Category: Science Dictionary

ångström (Å) : A unit of length primarily used to measure subatomic particles that is equal to 10⁻¹⁰ meters (one ten-billionth of a meter) or 0.1 nanometers.

Xylophone: A musical instrument made of wooden slats graduated so as to make the sounds of the scale when struck with a small drumstick-like hammer.

Worker ants: All worker ants are females and live about 1-4 years. They are the smallest, but they do the most work. They care for the queen and her eggs. Worker ants build and repair the nest, search for food and fight off enemies.

Work: Work is defined as the result of applying a force to an object in order to move it a certain distance.

Windmill: A windmill is a machine which converts the energy of wind to rotational motion by means of adjustable vanes or blades.

Wind vane: A mechanical device attached to an elevated structure. It rotates freely to show the direction of the wind.

White light: Light, having a mixture of frequencies, being perceived as having no specific colour, such as sunlight or a white-coloured light or lamp.

Weather forecast: A prediction of future weather, often for a specific locality, in a newspaper or on the radio or television.

Watts: The watt is a derived unit of power in the International System of Units (SI), named after the 18th-century Scottish engineer James Watt. One watt is the amount of energy used in one second by one ampere current under a voltage potential of one volt.

Water vapour: Water in its gaseous state, produced from liquid water by evaporation. Its presence in the atmosphere contributes to humidity.

Water turbine: A water turbine is similar to a waterwheel and is a device that uses falling or flowing water to create energy. There are a set of paddles or rotors mounted around the wheel. The force of the water moves the paddles, causing the wheel to turn. The wheel then transmits power to a shaft.

Water pressure: The force exerted by water that has been compressed.

Vortex: A vortex is the spinning flow of any fluid. The motion of the fluid swirling rapidly around a centre is called a vortex. A powerful circular current of water is referred to as a whirlpool.

Von Frey: Max von Frey was a German physiologist, best known for his investigations into the sensations of pain and touch. Born in 1852, he is known to have established that the skin has separate spots for cold, warmth, touch and pain. Von Frey used a set of hairs, carefully graded from ‘soft’ to ‘stiff’ in experiments investigating physical senses which became known as ‘Von Frey’s hairs’ or a ‘Von Frey device’.

Volt: The volt (symbol: V) is the SI derived unit of electromotive force, commonly called “voltage”. A unit of potential equal to the potential difference between two points on a conductor, carrying a current of 1 ampere when the power dissipated between the two points is 1 watt; equivalent to the potential difference across a resistance of 1 ohm when 1 ampere of current flows through it.

Volcano: A rupture in the earth’s or another planet’s crust through which molten lava and gases erupt.

Vitamin E: A fat-soluble vitamin that is essential for normal reproduction; an important antioxidant that neutralizes free radicals in the bodies of plants, animals and humans.

Vitamin C: Vitamin C, also known as ‘ascorbic acid’, is a water-soluble nutrient essential for life, synthesized by most animals and plants, but not humans, although used in our bodies for many purposes. It is plentiful in citreous fruits and many vegetables. A vitamin C deficiency causes a disease called scurvy.

Viscosity: The resistance of a liquid to shear forces and hence its ability to flow. For example: Water or alcohol has a low viscosity while oil or honey has a high viscosity.

Venation: The arrangement of veins in a leaf.

Variable resistor or ‘Rheostat’: An electrical resistor, with two terminals, whose resistance are continuously variable by moving a knob or slider and correspondingly decrease or increase the current flowing.

Umbra / Penumbra: The umbra, penumbra and antumbra are the names given to three distinct parts of a shadow, created by any light source. The umbra is the area of total darkness in a shadow caused by an eclipse, while the penumbra is a fringe region of partial shadow around an umbra.

Turbulent: he unstable flow of a liquid or gas.

True North: True north is the direction along the earth’s surface towards the geographic North Pole.

Triceps: The upper arm muscles used for extending the elbow.

Transmission: A transmission, also called a ‘gearbox’, is a set of gears that provides speed and torque conversions from a rotating power source to another device using gear ratios.

Totality: The period during a solar eclipse when the Sun is completely blocked by the Moon.

Torque: Torque, also called ‘moment’ or ‘moment of force’, is the tendency of a force to rotate an object about an axis, fulcrum, or pivot. Just as a force is a push or a pull, a torque can be thought of as a twist.

Tornado: A destructive windstorm occurring over land, characterized by a funnel-shaped cloud extending toward the ground.

Time: We think of time as the ways in which we measure the passing of time, such as a clock or watch, or perhaps a measured interval of time such as an hour or minute.

Thermodynamic: Thermodynamics is the study of heat. In science, thermodynamics is the study of energy conversion between heat and mechanical work.

Thermal insulator: A method or material used to help prevent or reduce the flow of heat.

Theory of Relativity: Einstein’s ‘Theory of Relativity’ is seen as one of the most important scientific advances of modern time. Einstein recognized that the speed of light in a vacuum is constant, and an absolute physical boundary for objects in motion. For objects travelling near light speed the theory of relativity states that: objects will move slower and shorten in length from a point of view on Earth. Einstein derived the famous equation, E = mc2, which means that Energy is equal to Mass times the speed of light squared. In simpler terms, it states that there is equivalence between mass and energy.

