Science Facts---Metals, Gravity, Magnet, Vehicle, Engineering, Recycling

Metal
    Metals are usually solid, good conductors of electricity and heat, shiny when clean, strong and malleable (meaning they can be bent and shaped).

    Gold is shiny and doesn’t corrode, this means it is a great metal for making jewelry. More gold facts.

    The chemical symbol used for silver is Ag, this comes from the Latin word for silver, argentum. More silver facts.

    While aluminum is the most common metal found in the Earth's crust, the most common metal found on Earth is iron, mostly because it makes up such a large part of the Earth's core. More iron facts.

    Copper is a good conductor of electricity and is often used for making wires.

    At room temperature, mercury is the only metal that is in liquid form.

    Aluminum is a good conductor of heat and is often used to make cooking pots.

    Alkali metals such as sodium, potassium, rubidium, caesium and francium are extremely reactive elements, just putting them in water can result in an explosion! They are carefully stored in oil to prevent this happening. More alkali metals facts & properties.
    Tungsten has a very high melting point, after carbon it has the second highest melting point of all elements.

    Metals are strong and are useful for making tools, buildings, bridges and other structures where strength is important.

    Steel is an important alloy (combination of metals) that is created from a mixture of metals, mostly iron. There are many different types of steel including stainless steel, galvanized steel and carbon steel. Steel is commonly used to make a number of products including knives, machines, train rails, cars, motors and wires.

    Bronze is a metal alloy made from copper and tin. Copper makes up the larger amount, usually between 80 to 95%.



Copper
    Copper is a chemical element with the symbol Cu and an atomic number of 29.

    The word copper and its symbol Cu come from the Latin word for Cyprus "Cuprum", where the Ancient Romans mined much of their copper.

    Pure copper is red-orange in color. When it is exposed to air it darkens to a brown color and if exposed to air and water, it becomes a blue-green color called verdigris.

    The only two metals used by humans before copper were gold and meteoric iron. Copper is believed to have been in use since ancient times over 10,000 years ago.

    Small amounts of copper can be found in a natural state while the metal is also found in minerals such as cuprite, malachite, azurite, chalcopyrite and bornite.

    Copper is an essential nutrient to all living organisms. Copper deficiency in the human body is as big an health issue as iron deficiency.

    Foods rich in copper include oysters, beef, nuts, cocoa, black pepper, lobster, sunflower seeds, green olives, avocados, and wheat.

    Due to its versatility and durability, copper is referred to as "man's eternal metal".

    Copper has a melting point of 1,984.28 °F (1,084.6 °C) and a boiling point of 4,643.6 °F (2,562 °C).

    Numerous important copper alloys have been produced over human history. Brass is a mixture of copper and zinc, bronze is an alloy of copper and tin. While cupronickel is a combination of copper and nickel.

    60% of copper is used in electrical wiring, 20% is used in roofing and household plumbing, while 15% is used in the making of industrial machinery.

    Copper is used in the making of coins for a number of countries. Coins in the U.S  contain a solid copper core and layer of copper-nickel alloy.

    Copper is also found in TVs, radios, washers, dryers and some cookware.

    Over 81,000 kgs (179,000 lbs) of copper was used to build The Statue of Liberty.

    Copper is a natural antibacterial. To prevent the spread of bacteria, brass doorknobs and handrails are often used in public buildings.

    Because bacteria will not grow on it, copper has been used for centuries to line parts of ships so that barnacles and mussels do not stick to the boats.

    Nearly 80% of all the copper we have ever produced is still in use today due to the fact that copper is 100% recyclable and retains 95% of its original value.

    Copper is a plentiful natural resource on Earth. At the current rate of extraction there is enough copper in the top kilometer of the Earths crust to meet demand for 5 million years.
    A mine in Sweden called "The Great Copper Mountain" operated from the 10th century to 1992. It produced two thirds of Europe's copper requirements in the 17th century.


Gold
    Gold is a chemical element. Its chemical symbol is Au and its atomic number is 79.
    Compared to other metals, gold is less chemically reactive.
    Gold is a good conductor of electricity and heat.
    Gold is shiny, soft and dense. It is also malleable, which means it can easily be beaten into thin sheets or other shapes.
    Gold is malleable enough for just 1 gram to be hammered into a sheet 1 square meter in size. It can also be made so thin that it appears transparent.
    Due to a similar appearance to gold, the mineral pyrite has the nickname fool’s gold.
    The amount of gold in various alloys (a combination of gold and another metal such as silver) is measured in carats (k). Pure gold is 24k.
    As of 2009, it has been estimated that humans have mined around 160000 tonnes of gold.
    Over the last 100 years South Africa has been the biggest producer of gold. In recent times however it has been surpassed by China.
    As of 2009, the USA has 8133 tonnes of gold reserves while Canada only has 3.
    Throughout history gold has often been seen as a symbol of wealth.
    Gold is the most popular precious metal for investments.
    The price of gold continually fluctuates and is often linked to major economic events.
    There is a monetary system called the ‘gold standard’ which fixes a unit of money to a certain weight of gold.
    Over the years gold has been used to create expensive jewelry, coins and various forms of art such as the Egyptian pharaoh Tutankhamun’s famous burial mask. In modern times it has also been used for things such as electronics and dentistry.
    Injectable gold has been proven to help reduce pain and swelling in patients suffering from tuberculosis and rheumatoid arthritis.
    Gold is a popular choice when it comes to rewarding achievement with medals, statues and trophies. Academy Award, Olympic and Nobel Prize winners all receive golden items in recognition of their achievement.


Iron
    Iron is a chemical element and metal. Its chemical symbol is Fe and its atomic number is 26.
    When iron and oxygen react in the presence of water or moisture, rust (iron oxide) is formed. You might have noticed your bike chain (or other parts) rusting from time to time (especially if you haven’t been taking care of it). Another word for rusting is corrosion, which describes the disintegration of materials such as iron and steel.
    Because iron oxidizes so easily, it is rarely found in a pure metal form on the Earth’s surface. It is instead removed from ores (rocks containing important minerals and elements).
    Iron is the 4th most common element in the Earth’s crust, making up around 5% of the total (usually found as iron oxide in minerals like hematite).
    The Earth’s core is thought to be made up of an iron and nickel alloy.
    Gas giant plants such as Saturn and Jupiter have cores that are rich in iron.
    Iron is the 6th most common element found in the Universe.
    Steel is a well known and commonly used alloy made from iron and a small amount of carbon (or sometimes other elements). The amount of carbon is small (usually between 0.2% and 2.0%) but it makes a huge difference to the strength.
    Steel can be around 1000 times stronger than iron in its pure form.
    The Eiffel Tower in Paris, France is made from puddle iron. Puddle iron is a form of wrought iron, an iron alloy with a very low level of carbon content. Wrought iron was used commonly throughout western history but is no longer produced in large amounts due to the availability of steel.
    The early wrought iron used in human history actually came from meteors!
    Cast iron is a type of iron that contains carbon, silicon and small amount of manganese. It was used in earlier times to build structures like cast iron bridges. Like wrought iron however, most of its uses have been replaced by steel.
    The Iron Age was a prehistoric time when useful tools and weapons were first made from iron and steel. The dates this occurred in various parts of the world varies, with historians suggesting around 12th century BC in ancient Greece and 6th century BC in Northern Europe.
    In 2006, China was the world’s largest producer of iron, making up around 33% of the world’s total production.
    Iron is relatively cheap to produce and has a large number of different uses.
    Machines, vehicles and building structures are commonly built from iron (usually in the form of steel).
    To prevent iron and steel suffering from rust damage, they can be painted, coated with plastic, galvanized (coated with zinc) or by other methods that keep out water and oxygen.
    Iron in the human body has a number of important functions including carrying oxygen to the body in the form of hemoglobin. Iron deficiency can be quite common (especially among women), with a number of possible symptoms including fatigue and weakness.
    Iron rich foods include red meat, fish, tofu, beans and chickpeas.


Lead
    Lead is a chemical element with the symbol Pb and atomic number 82.

    The symbol for lead, Pb, comes from the Latin name for the metal, plumbum. The English words "plumbing" and "plumber" are derived from this Latin name.

    Lead is a soft, malleable, ductile (drawn out into a thin wire) and heavy metal. It initially has a bluish-white color that tarnishes to a dull gray color when exposed to air. It is corrosion resistant and when melted into a liquid has a shiny chrome-silver look.

    Lead has been used since ancient times due to the fact it is easily extracted from ore and generally easy to work with.

    The ancient Romans used lead to make plumbing pipes, as joining pins for limestone building blocks and it was popular amongst Roman alchemists.

    Historically, tin and lead were hard to distinguish between. The Romans called lead 'plumbum nigrum' (black lead) and tin was called 'plumbum candidum' (bright lead).

    The melting point of lead is 621.4 °F (327.46 °C) and the boiling point is 3,180.2 °F (1,749 °C).

    In 2008, Australia, China and the United States produced the most lead. Other lead producing countries include Peru, Canada, Mexico, Sweden, Morocco, and South Africa.

    Metallic lead is rarely found in nature as a free metal. It is usually found in ore with other metals such as copper, zinc and silver.

