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Science and technology: Sample articles
Apollo project
US space project to land a person on the Moon, achieved on 20 July 1969, when Neil Armstrong was the first to set foot there. He was accompanied on the Moon's surface by Buzz Aldrin; Michael Collins remained in the orbiting command module.
The programme was announced in 1961 by US president John F Kennedy. The world's most powerful rocket, Saturn V, was built to launch the Apollo spacecraft, which carried three astronauts. When the spacecraft was in orbit around the Moon, two astronauts would descend to the surface in the lunar module to take samples of rock and soil and set up experiments that would send data back to Earth. After four preparatory flights, Apollo 11 made the first lunar landing. Five
more crewed landings followed, the last in 1972. The total cost of the programme was over US$24 billion.
The Apollo-Saturn rocket complex stood 111 m/364 ft tall. Saturn's first stage separated and second stage fired at 72 km/45 mi; the third stage ignited at 177 km/110 mi for extra power to put Apollo into Earth orbit at 28,000 kph/17,400 mph, and later fired to send Apollo towards the Moon.
Apollo 1
During a preliminary check on the ground the three crew were killed by a fire on 27 January 1967. After this, NASA conducted five uncrewed test flights.
Apollo 7
The first successful Apollo mission to carry a crew, Apollo 7 was a test flight sent into orbit around the Earth on 11 October 1968.
Apollo 8
Launched on 21 December 1968, this was the first mission to take a crew around the Moon.
Apollo 9
Launched on 3 March 1969, this mission tested the lunar module in orbit around the Earth.
Apollo 10
Launched on 18 May 1969, this mission successfully tested the lunar module 14.5 km/9 mi above the surface of the Moon. Apollo 11
After a launch on 16 July 1969, Armstrong and Aldrin landed the lunar module (named Eagle) in an area called the Sea of Tranquillity on the Moon's surface on 20 July 1969. Armstrong had to land manually because the automatic navigation system was heading for a field of boulders. On landing, Armstrong announced, 'Tranquillity base here. The Eagle has landed.' The module remained on the Moon for 22 hours, during which time the astronauts collected rocks, set up experiments, and mounted a US flag. Apart from a slight wobble when rejoining the command module, the return flight went without a hitch. After splashdown, the astronauts were quarantined as a precaution against unknown illnesses from the Moon.
Apollo 12
Launched on 14 November 1969, this mission achieved another successful Moon landing, in spite of twice being struck by lightning.
Apollo 13
Intended to be the third Moon landing, Apollo 13 was launched on 11 April 1970 with the crew of John Swigert, Fred Haise, and James Lovell. On the third day of the mission Swigert reported to Houston, 'We've had a problem here.' An electrical fault had caused an explosion in one of the oxygen tanks in the service module, cutting off supplies of power and oxygen to the command module. The planned landing was abandoned and the rocket was sent round the Moon before heading back to Earth. The crew used the lunar module Aquarius as a 'lifeboat', though they had to endure near-freezing temperatures to save power, making sleep almost impossible. Attempting re-entry in the crippled ship almost led to disaster but the crew splashed down safely on 17 April.
Apollo 14
Launched on 31 January 1971, this mission reached the Moon on 5 February and returned to Earth on 8 February with samples of lunar rock.
Apollo 15
Launched on 26 July 1971, this mission used the first surface vehicle on the Moon, the lunar roving vehicle.
Apollo 16
Launched on 16 April 1972, this mission gathered lunar soil and rock during 71 hours 2 minutes on the Moon.
Apollo 17
Launched on 7 December 1972, this was the last of the Apollo Moon landings. Detailed geological studies were carried out
during a record 74 hours on the Moon, and large amounts of rock and soil were brought back.
artesian well
Well that is supplied with water rising naturally from an underground water-saturated rock layer (aquifer). The water rises from the aquifer under its own pressure. Such a well may be drilled into an aquifer that is confined by impermeable rocks both above and below. If the water table (the top of the region of water saturation) in that aquifer is above the level of the well head, hydrostatic pressure will force the water to the surface.
Artesian wells are often overexploited because their water is fresh and easily available, and they eventually become unreliable. There is also some concern that pollutants such as pesticides or nitrates can seep into the aquifers.
Much use is made of artesian wells in eastern Australia, where aquifers filled by water in the Great Dividing Range run beneath the arid surface of the Simpson Desert. The artesian well is named after Artois, a French province, where the phenomenon was first
observed.
enzyme
Biological catalyst produced in cells, and capable of speeding up the chemical reactions necessary for life. They are large, complex proteins, usually soluble, and are highly specific, each chemical reaction requiring its own particular enzyme. The enzyme's specificity arises from its active site, an area with a shape corresponding to part of the molecule with which it reacts (the substrate). The shape of the enzyme where the chemical binds only allows the binding of that particular chemical, rather like a specific key only working a specific lock (the lock and key hypothesis). The enzyme and the substrate slot together forming an enzyme–substrate complex that allows the reaction to take place, after which the enzyme falls away unaltered.
