• Earth, along with the other planets, is believed to have been born 4.5 billion years ago as a solidified cloud of dust and gases left over from the creation of the Sun. • For perhaps 500 million years, the interior of Earth stayed solid and relatively cool, perhaps 2,000°F. • The main ingredients were iron and silicates, with small amounts of other elements, some of them radioactive. • As millions of years passed, energy released by radioactive decay—mostly of uranium, thorium, and potassium—gradually heated Earth, melting some of its constituents. • The iron melted before the silicates, and, being heavier, sank toward the center. • This forced up the silicates that it found there. • After many years, the iron reached the center, almost 4,000 mi deep, and began to accumulate. No eyes were around at that time to view the turmoil that must have taken place on the face of Earth—gigantic heaves and bubblings on the surface, exploding volcanoes, and flowing lava covering everything in sight. • Finally, the iron in the center accumulated as the core. Around it, a thin but fairly stable crust of solid rock formed as Earth cooled. • Depressions in the crust were natural basins in which water, rising from the interior of the planet through volcanoes and fissures, collected to form the oceans. Slowly, Earth acquired its present appearance.

1. 1 | P a g e
ORIGIN OF EARTH, TEMPERATURE ON EARTH, SUN EARTH RELATIONSHIP AND
ATMOSPHERE
*Shalini Pandey
Research Scholar
MPUAT, Udaipur
ORIGIN OF EARTH
 Earth, along with the other planets, is believed to have been born 4.5 billion years ago as a
solidified cloud of dust and gases left over from the creation of the Sun.
 For perhaps 500 million years, the interior of Earth stayed solid and relatively cool, perhaps
2,000°F.
 The main ingredients were iron and silicates, with small amounts of other elements, some of
them radioactive.
 As millions of years passed, energy released by radioactive decay—mostly of uranium,
thorium, and potassium—gradually heated Earth, melting some of its constituents.
 The iron melted before the silicates, and, being heavier, sank toward the center.
 This forced up the silicates that it found there.
 After many years, the iron reached the center, almost 4,000 mi deep, and began to
accumulate. No eyes were around at that time to view the turmoil that must have taken place
on the face of Earth—gigantic heaves and bubblings on the surface, exploding volcanoes,
and flowing lava covering everything in sight.
 Finally, the iron in the center accumulated as the core. Around it, a thin but fairly stable
crust of solid rock formed as Earth cooled.
 Depressions in the crust were natural basins in which water, rising from the interior of the
planet through volcanoes and fissures, collected to form the oceans. Slowly, Earth acquired
its present appearance.
TEMPERATURE ON EARTH
Earth is the only planet we know of that can support life. The planet is not too close or too far away
from the sun. It lies in a "Goldilocks zone" that is just right — not too hot, not too cold.
The distance from Earth to the sun is one of the most important factors in making Earth habitable.
The next closest planet to the sun, Venus, for example, is the hottest planet in the solar system.
Temperatures there reach more than 750 F (400 C), while the average temperature on Mars is
minus 80 F (minus 60 C).
Earth atmosphere also play a vital role in regulating the temperature by providing a blanket of gases
that not only protects us from excessive heat and harmful radiation from the sun, but also traps heat
rising from the Earth's interior, keeping us warm.
The average temperature on Earth is about 61 degrees F (16 C). But temperatures vary greatly
around the world depending on the time of year, ocean and wind currents and weather conditions.
Summers tend to be warmer and winters colder. Also, temperatures tend to be higher near the
equator and lower near the poles.
Temperature extremes

2. 2 | P a g e
According to the World Meteorological Organization, the coldest place on Earth is Vostok Station
in Antarctica, where it reached minus 128.6 F (minus 89.2 C). The coldest inhabited place is
Oymyakon, Russia, a small village in Siberia, where it dips down to an average of minus 49 F
(minus 45 C) and once hit a low of minus 96.16 F (minus 71 C).
The hottest place on Earth is Greenland Ranch (Furnace Creek) in Death Valley, Calif., where it
reached 134 F (56.7 C). Death Valley's record is for the highest air temperature. A higher surface
temperature of 159.3 F (70.7 C) was recorded by a Landsat satellite in the Lut Desert in Iran.
SUN EARTH RELATIONSHIP
Figure 1 below shows that the orbit of the Earth about the sun is not circular. The path is elongated
or ellipitcal. This means that the distance from the Earth to the sun varies through the year. Two
special events are depicted in the diagram. Aphelion (July 4) is when the Earth is as far away from
the sun as it ever gets. Perihelion (Jan. 3) is when the Earth is as close to the sun as it ever
gets. Note that these events do not correspond to the coldest and hottest months for us in the
Northern Hemisphere. The purpose of this is to show that distance from the sun has nothing to do
with seasons.
Additional:
 One orbit around the sun is called a Revolution.
 One revolution takes 365 days or 1 year to complete (on each birthday, you have completed
one more lap around the sun!).
 Aphelion distance is 9.45 x 107
miles.
 Perihelion distance is 9.15 x 107
miles.
Figure 2 reveal some very important facts about the Earth
and its orbit around the sun. First note the purplish
rectangle. This represents the plane of the Earth's orbit
about the sun or the Plane of the Ecliptic. We now want
to measure the orientation of the Earth with respect to the
plane of its orbit, the plane of the ecliptic. Now note the
orange rectangle which represents the plane of the
equator. We can clearly see that the two planes do not
coincide. That is to say, the Earth is tilted with respect to
the plane of the ecliptic. Figure 2 also shows the Earth's axis of rotation. If the Earth were not
tilted with respect to the plane of the ecliptic, then there would be a right angle (90°) between the
axis and the plane of the ecliptic. Note that the axis is shy of 90° by 23°30'. This deviation, or tilt,
is called Inclination. We will find that this inclination is vital for seasons on Earth. Make sure to
memorize the amount of inclination as we will see this number pop up time and again!
Additional:
 The spinning of the Earth about its axis is called Rotation.