    Today, over half of the lead produced is used as electrodes in lead-acid car batteries.

    Lead is also used in the construction industry for roofing, cladding, gutters and glazing bars for stained glass. Its high density and resistance to corrosion makes it useful as the ballast keel of sailboats and as scuba diving weight belts.

    Lead is still widely used to make statues and sculptures. It is used to make bullets and shot ammo and is also used in radiation shields around X-ray equipment.

    Historically, lead has been used as a paint additive, in face whitening make-up, as water pipes, as a preservative for food and drink, as a pesticide, and in paint used on children's toys. However, due to its highly toxic nature, these uses have been stopped in most countries due to the dangers of lead poisoning.

    If inhaled or swallowed, lead is very poisonous. Lead poisoning can have a major effect on the body's nervous system. It can damage the body's organs and can cause weakness in the body's joints.

    Wooden pencils have never actually contained lead. The 'lead' of a pencil is in fact a type of graphite that in Roman times was called plumbago meaning 'act for lead', or 'lead mockup'.



Magnesium
    The chemical element magnesium has the symbol Mg and atomic number 12.

    Sir Humphry Davy was the first to isolate magnesium in England, in 1808, calling it 'magnium'. While Antoine Bussy first prepared magnesium in a consistent form in 1831.

    Magnesium is an alkaline earth metal. While it is not present in a free pure form its compounds are found in large deposits as magnesite, dolomite and other minerals.

    Magnesium is the 8th most abundant element in the Earth's crust and after iron, oxygen and silicon it is the 4th most common element in the Earth as a whole making up 13% of our planet's mass.

    Elemental magnesium is a light, fairly strong, silvery-white metal that tarnishes slightly when exposed to air.

    Magnesium has a melting point of 1,994 °F (1,090 °C) and a boiling point of 1,202 °F (650 °C).

    When in a powdered or thinly shaved form magnesium is highly flammable, burning with a brilliant-white flame. The metal is more difficult to ignite as a large mass.

    Once ignited, magnesium is extremely difficult to extinguish. Attempting to put out the fire using water produces hydrogen, which only intensifies it. Magnesium also burns in both pure nitrogen and pure carbon dioxide, so a carbon dioxide fire extinguisher will feed the flames too. The most effective way to stop it burning is by using a dry chemical fire extinguisher, or covering it with sand.

    Magnesium's bright and quick lighting flame has made it useful in products such as flashlight photography, flares and pyrotechnics.

    China produces around 80% of the worlds magnesium supply.

    After iron and aluminium, magnesium is the 3rd most commonly used structural metal due to its lightness.

    Magnesium can be compared with aluminium, but being a third lighter than aluminium makes it useful in alloys that are used in the construction of airplanes and missiles.

    Automobile manufacturers such as Volkswagen, Porsche, BMW, Corvette, and Mitsubishi have all dabbled in using magnesium in engine components.

    Because of its good mechanical and electrical properties and lightness, magnesium is useful in the manufacturing of electronic devices such as mobile phones, laptops and cameras.

    Specialty car wheels called 'mag wheels' got there name due to the use of magnesium in their construction. However, today mag wheels no longer include magnesium they are mainly made of aluminium.

    Magnesium compounds, mainly magnesium oxide (MgO) are used in the manufacturing, agricultural, chemical, and construction industries.

    Magnesium is the 11th most common element in the human body with around 60% found in the skeleton and 39% found in the muscle cells.

    Magnesium rich foods include spices, nuts, cereals, coffee, cocoa, tea, and leafy green vegetables like spinach.



Nickel
    Nickel is a chemical element with the symbol Ni and an atomic number of 28.

    In Germany during medieval times, a red mineral was found that looked like copper ore (rock). When miners couldn't extract any copper from it, they blamed a mischievous sprite of German mythology, Nickel. They decided to call this ore Kupfernickel, with the German word for copper being Kupfer.

    In 1751, Baron Axel Fredrik Cronstedt discovered nickel while trying to extract copper from the ore kupfernickel. He named the white metal substance nickel after the spirit that had given its name to the ore.

    Unintentional use of nickel has taken place since ancient times around 3500BC.

    Based on writings the alloy cupronickel is believed to have been used by the Chinese from 1400BC and exported to Britain in the 17th century.

    Nickel is a transition metal that is hard and ductile. It is a silvery-white shiny metal with a slight golden tinge.

    Nickel has a melting point of 2,651 °F (1,455 °C) and a boiling point of 5,275.4 °F (2,913 °C).

    Along with iron, cobalt and gadolinium, nickel is one of just 4 elements that are magnetic at or near room temperature.

    Major nickel deposit sites have been found in the Sudbury region of Canada (possibly of meteoric origin), New Caledonia, Russia, South Africa, Philippines, Indonesia, and Australia.

    Most uses of nickel are as an alloy metal, namely in nickel steels, brasses, bronzes and nickel cast irons. The metal is often alloyed with copper, chromium, aluminium, lead, cobalt, silver, and gold.

    Nickel was commonly used in the making of coins, however, due to the metal being a skin allergen for some people, and the fact that today cheaper metals are available the element is no longer widely used in coinage.

    People can have allergic reactions to nickel through skin contact. Traditionally, nickel has been used to make jewelry such as earrings. Nickel allergies affecting pierced ears often result in itchy, red skin, therefore many earrings are now made nickel-free.

    Nickel is also used in many other products such as magnets, rechargeable batteries, electric guitar strings, microphone capsules, and as a green tint in glass.

    Nickel is quite rare in the Earth's crust. It is 100 times more likely to be found in the Earth's core, where it is the second most abundant element behind iron.

    Nickel is one of the elements used to make stainless steel partly due to its corrosion resistant properties.

    In the U.S, a five cent coin is called a "nickel" despite being 75% copper and only 25% nickel.


Platinum
    Platinum is a chemical element with the symbol Pt and atomic number 78.

    The name platinum comes from the Spanish word 'platina' which means "little silver".

    Platinum is a dense, malleable (can be thinned), ductile (can be stretched), shiny gray-white transition metal that is rare enough to be deemed a precious metal.

    Platinum can be found chemically un-combined in its native form. Because of this  pre-Columbian South American natives used platinum found in the alluvial sands of various rivers to produce artifacts of a white gold-platinum alloy.

    Platinum was first mentioned in European writings by Italian Julius Caesar Scaliger in 1557. He described an unknown noble metal found near Mexico, "which no fire nor any Spanish artifice has yet been able to liquefy."

    The melting point of platinum is 3,215 °F (1,768.4 °C) and the boiling point is 6,917 °F (3,825 °C).

    Native deposits of platinum are rare and difficult to locate, South Africa accounts for 80% of the worlds production. Alluvial deposits are also mined from the Ural Mountains, Russia.

    Platinum can also be produced commercially as a by-product of nickel refined from copper and nickel ores.

    Nearly half of all platinum produced is used in catalytic converters, these are devices which control harmful vehicle emissions.

    Platinum's resistance to tarnish and corrosion as well as its silver-like shine and extreme rarity make it ideal for making jewelry (its second largest usage).

    Watchmakers such as Vacheron Constantin, Patek Philippe, and Rolex, use platinum for producing limited edition watch series.

    Like the other main precious metals gold and silver, platinum is used as currency and investment. The commodity is traded and collected in the form of coins, bars, ingots and jewelry.

    Other uses of platinum include in oxygen sensors, spark plugs, turbine engines dentistry equipment and dental crowns, as an anti-tumor agent, to make standard weights and measures, and to make powerful magnets.

    Platinum's rarity as a metal means the word is often associated with wealth, value and exclusivity making it a very marketable word widely used by advertisers. "Platinum" awards, credit cards and music album sales are seen as of a higher rank than "gold", "silver" and "bronze" but lower than "diamond".
    Meteorites and our moon have a higher percentage of platinum than Earth.



Silver
    Silver is a chemical element. Its chemical symbol is Ag and atomic number is 47.
    Silver is a soft, shiny metal that is a good conductor of electricity.
    Silver is precious metal that has been used for many years to make fine pieces of jewelry, coins, utensils and various pieces of art.
    In modern times silver is also used in dentistry, electronics, photography, mirrors and in a number of industrial applications that make use of its unique properties.
    You may have heard of the term sterling silver, this is the name given to an alloy (combination of metals) that is at least 92.5% silver by weight. The other 7.5% is made up of other metals, usually copper.
    Silver is found naturally by itself, as an alloy with gold or in an ore (a rock containing various metals and elements). Silver is often found in copper and lead ores.
    The price of silver has fluctuated dramatically over the last century, climbing as demand increases but dropping when large silver deposits are found.
    As of November 2009, gold was valued at around 65 times the value of silver by mass.
    The word silver is one of the few words in the English language that is nearly impossible to rhyme. Words such as orange, purple, breadth, wolf, depth, angst, gulf, ninth and twelfth are also difficult or impossible to rhyme. While there are some words that do actually rhyme with these examples they are usually very rare or hardly used in the modern English language.



Titanium
    The chemical element Titanium has the symbol Ti and atomic number 22.