Theory of Relativity: Einstein’s ‘Theory of Relativity’ is seen as one of the most important scientific advances of modern time. Einstein recognized that the speed of light in a vacuum is constant, and an absolute physical boundary for objects in motion. For objects travelling near light speed the theory of relativity states that: objects will move slower and shorten in length from a point of view on Earth. Einstein derived the famous equation, E = mc2, which means that Energy is equal to Mass times the speed of light squared. In simpler terms, it states that there is equivalence between mass and energy.

Terminal velocity: An object is moving at its terminal velocity if its speed is constant due to the restraining force exerted by the air, water or other fluid through which it is moving.

Temperature: Temperature is the measure of the average kinetic energy of the particles in a substance, which is related to how hot or cold that substance is.

Taste buds: Taste buds are receptors for taste. They are located around the upper surface of the tongue, soft palate, and throat.

Sympathetic resonance: Sympathetic resonance is a harmonic phenomenon wherein a formerly passive string or vibratory body responds to external vibrations to which it has a harmonic likeness.

Symmetrical: Involving or exhibiting symmetry; proportional in parts; having its parts in due proportion as to dimensions; as a symmetrical body or building

Surface tension: A property of liquids in which the exposed surface tends to contract to the smallest possible area, as in the formation of a meniscus. It is caused by unequal molecular cohesive forces near the surface.

Supersaturated: A solution that contains more than the maximum amount of solvent that can normally be dissolved in a given amount of solvent at normal ambient temperature.

Supercontinent: A supercontinent is a landmass comprising more than one continental core, or craton.

Suet:  Animal fat mixture. Woodpeckers are attracted to suet hung in bags from trees.

Submarine: A vessel that is capable of operating submerged under water or below the sea. Also called a ‘sub’ for short.

Stomata: Tiny pores on the underside of plant leaves. Carbon dioxide, oxygen and water enter and leave the plant through these tiny pores.

Stethoscope: A stethoscope is a medical device that doctors use for listening to sounds inside the body like breathing or a heartbeat.

Stereoscopic vision: The single perception of a slightly different image from each eye, resulting in depth perception.

Steganography: The art and science of writing hidden messages in such a way that no one, apart from the sender and intended recipient can see or read it.

Static electricity: Static electricity refers to the build up of electric charge on the surface of objects.

Starch: Starch is a carbohydrate consisting of a large number of glucose units joined together. Food rich in natural starch is potatoes, rice and bread

Spores: A spore is a reproductive structure that is adapted for spreading and surviving for extended periods of time in unfavourable conditions similar to a plant seed.

Sphere: A sphere is a perfectly round geometrical object in three-dimensional space, such as the shape of a ball.

Speed of light: The speed at which light travels in a vacuum; the constancy and universality of the speed of light is recognized by defining it to be exactly 299,792,458 meters per second. Einstein’s ‘Theory of Relativity’ implies that nothing can go faster than the speed of light and only objects without mass can travel at this speed.

Spectrum: The portion of the electromagnetic spectrum that is visible to the human eye. Electromagnetic radiation in this range of wavelengths is called visible light or simply light. A typical human eye will respond to wavelengths from about 390 to 750 nm.

Sound resonance: Soundwaves hitting and bouncing back on the walls of a container in which it travels. The soundwaves are reinforced or enriched by the added sound vibrations.

Sound conductor: A material helping to pass on sound waves.

SOS Signal: SOS (Save Our Souls) is the best known international distress signal. Everyone should be familiar with SOS. The SOS signal can be transmitted by any method, visual or audio. The code for SOS is 3 short, 3 long and 3 short signals. Pause. Repeat the signal.

Sonar: Ships and Submarines often use Sonar to communicate and find their way. Sonar stands for: Sound Navigation & Ranging.

Solar energy: Energy from the sun that is converted into thermal or electrical energy.

Solar: Relating to, or derived from the sun or utilizing the energies of the sun.

Soil-burrowing insects: Insects or bugs that live in soil and come out at night when it is dark to consume plants.

Sodium thiosulfate: Also called ‘hypo’ by photographers, is used to stop development of exposed film and is the last stop for a print before it is rinsed. Thiosulfate converts undeveloped silver bromide grains in the film into water-soluble silver thiosulfate complexes that can be removed when the film is washed.

Soap bubble: A soap bubble is a very thin film of soapy water that forms a sphere with a sparkling surface.

Snow: Snow is a type of ‘rain’ within the earth’s atmosphere in the form of ‘crystal-like’ ice water, consisting of many snowflakes that fall from clouds.

Snellen chart: A chart with letters and numbers in lines of decreasing size; used to test visual acuity

Smoke: A hot vapour containing fine particles of carbon being produced by combustion

Siphon: A tube running from the liquid in a container to a lower level outside the container so that atmospheric pressure forces the liquid through the tube.

