Science Trivia    Did You Know?

~ During the day the temperature of the land increases more quickly than that of the sea (because the specific heat capacity of the land is much smaller). The hot air above the land rises and is replaced by colder air from the sea. A breeze from the sea results.  At the night the opposite happens. The sea has more heat to lose and cools more slowly. The air above the sea is warmer than that over the land and a breeze blows from the land.

~ Dull black surfaces are better absorbers of radiation than white shiny surfaces – the latter are good reflectors of radiation. This is why buildings in hot countries are often painted white and why light colored clothes are cooler in summer. Also, reflectors on electric fires are made of polished metal because of their good reflecting properties.

~ The same note on different instruments sounds different; we say the notes differ in quality or timbre. The difference arise because no instruments (except a tuning fork and a signal generator emit a ‘pure’ note, i.e. of one frequency. Notes consist of a main or fundamental frequency, mixed with others, called overtones, which are usually weaker and have frequencies that are exact multiples of the fundamental. The number and strength of the overtones decides the quality of a note. A violin has more and stronger higher overtones than a piano.

~ They can often be seen on a hot day as a pool of water on the road some distance ahead. One explanation is that the light from the sky is gradually refracted away from the normal as it passes through layers of warm but less dense air near the hot road. Warm air has a slightly smaller refractive index than cool air and when the light meets a layer at the critical angle, it suffers total internal reflection. To an observer the reflection of the sky appears as a puddle in the road.

~ A shadow has two parts: the umbra (the darker part of a shadow) and the penumbra (the lighter part of a shadow). During a solar eclipse, the Moon blocks the Sun’s light and casts a shadow on Earth. Observers on Earth in the umbra see a total solar eclipse (all of the sun’s light is blocked), while those in the penumbra see a partial solar eclipse (part of the Sun’s light is blocked) and those outside the shadow see no eclipse.

~ The moon has a diameter of 2,173 miles (3,476km) while the Sun has a diameter of 870,000 miles (1.39 million km).

~ Toothed whales, such as killer whales and sperm whales, are said to “see” with their ears because they send out sharp clicking sounds. These sounds reflect off objects such as fish and return to the whale. The time it takes for the sound to go out and come back is called the echo time. If the echo time is long, the whale knows the fish are are far away. This process of finding the direction and distance of objects by the sounds reflected from them is called echolocation.

~ Insects like grasshoppers and crickets use parts of their body to produce sound. These insects make sounds by rubbing two body parts, usually one sharp-edged and the other rough or fire-like, against each other. This process is called stridulation.

~ One can determine the gender of a cricket by examining its abdomen. Every cricket has two feelers on its hind end, but the female has a third tube. It looks sort of like a stinger, but it is not. It is an egg-laying tube called ovipositor.

~ Bananas and other fruit, such as apples and pears, discolor when bruised or peeled and exposed to air. This discoloration is cased by changes that occur when the cells are broken. The chemicals released by the damaged cells are oxidized (combined with oxygen), resulting in changes in the fruit. This process is called oxidation.

~ All things would fall on Earth at the same rate of 32 feet per second squared (9.8ms-2) if there was no air pushing on them. But air molecules in the Earth’s atmosphere push against falling objects and slow their falling rate. Heavier objects, such as a coin, push through the air with more force than do lightweight objects, such as paper. The air pushing on the lightweight paper lifts and slows its falling rate. Thus, heavier objects fall through air faster than do lightweight objects.

~ Electricity usually comes to our homes by a cable containing two wires, the live (L) and the neutral (N). The neutral is earthed at the local sub-station and so is at zero potential.

~ Earthing and Safety: sometimes power sockets, especially those in places like kitchens and garages where water may be present, have a third connection, called earth. The earth connection of sockets is joined to a metal water pipe in the house or to an earth connection on the supply cable. It is a safety precaution to prevent electric shock in case an appliance develops a fault. The earth pin, on a three-pin plug, is connected to the metal case of the appliance, which is thus joined to earth by a path of almost zero resistance. If then, for example, a live wire breaks or sags and touches the case, a large current flows to earth and ‘blows’ the fuse. Otherwise, the case becomes ‘live’ and anyone touching it receives a shock, which might be fatal, especially if they were ‘earthed’ by, say, standing on a concrete floor or holding a water tap.

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