    Pure titanium is a transition metal with a lustrous silver-white color.

    Titanium will always be found bonded with another element it does not naturally occur on its own in a pure form.

    British pastor William Gregor discovered titanium in 1791. It was later named by German chemist Martin Heinrich Klaproth who called it titanium after the Titans of Greek mythology. It was not until 1910 that titanium was produced to 99.9% purity by New Zealander Matthew A. Hunter, the method became known as the Hunter Process.

    Titanium has two very useful properties, it is resistant to corrosion (including in sea water and chlorine) and has the highest strength-to-weight ratio of any metal.

    Titanium is as strong as a lot of steels, yet it is 45% lighter. The metal is also 60% denser than aluminium but is over two times as strong.

    Titanium has a melting point of 3,034 °F (1,668 °C) and a boiling point of 5,949 °F (3,287 °C).

    Titanium is non-magnetic and is not very good at conducting heat or electricity.

    Even in large doses titanium remains non-toxic and does not have any natural role inside the human body, usually passing through without being absorbed.

    Titanium is present in most igneous rocks and their sediments, it is the 9th most abundant element in the Earth's crust and the 7th most abundant metal.

    Many elements such as iron, aluminium, nickel and vanadium are alloyed with titanium to produce strong lightweight alloys. These titanium alloys are used in the manufacturing of naval ships, spacecraft, missiles and aircraft, with around two thirds of all titanium metal produced is used in aircraft engines and frames.

    Titanium metal is also used in the production of high-end racing cars and motorcycles where reducing weight but maintaining strength is important.

    Titanium's strength-to-weight superiority has seen the metal used as a component in many other products in recent times including, laptops, firearms, tennis rackets, golf clubs, lacrosse sticks, football helmet grills, bicycles frames, camping cookware and utensils.

    Around 95% of all titanium is used to produce the compound titanium dioxide, which is a very bright and refractive white pigment that is used in paints, plastics, toothpaste, sunscreens, sports equipment and paper.

    The famous Guggenheim Museum in Bilbao, Spain, is covered in titanium panels.

    The fact that titanium is strong, light, non-toxic and does not react with out bodies makes it a valuable medical resource. Its used to make surgical implements and implants, such as hip joint replacements that can stay in place for up to 20 years.

    Titanium is now popular in designer rings and other jewelry due to its durability, its resistance to seawater and chlorine in swimming pools and as it is non-toxic.

    Titanium is present in meteorites, the sun, and other stars.



Uranium
    Uranium is a chemical element, its symbol is U and its atomic number is 92.

    Refined uranium is a silvery-white weakly radioactive metal.

    Uranium is hard, malleable, ductile, and a poor electrical conductor. The metal has a very high density, around 70% denser than lead, yet less dense than gold.

    There are three naturally occurring uranium isotopes. Uranium-238 is the most stable of these and makes up over 99%, uranium-235 makes up 0.72% of natural uranium and uranium-234 just 0.005%.

    German chemist Martin Heinrich Klaproth is credited with discovering uranium in 1789. He named the new element after the recently discovered planet Uranus.

    In 1841, Eugène-Melchior Péligot became the first person to isolate uranium and in 1896 Henri Becquerel discovered it had radioactive properties.

    Uranium has a melting point of 2,075 °F (1,135 °C) and a boiling point of 7,468 °F (4,131 °C).

    Uranium has been in use as far back as ancient Rome and during the Middle Ages when its orange-red to lemon-yellow shades were used as coloring agents in ceramic glazes and glass.

    Fissile isotopes of uranium have the ability to cause a nuclear chain reaction making the metal important for generating heat in nuclear power reactors and producing fissile material for nuclear weapons.

    Uranium-235 is the most important uranium isotope for the creation of nuclear reactors and weapons because it is the only naturally occurring isotope that is fissile (meaning it can be split into 2 or 3 fission fragments by thermal neutrons).

    One kilogram of 235U can theoretically produce 20 terajoules of energy, equivalent to the energy produced from 1500 tonnes of coal.

    The first atomic bomb used in World War II, dropped on Hiroshima, Japan, in 1945, contained a uranium core. Today nuclear bombs are usually made from other materials such as plutonium.

    The military uses uranium when making special ammunition. It helps make bullets and larger projectiles hard and dense enough to punch through armor.

    Over 33% of the world's uranium is mined in Kazakhstan. Other uranium mining countries include Canada, Australia, Namibia, Niger, and Russia.

    Marie Curie's discovery of radium in uranium ore meant uranium mining increased so radium could be extracted to make glow-in-the-dark paints. It takes 3 tonnes of uranium to get 1 gram of radium, leaving massive amounts of uranium waste material which was sent for use in the glazing and tiling industry.

    In addition to being weakly radioactive, uranium is also deemed a toxic metal and over exposure can affect the normal functioning of our vital organs.



Zinc
    Zinc is a chemical element with the symbol Zn and atomic number 30.

    Another name for zinc, in non-scientific terms, is "spelter".

    Pure zinc is a shiny bluish-white colored metal, while commercial grades of the metal usually have a dull finish to it.

    Zinc is the 24th most abundant element in the Earth's crust.

    The melting point of zinc is 787.1 °F (419.5 °C) and the boiling point is 1,664.6 °F (907 °C).

    Brass is a zinc and copper alloy that has been used by humans since ancient times. Zinc metal however, was first produced on mass in 12th century India. While Europe did not know about zinc metal until the end of the 16th century.

    An important quality of zinc is its ability to resist corrosion and therefore protect other metals. Half of all zinc produced today is used to galvanize steel to prevent against corrosion. It is used to protect buildings, cars, nails, wire, pipes and more.

    Zinc compounds such as zinc oxide are found in many common commercial products, including batteries, paint, plastics, rubber products, pharmaceuticals, floor coverings, inks, cosmetics, soap, and textiles. Zinc is also a natural insect repellent and sun screen, helping to protect our skin.

    Zinc is an essential nutritional mineral for humans and animals alike. After iron, it is the second most common trace metal found naturally in our bodies.

    Zinc helps our immune system fight off invading bacteria and viruses while our cells require zinc to help build DNA. Our bodies need zinc to grow and develop properly making it very important for children and during pregnancy.

    Foods that are a great source of zinc include lean red meats like beef, lamb and liver and seafood such as oysters and lobster. Whole grains, seeds, beans, nuts, and almonds are all good sources if grown in zinc rich soil.

    Zinc carbonates were identified in the oldest known pills which were believed to be used for sore eyes, found aboard a Roman ship that wrecked in 140 BC.

    Zinc deficiency is associated with many diseases and is believed to affect around 2 billion people in the developing world.

    Even though zinc is an essential requirement for good health, excess zinc can be harmful, suppressing copper and iron absorption. The U.S penny coin is made of 97.5% zinc and there have been cases of zinc toxicity after humans and dogs ingested the coins.

    In 2010, China produced nearly a third of the global zinc output. Other notable zinc mining countries include Australia and Peru.

    After iron, aluminium, and copper, zinc is the fourth most common metal we use today.

    Around 70% of the world's zinc comes from mining, the remaining 30% comes from recycling the metal because zinc is 100% recyclable.




Gravity

    Objects with mass are attracted to each other, this is known as gravity.

    Gravity keeps Earth and the other planets in our solar system in orbit around the Sun. It also keeps the Moon in orbit around Earth.

    Tides are caused by the rotation of the Earth and the gravitational effects of the Moon and Sun.

    Because Mars has a lower gravity than Earth, a person weighing 200 pounds on Earth would only weigh 76 pounds on Mars.

    It is thought that Isaac Newton’s theories on gravity were inspired by seeing an apple fall from a tree.

    While Newton’s older law of universal gravitation is accurate in most scenarios, modern physics uses Albert Einstein’s general theory of relativity to describe gravity.

    Acceleration of objects to due to the gravity on Earth is around 9.8 m/s2. If you ignore air resistance (drag) then the speed of an object falling to Earth increases by around 9.8 metres per second every second.

    The force of gravity 100 kilometres (62 miles) above Earth is just 3% less than at the Earth’s surface.

    The human body can handle increased g-forces as seen in activities such as dragster races, airplane acrobatics and space training. The highest known acceleration voluntarily experienced by a human is 46.2 g by g-force pioneer John Stapp.

    While formula one racing drivers may feel around 5 g’s under heavy braking, they can experience over 100 g’s if a crash causes them to decelerate extremely quickly over a very short distance.

    Some roller coasters have been known to include g-forces of around 4 to 6 g.

    The higher something is, the greater its gravitational potential energy. Back in the Middle Ages, weapons called trebuchets were used to take advantage of this principle, using mechanical advantage and the gravitational potential energy of a counterweight to hurl rocks and other projectiles at or over walls. In modern times we use the gravitational potential of water to create hydroelectricity.



Magnet
    Magnets are objects that produce an area of magnetic force called a magnetic field.

    Magnetic fields by themselves are invisible to the human eye.

    Iron filings can be used to show magnetic fields created by magnets (such as in the picture to the right).

    Magnets only attract certain types of metals, other materials such as glass, plastic and wood aren't attracted.