The activity and efficiency of enzymes are influenced by various factors, including temperature and acidity (pH). Temperatures above 60°C/140°F damage (denature) the intricate structure of enzymes, inactivating them and causing reactions to stop. Each enzyme operates best – at its maximum rate – within a specific pH range and temperature, and is denatured by excessive acidity or alkalinity or extremes of temperature.
In digestion, digestive enzymes include amylases (which digest starch), lipases (which digest fats), and proteases (which digest protein). Other enzymes play a part in the conversion of food energy into ATP, the manufacture of all the molecular components of the body, the replication of DNA when a cell divides, the production of hormones, and the control of movement of substances into and out of cells.
Enzymes have many uses in medical and industrial biotechnology, from washing powders to drug production, and as research tools in molecular biology. They are involved in the making of beer, bread, cheese, and yogurt. They can be extracted from bacteria and fungi and genetic engineering now makes it possible to tailor an enzyme for a specific purpose.
The most abundant enzyme is ribulose biphosphate carboxylase. It is found in chloroplasts and is associated with photosynthesis.
ionization
Process of ion formation. It can be achieved in two ways. The first way is by the loss or gain of electrons by atoms to form positive or negative ions.
Na – e–  Na+
½Cl2 + e– Cl–
In the second mechanism, ions are formed when a covalent bond breaks, as when hydrogen chloride gas is dissolved in water. One portion of the molecule retains both electrons, forming a negative ion, and the other portion becomes positively charged. This bond-fission process is sometimes called dissociation.
HCl(g) + aq  H+(aq) + Cl–(aq)
liver
In vertebrates, large organ with many regulatory and storage functions. The human liver is situated in the upper abdomen, and weighs about 2 kg/4.5 lb. It is divided into four lobes. The liver receives the products of digestion (food absorbed from the gut and carried to the liver by the bloodstream), converts glucose to glycogen (a long-chain carbohydrate used for storage), and then back to glucose when needed. In this way the liver regulates the level of glucose in the blood. This is partly controlled by a hormone, insulin. The liver removes excess amino acids from the blood, converting them to urea, which is excreted by the kidneys. The liver also synthesizes vitamins, produces bile and blood-clotting factors, and removes damaged red cells and toxins such as alcohol from the blood.
If more protein is eaten than is needed to make different proteins for the body, the excess is broken down. This breakdown takes place in the liver. One product of this breakdown is urea and this has to be lost from the body in the urine. The liver also stores some vitamins, produces bile, and breaks down red blood cells.
logarithm
or log
The exponent or index of a number to a specified base – usually 10. For example, the logarithm to the base 10 of 1,000 is 3 because 103 = 1,000; the logarithm of 2 is 0.3010 because 2 = 100.3010. The whole-number part of a logarithm is called the characteristic; the fractional part is called the mantissa.
Before the advent of cheap electronic calculators, multiplication and division could be simplified by being replaced with the addition and subtraction of logarithms.
For any two numbers x and y (where x = ba and y = bc), x × y = ba × bc = ba + c; hence one would add the logarithms of x and y, and look up this answer in antilogarithm tables.
Tables of logarithms and antilogarithms are available that show conversions of numbers into logarithms, and vice versa. For example, to multiply 6,560 by 980, one looks up their logarithms (3.8169 and 2.9912), adds them together (6.8081), then looks up the antilogarithm of this to get the answer (6,428,800). Natural or Napierian logarithms are to the base e, an irrational number equal to approximately 2.7183.
The principle of logarithms is also the basis of the slide rule. With the general availability of the electronic pocket calculator, the need for logarithms has been reduced. The first log tables (to base e) were published by the Scottish mathematician John Napier in 1614. Base-ten logs were introduced by the Englishman Henry Briggs (1561–1631) and Dutch mathematician Adriaen Vlacq (1600–1667).
Newton's laws of motion
In physics, three laws that form the basis of Newtonian mechanics, describing the motion of objects. (1) Unless acted upon by an unbalanced force, a body at rest stays at rest, and a moving body continues moving at the same speed in the same straight line. (2) An unbalanced force applied to a body gives it an acceleration proportional to the force (and in the direction of the force) and inversely proportional to the mass of the body. (3) When a body A exerts a force on a body B, B exerts an equal and opposite force on A; that is, to every action there is an equal and opposite reaction.
The first law
As an example, if a car is travelling at a certain speed in a certain direction, it will continue to travel at that speed in the same direction unless it is acted upon by an unbalanced force such as friction in the brake mechanism, which will slow down the car. A person in the car will continue to move forward (in accordance with the first law) unless acted upon by a force; for example, the restraining force of a seat belt.
