Tnpsc group 1, 2, 4 syllabus material Nature Of Universe Part – 1

Introduction

In the earlier days, before the invention of astronomical instruments, people thought that Earth is the centre of all the objects in the space. This was known as the geocentric model, held by Greek astronomer Ptolemy (2nd Century), Indian astronomer Aryabhatta (5th Century) and many astronomers around the world.

Later Polish astronomer Nicolaus Copernicus proposed the heliocentric model (helios = Sun), with Sun at the centre of the solar system. Invention of the telescope in the Netherlands, in 1608, created a revolution in astronomy.  In this lesson, we will study about the building blocks of the universe, Kepler’s laws of motion, time period of satellites and  International Space Station (ISS).

Building block of the Universe

The basic constituent of the universe is luminous matter i.e., galaxies which are really the collection of billions of stars. The universe contains everything that exists including the Earth, planets, stars, space, and galaxies. This includes all matter, energy and even time. No one knows how big the universe is.

It could be infinitely large. Scientists, however, measure the size of the universe by what they can see. This is called the ‘observable universe’. The observable universe is around 93 billion light years

 (1 light year = the distance that light travels in one year, which is 9.4607 × 1012 km) across. One of the interesting things about the universe is that it is currently expanding. It is growing larger and larger all the time. Not only is it growing larger, but the edge of the universe is expanding at a faster and faster rate.

However, most of the universe what we think of is empty space. All the atoms together only make up around four percent of the universe. The majority of the universe consists of something scientists call dark matter and dark energy. 

Age of the Universe

Scientists think that the universe began with the start of a massive explosion called the Big Bang. According to Big Bang theory, all the matter in the universe was concentrated in a single point of hot dense matter. About 13.7 billion years ago, an explosion occurred and all the matter were ejected in all directions in the form of galaxies.

Nearly all of the matter in the universe that we understand is made of hydrogen and helium, the simplest elements, created in the Big Bang. The rest, including the oxygen, the carbon, calcium, and iron, and silicon are formed in the cores of stars. The gravity that holds these stars together generally keeps these elements deep inside their interiors. When these stars explode, these fundamental building blocks of planetary systems are liberated throughout the universe.

Galaxies

Immediately after the Big Bang, clouds of gases began to compress under gravity to form the building blocks of galaxies. A galaxy is a massive collection of gas, dust, and billions of stars and their solar systems. Scientists believe that there are one hundred billion (1011) galaxies in the observable universe. Galaxies are also in different shapes.

Depending on their appearance, galaxies are classified as spiral, elliptical, or irregular. Galaxies occur alone or in pairs, but they are more often parts of groups, clusters, and super clusters. Galaxies in such groups often interact and even merge together. Our Sun and all the planets in the solar system are in the Milky Way galaxy. There are many galaxies besides our Milky Way. Andromeda galaxy is our closest neighboring galaxy. The Milky Way galaxy is spiral in shape.

It is called Milky Way because it appears as a milky band of light in the sky. It is made up of approximately 100 billion stars and its diameter is 1,00,000 light years. Our solar system is 25,000 light years away from the centre of our galaxy. Just as the Earth goes around the Sun, the Sun goes around the centre of the galaxy and it takes 250 million years to do that.

The distance of Andromeda, our nearest galaxy is approximately 2.5 million light-years. If we move at the speed of the Earth (30 km/s), it would take us 25 billion years to reach it!

Stars

Stars are the fundamental building blocks of galaxies. Stars were formed when the galaxies were formed during the Big Bang. Stars produce heat, light, ultraviolet rays, x-rays, and other forms of radiation. They are largely composed of gas and plasma (a superheated state of matter). Stars are built by hydrogen gases.

Hydrogen atoms fuse together to form helium atoms and in the process they produce large amount of heat. In a dark night we can see nearly 3,000 stars with the naked eye. We don’t know how many stars exist. Our universe contains more than 100 billion galaxies, and each of those galaxies may have more than 100 billion stars.

Though the stars appear to be alone, most of the stars exist as pairs. The brightness of a star depends on their intensity and the distance from the Earth. Stars also appear to be in different colours depending on their temperature. Hot stars are white or blue, whereas cooler stars are orange or red in colour. They also occur in many sizes.

A  group of  stars forms an imaginary outline or meaningful pattern on the  space. They represent an animal, mythological person or creature, a god, or an object. This group of stars is called constellations. People in different cultures and countries adopted their own sets of constellation outlines. There are 88 formally accepted  constellations. Aries, Gemini, Leo, Orion, Scorpius and Cassiopeia are some of the constellations.

TNPSC TAMIL STUDY MATERIAL

10 std tamil study material

அன்னை மொழியே 

இரட்டுற மொழிதல் 

காற்றே வா

முல்லைப்பாட்டு 

காசிக்காண்டம் 

மலைபடுகடாம் 

பெருமாள் திருமொழி 

பரிபாடல் 

நீதி வெண்பா 

திருவிளையாடற்புராணம் 

பூத்தொடுத்தல் 

முத்துக்குமாரசாமி பிள்ளைத்தமிழ் கம்பராமாயணம் 

ஏர் புதிதா ? 

மெய்க்கீர்த்தி 

சிலப்பதிகாரம் 

ஞானம் 

காலக்கணிதம் 

சித்தாளு 

தேம்பாவணி 

9 std tamil study material

தமிழோவியம் 

தமிழ்விடு தூது 

பட்டமரம் 

பெரியபுராணம் 

புறநானூறு

மணிமேகலை 

ஓ , என் சமகாலத் தோழர்களே

உயிர்வகை 

குடும்ப விளக்கு 

சிறுபஞ்சமூலம் 

இராவண காவியம்

நாச்சியார் திருமொழி 

சீவக சிந்தாமணி 

முத்தொள்ளாயிரம்

மதுரைக்காஞ்சி 

ஒளியின் அழைப்பு 

தாவோ தே ஜிங் 

யசோதர காவியம் 

அக்கறை 

குறுந்தொகை 

8 std tamil study material

தமிழ்மொழி வாழ்த்து 

தமிழ்மொழி மரபு 

ஓடை 

கோணக்காத்தும் பாட்டு 

நோயும் மருந்தும் 

வருமுன் காப்போம் 

கல்வி அழகே அழகு 

புத்தியைத் தீட்டு 

திருக்கேதாரம் 

பாடறிந்து ஒழுகுதல் 

வளம் பெருகுக 

மழைச்சோறு 

படை வேழம் 

விடுதலைத் திருநாள் 

ஒன்றே குலம் 

மெய்ஞ்ஞான ஒளி 

உயிர்க்குணங்கள் 

இளைய தோழனுக்கு

7 std tamil study material

எங்கள் தமிழ் 

ஒன்றல்ல இரண்டல்ல 

காடு 

புலிதங்கிய குகை 

கலங்கரை விளக்கம் 

இன்பத்தமிழ்க் கல்லி 

ஒரு வேண்டுகோள் 

விருந்தோம்பல் 

வயலும் வாழ்வும் 

புதுமை விளக்கு 

அறம் என்னும் கதிர் 

மலைப்பொழிவு  

6 std tamil study material

காணிநிலம் 

அறிவியல் ஆள்வோம் 

மூதுரை 

துன்பம் வெல்லும் கல்வி 

ஆசாரக் கோவை 

கண்மணியே கண்ணுறங்கு 

நானிலம் படைத்தவன் 

கடலோடு விளையாடு 

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