    Metals such as iron, nickel and cobalt are attracted to magnets.

    Most metals however are not attracted to magnets, these include copper, silver, gold, magnesium, platinum, aluminium and more. They may however magnetize a small amount while placed in a magnetic field.

    Magnetism can attract magnetic objects or push them away.

    Magnets have a magnetic north pole and a magnetic south pole. If the same pole of two magnets are placed near each other they will push away (repel), while if different poles are placed near each other they will pull together (attract).

    Magnetic objects must be inside the magnetic field to respond, which is why you may have to move a magnet closer for it to have an effect.

    The Earth's core is believed to be a mix (alloy) of iron and nickel, giving the Earth its own magnetic field.

    The Earth's magnetic field is responsible for deflecting the solar wind, charged particles that come from the Sun.

    Magnetic compasses use the Earth's magnetic field to help navigate in north, south, east and west directions.

    Electromagnets are created by an electric current running through a surrounding coil. They have many uses including the generation of electricity in hydroelectric dams.




Vehicle

Airplane
    Airplanes are fixed-wing aircraft that are propelled through the air by engines.

    They are used for transportation, recreation, research and military purposes.

    Engines provide the thrust needed to move a plane forward, overcoming drag and allowing the wings to create lift.

    Aircraft wings feature a shape called an airfoil which is designed to create lift as the plane moves through the air.

    The long, thin body of an aircraft is typically called the fuselage.

    Pilots usually control the plane from a cockpit located at the front of the fuselage.

    Some aircraft (usually military or experimental) are capable of supersonic flight (breaking the sound barrier) by traveling at speeds faster than sound (1235kph, 768mph).

    There have only been two commercial aircraft capable of supersonic transport, the most well known of these was the Concorde which flew between major cities such as London, New York and Paris until 2003.

    It took Concorde just three and a half hours to travel from New York to Paris while it took other commercial aircraft around eight hours.

    Unmanned aircraft controlled remotely or by computers are known as drones.

    American aviation pioneers Orville and Wilbur Wright (The Wright Brothers), are believed to be have created the first successful airplane.


Bicycle
    Bicycles are human powered vehicles, typically featuring pedals, a seat, two wheels and a frame.

    There are over one billion bicycles found throughout the world.

    Bicycles are used for transport, recreation, competitive racing, courier delivery and a range of other tasks.

    Competitive cycling includes track cycling inside velodromes, time trials, mountain biking, BMX and longer events such as the Tour de France.

    The Tour de France was first held in 1903 and his since become the most famous cycling race in the world. Held over three weeks, the annually changing route goes through the Pyrenees and Alps before finishing in Paris.

    Tandem bicycles are made to be ridden by two or more people.

    Although unicycles (one wheel) and tricycles (three wheels) don’t have two wheels, they are sometimes still referred to as ‘bikes’.

    The energy required to cycle at low to medium speeds is roughly the same as the energy required to walk.

    Bicycles typically use a chain to transmit power to the rear wheel.

    To get efficient use of their pedaling, cyclists use a high gear when going downhill, a medium gear on flat surfaces and a low gear when going uphill.

    Different brake types include rim brakes, internal hub brakes and disc brakes.

    Some bicycles feature suspension. This is especially common in mountain bikes where they are used to help deal with the vibration caused by uneven surfaces.

    Road bikes typically have thinner tires inflated to higher pressures than those found on mountain bikes, taking advantage of the smoother surfaces that roads generally provide.

    Before the word ‘bicycle’ become popular (coming from the French word ‘bicyclette’), bikes were typically called ‘velocipedes’.

    Two wheeled transportation developed in the 1800s, from pushed powered bikes through to mechanical crank drives with pedals.

    You may have heard of the Penny-farthing, an early type of bicycle that featured a front wheel significantly larger than the rear. The name comes from the old British Penny and Farthing coins which represent the large and small wheels.

    The pneumatic tire came along in the later years of the 19th century along with the rear freewheel and coaster brakes.

    Cycling became increasing popular in the early stages of the 20th century as cycling clubs and races caught on.


Boat
    Large watercraft are generally called ships.

    Smaller watercraft are generally called boats.

    They are designed to float on water, whether it be in lakes, rivers or seas.

    Boats and ships serve a variety of purposes including transport, recreation, fishing, sporting competition and military operations.

    Some boats are human powered, including kayaks, canoes and gondolas.

    Sailboats are propelled by wind and sails.

    The tall upright post on a sailboat is called a mast.

    Motorboats are propelled by engines.

    Cargo ships carry goods between ports around the world.

    The hull is the main body of a boat or ship.

    Starboard and port are nautical terms which describe the right (starboard) and left (port) sides when facing the the front (bow) of a ship or boat.

    The rear part of a ship or boat is called the stern.

    The America’s Cup is awarded to the winner of a series of races between sailing yachts. Originally awarded in 1851, it is the oldest international sporting trophy in the world.

    Some luxury yachts (also called superyachts or megayachts) are over 70 metres (230 feet) in length with the longest examples reaching over 150 metres (492 feet).


Car
    The car, automobile, motor car or autocar usually has four-wheels and is a vehicle that uses its own motor engine system to transport passengers over purposely built roads.

    In 1769 Nicolas-Joseph Cugnot of France arguably invented the first full-scale, self propelled mechanical vehicle or automobile. It was a steam-powered tricycle.

    In 1807 Nicéphore Niépce and his brother Claude are believed to have built the world's first internal combustion engine. They called it a Pyréolophore. However, they chose to install it in a boat not a car. That same year a Swiss inventor François Isaac de Rivaz finished his own internal combustion engine and used it to create the world's first internal combustion engine vehicle.

    The Benz Patent-Motorwagen is believed to be the first modern automobile. It was built in 1886 by German inventor Carl Benz.

    In August 1888, Carl Benz's wife, Bertha Benz, became the first person to drive a car over a long distance. Without telling her husband she drove one of their Benz Patent-Motorwagens along with her two eldest sons from a town called Mannheim in southern Germany to Pforzheim. Automobile trips before this were usually short drives, she wanted to prove the automobile they had invented was a useful contraption, that the general public could use.

    Bertha Benz's road trip was a pioneering drive and a key event in the technical development of the car. Covering 106 km (66 miles) each way she did the round trip in two days, solving numerous problems on the way. When the brakes needed repairing she invented brake lining. She used a hatpin to clean a blocked fuel pipe and insulated a wire with a garter. She located fuel at the city pharmacy in Wiesloch (hailed as the first fuel station in the world) and on her return home made other suggestions, such as the need of another gear for climbing hills.

    In 1892, Rudolf Diesel a German engineer invented a "New Rational Combustion Engine" which lead him to building the first Diesel Engine in 1897.

    As automobiles became more popular a need arose to manufacture affordable cars on a large-scale basis. Ransom Olds in 1902, debuted a production-line manufacturing system at his Oldsmobile factory in Michigan, USA.

    Henry Ford's Model T car, introduced in 1908, is often regarded as the most famous of all early automobiles. It was the first car to become publically affordable, especially after Ford massively improved the production-line manufacturing system.

    In 1914, Ford created a production-line system that focused on synchronization, precision, and specialization. Ford's cars came off the line much faster than previous methods (from 12.5 man-hours down to just 1.5), which increased productivity yet used less manpower. By assigning each worker a specified area rather than allowing them to roam about, injuries were dramatically reduced.

    Ford could afford to pay workers more as the number of workers needed decreased. Combined with the high efficiency output a term called "Fordism" was surmised. It lead to most major manufacturing industries adopting the method for various products which contributed to the economic rise of the United States.

    Today, various body styles for the car exist such as the sedan/saloon, hatchback, station wagon/estate and van.

    In 2010 it was estimated that there were over 1 billion vehicles in the world, up from half a billion in 1986. The number of cars on the road continues to increase rapidly year on year especially in developing countries such as India and China.

    Petrol (gasoline) and diesel are still used to fuel the internal combustion engine today. However, both of these fuels cause air pollution and contribute to climate change. With rapidly increasing oil prices and concerns about the environmental impacts there is a lot of work underway to produce viable future alternative power systems for cars. Hybrid vehicles, plug-in electric vehicles, hydrogen vehicles and vehicles using alternative fuels such as natural gas are gaining popularity.

    Fully autonomous vehicles (driverless cars) currently exist in prototype (Google has developed a driverless car). These cars are expected to be available commercially around the year 2020. Autonomous cars could help to reduce the amount of vehicles needed on the road and dramatically increase safety.



Helicopter
    Helicopters are agile aircraft capable of taking off and landing vertically, hovering and flying in different directions.

    The lift and thrust of helicopters are provided by spinning rotors, usually featuring two or more blades.

    Helicopters typically have one main rotor and one smaller rotor in the tail which counters the torque effect, stopping the helicopter from spinning in the opposite direction.

    Some helicopters have two horizontal rotors which spin in opposite directions, allowing the helicopter to lift heavier objects.

    Helicopters have advantages over fixed-wing aircraft that allow them to access hard to reach areas, particularly useful in rescue situations.

    As well as search and rescue, helicopters are useful for tourism, medical transport, fighting fires, aerial photography, military activity and more.

