Friday January 19, 2018
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# Explained: Physics related to everyday life

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By Aakash Sinha

When I was a child, many unusual questions used to trigger my mind, some I got the answers and rest are still unexplored. Human is a social animal with brains. We have got a special ability, we can reason. In our day-to-day life, we come across several stuff which we accept it without knowing the cause of that activity. But the question is why? How?

In this article, we will see the reason behind some of the activities that we see every day but never questioned about it.

Why the wheels of any vehicle are circular?

• Quite interesting! I noticed it when I was 12 years old. Well, everyone uses a cycle, bike or a car, watching the wheels every day. But, why can’t the wheels be rectangular or square? Why circular? There is the force that opposes every force called friction force. We can walk, run & stop; all due to this force. Wheels of the automobiles are made circular to reduce the frictional force. On a circular body, rolling friction acts which is less than the sliding friction (a type of friction that acts on all bodies other than circular) which is responsible for the wheels to be circular. If wheels would have some other shape, sliding friction would come into picture increasing the resistance in movement of automobiles.

Why tube light blinks before turning ON?

• Every day we come across this phenomenon but the reason remains unnoticed. A tube light has a low-pressure mercury vapour with a phosphorous coating, white in colour which we can see from our eyes. When the tube light is turned ON, it flickers. That flicker is caused because the gas inside the lamp is relatively cold and cannot establish glow discharge between the two electrodes. Once the heat is developed, gas ionizes and gives out the ultraviolet light enabling the phosphorous coating to glow.

Why the moon looks bright yellow at night?

• Moon is connected to humans involving different emotions and expressions. Moon does not have its own light. It is just an illusion. Then, how does it shine? That bright colour of the moon is due to the reflected light from Sun which bounces off the dark grey and bumpy surface of the celestial body, falling on our eyes. The shocking fact is that only 3% to 12% of light is reflected from the surface of the moon but still the brightness is more than a star. We can see the moon during day time but we can’t see the stars.

Why do stars twinkle at night?

• Twinkle- Twinkle little star….. The poem taught to every child always tickled my mind when I was 16. Our Earth atmosphere is very turbulent and made up of different layers of air moving in all directions at different intensities. Light from the stars travel a very long distance before falling on our eyes. When it passes through the atmosphere, it bends due to refraction which makes it appear to twinkle. The Scientific name of the twinkling of stars is ‘astronomical scintillation’. Thank God! The poem was not written by a scientist.

Why the sky is blue in colour?

• The rays of the sun are made of 7 colours (Violet, Indigo, Blue, Green, Yellow, Orange, and Red). As the white light passes through Earth’s atmosphere, it collides with particles of air. The different colours or wavelengths of light are scattered by this collision by different amounts. Blue light (shorter wavelength) is scattered more than red light (longer wavelength).When sun is high in the sky, blue light is scattered in all directions and sky appears blue.

How water comes inside the coconut?

• Clusters of coconut palms thrive on seashore outside the tidal zone provided there should be a plenty of subterranean fresh water. As the fresh water accumulated by the roots is conveyed right up to the crowns of the coconut palms through osmosis process, any dissolved salts which exist in that water is eliminated through natural filtration. The water inside the coconut is actually ‘endosperm’ or the food or the nourishment for the coconut’s growth. As the coconut ripens the water becomes less pleasant to drink.

How does water come on Earth?

• After the big bang almost 13.8 billion years ago, the energy that sparkled in the Milky Way galaxy lead to the formation of Earth. That time Earth was boiling at a very high temperature. The water we have today came into existence much after the formation of the blue planet (Earth). Comets and asteroids can contain ice. The collision of wet comets and asteroids is responsible for the existence of life-giving liquid, “water” on Earth. The study shows that meteorites from Vesta (a group of meteors near to Jupiter) have the same chemical makeups (rocks) as that of our Earth. The mystery is not yet solved, but suspects’ asteroids.

How a program recorded in a studio reaches our Television sets?

• We enjoy watching different programs on T.V but we never think of the engineering behind the telecasting of any program. There are three divisions of a Television station:-
• Studio
• Earth Station
• Transmitter

A studio is the action area of artists where they perform any act. When the program is recorded it is sent to the Earth Station via cables. Earth station is a terrestrial terminal station designed to uplink and downlink data (programs) to and fro from the satellite. Once the program is uplinked to the satellite it can be viewed in any part of the country using the transmitter and receiver unit (at home, DTH). The program is downlinked at a T.V tower unit, then the different frequency is embedded for different programs (for DD News= 224.5MHz) in the form of electromagnetic waves. These waves are then transmitted in the air through an antenna. Now the same frequency is identified by the T.V receiver, it decodes it and we can see the desired program.

Have you ever noticed the direction of your DTH antenna?

• Once I was standing on the terrace, I observed that all the antenna of DTH is pointing towards the same direction. I was amazed. That dish antenna points towards the satellite of the country from where it can receive the signals (Radio frequency). In India, every dish antenna points towards South-East.

We cannot solve the problems with the same thinking we used when we created them – ALBERT EINSTEIN

Aakash is a student of engineering at Sir M. Visvesvaraya Institute of Technology, Bangalore. Twitter @aakashsinha1994

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# Astronomers building small space telescope to explore nearby stars

The telescope uses a mirror system with coatings optimized for ultraviolet light. Together with the camera, the system can measure very small changes in the brightness of M dwarf stars to carry out the primary science of the mission.

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• Astronomers are building a space telescope to study the nearby stars.
• the telescope will be small along with a camera attached to it.
• Studying these nearby stars will help astronomers help study the way planets orbit around the stars.

Astronomers are in the process of building a small space telescope to explore the flares and sunspots of small nearby stars to assess how habitable the space environment is for planets orbiting them.

The telescope with a diameter of 9 centimetres, or 3.6 inches, will be fitted on a spacecraft known as the Star-Planet Activity Research CubeSat, or SPARCS to be launched in 2021, to focus on stars that are small, dim and cool by comparison to the sun.

These stars — known as M dwarfs — are less than half the sun’s size and temperature and they shine with barely one per cent of its brightness.

The telescope will be built alongside a camera with two ultraviolet (UV)-sensitive detectors to be optimised for observations using UV light, which strongly affects the planet’s atmosphere and its potential to harbour life on the surface.

“People have been monitoring M dwarfs as best they can in visible light. But the stars’ strongest flares occur mainly in the ultraviolet, which Earth’s atmosphere mostly blocks,” said Evgenya Shkolnik, Assistant Professor at the Arizona State University.

Although the orbiting Hubble Space Telescope can view stars at ultraviolet wavelengths unhindered, its overcrowded observing schedule would let it dedicate only the briefest of efforts to M dwarfs.

The telescope uses a mirror system with coatings optimized for ultraviolet light. Together with the camera, the system can measure very small changes in the brightness of M dwarf stars to carry out the primary science of the mission.

M dwarfs are exceedingly common that they make up three-quarters of all the stars in our Milky Way galaxy as well as nearly 40 billion rocky planets in habitable zones around these stars, meaning that most of the habitable-zone planets in our galaxy orbit M dwarfs.

Capturing lengthy observations of M dwarfs will let astronomers study how stellar activity affects planets that orbit the star. IANS