Page 17 - Geography for Secondary Schools Student’s Book Form One
P. 17
Geography for Secondary Schools
Student’s Book Form One
FOR ONLINE READING ONLY
Figure 2.1: Origin of the Earth in the universe
https://www.reddit.com.space for decades of astronomy
Some of the assumptions that explain rotation increased. This caused the cloud to
about the origin of the Earth include the flatten, and created an accretion disk. Matter
Big Bang theory, Nebula hypothesis, Inter- continued to collect as the force of gravity
stellar dust hypothesis, and the Creation toward the centre increased. Eventually, the
theory. However, various critiques have gas warmed from increasing pressure. As
emerged against these theories, and the mass further increased, also the gravity
hypotheses, though they remain important increased, and the temperature continued to
for understanding the evolution of the rise. A ball of hot gas formed in the centre
universe and the planet Earth in particular. of accretion disk, creating a protostar, also
known as the Sun.
Nebular hypothesis Finally, when enough gas gathered in
This is an hypothesis that explains about the centre of the protostar, the pressure
the origin of the Earth. The hypothesis was generated enough heat to fuse the atoms
proposed by Immanuel Kant in 1755. This to form a star. Outside the star, matter was
hypothesis states that solar system was forming into clumps of gas, dust and rocks,
formed from cold spinning cloud of gases which created protoplanets that are believed
called the Solar nebular. It resulted from to give rise to the planets. The theory was
uneven distribution of gases throughout modified by Pierre Laplace in 1796. The
the universe in the Milky Way Galaxy. As critiques of the theory were put forward by
the gravitational pull began to condense Pierre Laplace who challenged Immanuel
the gas towards the centre, the speed of the Kant through the following: large amount of
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