    Helicopters have a number of limitations. They can be noisy, vibrate a lot and aren't as fast as fixed-wing aircraft.

    Vertical flight has existed in some form as far back as 400 BC when children in China played with flying toys made from bamboo which created lift when spun.

    Around 1480 Leonardo da Vinci designed a machine resembling a helicopter which can be described as an ‘aerial screw’.

    The first working helicopter is believed to have been the Focke-Wulf Fw 61, first flown in 1936.

    The fastest speed recorded by a helicopter is around 400 kph (248 mph).

    The longest distance traveled in a helicopter without landing is 3562 km (2213 miles).

    Helicopters can be used to fight fires by carrying tanks or helibuckets filled with water.

    Hovering can be the most difficult skill when flying a helicopter. Constant control is required to offset gusty air created by the helicopter.

    Small quadcopters are popular among researchers, the military and amateur enthusiasts due to their ease of control and affordable construction.

    Helicopters are sometimes called choppers.



Hot Air Balloon
    The first human carrying flight technology was the hot air balloon.

    While unmanned balloons have been around in some form for thousands of years, the first untethered flight with people on board was in 1782.

    The large balloon on top is called an ‘envelope’. It holds hot air created by a heat source known as a burner.

    The burner creates an open flame by burning a mix of liquid propane and air.

    Hot air balloons are buoyant because the hot air inside the envelope has a lower density than the colder air outside.

    Passengers typically stand in a wicker basket beneath the envelope.

    While most envelopes have a standard balloon shape, others are designed to look like animals, cartoon characters and other fun objects.

    The top of the balloon usually has a vent which allows the pilot to control the speed of ascent/descent (along with the burner).

    Hot air balloons can fly to amazing heights, the world record is over 21,000 metres! (68,900 feet). It’s tough to breathe up there so oxygen is needed from around 5,000 metres (16,400 feet).

    The temperature inside a hot air balloon is usually kept below 120 degrees Celsius (248 Fahrenheit).

    A typical envelope is made from nylon with a melting point around 230 degrees Celsius (446 Fahrenheit).

    Hot air balloon flights and festivals are popular in various destinations around the world. Well known locations include Cappadocia (Turkey), Albuquerque (New Mexico, USA), Luxor (Egypt) and the Serengeti (Tanzania).



Submarine
    Submarines are a special type of watercraft that can operate underwater.

    They are typically large vessels with a high number of crew. Nuclear submarines may have a crew of over 100.

    Submarines are used by the military as part of navy forces, protecting aircraft carriers, performing reconnaissance and carrying out other tasks.

    Submarines are also used in other areas such as marine research, undersea exploration and salvage missions.

    Some submarines can remain submerged for months at a time.

    Submarines typically feature a raised tower which holds radar equipment, the periscope and other systems.

    Submarines use ballast tanks to hold water, allowing them to submerge when necessary.

    Early submersibles were developed in the 1600s before the first known military submarine was built in 1775. Named the ‘Turtle’, it held one person and was controlled underwater independently, the first verified submarine capable of doing so.

    Both sides of the American Civil War built and used submarines.

    The first submarine not propelled by human power was the French vessel named ‘Plongeur’. Launched in 1863, it used compressed air for propulsion.

    Developed in the 1800s, torpedoes became an important part of submarine warfare.

    French writer Jules Verne published ‘20,000 Leagues under the Sea’ in 1870, a popular science fiction novel that boosted interest in submarine design.

    Submarine development and use continued through World War I and II, with German U-boats particularly effective in blocking supply lines to the UK.

    Launched in 1954, the first nuclear powered submarine was the USS Nautilus. Nuclear power allowed submarines to operate at high speeds while staying underwater longer than other forms of propulsion such as diesel-electric.

    Both the United States and Soviet Union maintained significant submarine fleets during the cold war.

    In August 2000, a Russian submarine named ‘Kursk’ sank in the Barents Sea after a series of explosions inside the vessel, killing all 118 crew.


Train
    Trains are built to transport passengers or cargo along rail tracks.

    There are all kinds of different trains that are built for a range of purposes and environments.

    Trains can be powered by a variety of energy sources including steam, diesel and electricity.

    Early trains relied on ropes, horses or gravity.

    The use of steam locomotives developed through the 19th century before diesel and electric locomotives began to replace them in the 20th century.

    Cargo trains are typically powered by a locomotive which pulls from the front.

    Some trains have a second locomotive which helps by pushing from the back.

    Passenger trains often feature self-propelled carriages (multiple units) that can be joined with other units. Trains such as these are more energy efficient but may require more maintenance than a single locomotive vehicle.

    Some high speed rail services can reach speeds over 300 kph (186 mph).

    In operation since 1964, Japan’s Shinkansen (bullet train) is a well known example of a high speed passenger rail system.

    Opened in 1994, the Channel Tunnel carries passengers between the UK and France on a high speed railway.

    Technologies such as magnetic levitation may provide faster, more efficient train travel in the future. Magnetic levitation propels trains forward using magnets, keeping the vehicle levitated but close to the track.

    Monorails feature a single rail and are often elevated above ground.

    Funicular (or venicular) railways feature two cars/trams attached by cables that counterbalance each other as they move up and down a steep slope.

    There are many train enthusiasts around the world interested in everything from rail history to famous train journeys, model trains, railway photography and other hobbies related to railways.

    You may have heard of Thomas the Tank Engine, a popular character from British television and literature. Thomas is a small steam locomotive who starred in the children’s television series with a variety of other railway friends.




Engineering
    Engineers solve practical problems by applying mathematical and scientific knowledge.

    The word engineer comes from a Latin word meaning ‘cleverness’.

    Learn about different types of engineering jobs such as civil, mechanical and electrical with our engineering job facts.

    As of 2010, the tallest building in the world is the Burj Khalifa in Dubai, UAE. It reaches an incredible 828 metres (2717 feet) in height. Check out more building facts or our list of the tallest buildings in the world.

    The Great Pyramid of Giza is the oldest of the Ancient Wonders of the World and the last one that remains largely intact. Enjoy more pyramid facts or learn about the Ancient Egyptian pyramids.

    The building of the Panama Canal, which links the Atlantic and Pacific Oceans, was one of the most difficult engineering projects ever. It is estimated that over 25000 workers lost their lives during the long and dangerous project, with most dying from disease and landslides.

    Golf balls have dimples because they help reduce drag, this allows the ball to fly further than a smooth ball would.

    As of 2010, the longest suspension bridge in the world is the Akashi Kaikyo Bridge in Kobe, Japan. Opened in 1998, it spans an amazing 1991 metres (6529 feet). Check out more interesing bridge facts or our list of the longest bridges in the world.

    Used for water distribution, the Delaware Aqueduct in New York, USA is the longest tunnel in the world (as of 2010). Drilled through solid rock, it reaches a staggering 137 kilometres (85 miles) in length. More tunnel facts.

    The Hoover Dam, built along the Colorado River between 1931 and 1936 reaches 726 feet in height (221 metres). More interesting dam facts.

    High speed passenger trains in China reach speeds of up to 350 kph (220 mph).

    The Titanic was 882 feet (269 metres) long.

    The London Eye in England is the largest Ferris wheel in Europe, standing at a height of 135 metres (442 feet).

    The tallest wind turbine in the world has rotor tips that reach over 200 metres (656 feet) above the ground.

    Branches of engineering include aerospace, biomedical, chemical, civil, computer, electrical, environmental, forensic, genetic, mechanical, military, nuclear, reverse, software and structural.



Bridge
    Common types of bridges include beam bridges, arch bridges, suspension bridges, cantilever bridges, truss bridges, and cable-stayed bridges.
    Bridge designs depend on their intended function, financial resources and also the type of terrain where they are constructed. While an arch bridge might be suited in one situation, a suspension bridge might be suited in another.
    The Zhaozhou Bridge is the oldest standing bridge in China and the world’s oldest stone segmental arch bridge. Built in 605 AD, it is still standing strong today, over 1400 years later.
    The Inca civilization in South America made use of rope bridges in the Andes Mountains before the Europeans colonized in the 1500’s. These rope bridges spanned canyons and gorges, allowing easy access to otherwise difficult to reach areas. While they were strong and reliable, repairing the bridges was a dangerous job that often ended in death.
    During the Industrial Revolution of the 19th century wrought iron was introduced into the design of large bridges. Wrought iron was later replaced by steel because it has a higher tensile strength.
    The first welded road bridge was designed by Polish engineer Stefan Bryla in 1927.
    The Sydney Harbour Bridge in Australia can rise or fall up to 18 cm (7.1 inches) depending on the temperature due to the steel expanding or contracting. It also features 6 million rivets and weighs 39006 tonnes.
    The Brooklyn Bridge in New York, USA joins Manhattan and Brooklyn over the East River. When completed in 1883, it was the longest suspension bridge in the world (remaining so until 1903). It features average daily traffic of around 145000 vehicles.
    The Golden Gate Bridge in San Francisco, USA is a well known suspension bridge that was completed in 1937. It has a total length of 8981 feet (2737 metres) and features 80000 miles (129000 kilometres) of wire in its two main cables.
    The longest suspension bridge in the world (as of 2010) is the Akashi Kaikyo Bridge in Kobe, Japan. It opened in 1998 and spans an incredible 1991 metres (6529 feet). Check out our top ten list of the longest bridges in the world.



