Big Bang Theory
Lesson:22 [Astronomy] THE EARTH AND SPACE bhattaraihemraj753@gmail.com
v
Big Bang theory:
The Big Bang theory is the prevailing
cosmological model for the universe from the earliest known periods through its
subsequent large-scale evolution.
The
universe was originated about 13.7 billion years ago according to big
bang theory.
v Cosmology: Cosmology is the study of the origin, evolution, and eventual
fate of the universe.
v Origin of Earth:
There are 2
major hypothesis about the origin of earth which are as follows:
i.
Origin
of solar system at very hot condition in a
very short period
ii.
Origin
of solar system at cold condition by very slow process
1.
Origin of solar system at very hot condition in a very short period
A .Planetesimal hypothesis:
There
are two planetesimal hypothesis given by different scientists at different
times.
i).
Old planetesimal hypothesis:[ Given by, George Buffon in 1949 AD]
According to this hypothesis, when the hot
gaseous of space is collided with a comet, some gas matters were thrown out
from main mass. Through condensation of thrown mass, planets, satellites and
other members are formed and sun is formed by from main mass. Finally, heavenly
bodies start to revolve around the sun due to gravity, hence solar system was
formed.
ii).
New Planetesimal hypothesis: [Given by,T.C. Chamberlin & F.R. Moulten in
1905 AD]
According
to this hypothesis, The comet was not struck by gaseous but it just passed
nearby it and forms two bulges at either sides. By condensation of bulge
materials it divided in to different
planets, satellites and other members and sun is formed by from remaining mass.
In such way solar system was formed.
B.
Nebular hypothesis:[ Given by, Immanual Kant in 1755 AD, corrected by Laplace
in 1796 AD]
According
to this hypothesis, in ancient time a very huge gaseous mass ball was spinning
on an axis. Later when it was cooled, more dense matters were collected and
forms a ring whereas, main body was separated form main mass. Such process was
repeated again and again and finally solar system was formed.
C.
Tidal hypothesis:[ Given by, Sir James Jeans & Sir Harold Jeffery in 1917
AD]
According
to this hypothesis, when comet was just passed nearby hot gaseous, a part of
mass was splitted out from it and planets, satellites and other members are
formed whereas, remaining mass formed sun. Hence solar system was originated.
2. Origin of solar system at cold condition by very slow process:
A.
Origin of solar system from milky way galaxy or dust cloud aggregation
hypothesis:[ Given by group of scientists,1944 AD]
According
to this hypothesis, due to force of gravity dust particles and gases found in
space got collected gradually which forms big lumps which pulled forcefully due
to such gravity. Between them temperature reached 107oC at
core which causes nuclear fusion there. Consequently, fused particles formed
sun and remaining particles forms members of solar system.
v Origin of life on Earth and its Evidences:
According
to scientists, the earth was originated about 4600 million years ago.
The first life was formed about 3800 million years was in water was 'bacterium'.
Paleontological study suggested that algae were found about 32000
million years ago. Human (Homo sapiens) was originated
about 2 million years ago who is youngest in universe. In this way
organic evolution exists from simpler to complex organisms.
Existence
of living beings on earth and evidences:
i.
Presence
of O2, N2 and CO2 in air.
ii.
Presence
of enough water on earth.
iii.
Presence
of suitable temperature on earth.
iv.
Presence
of nutrients in soil in which plants can grow well.
v.
Presence
of ozone(O3) layer in atmosphere which protects from UV rays.
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