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How And When Did The Earth Form?
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How old is
the earth? A baffling question indeed, but not for scientists
who doggedly persevered and came up with an answer. Using a
method called Radiometric dating,
scientists have claimed the age of the earth is an estimated
4.65 billion years.
Although the oldest earth rocks dated using the Radiometric
method are not quite four billion years old, meteorites, which
correlate geologically with the earth’s core, give dates of
about 4.5 billion years. Crystallization of the core and
meteorites are considered to have occurred at the same time,
some 150 million years after the earth and solar system first
formed. After executing the simple operation of addition, the
scientists worked out the age of the earth. |
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The
scientists also claim that the earth would have remained homogeneous
and relatively cool, after the original condensation and
gravitational attraction of cosmic dust and gas. However, continued
contraction of these materials caused them to get heated. The
radioactivity of some of the heavier elements also caused them to
get hot.
In
the next stage of its formation, as the earth became hotter, it
began melting under the influence of gravity. The melting caused the
differentiation into crust, mantle, and core. The lighter silicates
began moving up and outwards, forming the mantle and the crust. The
heavier elements, mainly iron and nickel, began to sink towards the
centre of the earth, forming the core of the earth.
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Even
as these were happening, because of volcanic eruptions, light,
volatile gases and vapors continuously escaped from the mantle and
crust. Some of these, mainly carbon dioxide and nitrogen, were held
by the earth’s gravity. They formed the primitive atmosphere. The
water vapor that condensed formed the first oceans.
In
the year 1995, scientists at the Carnegie Institute in the USA, said
that computer models of the earth’s inner core appear to show one
huge, remarkably aligned iron crystal. They seem to believe that the
atoms in the core are arranged in such a fashion that each atom is
packed with 12 neighboring atoms in a tightly packed hexagonal
structure. A crystalline inner core would also explain why shock
waves caused by earthquakes take about four seconds longer to go
from east to west through the earth than from north to south,
because the waves would travel more quickly with the “grain” than
across the “grain” of the crystal.
Scientists say that the surface of the earth has a negative charge
of electricity. Although the conductivity of air near the earth is
small, air is not a perfect insulator. Therefore, the negative
charge would drain off quickly, if it were not being continuously
replenished in some way. Negative charge is transferred to the earth
from thunder clouds, and the rate at which storms develop electric
energy is sufficient to replenish the surface charge. It has also
been noticed by scientists that the frequency of storms appears to
be greatest during the time of day when the negative charge of the
earth increases most rapidly. |
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