Building
    The word skyscraper originally referred to a type of sail on a sailing ship.
    A skyscraper is held together by a steel skeleton of vertical columns, horizontal girder beams and often diagonal beams for extra support. This structure distributes the immense weight in a way that ensures the integrity and safety of the building.
    Restoration work in 1990 and 2001 shifted the Leaning Tower of Pisa back to an angle of 4 degrees after it was previously leaning at an angle of 5.5 degrees.
    The roofs of the Sydney Opera House are covered in a total of 1056006 tiles.
    The Colosseum in Rome, Italy, is an elliptical amphitheatre that was completed in 80 AD. It held around 50000 spectators and was used for a variety of events including gladiator contests, animal hunts and mythology based dramas.
    Around 20000 workers helped build the Taj Mahal, a famous mausoleum and landmark in Agra, India, that attracts millions of visitors every year.
    The world’s largest office building by floor size is the Pentagon in Virginia, USA, with over half of its 6500000 square foot (604000 square metre) floor area used as offices.
    The Empire State Building in New York was the first building to have over 100 floors and was the tallest building in the world from 1931 until 1972.
    The Chrysler Building in New York was built at a time when there was a strong desire to build the world’s tallest skyscraper, before being overtaken by the Empire State Building, the Chrysler Building was the world’s tallest for around 11 months. During the construction, floors were being completed at a staggering four per week. Despite the rush, no workers died during its construction.
    The Petronas Towers in Kuala Lumpur, Malaysia, are the world’s tallest twin buildings, standing at a height of 452 metres (1483 feet).
    The Burj Khalifa in Dubai, UAE, is the tallest building in the world. It reaches an amazing 828 metres (2717 feet) in height. Check out our top ten list of the tallest buildings in the world.
    Tall buildings need fast elevators, recent developments have led to elevators that can travel up to, and sometimes over, 1000 metres a minute (3280 feet a minute).


Dam
    A dam is a barrier designed and constructed to contain the flow of water. It is often built in conjunction with a hydroelectric power station to provide electricity.
    Dams are built for purposes such as generating hydroelectricity, creating recreational areas, minimizing flood risks, diverting water for irrigation, and providing water for towns and cities.
    The type of dam built in any given situation depends on factors such as the intended purpose, environmental considerations, available finances and the location.
    Different types of dams include masonry dams, embankment dams and arch-gravity dams.
    Beavers create their own dams from sticks and mud as protection from predators and also to help provide easy access to food.
    Dams are huge engineering projects that require vast financial resources. For example, the construction of the Itaipu Dam on the border of Brazil and Paraguay (completed in 1984) cost around US$20 billion.
    Built along the Colorado River between 1931 and 1936, The Hoover Dam reaches 726 feet in height (221 metres).
    When the Hoover Dam was completed it was both the world’s largest concrete structure and largest hydroelectric power station.
    The Hoover Dam is made of enough concrete to make a two lane highway from New York to San Francisco, that’s around 4000 miles (2500 kilometres).
    As of 2010, the tallest dam in the world is Nurek Dam in Tajikistan. Completed in 1980, it reaches 300 metres (984 feet) in height.
    Many dam failures have occurred in the past, these disasters can cause significant damage and threaten lives.
    In 1889 a failure of the South Fork Dam near Johnstown, Pennsylvania, USA, killed over 2200 people.
    In 1975, the Banqiao Dam in China was among many dams that were destroyed after the extreme rains of Typhoon Nina. It is estimated that between 90000 and 230000 lives were lost as a result of the Banqiao Dam breaking.



Pyramid
Pyramids in Geometry
    In geometry, pyramids have triangular sides that come together at the top (apex).
    If they have 4 sides and a square base they are called a square pyramid.
    If they have 3 sides and a triangular base they are called a tetrahedron.

Early Pyramids

    Humans have been building structures using pyramid shapes for thousands of years.
    The first pyramid type structures are believed to have been built by the Mesopotamians around 5000 years ago. These structures were called ziggurats. Pyramid type structures found in Caral, Peru also date back to around this time.

Ancient Egyptian Pyramids

    Ancient Egyptian pyramids are the most well known pyramid structures.
    Most Ancient Egyptian pyramids were built as tombs for Pharaohs and their families.
    Over 130 pyramids have been discovered in Egypt.
    The first Egyptian pyramid is believed to be the Pyramid of Djoser, it was built in Saqqara around 4650 years ago (2640 BC).
    The Great Pyramid of Giza is the oldest and largest of three pyramids in the Giza Necropolis.
    Also known as the Pyramid of Khufu, it is the oldest of the Ancient Wonders of the World and the last one still largely intact.
    Enjoy more facts about Ancient Egyptian pyramids.

Aztec and Mayan Pyramids
    Most Aztec and Mayan pyramids were step pyramids with temples on top.
    The Mayan civilization stretched from Southern Mexico the northern part of Central America.
    Mayan pyramids date back to around 3000 years ago.
    Aztec pyramids in central Mexico date back to around 600 years ago.
    El Castillo (also known as the Temple of Kukulkan) is perhaps the most famous Mayan pyramid. Located in the archaeological site of Chichen Itza, in the Mexican state of Yucatan, it is a popular tourist destination with over 1 million visitors every year.
    The world’s largest pyramid by volume is the Great Pyramid of Cholula in Puebla, Mexico.

Other Regions
    Sudan is home to a large number of Nubian pyramids which are smaller and steeper than those found in Egypt.
    Although Greeks aren’t known for their pyramid building, a number of pyramid like structures do exist, with the best known being the Pyramid of Hellinikon.
    Pyramids were built in China to house the remains of some early Chinese emperors.
    The Roman Empire built a number of pyramids including the Pyramid of Cestius in Rome, Italy which still stands today.

Modern Pyramids
    Not all pyramids are ancient, there are also a large number of modern structures that share the famous pyramid shape.
    The Louvre in Paris is home to a large glass pyramid.
    The Palace of Peace and Reconciliation in Astana, Kazakhstan is a 62 metre (203 feet) high pyramid.
    The 30 story Luxor Hotel in Las Vegas is a large pyramid that holds over 4000 rooms.
    The Slovak Radio Building in Bratislava, Slovakia is shaped like an inverted (upside down) pyramid.


Egyptian Pyramid
    Ancient Egyptian pyramids are the most well known pyramid structures.
    Most Ancient Egyptian pyramids were built as tombs for Pharaohs and their families.
    Over 130 pyramids have been discovered in Egypt.
    The first Egyptian pyramid is believed to be the Pyramid of Djoser, it was built in Saqqara around 4650 years ago (2640 BC).
    Saqqara is a huge ancient burial ground built near the Egyptian city of Memphis.
    The Great Pyramid of Giza is the oldest and largest of three pyramids in the Giza Necropolis.
    Also known as the Pyramid of Khufu, it is the oldest of the Ancient Wonders of the World and the last one still largely intact.
    For over 3800 years, the Great Pyramid of Giza was the tallest man made structure in the world.
    Although it has lost around 10 metres (33 feet) in height, it still stands around 146 metres (480 feet) above the ground.
    As well as Giza and Saqqara, important Egyptian Pyramid sites include Dashur, Abusir, Meidum, Lisht, Abu Rawash and others.
    Nearly all Egyptian Pyramids are located on the west bank of the Nile.
    Egyptian Pyramids often contain multiple chambers and passages.
    Bodies placed in the tombs were preserved by mummification.
    Egyptians buried their dead with burial goods that ranged from everyday items they believed would useful in the afterlife to more expensive items such as jewelry.
     Tomb robbers targeted many of the royal tombs and most were eventually robbed.
    One tomb that was left largely intact was that of Tutankhamun in the Valley of the Kings. Rediscovered in 1922 by Howard Carter, this famous tomb is best known for the solid gold funerary mask of Tutankhamun.
    Tutankhamun was a pharaoh from 1332 BC to 1323 BC.


Eiffel Tower
    Located on the Champ de Mars in Paris, France, the Eiffel Tower is one of the most well known structures in the world.
    The Eiffel Tower was originally built as the entrance arch for the World's Fair in 1889.
    It is named after Gustave Eiffel, whose company was in charge of the project.
    The Eiffel Tower is 320 metres (1050 feet) in height and was the tallest man made structure in the world for 41 years before being surpassed by the Chrysler Building in New York.
    The Eiffel Tower is made of iron and weighs around 10000 tonnes.
    Around 50 tonnes of paint are added to the Eiffel Tower every 7 years to protect it from rust.
    Despite its height, the Eiffel Tower was designed to be wind resistant, swaying only a few inches in the wind. It actually moves further when the iron on the sun facing side heats and expands, moving the top up to 7 inches (18 centimetres) away from the sun.
    Temperature also alters the height of the Eiffel Tower by up to 6 inches (15 centimetres).
    Millions of people climb the Eiffel Tower every year and it has had over 250 million visitors since its opening.
    Visitors can climb up stairs to the first two levels or take a lift which also has access to the third and highest level.
    Being so popular, the Eiffel Tower design has been recreated around the world, including the half scale replica at the Paris Las Vegas Hotel in Nevada, USA and the full scale Tokyo Tower in Japan.
    Not everyone liked the Eiffel Tower when it was first built, with many criticizing its bold design.
    The French name for the Eiffel Tower is La Tour Eiffel, it also has the nickname La dame de fer which means the iron lady.



