The Universe
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Unit – 12
Universe.
4) Answer the following questions:
(a) What is the universe?
Answer: The vast area around us is called universe.
(b) State the Big Bang theory?
Answer: The Big Bang theory states that the universe is originated from the big expansion of a single atom. Before the explosion all forces in the universe considered to have unified as a single force before the explosion.
(c) Write the conclusion of Hubble’s study.
Answer: Hubble’s study concludes that every single atom and molecules making universe were close to each other in the past, which in turn means they were all at the same point a long time ago. Thus, Hubble study helps to confirm Big Bang theory.
(d) According to the Big Bang theory, the universe is continuously expanding. Is there no limitation to the expansion of the universe? explain your arguments.
Answer: From Big Bang theory there is no limitations to the expansion of the universe because, the particles scatter and move away from each other in the explosion of an explosive. other celestial bodies are moving far away from each other after the huge explosion of that dense atom. So the size of the universe is also increasing day by day.
(e) Write the importance of gravitational force in the position of celestial bodies in the universe.
Answer: The importance of gravitational force is that it hold the celestial body easily in the universe.
(f) Earth revolves around the sun, moon rotates around the earth. They have their force of gravity as well as the gravitational force between them, but they never collide with each other. clarify this with reasons. clarify this with reasons.
Answer: Because, earth moon and sun each have their own gravitational force which attract them each other like the earth is attracting
the Earth and due to it they never collide with each other.
(g) Explain the concept of a flat universe.
Answer: If the average density of the universe is equal to the critical density, then the expansion rate of the continuously expanding universe gradually decreases and, stops. Till then, there will be an infinite distance between each celestial body because of this they will not be affected by mutual gravitational force, such universe is called flat universe.
(h) In your opinion, what might be the future of the universe, open, flat or closed? explain your answer with suitable argument.
Answer: In my opinion the future of the universe will be open because, it states that the universe will expand forever which also state the Big Bang theory and Hubble’s study which is due to an massive explosion the particles of that atoms are constantly moving far from each other and have no limitation.
5) Differentiate between:
(a) Closed universe and open universe.
| Closed universe | Open universe |
|---|---|
| This theory suggests if the gravitational effect remains non zero when the speed of the celestial bodies becomes zero, the celestial will start to come closer and the universe will come to a single point. | This theory suggests if the celestial bodies retain same velocity when the gravity becomes zero, they will then continue to move away from each other forever and the size of the universe will continue to increase. |
| It will occur if the vast universe will of unlimited mass and energy. | It will occur if the average density of the universe is less than the critical density. |
(b) Flat universe and closed universe.
| Flat universe | Closed universe |
|---|---|
| If the average density of the universe is equal to critical density, then the expansion rate of universe will gradually stop. | If the gravitational effect remains non-zero when the speed of the celestial bodies become zero, then universe will come at the single point. |
| The size of universe is fixed. | In this the universe have fixed life span. |
3) Give reason:
(a) Celestial bodies continue to remain in their own place.
Answer: Because, gravitational force between the planets pull each which cause to remain in their own place.
(b) As the distance between celestial bodies increase their separating speed increases.
[No answer is written under this question in the supplied source.]
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