The second law
This can be demonstrated using a ticker timer and a trolley with mass that can be varied. If the mass is kept constant and the amount of force applied in pulling the trolley varies, then the dots on the ticker timer tape become further apart; the trolley is changing velocity and therefore accelerating. The acceleration (a) is proportional to the force (F) applied. This can be expressed as acceleration/force = a constant, or a/F = a constant.
If the force applied in pulling the trolley is kept the same (constant), and the mass placed on the trolley is varied (from low to high), then the dots on the ticker timer tape become closer together as the mass gets larger; the acceleration decreases as mass increases. This can be expressed as acceleration being inversely proportional to mass (m), or a  1/m.
The two equations can be combined to give an overall equation, expressing Newton's second law of motion. This is: force = mass × acceleration, or F = ma.
The third law
As an example, a book placed on a table will remain at rest. The force of gravity acting on the book pulls the book towards the ground. The table opposes the force (weight) exerted on the book by gravity. The table exerts the same amount of force in an upward direction. Hence the book remains at rest on the table.
non-renewable resource
Natural resource, such as coal, oil, or natural gas, that takes millions of years to form naturally and therefore cannot be replaced once it is consumed; it will eventually be used up. The main energy sources used by humans are non-renewable; renewable resources, such as solar, tidal, wind, and geothermal power, have so far been less exploited.
Fossil fuels like coal, oil, and gas generate a considerable amount of energy when they are burnt (the process of combustion). Non-renewable resources have a high carbon content because their origin lies in the photosynthetic activity of plants millions of
years ago. The fuels release this carbon back into the atmosphere as carbon dioxide. The rate at which such fuels are being burnt is thus resulting in a rise in the concentration of carbon dioxide in the atmosphere, a cause of the greenhouse effect.
seasonal affective disorder
SAD
Form of depression that occurs in winter and is relieved by the coming of spring. Its incidence decreases closer to the Equator. One type of SAD is associated with increased sleeping and appetite.
It has been suggested that SAD may be caused by changes in the secretion of melatonin, a hormone produced by the pineal body in the brain. Melatonin secretion is inhibited by bright daylight.
Research into winter sleep patterns 1994 showed that volunteers deprived of artificial light slept for part of the 14-hour winter nights, but also laid awake for as long as 5 hours at a time. During this period of quiet wakefulness their brainwaves resembled those produced during meditation. They felt more rested and energetic after these 'natural' winter nights. Hormone production was also affected with the volunteers secreting more growth hormone, prolactin, and melatonin. Both a shortage of sleep and a disruption in natural hormone production may contribute to SAD.
transpiration
Loss of water from a plant by evaporation. Most water is lost by diffusion of water vapour from the leaves through pores known as stomata to the outside air. The primary function of stomata is to allow gas exchange between the plant's internal tissues and the atmosphere. Transpiration from the leaf surfaces causes a continuous upward flow of water from the roots via the xylem, which is known as the transpiration stream. This replaces the water that is lost, and allows minerals absorbed from the soil to be transported through the xylem to the leaves. This is important because many plant cells need the minerals as nutrients.
A single maize plant has been estimated to transpire 245 l/54 gal of water in one growing season.
turbine
Engine in which steam, water, gas, or air is made to spin a rotating shaft by pushing on angled blades, like a fan. There are two sets of blades, the stator (does not rotate) and the rotor (does rotate). The rotating turbine shaft can be connected to an electricity generator. Turbines are among the most powerful machines.
Steam turbines are used to drive generators in power stations and ships' propellers; water turbines spin the generators in
hydroelectric power plants; and gas turbines (as jet engines) power most aircraft and drive machines in
industry.
The high-temperature, high-pressure steam for steam turbines is raised in boilers heated by furnaces burning coal, oil, or gas, or by nuclear energy. A steam turbine consists of a shaft, or rotor, which rotates inside a fixed casing (stator). The rotor carries 'wheels' consisting of blades, or vanes. The stator has vanes set between the vanes of the rotor, which direct the steam through the rotor vanes at the optimum angle. When steam expands through the turbine, it spins the rotor by reaction. The steam engine of Hero of Alexandria (130 BC), called the aeolipile, was the prototype of this type of turbine,
called a reaction turbine. Modern development of the reaction turbine is largely due to English engineer Charles Parsons. Less widely used is the impulse turbine, patented in 1882 by Carl Gustaf Patrick de Laval (1845–1913). It works by directing a jet of steam at blades on a rotor. Similarly there are reaction and impulse water turbines. Impulse turbines work on the same principle as the water wheel and consist of sets of buckets arranged around the edge of a wheel; reaction turbines look much like propellers and are fully immersed in the water.
In a gas turbine a compressed mixture of air and gas, or vaporized fuel, is ignited, and the hot gases produced expand through the turbine blades, spinning the rotor. In the industrial gas turbine, the rotor shaft drives machines. In the jet engine, the turbine drives the compressor, which supplies the compressed air to the engine, but most of the power developed comes from the jet exhaust in the form of propulsive thrust.
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