Empire State Building
    The Empire State Building is a skyscraper in Manhattan, New York City, USA.
    The building has 103 floors and at roof height is 1250 ft (381 m) tall. The height when including the antenna spire is 1454 ft (443.2 m).
    The Empire State Building was designed by William Lamb of the architect firm Shreve, Lamb & Harmon Associates.
    The contracting construction firm was Starrett Brothers and Eken.
    Around 3,400 workers were involved in the construction of the Empire State Building, with official records showing five workers died.
    It took just 410 days for the Empire State Building to be constructed, quicker than anticipated.
    The building was officially opened on May 1, 1931 when President Herbert Hoover turned the lights on with a push of a button from Washington, D.C.
    For 41 years between 1931 and 1972 the Empire State Building was the tallest building in the world.
    There are 6,514 windows in the Empire State Building.
    From street level to the 103rd floor there are 1,872 steps. A race up the stairs to the 86th floor is held annually, the athletes must climb a total of 1,576 steps.
    There are 73 elevators in the building, including 6 freight elevators.
    Because so many businesses are housed in the building the Empire State has its own zip code, 10118.
    The building itself cost $24,718,000 to build, when the cost of the land is included this figure climbs to $40,948,900. This cost was less than half of the total anticipated cost due to the Great Depression.
    The Empire State Building has a lightning rod near the top which is struck by lightning around 23 times every year.
    There are observation decks on the 86th and 102nd floors. These tourist attractions are visited by around 4 million people annually.
    The Empire State Building became the tallest building in New York City again after the collapse of the World Trade Center in 2001. In April 2012 the new One World Trade Center surpassed the Empire State Building in height.



Great Wall of China
    Rather than being one long continuous wall, the Great Wall of China is made up of a number of different sections. These sections were built by various dynasties over a long period of time from stone and other materials.
    Its main purpose was protection against attacks and invasions from the north.
    The Great Wall of China stretches around 6300 kilometres (3915 miles) in length. If you measure the length of all the different sections of wall, the distance is more like 22000 kilometres (13670 miles).
    The Great Wall of China is the longest structure ever built by humans.
    The widest section of the wall is around 9 metres (30 ft).
    The highest point of the wall is around 8 metres (26 ft)
    The first parts of the wall were built over 2000 years ago.
    A large number of workers have lost their lives while building the wall.
    Major rebuilding of the Great Wall of China took place during the Ming Dynasty that began in the 14th century. Construction during this time was strong due to the use of stone and brick.
    Earlier sections of the wall were made from stone, wood and compacted earth.
    Some of the well maintained areas of the wall, such as those near Beijing, are popular tourist destinations.
    While some parts of the wall have been preserved or renovated, other parts have been vandalised or destroyed to make way for construction.
    Rumours that astronauts can see the Great Wall of China from the Moon with the naked eye are untrue.


Leaning Tower of Pisa
    The Leaning Tower of Pisa (Torre pendente di Pisa) is a bell tower in Pisa, Italy.
    The Tower of Pisa is world famous for its prominent tilt to one side.
    The tower's foundations were built on soft subsoil which had difficulty supporting the tower's weight (14,500 ton). When the second storey was started the lean became noticeable and only got worse as construction continued.
    Originally the tower leaned at an angle of 5.5 degrees. After restoration work between 1990 and 2001 this angle was reduced to 3.97 degrees.
    The tower is 8 stories high, 55.86 m (183.27 ft) on the low side and 56.67 m (185.93 ft) on the high side.
    Construction of the Tower of Pisa started in the year 1173 and was completed in 1372. Construction stopped and restarted twice over those 199 years due to wars.
    War stopped construction the first time for almost a century which gave the underlying soil time to settle and compact. If construction had not halted, the tower would most likely have toppled.
    As well as the tower, Pisa's Cathedral Square (Piazza del Duomo or Piazza dei Miracoli) also has a cathedral, a baptistery and a cemetery.
    The entire Cathedral Square was declared a UNESCO World Heritage Site in 1987.
    There are 294 steps on the north side of the tower and 296 steps on the south side.
    Seven bells sit in the bell-chamber at the top of the tower, one bell for each note of the musical major scale.
    The tower's design has widely been attributed to Guglielmo and Bonanno Pisano however recent studies suggest the architect Diotisalvi may have been involved in the design.
    While the original architect of the tower has never been verified many are known to have worked on it including: Bonanno Pisano and Gerardo di Gerardo in phase 1, Giovanni Pisano and Giovanni di Simone during phase 2 before Tommaso di Andrea Pisano oversaw its completion.
    Because of the marshy underlying subsoil there are several other towers in Pisa with less prominent tilting issues.
    Germans used the tower as a lookout during World War II. The Allies new this but decided against bombing the area due to the impressive beauty of the tower and cathedral.
    To demonstrate that speed of descent is independent of an object's mass Galileo Galilei is said to have dropped two cannonballs of differing mass from the tower. However, this is believed to be an old wives' tale.


Machu Picchu
    Machu Picchu was build at the height of the Inca Empire around 1450 but abandoned just over a century later in 1572 after the Spanish arrival in Peru.
    Archaeologists believe Machu Picchu was constructed for use as a Royal Estate.
    Machu Picchu is located 2430 m (7970 ft) above sea level on a ridge between the Huayna Picchu and Machu Picchu mountains in Peru.
    On July 24, 1911, American explorer Hiram Bingham III with the help of Melchor Arteaga, re-discovered Machu Picchu.
    Bingham bought word of the ruins to the outside world. Only locals and a handful of missionaries and engineers had known of the site's existence.
    It is believed Bingham was actually looking for a different 'lost' city, known as Vilcabamba.
    Bingham's team excavated an estimated 40,000 artifacts to Yale University for further study including mummies, ceramics, silver statues, jewellery and bones. Peru has long wanted these artifacts back and an agreement was recently agreed for the majority of these items to be returned.
    Since re-discovery over 30% of Machu Picchu has been reconstructed to give a better idea of how the original structures looked, restoration continues today.
    In 1983, Machu Picchu became an UNESCO World Heritage Site. In 2007 it was voted one of the New Seven Wonders of the World in a worldwide Internet poll.
    Machu Picchu was built in a typical Inca style, with beautiful, polished dry-stone walls of quarried granite stone.
    The Incas were experts at using a building technique called ashlar in which blocks of stone are cut so precisely as to fit together tightly without mortar.
    The incredible civil engineering techniques of the Incas reduced the affects of frequent earthquakes. Mortar-free walls, Trapezoidal, tilted inward and round corner doors and windows helped protect many of the buildings from collapsing.
    It is estimated that 60% of the construction done at Machu Picchu was underground, including deep building foundations and crushed rock for drainage.
    Machu Picchu's construction is amazing considering the Inca's did not use draft animals, iron tools, or the wheel. It's a mystery how the massive blocks of stone were moved up steep terrain and through dense bush, but it is generally believed that hundreds of men were used to push the stones up.
    Machu Picchu had access to springs for water and enough terraced and irrigated land to grow food for around four times as many people as ever lived there.
    The Machu Picchu site is divided in an urban area and an agricultural area. With an upper town area where royalty lived and temples built and a lower town area that included workers quarters and warehouses.
    The Incas built a road to the Machu Picchu region and today thousands of tourists trek the 2-5 day high-altitude Inca Trail to visit Machu Picchu.
    As Peru's most visited tourist attraction Machu Picchu is continually threatened by commercial forces. In the 1990s, the construction of a cable car, luxury hotel, and restaurants was allowed nearby. The Peruvian government has since set limits of a max of 2,500 visitors per day and only 400 visitors per day into the site.


