My Science School

The name anticyclone was first introduced by sir Francis Galton, the English meteorologist, in 1861 to describe weather conditions opposite to those of a cyclone. Anticyclones are characterized by fine weather and weak winds.

      In weather maps and climatic chances anticyclones appear as a region in which the pressure is higher than n its surroundings. So when the weather forecaster starts to talk about anticyclones you can be prepared for the weather to remain stable for some time, usually sunny and with occasional light rain.

      In a cyclone or low-pressure area the winds circulate anticlockwise in the northern hemisphere and clockwise in the southern hemisphere. Cyclones are usually areas of strong, violent winds and indicate bad weather.

Before man invented rulers and tae measures he often used his hands and feet to express the size of things. An old book published in 1561 says: “Fouregraines of barley make a finger; foure finger a hande; foure hands a Foote”.

     Today horses are still measured in hands. The measurement is taken from the ground to the withers, which is the highest part of the back lying between the shoulder blades.

A hand is reckoned to be four inches, the assumed width of a man’ palm. Formerly it was taken as equal to three inches, when a man’s hand was smaller.

    Early horses were probably around 12 hands (48 inches) at the withers, and one measuring 14 hands was exceptional. Some modern horses, however reach 17 hands and occasionally 20 had. A small horse under 14.2 hands is called a pony.

 

 

How can a train float in the air?

Some experimental trains have been made to float a few centimeters above the ground by using a system of electromagnetic coils embedded in the track. Electromagnetic force can also be made to propel these trains. They have no wheels, so there is very little friction to waste energy. This magnetic propulsion system, which is completely silent, is called magnetic levitation.

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Magnetic motors

One of the most important uses of magnets is electric motors, which are used to power machines ranging from small toys to enormous railway engines. Video and audio tape recorders also depend on magnetism. Their tapes contain tiny metal particles that are magnetized by the recording heads. When played back, another part of the head decodes the magnetic patterns. The hard drive and floppy disks in a computer work in a similar way.

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Is the Earth a magnet?

The Earth is actually a huge magnet, with a magnetic north and a magnetic south pole. These poles are not quite the same as the true geographical poles, and they wander about slightly. There is geological evidence that the magnetic north and south poles sometimes switch their positions completely. The reasons for the Earth’s magnetism are not really understood, but it is thought to be due to the movement of electrical charges around the Earth’s core, which is probably mostly made up of iron.

The Earth’s magnetic field extends out into space. The Sun and the other planets in the Solar System also have magnetic fields. Some distant stars are known to have exceptionally powerful magnetic fields.

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Why do some metals stick to magnets?

An ordinary magnet has two poles, which are usually referred to as the North Pole and South Pole. Similar (like) poles repel each other, while unlike poles attract each other. You can easily see this happening if you hold two magnets close together. The north pole of one magnet will stick firmly to the south pole of the other magnet, while any two similar poles will be forced apart.

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What is magnetism?

Electrical currents are able to influence other electrical currents, and this force is called magnetism. Permanent magnets are materials in which this magnetic effect occurs because of the natural movement of electrons. Magnetism can also be caused by the flow of an electrical current through wires. The magnetic force of a magnet can repel (push) or attract (pull) another magnet or magnetic material.

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What are silicon chips?

A silicon chip is a tiny wafer of silicon (a semiconductor) on which a complete electronic device can be produced. An image is produced photographically and etched onto the chip, but it differs from a printed circuit in some important ways. The chip is often microscopically small and contains huge amounts of ‘wiring’. More importantly, part of the process allows other devices to be produced in the manufacturing process, such as tiny resistors and capacitors. So a silicon chip, or integrated circuit, which measures just a few millimeters across, is a complete electronic device.

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What is a printed circuit?

Any modern electrical device requires a huge number of connections to join together all the small components needed for it to work effectively. At one time these connections were made by wires that had to be soldered together. The wires have now been replaced by the printed circuit, which is effectively a picture of the wiring that works just as well.

A thin sheet of copper is attached to a special board made of insulating material. An image of the electrical circuit is then printed photographically onto the copper sheet. Chemicals are used to dissolve most of the copper, leaving behind a thin film of metal bands, to which all the necessary components can be attached. This process can be carried out automatically.

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What are radio waves?

Radio waves form part of the electromagnetic spectrum. They are not part of the visible spectrum of light, and they have even longer wavelengths than infrared radiation. Radio waves with the longest wavelengths are bounced off a layer high up in the Earth’s atmosphere, called the ionosphere. In this way radio messages can be bounced for very long distances. Radio waves with shorter wavelengths penetrate the Earth’s atmosphere completely and can be used to communicate with spacecraft.

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How does radio communication work?

Radio signals are transmitted using a carrier wave. A radio transmitter changes, or modulates, this radio wave in order to convey information. In AM radio the height of the carrier wave is altered according to the sound picked up by a microphone. In FM radio the frequency, or distance between the peaks in the radio wave, is changed. The radio receiver picks up these signals and amplifies and decodes them. If the signal is weak, AM radio sounds crackly. It is now being replaced by FM radio, which gives much clearer reception.

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