EARTH AND UNIVERSE
EARTH
Earth is the third planet from
the Sun and the only object in the Universe known to
harbor life. According to radiometric dating and other sources
of evidence, Earth formed over 4.5 billion years ago. Earth’s
gravity interacts with other objects in space, especially the Sun and
the Moon, Earth’s only natural satellite. Earth revolves around
the Sun in 365.26 days, a period known as an Earth year. During this
time, Earth rotates about its axis about 366.26 times.
LAYERS OF EARTH :
Crust
·
The solid crust is the outermost and thinnest layer of our
planet. The crust averages 25 miles (40 kilometers) in thickness and is divided
in to fifteen major tectonic plates that are rigid in the center and have
geologic activity at the boundaries, such as earthquakes and volcanism.
·
The most abundant elements in the Earth’s crust include (listed
here by weight percent) oxygen, silicon, aluminum, iron, and calcium. These
elements combine to form the most abundant minerals in the Earth’s crust,
members of the silicate family – plagioclase and alkali feldspars, quartz,
pyroxenes, amphiboles, micas, and clay minerals.
Mantle
·
Mantle material is hot (932 to 1,652 degrees Fahrenheit, 500 to
900 degrees Celsius) and dense and moves as semi-solid rock. The mantle is
1,802 miles (2,900 km) thick and is composed of silicate minerals that are
similar to ones found in the crust, except with more magnesium and iron and
less silicon and aluminum.
·
The base of the mantle, at the boundary with the outer core, is
termed the Gutenberg discontinuity. It is at this depth (1,802 miles, 2,900 km)
where secondary earthquake waves, or S waves, disappear, as S waves cannot
travel through liquid.
·
Scientists are utilizing seismic tomography to
construct 3-dimensional images of the mantle, but there are still limitations
with the technology to fully map the Earth’s interior.
Outer Core
The outer core is composed
mostly of iron and nickel, with these metals found in liquid form. The outer
core reaches between 7,200 and 9,000 degrees Fahrenheit (4,000 and 5,000
degrees Celsius) and is estimated to be 1,430 miles (2,300 km) thick. It is the
movement of the liquid within the outer core that generates Earth’s magnetic
field.
Inner Core
·
The inner core is the hottest part of our planet, at
temperatures between 9,000 and 13,000 degrees Fahrenheit (5,000 and 7,000
degrees Celsius). This solid layer is smaller than our Moon at 750 miles (1,200
km) thick and is composed mostly of iron. The iron is under so much pressure
from the overlying planet that it cannot melt and stays in a solid state.
·
The inner core is the hottest part of our planet, at
temperatures between 9,000 and 13,000 degrees Fahrenheit (5,000 and 7,000
degrees Celsius). This solid layer is smaller than our Moon at 750 miles (1,200
km) thick and is composed mostly of iron. The iron is under so much pressure
from the overlying planet that it cannot melt and stays in a solid state.
Lithosphere
The lithosphere is the
outermost layer of the Earth 100 km thick and is defined by its mechanical
properties. This rigid layer includes the brittle upper portion of the mantle
and the crust. The lithosphere is divided into 15 major tectonic plates, and it
is at the boundary of these plates where major tectonic occurs, such as
earthquakes and volcanoes. The lithosphere contains oceanic and continental
crust that varies in age and thickness across locations and geologic time. The
lithosphere is the coolest layer of the Earth in terms of temperature, with the
heat from the lower layers generating the plate movements. The term
“lithosphere” should not be confused with the use of “geosphere,” which is used
to indicate all of Earth’s systems, including the atmosphere, hydrosphere, and
biosphere.
Mesosphere
The mesosphere refers to the
mantle in the region under the lithosphere and the asthenosphere, but above the
outer core. The upper boundary is defined as the sharp increase in seismic wave
velocities and density at a depth of 660 kilometers (410 mi). This layer should
not be confused with the atmospheric mesosphere.
UNIVERSE
The
word universe derives from the Old
French word univers, which in turn derives from
the Latin word universum. The Latin word was used
by Cicero and later Latin authors in many of the same senses as the
modern English word is used.
·
The Universe is
all of space and time and their contents, including planets, stars, galaxies,
and all other forms of matter and energy. While the spatial size
of the entire Universe is still unknown, it is possible to measure
the observable universe.
·
Further observational improvements led to the realization that
our Sun is one of hundreds of billions of stars in a galaxy we call
the Milky Way, which is one of hundreds of billions (perhaps trillions) of
galaxies in the Universe. Many of these stars have planets. At the
largest scale galaxies are distributed uniformly and the same in all
directions, meaning that the Universe has neither an edge nor a center.