Mount Rushmore
    Mount Rushmore National Memorial is a sculpture carved into the side of Mount Rushmore in the Black Hills of South Dakota, USA.
    Local historian Doane Robinson came up with the idea for Mount Rushmore in 1923 in order to promote tourism in South Dakota.
    Gutzon Borglum, a famous Dutch-American sculptor, was selected for the Mount Rushmore project. At his death in March 1941 his son, Lincoln Borglum, continued the work and it was completed later that year.
    The Memorial depicts 4 American Presidents, George Washington, Thomas Jefferson, Theodore Roosevelt, and Abraham Lincoln who represent the first 130 years of American history.
    Carving of Mount Rushmore started on October 4, 1927, and finished 14 years later on October 31, 1941.
    Over 400 workers helped to sculpt Mount Rushmore climbing 506 steps to its top each day and amazingly there were no fatalities.
    Originally the plan was to carve the sculpture into nearby granite pillars known as the Needles. However, these were deemed to thin and eroded to support the sculpture.
    Mount Rushmore standing 5,725 ft (1,745 m) above sea level was chosen due to its grand location, quality granite and because it faced southeast so enjoyed maximum exposure to the sun which helped maximise working hours.
    Initially, it was planned for the figures to be carved from head to waist, but a shortage in funding didn't allow for this.
    The whole project cost US $989,992.32.
    Dynamite was used to carve Mount Rushmore followed by a process called 'honeycombing'. About 450,000 tons (over 800 million pounds) of stone was removed of the side of the mountain during construction.
    To start with Thomas Jefferson was carved to the right of George Washington. However, after 18 months it was decided that this wasn't working so Jefferson's face was dynamited off and his face carved on the opposite side.
    Maintenance of the Rushmore memorial requires annual monitoring, cleaning and sealing of cracks, work that is undertaken by trained mountain climbers.
    The monument is 60 foot (18 m) high. Each of the President's heads are the height of a six-story building, their eyes are 11 ft across, their noses are 20 ft long and their mouths 18 ft wide.
    A cave called the 'Hall of Records' sits behind the monument and contains a vault of 16 porcelain enamel panels with text of the Declaration of Independence, the Constitution, biographies of the 4 presidents and Borglum, and history of the U.S.


Statue of Liberty
    The Statue of Liberty is located on Liberty Island, in the New York harbor, USA.
    The Statue of Liberty commemorates the American Declaration of Independence and was a gift from the people of France.
    The statue was assembled on its pedestal after being constructed in France and sent to the US in crates.
    It was dedicated on October 28, 1886.
    The Statue of Liberty was designed by French sculptor Frederic Bartholdi.
    The female form represented by the sculpture is based on Libertas, the Roman goddess of liberty. She holds a torch and a tabula ansata (tablet) that has the date of the American Declaration of Independence inscribed in it (July 4, 1776).
    A broken chain also lies at the feet of the statue which is hard to see from the ground.
    The official name of the Statue of Liberty is ‘Liberty Enlightening the World’.
    The statue has been closed for renovation a number of times, including between 1984 and 1986 when the torch and much of the internal structure was replaced.
    The Statue of Liberty stands 151 feet (46 metres) in height, and 305 feet (93 metres) from the ground to the torch.
    The head of the statue was displayed at the World's Fair in Paris, 1878.
    There was difficulty in the United States finding money to fund the project, especially after a financial crisis in 1873. A fundraising drive led by newspaper publisher Joseph Pulitzer was embraced by New Yorkers and helped push work forward. 80% of the donations were of less than $1.
    Liberty Island was previously called Bledloe's Island.
    There are replicas of the Statue of Liberty found in Paris, Las Vegas and many other cities around the world.


Taj Mahal
    The Taj Mahal is a famous mausoleum in India.
    A mausoleum is a building that contains burial chambers (tombs) for the deceased, they can be large or small and are often created in honor of influential people.
    The Taj Mahal is located in Agra, a city in the Uttar Pradesh region of northern India.
    It was built as the final resting place for Mumtaz Mahal, the third wife of Mughal emperor Shah Jahan.
    The name Taj Mahal means “crown of palaces”.
    Construction of the Taj Mahal took around 20 years, beginning around 1632 and finishing around 1653.
    The Taj Mahal is made of white marble.
    One of the Taj Mahal’s most recognizable features is a large white dome that is often called an ‘onion dome’ due to its shape. It has a height of around 35 metres (115 feet) and is surrounded by 4 smaller domes.
    The full height of the Taj Mahal is 171 metres (561 feet).
    The Taj Mahal is considered to be one of India’s most admired works of art, as well as a famous landmark and a tourist attraction that draws millions of visitors every year.
    The Taj Mahal complex includes a large garden, a reflecting pool, a mosque and other mausoleums.


Titanic
    The Titanic was built between 1909 and 1911.
    It was 882 feet (269 metres) in length and 175 feet (53 metres) in height.
    The Titanic had a crew of around 900 people.
    The Titanic’s engines were powered by pressurized steam from burning coal.
    It was a luxury passenger liner that carried some of the world’s richest people as well as others looking for a new life in North America.
    The Titanic's intended course was from Southampton, England to New York City, USA.
    It left Southampton on April 10, 1912 and stopped at destinations in France and Ireland before heading west towards New York.
    It collided with an iceberg and sank on April 15, 1912.
    While the Titanic carried over 2200 people, there were only enough life boats for around 1200 of them.
    Over 1500 people died because of the sinking.
    The remains of the Titanic wreck sit on the sea bed over 12400 feet (3780 metres) beneath the surface.


Tunnel
    The Channel Tunnel is an undersea rail tunnel that links the United Kingdom and France. Opened in 1994, it carries both passenger and freight trains. The tunnel stretches 50.5 kilometres (31.4 miles) in length and is 75 metres (246 feet) deep at its lowest point.
    The first ever proposal for a tunnel between the UK and France was put forward by a French mining engineer named Albert Mathieu back in 1802.
    As well as being built for human use, tunnels can also be built for the safety and convenience of animals. More than 600 tunnels have been built under roads in the Netherlands to help increase the population numbers of endangered animals such as the European Badger.
    Tunnel boring machines are often used to excavate major tunnels. These huge machines can bore through all kinds of sand, clay and hard rocks. The largest tunnel boring machines feature diameters of over 14 metres (46 feet).
    When dealing with water crossings, building a tunnel is usually more expensive than building a bridge. Tunnels however preserve the above water scenery, are unaffected by weather conditions, and require less land on the shore.
    The Lincoln Tunnel is a well known tunnel in the USA, it connects Weehawken, New Jersey and Manhattan, New York. Stretching 1.5 miles (2.4 kilometres) under the Hudson River, the Lincoln Tunnel has an average daily traffic of around 110000 vehicles.
    At 137 kilometres (85 miles) in length, the Delaware Aqueduct in New York, USA, is the longest tunnel in the world.
    The longest undersea tunnel in the world (as of 2010) is the Seikan Tunnel in Japan. Connecting the Japanese islands of Honshu and Hokkaido, the tunnel is 53.85 kilometres (33.46 miles) in length.
    The Cu Chi tunnels found under the Cu Chi district of Ho Chi Minh City in Vietnam are a complex network of connecting tunnels that form part of an even larger network that spread throughout Vietnam. The tunnels were used frequently during the Vietnam War by Viet Cong to store food and weapons, hide, communicate, and provide sheltered areas for medical attention.
    Aware of the Viet Cong’s strategic use of the tunnels, the US tried to destroy them. The tunnels however featured a range of booby traps and explosives that, combined with the difficulty in navigating the caves, made it too dangerous for the US to be very successful in their attempts to destroy the tunnels.



Recycling
    Recycling is the process of turning used waste and materials into new products. This prevents potentially useful materials from being wasted as well as reducing energy use and pollution.

    Recycling is part of the waste disposal hierarchy - Reduce, Reuse, Recycle.

    A wide variety of different materials can be recycled, including paper, plastic, glass, metal, textiles and electronic equipment.

    The idea of recycling isn’t something new, historical evidence shows that humans have been recycling various materials for thousands of years.

    There are different methods of waste collection. These include drop off centers (where waste materials are dropped off at a specified location), buy back centers (where certain materials are exchanged for money), and curbside collection (where recycling vehicles are used to pick up waste material intended for recycling along residential streets).

    Powerful magnets are used to sort through different types of metals.

    Recycled paper can be made from three different types of paper; mill broke (paper scrap and trimmings), pre-consumer waste (paper that was discarded before consumer use), and post-consumer waste (paper discarded after consumer use, such as old newspapers).

    Recycling plastic can be more difficult than other materials and plastics are not typically recycled into the same type of plastic.

    Different types of plastics are labeled by numbers (plastic identification code), for example polyethylene (PET) is number 1 and polyvinyl chloride (PVC) is number 3.

    Recycling old aluminum uses only 5% of the energy used to make new aluminum.

    Aluminum can be recycled from cans, bicycles, computers, cookware, wires, cars, planes and other sources.

    Glass recycling is often separated into colors because glass keeps its color after recycling.

    For every ton of recycled glass turned into new products, 315 kilograms of extra carbon dioxide that would have been released during the creation of new glass are saved.


More Science
    The noise that is thunder is created when the air around lightning gets rapidly heated and expands at a rate faster than the speed of sound.

    Rather than putting on weight from eating celery you actually lose it, you burn more calories from the chewing than you put on from the food itself.

    Sound travels 4 times faster in water than it does through air.

    Cranberries can be tested for ripeness by bouncing them, if they are ripe they should have a bouncing quality.

    Travelling at 80 kilometres per hour, a car uses half its fuel to overcome wind resistance.

    The largest living structure on Earth is the Great Barrier Reef. Found in Australia, it is over 2000 kilometres long.

    The QWERTY keyboard layout used on most computers was invented way back in the 1860's.

    Some types of bamboo can grow nearly a metre a day!

    Diamonds are the hardest known substance.

    Light from the sun can reach a depth of 80 metres in the ocean.

    When you crack a whip, it makes a loud noise because the tip is actually moving faster then the speed of sound!