Category Forces of nature

By using acoustic or sound signals, the geologists identify the places where oil can occur on the Earth. They study these regions by looking in the rocky layers and taking samples at different depths. If the studies point to a deposit of oil, a hole is drilled in the ground in the hope of finding oil. Scientists believe that crude oil arose from the smallest sea organisms, the planktons. After dying, the planktons sank to the seabed and were covered with sand and sludge over a long period of time. Because of the high pressure exerted by this layer, the dead mass got converted into digested sludge, which gradually got converted into crude oil. Since oil is lighter than rock, it rose up and was held in pores of the rock, like water in a sponge. 

At places where crude oil is found, huge, hollow chisels drill several hundred metres deep in the Earth to reach the rocky layers containing oil. In some cases, the oil shoots out because of the pressure of the natural gas, which is found frequently with crude oil. Pumps are used to bring the oil to the surface if the pressure is not adequate. The oil is then transported to the big harbours with ships or through pipelines—hundreds of kilometres long. Sometimes it is also transported directly to a refinery, where it is processed further. 

Natural gas is a combustible gas or a gas that burns easily, which is formed in the same way as crude oil. Since natural gas is lighter than crude oil, it is often found above the deposits of crude oil, in the form of a cap. Methane is the main component of natural gas which is made up of different gases. Natural gas itself is colourless, odourless, and lighter than air and it burns at a temperature of approximately 600°C. It is offset with an artificial smell, faintly resembling that of rotten eggs. This warns us against the explosive gas when a gas pipeline leaks. 

Crude oil is a mixture of different substances and must first be ‘refined’ in a refinery—it must be broken down to its components. For this, it is heated at about 300°C in a distillation set-up. The individual substances evaporate at different temperatures. Petrol, used as fuel in many cars, becomes gaseous at temperatures between 35°C and 140°C, whereas diesel oil becomes gaseous at about 300°C. The different vapours are collected and cooled or liquefied. In this way, the individual components of crude oil are separated from one another and stored as diesel oil, kerosene, or petrol. 

Bats cannot see very well. To orient themselves during their night flights, they emit ultrasounds. We cannot hear these sounds. The ultrasonic waves falling on obstacles or preys get ‘reflected’ back and reach the sensitive ears of bats. Thus, they come to know what all is present around them and where their prey is. This concept is also used in shipping to determine the depth of the sea using a device called sonar. It comprises a sound transmitter, a receiver, and a clock. The time difference between sending and receiving sound waves is measured, which is used to calculate the depth of the sea. 

If you call out your name in the direction of a vertical, bare rocky wall, you will hear it again after some time. An echo comes because the sound waves are reflected back from the wall. When sound is produced in enclosed spaces, such as churches and gymnasiums, multiple reflections build up and blend together. This phenomenon is known as reverberation. 

Ultrasonic waves are those sound waves that are inaudible to our ears because they have a very high frequency. These energy-rich waves are used in many ways such as cleaning dental braces or spectacle glasses. Ultrasonic waves excite the liquid to vibrate so fast that it removes the dirt. Ultrasonic waves are also reflected from the inner organs of our body; thus, an echo is produced. This echo can be recorded and displayed by medical devices. In this way, doctors can safely monitor the development of a foetus inside the mother’s womb. 

As the police car approaches us, the pitch increases, and when it moves away from us, the pitch decreases. When the car approaches us, the sound waves of the siren are ‘compressed’ more towards us, resulting in higher pitch. When the car is moving away, the sound waves get stretched; as a result sound fades away. This effect can be noticed only by an outside observer; the driver hears the same pitch of sound at all times. This phenomenon is called the Doppler effect, which is named after its discoverer.

Jets that fly faster than sound compress the air at the front. This forms a head wave. After a certain point of time, the pressure of the air gets discharged like an explosion. As a result, a loud bang takes place and we hear a loud sound. However, ultrasonic sounds are not audible to us. Bats and other animals use ultrasonic waves for orientation. Sound always propagates in the form of waves. Because of this reason we notice a change in the pitch of the siren of the vehicle passing us.

There are two types of sensory cells present on our retina: rods and cones. At twilight more than 100 million rods permit us to distinguish between the colourless bright light and the dark. During the day around 6 million cones help us see a variety of colours. The eyes of dogs possess very few cones, which are sensitive only to blue and yellow. For this reason, dogs see the world differently from us. Even there are many people who are blind to red and green and cannot correctly distinguish between these two colours.