3. 3 | P a g e
 One rotation takes about 24 hours or 1 day.
Figure 3 reveals two more important parts of the seasons story. First note that 50% of the Earth is
in daylight and 50% is in darkness. This is always the case for the whole Earth, but equal parts of
each hemisphere may not be in daylight and darkness. The dividing line between day and night is
called the Circle of Illumination. The orientation of the circle of illumination changes with the
seasons. Note in Figure 3 that the circle of
illumination does not pass through the poles. Look
carefully and you will see that more of the Northern
Hemisphere is in daylight than in darkness which
means that the day is much longer than the
night! What is important here is that the changing
orientation of the circle of illumination alters the
lengths of daylight and nighttime hours.
The second major concept shown in Figure 3 is
the Subsolar Point. The subsolar point is the
latitude on the Earth's surface where the sun's rays
strike at a 90° angle which is the highest possible
solar angle. Figure 3 shows a special event when the subsolar point is as far north as it ever gets,
the Tropic of Cancer. The subsolar point is where the sun's rays are most direct and, therefore,
most concentrated. The concentration of the solar energy heats the surface. Important rules emerge
from this fact:
 When the subsolar point is as far north as it can go, it is the Northern Hemisphere's
Summer.
 When the subsolar point is as far south as it can go, it is the Northern Hemisphere's Winter.
EARTH ATMOSPHERE
The atmosphere of Earth is the layer of gases that surrounds the planet Earth and is retained by
Earth's gravity. The atmosphere protects life on Earth by absorbing ultraviolet solar radiation,
warming the surface through heat retention (greenhouse effect), and reducing temperature extremes
between day and night (the diurnal temperature variation).
Composition of atmosphere
 nitrogen- 78.09%
 oxygen- 20.95%
 argon- 0.93%
 carbon dioxide- 0.039%
 small amounts of other gases
 water vapor- 0.4%
Layers of the Atmosphere
The atmosphere of the Earth may be divided into several distinct layers, as the following figure
indicates.
Troposphere

4. 4 | P a g e
The troposphere is the lowest region in the Earth's atmosphere. On the Earth, it goes from ground
(or water) level up to about 11 miles (17 kilo meters) high. This part of the atmosphere is the
densest. Almost all weather and clouds occur in the troposphere. In the troposphere, the
temperature generally decreases as altitude increases.
Tropopause: The tropopause is the boundary zone (or transition layer) between the troposphere
and the stratosphere. The tropopause is characterized by little or no change in temperature altitude
increases.
Stratosphere
The stratosphere starts just above the troposphere and extends to 50 kilometers (31 miles) high. The
stratosphere is characterized by a slight temperature increase with altitude and the absence of
clouds. The stratosphere extends between 11 and 31 miles (17 to 50 kilometers) above the earth's
surface. The ozone layer, which absorbs and scatters the solar ultraviolet radiation, is in this layer.
Only the highest clouds (cirrus, cirrostratus, and cirrocumulus) are in the lower stratosphere.
Mesosphere
The mesosphere starts just above the stratosphere and extends to 85 kilometers (53 miles) high.
Meteors burn up in this layer. The mesosphere is characterized by temperatures that quickly
decrease as height increases.
Thermosphere
The thermosphere starts just above the mesosphere and extends to 600 kilometers (372 miles) high.
Aurora and satellites occur in this layer.
Ionosphere
The ionosphere is an abundant layer of electrons and ionized atoms and molecules that stretches
from about 48 kilometers (30 miles) above the surface to the edge of space at about 965 km (600
mi), overlapping into the mesosphere and thermosphere. This dynamic region grows and shrinks
based on solar conditions and divides further into the sub-regions: D, E and F; based on what
wavelength of solar radiation is absorbed. The ionosphere is a critical link in the chain of Sun-Earth
interactions. This region is what makes radio communications possible. Auroras occur in the
ionosphere.
Exosphere
The exosphere is the outermost layer of the Earth's atmosphere. The exosphere goes from about 400
miles (640 km) high to about 800 miles (1,280 km). The lower boundary of the exosphere is called
the critical level of escape, where atmospheric pressure is very low (the gas atoms are very widely
spaced) and the temperature is very low.
REFERENCES
http://new-learn.info/packages/clear/thermal/climate/sun/relationship.html
http://www.space.com/17816-earth-temperature.html
http://www.infoplease.com/ipa/A0004438.html

5. 5 | P a g e
http://www.enchantedlearning.com/subjects/astronomy/planets/earth/Atmosphere.shtml
http://csep10.phys.utk.edu/astr161/lect/earth/atmosphere.html
http://www.nasa.gov/mission_pages/sunearth/science/atmosphere-layers2.html