Sidereal day: The exact time for one complete rotation of the earth relative to a particular star. A sidereal day is about 4 minutes shorter than a mean solar day. Astronomers use sidereal time as a way to keep track of the direction in which their telescopes need to be pointed to view any given star in the night sky. A sidereal day is about 1436.07 minutes.

Sheet erosion: Relatively even erosion of a layer of soil without channel formation and generally takes place on sloping land.

Shadow clock: An ancient time telling device consisting of a straight base with a raised crosspiece at one end, which uses the length of the sun’s shadows because of its position, in relation to a specific location on earth, to tell the time.

Semi-permeable: It allows certain things to pass through while blocking others.

Seismograph: A device that is used to accurately record the motion of the ground during an earthquake.

Scurvy: A deficiency of ‘Vitamin C’. Symptoms include nausea, weakness, loss of hair and teeth, and eventual death. It is caused by a lack of fruits and vegetables in the diet. More sailors at sea died of this than any other cause.

Saturated: A ‘saturated’ solution is the most concentrated solution possible at a given temperature. The solution is unable to dissolve still more of a specific substance.

Samuel Morse: Samuel Finley Breeze Morse was born in Charlestown, Mass. on 27th April 1791. He was a professional artist, inventor of the electric telegraph and the originator of ‘Morse’ Code. Morse is remembered for his Code, still used, and less for the invention that enabled it to be used, probably since landline telegraphy eventually gave way to wireless telegraphy.

Salivary gland: Any of three pairs of glands in the mouth and digestive system that secrete saliva for food digestion.

Saliva: Saliva, also known as spit, or slobber, is the watery substance produced in the mouths of humans and most other animals by the salivary glands. The saliva moistens the mouth and starts the digestion of starches in the mouth.

Rust: A red or brown oxide coating on iron or steel caused by the action of oxygen and moisture. Rusting is the common term for the ‘corrosion’ or the disintegration of a material into its constituent atoms, due to chemical reactions with its surroundings.

Rudder: A rudder is a device (vane) used to steer a ship, boat, submarine, hovercraft, aircraft, or other vessel that moves through a fluid (generally air or water).

Rotor: A rotating mechanism, consisting of an assembly of rotating airfoils, that extracts energy from a fluid or air flow and converts it into useful work.

Rocket: A rocket is a vehicle or object which obtains thrust by ejecting a jet of fast moving fluid exhaust from a rocket engine.

Richter scale: A logarithmic scale, invented in 1935 by United States geophysicist Charles Richter, for representing the energy released by earthquakes. A figure of 2 or less is barely perceptible, whereas an earthquake measuring over 5 may be destructive, and 8 or more is a major earthquake.

Rheostat: An electrical resistor, with two terminals, whose resistance are continuously variable by moving a knob or slider and correspondingly decrease or increase the current flowing.

Retina: A delicate, multilayered, light-sensitive membrane lining the inner eyeball and connected by the optic nerve to the brain.

Respiration: Respiration (or just breathing) is defined as the transport of oxygen from the outside air to the cells within tissues, and the transport of carbon dioxide in the opposite direction.

Resonance: Sympathetic resonance is a harmonic phenomenon wherein a formerly passive string or vibratory body responds to external vibrations to which it has a harmonic likeness.

Resistance: A material’s opposition to the flow of electric current. Resistance is measured in ‘ohms’.

Relay: A mechanical relay is an electromechanical device that closes contacts to complete a circuit or opens contacts to interrupt a circuit. A solid state relay is a switching device that completes or interrupts a circuit electrically and has no moving parts.

Relative humidity: This is the ratio of the amount of water in the air at a given temperature to the maximum amount it could hold at that temperature. Relative humidity is expressed as a percentage.

Refraction: The change in direction of a propagating wave (light or sound) when passing from one medium to another

Refracting telescope: A telescope in which a large biconvex lens causes light rays to converge to a focus, forming an image magnified by a biconvex eyepiece. A telescope is a device used to magnify distant objects.

Reflex: A reflex action, also known as a reflex, is an involuntary and nearly instantaneous movement in response to a stimulus.

Reflectivity: The fraction of radiant light that is reflected from a surface.

Rayleigh scattering: The elastic scattering of light or other electromagnetic radiation by particles much smaller than the wavelength of the light. Named after English physicist Lord Rayleigh.

Rainbow: An arc of coloured light in the sky caused by refraction of the sun’s rays by rain.

Rain gauge: An instrument meteorologists use to measure the amount of rainfall.

Radio: An electronic receiver that detects and demodulates and amplifies transmitted signals.

Radiation: The act or process of radiating; the radiation of heat and light from a fire.

Queen ants: The queen ant is the only ant that is capable of laying eggs and this is also her main role in an ant colony. She is brought food and is cleaned by workers ants and they also tend to the eggs that she lays. The queen ants do not make any decisions about the colony, the decisions are carried out by the entire colony.

PV (Photovoltaic) Panels: Man-made cells that are comprised of semiconductors, materials that are able to absorb light energy, arranged in a panel form to produce electric power