·
From studying the movement of galaxies, we know that the
universe contain much more matter than we can detect in usual ways.
This unseen matter is known as dark matter (dark means that
there is a wide range of strong indirect evidence that it exists, but
we have not yet detected it directly.
MILKY WAY GALAXY
·
The Milky Way is
the galaxy that contains our Solar System. The descriptive
“milky” is derived from the appearance from Earth of the galaxy – a band of
light seen in the night sky formed from stars that cannot be
individually distinguished by the naked eye. Galileo Galilei first
resolved the band of light into individual stars with his telescope in 1610.
Until the early 1920s, most astronomers thought that the Milky Way contained
all the stars in the Universe.
·
The Milky Way has several satellite galaxies and is
part of the Local Group of galaxies, which form part of
the Virgo Supercluster, which is itself a component of the Laniakea
Supercluster.
·
The constant rotation speed contradicts the laws
of Keplerian dynamics and suggests that much of the mass of
the Milky Way does not emit or absorb electromagnetic radiation. This mass
has been termed “dark matter”.
THE SOLAR SYSTEM :
·
We can see the Sun, Moon, and the five planets mentioned before
with Naked Eyes.
·
The Sun has Eight Planets, All Planets revolves around the sun.
·
The eight planets have been classified into Solid Planet and
Gaseous Planets. Mercury, Venue, Earth and Mars are called as Solid Planets.
While Jupiter, Saturn Uranus and Neptune are gaseous Planets.
DWARF PLANETS :
Pluto, Charon, Ceres, Eris were
newly grouped as “Dwarf Planets” in the year 2008. They also revolves around
the sun. They also revolve around the sun. They are very small in size. Their
Size is smaller than our Moon. So they are called DWARF
PLANETS.
ASTEROIDS :
Thousands of Asteroids are
found between Mars and Jupiter. Asteroids are Clusters of Celestial Bodies
which Includes tiny Stones and big rocks which can measure upto 300 to 400 km
in Diametre.
METEOROIDS :
The Sudden Streaks of light
seen on a starry night is called as METEOROIDS. This
can be seen when the remains of the rocky parts of the comets strike the
Earth’s atmosphere and streaks of light are generated. They are not stars that
fall down.
COMET :
·
It is exciting to see a comet in a Night Sky. A Comet is not a
star. It is a Rock made of Dust and Ice. The long tails is seen because, as the
comet comes near the sun, the ice melts and reflects the light of the sun.
·
The tail of the comet is seen in the opposite direction of the
sun. The tail of the comet appears because minute particles from the sun strike
the gaseous part emitted from the comet.
BLACK HOLE :
·
Black holes are not physically large regions of space. But when
you include their mass, they are among the top competitors for the largest things
in the universe. And quasar OJ287 is the largest black hole we’ve spotted.
·
It’s estimated to be 18 billion times the mass of our sun and is
a supermassive black hole located in the center of a galaxy. To put that in
perspective, it’s an object larger than our entire solar system. Just how big
can a black hole get? According to scientists, there is no theoretical upper
limit.
MOON :
·
The Moon is called by different names in Tamil. The moon is not
a Planet.
·
Moon does not revolve around the sun directly. It revolves
around the Earth. Hence it is called as a Satellite.
·
The Moon is the Satellite of the earth.
DARK MATTER :
·
Dark matter is a hypothetical kind of matter that is
invisible to the entire electromagnetic spectrum, but which accounts for
most of the matter in the Universe.
·
The existence and properties of dark matter are inferred from
its gravitational effects on visible matter, radiation, and
the large-scale structure of the Universe.
·
Other than neutrinos, a form of hot dark matter, dark
matter has not been detected directly, making it one of the greatest mysteries
in modern astrophysics. Dark matter neither emits nor absorbs
light or any other electromagnetic radiation at any significant
level. Dark matter is estimated to constitute 26.8% of the total mass–energy
and 84.5% of the total matter in the Universe.
DARK ENERGY :
·
Two proposed forms for dark energy are the cosmological
constant, a constant energy
density filling space homogeneously, and scalar fields such
as quintessence or moduli, dynamic quantities whose
energy density can vary in time and space.
·
Contributions from scalar fields that are constant in space are
usually also included in the cosmological constant. The cosmological constant
can be formulated to be equivalent to vacuum energy. Scalar fields having
only a slight amount of spatial in homogeneity would be difficult to
distinguish from a cosmological constant.
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