines classroom instruction with paid on-the-job training. Most states also require a license to work independently.

Apprenticeships are sponsored by trade unions and employers. They last from four to five years and include 2,000 hours of on-the-job training and classroom instruction. You will need a high school or equivalency diploma and must be at least 18 years old to be accepted into a program. In the classroom, you will learn about local codes and regulations, blueprint reading, and safety.

Plumbers are required to have a license to work in most states and municipalities in the U.S. In addition to needing two to five years of experience, depending on where the license is issued, you must also pass an exam.

 

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Electricians install and maintain all of the electrical and power systems for our homes, businesses, and factories. They install and maintain the wiring and control equipment through which electricity flows. They also install and maintain electrical equipment and machines in factories and a wide range of other businesses.



Electricians generally focus on either construction or maintenance, although many do both. Electricians specializing in construction primarily install wiring systems into factories, businesses, and new homes. Electricians specializing in maintenance fix and upgrade existing electrical systems and repair electrical equipment. All electricians including emergency electricians in Sydney must follow State and local building codes and the National Electrical Code when performing their work.



Electricians usually start their work by reading blueprints - technical diagrams that show the locations of circuits, outlets, load centers, panel boards, and other equipment. After determining where all the wires and components will go, electricians install and connect the wires to circuit breakers, transformers, outlets, or other components and systems.

Electricians in large factories usually do maintenance work that is more complex. These kinds of electricians may repair motors, transformers, generators, and electronic controllers on machine tools and industrial robots. They also advise management as to whether the continued operation of certain equipment could be hazardous. When working with complex electronic devices, they may consult with engineers, engineering technicians, line installers and repairers, or industrial machinery mechanics and maintenance workers.

 

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Bricklayers lay bricks, pre-cut stone and concrete blocks in mortar. They construct, extend and repair domestic and commercial buildings, and other structures such as foundations, walls, chimneys or decorative masonry work. Bricklaying offers a real sense of achievement.

There are several routes to becoming a bricklayer. You can gain the qualifications you need by doing a college course, an apprenticeship or on the job training.

You should explore these routes to find which one is right for you. Although some options will list qualification requirements, many employers are more interested in people who are enthusiastic, willing to learn and able to follow instructions.

You may need a Construction Skills Certification Scheme (CSCS) card to work on a construction site.

Bricklayers use many tools, including trowels, brick hammers, chisels, levels, and rulers. Helpers do the heavy work, such as carrying materials and mixing the mortar. These helpers are known as "hod carriers." Bricklayers read blueprints and other specifications to be sure their work is accurate. They constantly check for both horizontal and vertical straightness with a mason's level. Masons also build walls out of other materials, such as concrete block. Many masons specialize in one kind of construction material.

 

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Concrete is the most widely used construction material in the entire world. Rather than existing as an independent material, concrete is a mix of various materials. These materials include cement, water, fine aggregate, and crushed stones or gravel. Sand and gravel or crushed stones are examples of fine aggregate and coarse aggregate, respectively.

The many cement contractors Delaware folks look to for all their construction needs have one thing in common, they all use concrete. This prevalent use of concrete begs the question, why is concrete such an essential material for construction?

Well, concrete is similar to mortars in both composition and structure. This similarity means concrete works as a binder for the various masonry units in construction, just like any mortar. Unlike ordinary mortar, however, concrete has a wide range of applications. This versatility is as a result of concrete having both fine aggregates and coarse aggregates that are larger. The large size of the coarse aggregates confers strength attributes to concrete, that mortar doesn’t have. This makes it suitable for application in larger and heavier structures. Most mortars have sand as the sole aggregate and are hence weaker than concrete.

 

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Carpenters construct, erect, install, and repair structures and fixtures made from wood and other materials. Carpenters are involved in many different kinds of construction, from the building of highways and bridges to the installation of kitchen cabinets.

Carpenters may do many different carpentry tasks, or they may specialize in one or two. Carpenters who remodel homes and other structures, for example, need a broad range of carpentry skills. As part of a single job, they might frame walls and partitions, put in doors and windows, build stairs, install cabinets and molding, and complete many other tasks. Well-trained carpenters are able to switch from residential building to commercial construction or remodeling work, depending on which offers the best work opportunities.



Carpenters who work for large construction contractors or specialty contractors may perform only a few regular tasks, such as constructing wooden forms for pouring concrete, or erecting scaffolding. Some carpenters build tunnel bracing, or brattices, in underground passageways and mines to control the circulation of air through the passageways and to worksites. Others build concrete forms for tunnel, bridge, or sewer construction projects.



Carpenters employed outside the construction industry perform a variety of installation and maintenance work. They may replace panes of glass, ceiling tiles, and doors, as well as repair desks, cabinets, and other furniture. Depending on the employer, carpenters install partitions, doors, and windows; change locks; and repair broken furniture. In manufacturing firms, carpenters may assist in moving or installing machinery.

 

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A Bulldozer Operator is in charge of a bulldozer—a special tractor outfitted in front with a broad upright blade that’s used for clearing and smoothing ground. Capable of pushing boulders, soil, clay, sand, and vegetation, and of demolishing walls, sheds, and even small houses, bulldozers are ideal for use at construction sites, battlefields, mines, quarries, farms, and disaster zones.

Whatever the job—tearing down an old garage or clearing a construction site—your routine as a Bulldozer Operator involves showing up at the job site early, inspecting and cleaning the equipment, then driving, digging, and demolishing under the direction of your Supervisor, who is usually a Construction Foreman.

 It also means maintaining the equipment: It’s your job to fix the bulldozer when it breaks, or send it to a Bulldozer Mechanic, and to secure and store it at the end of every day.

 

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