Ch 2. The Origin And Evolution Of The Earth Flashcards
Who proposed Nebular Hypothesis and in which year and who revised it in 1796 ?
Proposed by German philosopher Immanuel Kant in the year 1755. Revised by mathematician Laplace in 1796
What does Nebular Hypothesis state ?
Kant argued that gaseous clouds – nebulae, which slowly rotate, gradually collapse and flatten due to gravity and eventually form stars and planets
Binary Theory / Planetesimal Hypothesis was given by ____ and ____ in the year ____
By Chamberlain and Moulton in 1900
What is Planetesimal Hypothesis / Binary Theory ?
According to this theory, a star collided with the Sun. As a result, a cigar shaped matter separated from the Sun. After the star moved away, the separated material gradually formed into planets.
Who gave the Revised Nebular Hypothesis and in which year ?
By Otto Schmidt of Russia and Carl Weizascar of Germany in 1950
What is Revised Nebular Hypothesis ?
The friction and collision of Hydrogen and Helium particles around the Sun helped in the creation of a disc shaped cloud and the planets formed by the process of accretion
Who proved Universal expansion and in which year ?
Proved by Sir Edwin Hubble in 1920
What is the Big Bang Theory / Expanding Universe Theory ?
A violent explosion of Singularity took place over 13.8 billion years ago from which the universe is formed and is still expanding
What is Steady State Theory ?
It asserts that new matter continually should be made to keep a constant density in the Universe
What is Cosmic Microwave Background (CMB) ?
The leftover electromagnetic radiation from the Big Bang, or the time when the universe began
What is a light year ?
The distance covered by light in one year (speed of light is 3 lakh Km/sec)
1 light year = 9.46 ×10^12 km
What is the average diameter of the stars ?
80,000 - 1,50,000 light years
What is a Cosmic year / Galactic year ?
250 million years
A cosmic year is the time needed for the solar system to revolve once around the centre of the Milky Way Galaxy.
When did the stars form in the Universe ?
Around 5-6 billion years ago
What is a Planetesimal ?
A minute planet; a body which could come together with many others under gravitation to form a planet.
Nebula of our solar system started to collapse about ____ billion years ago
5-5.6 billion years ago
Who gave the dumb-bell shape theory of the Moon formation ?
Sir George Darwin in 1838
What is Giant Impact hypothesis / Big splat hypothesis ?
An enormous body which is one to thrice the size of Mars slammed into the Earth not long after its development and shot a huge bit of the Earth into space which later became the Moon
When was Moon formed ?
4.4 billion years ago
What is Degassing ?
Ejection of gases from the inside of the Earth
When was Hydrosphere on Earth formed ?
4000 million (4 billion) years ago
Life on Earth started as unicellular creatures ____ million years ago
3800 million (3.8 billion) years ago
Name different layers present inside the Earth
Crust, Mantle, Outer core and Inner core
When was Photosynthesis evolved on Earth
About 2500 - 3000 million (2.5 - 3 billion) years ago
Oxygen content increased in the atmosphere ____ million years ago
2000 million (2 billion) years ago
