Wednesday, August 19, 2009

Cosmology: Science dealing with the nature and origin of the universe.
Big Bang Theory: Canon Lemaitre
Steady State Theory: Hermann Bond and Thomas Gold.
Pulsating universe theory: Allan Sandage.
One Parsec = 3.26 light years.
Hydra is the largest constellation.
When brightness of a star increases 20 magnitudes or more, it is called a supernova.
Sun accounts for 99.85% of the mass of the solar system.
Suns Revolutionary period= 250 m years
Rotation time = 25 days
Planets are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune
Venus and Uranus rotate anti- clockwise at their axis, whereas all other planets rotate clockwise.
Largest Terrestrial Planet:- Earth
Smallest Jovian Planet:- Neptune
Mercury and Venus have no satellites.
Jupiter has the largest rotational velocity.
Genemede of Jupiter :- Largest Satellite
Titan is the only satellite in the solar system with an atmosphere of its own.
Saturn has the least density among all the planets.
Uranus is also known as Green planet.
Greatest satellite of Neptune : Triton

Movement of the Earth.
1) Rotation: West to east in 24 hours (produces day and night) – Line separating light and dark halves is known as the circle of illumination.
2) Revolution: Movement around the sun 365 ¼ days (produces seasons) – Jan 2 : Closest to the sun- called Perihelion. July 4 : Farthest from the sun- called Apehelion.
3) Eccentricity: (Produces Ice-age and Global Warming) Shape of the earth’s orbit changes in a cyclic period running between 90,000- 1,00,000 years.
4) Precession: This is the conical motion of the axis of the spinning earth, like a spinning top. Takes about 26,000 years to complete one cycle.
Presently – pointing at Pole star.
AD 4000- pointing at Alpha cephai
A D 14,000 – pointing at Star vega
Summer Solistice: 21st June: Sun overhead at tropic of cancer.
Winter Solistice: 22nd Dec : Sun overhead at the tropic of Capricorn.
Vernal Equinox: 21st March.
Autumn Equiox: 23rd Sep
Our moon is 1/4th of the size of Earth.
Blue Moon is said to occur when the second full moon appears within the same month.
Highest Mountain on Moon: Liebnitz: 10,660m
Neil Armstrong and Edwin Aldrin: Set foot on the ocean of Tranquility
In a calendar year, a maximum of seven eclipses can occur( combining solar and lunar eclipses)
Remember 1 degree latitude or longitude represents 111 Km ( along equtor)
Longitude and Time
Rem: E-G-A [ East- gain- add]
W-L-S[ West- lose- subtract]
Earth moves 1 degree in 4 minutes.

Standard meridians differ from Greenwich Meridian by the multiples of 15degree or 7.5degree.
USA and Canada have 5 time zones.
India has one time zone.
-82.5 degree east from the Standard time
- 5 hours and 30 minutes ahead of GMT
The International Date Line:
- 180 degree Meridian is the international date line.
- A traveler crossing this date line from east to west will lose a day.
- A traveler going from west to east will gain a day

1. Earth Moves 1 deg in 4 minutes.
2. Standard meridians differ from Greenwich Meridian by the multiples of 15 deg or 7.5 deg.
3. USA and Canada have 5 time zones
4. India has one time zone
a. 82.5 deg E from the standard time
b. 5 hours and 30 minutes ahead of GMT

The International Date Line
1. 180 deg meridian is the international date line
2. A traveller crossing this date line from east to west will lose a day.
3. A traveller going from west to east will gain a day.

Construction of Earth's Interior
1. Relative Density= 5.5
2. Seismic Waves
a. p-waves or primary waves: Also called longitudinal or compressional waves- like sound waves- fastest
b. Secondary waves or S-waves: Also called transverse or distortional waves- like water ripples- cannot pass through liquid material.
c. Surface Waves or L waves: Long wave length waves- cause most destruction.

Earth's Surface

1. The Crust: It has two layers: Sial and Sima. These two layers extend to a distance of 30-40 km from the earth's surface. The join of Crust and Mantle is called Mohorovic Discontinuity.
2. The Mantle: It extends from 35-2900 km. The join of Mantle and Core is called the Gutenberg Discontinuity.
3. The Core: It extends from 2900-5150. It is also called NiFe because of the presence of Nikel and Iron.

Mechanical Division of Mantle
1. Lithosphere:
It constitutes 80-100 km of upper most mantle. It is rigid and cool
2. Asthenosphere: It is also a part of the upper mantle. It is hot, soft and pliable.

Remember: All the meridians and only the equator form great circles.

Composition of Earth
1. Crust Composition: Oxygen: 46.8%, Silicon: 27.7%
2. Total Earth Composition: Iron: 35%, Oxygen: 30%, Silicon: 15%

Continental Drift Theory
1. According to Alfred Wegner about 250m years ago, all continents were united on a super continent called as Pangaea, which was surrounded by a large ocean called Panthalsa.

2. Continents Drifted in Two Directions:
a. Towards Equator: Due to Gravitational attraction of equatorial bulge ( caused the formation of Himalayas, Alps, and Atlas)
b. Towards West: Owing to tidal forces of moon and sun ( Caused the formation of Rockies and Andes)

Rocks, Earthquakes and Volcanism

1. About 90% of rock forming minerals are silicates.
2. Felspar is the most abundant rock forming silicate material.
3. About 75% of the surface area of the globe is covered by the sedimentary rocks while rest 25% area is occupied by the igneous and metamorphic rocks.
4. Shale is the most abundant sedimentary rock.
5. Marble is a metamorphic rock from limestone, Diamond from Carbon etc.
6. Richter Scale is used to assess the magnitude of an earthquake. It is logarithmic, it means each whole no on the scale represents a ten fold increase in the measured wave amplitude. It is a quantitative scale.
7. Intensity of earthquake is measured by Mercalli Scale. It is a qualitative scale.

Earth's Movements
1. Faults: Here the rock beds are dislocated and displaced resulting in the formation of faults.
2. Rift Valley: Is a linear depression on earth eg. Narmada and Tapti. Dead sea, the most saline lake after lake Van are situated in a rift valley.
3. 66% of the earthquakes of the world are recorded in Circum-Pacific Zone.
4. With the increasing depth, the temperature rises gradually at 1 deg C per 32 m.
5. Molten rock material below Earth's surface is called Magma, above Earth's surface is called Lava.

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