Monday, January 26, 2009

Test for class X students (new batch)of Don Bosco

Answer these questions to earn a prize. Be a first person to get the right answers. Whoever answers all the questions and sends it to me, they earn 25 points. Every time you answer my quiz or test, you get 10 points.(even if you dont get a prize). All these points will be added to your account. These tests are open only to Don Bosco students. Why wait? Nothing to lose. You will get points even if you don't get good marks. Send your anwers to by 28th Januray, 2009.

1. Which are the two broad classification of peninsular plateau? .
2. What is a Doab?
3. Differentiate between the Himalayan Mountain and the Peninsular Plateau?
4. Differentiate between the Khaddar and the Banger soils?

5. Why is the Deccan trap famous for Cotton crops?
6. Explain the difference between the Western coastal plain and the Eastern coastal plain?
7. Discuss briefly the Great Mountain Wall of the North?
8. Differentiate between the Himalayan Mountain and the Peninsular Plateau?

9. Whatare Duns?
10.Why is the Chota Nagpur plateau known as the storehouse of minerals?

11. Differentiate in between the Western Ghats and the Eastern Ghats

Sunday, January 25, 2009

quiz - part 2.

Hello boys and girls,

This is the continuation of the previous test. First and highest scorer will get a prize. Even the first to send a reply too will get a prize. For the multiple choice question, write the question number and the full answer. for example for the question number 1, if your answer is a, then type a. the only star in our galaxy.

So be quick to reply. Send answers of part 2 only to my email and not geoblog. If you need clarifications, do call me.


1. The sun is
a. the only star in our galaxy.

b. just one of billions of stars that make up our galaxy.

c. the largest planet in our solar system.technically speaking,

d. one of Earth’s moons.

2. Which of these features makes the Earth unique among planets?

a. It is the only round planet.

b. It is the only planet with its own moon.

c. It is the only planet that has enough oxygen in its atmosphere to sustain life.

d. It is the only ringed planet.

3. Comets are icy masses of frozen gases and dust particles. What happens when a comet gets too close to the sun?

a. The gases catch fire, making the comet glow.

b. The ice begins to melt, leaving a trail of gases and debris.

c. The comet explodes, which is called a supernova.

d. The comet bounces off the sun’s magnetosphere.

4. What did 17th-century astronomer Edmund Halley notice about the comet later named after him?

a. The comet passed by the Earth on a predictable schedule.

b. The comet passed by the Earth at random intervals.

c. The comet passed by Earth only once in a million years.

d. The comet was on a collision course with Earth.

5. What is a meteorite?

a. a chunk of comet (rock) that survives our atmosphere and falls to Earth

b. a meteor that hasn't hit Earth yet

c. a piece of rock that is in orbit around the Earth

d. a radioactive moon rock

6. What is the central and largest body of our solar system?

a. Jupiter

b. the Milky Way

c. Earth

d. the sun

7. The fates of the sun and the Earth are linked. Which of the following explains why this statement is true?

a. Without the Earth in orbit, the sun would quickly burn up.

b. Without the heat and light from the sun, life on Earth will cease.

c. Without each other, they would both spin out of control.

d. Without the sun to cool things off, the interior of the Earth would burn up the planet.

8. Planets have elliptical orbits. This means that -

a. their orbits are perfectly round.

b. their orbits are in the shape of a figure eight.

c. at some point of its orbit, a planet is closer to the sun.

d.their orbits change direction from time to time.

9. We have a 24-hour day because that is -

a. the length of time it takes for the moon to travel around the Earth.

b. the length of time it takes the Earth to rotate once around its axis.

c. the length of time it takes the Earth to travel once around the sun.

d. the length of time it takes the sun to rotate once around its axis.

10. On Earth one year is -

a. the length of time for the moon to travel once around the Earth.

b. the length of time for the Earth to rotate once around its axis.

c. the length of time for the sun to travel once around the Earth.

d. the length of time for the Earth to travel once around the sun.

11. About how fast does the earth orbit around the Sun?

a. 300 m/sec (600 miles per hour)

b. 2 km/sec (4,000 miles per hour)

c. 10 km/ sec (20,000 miles per hour)

d. 30 km/sec ( 60,000 miles per hour)

12. How old is the Universe?

a. 15 Million Years

b. 150 Million Years

c. 4 Billion Years

d. 15 Billion Years

13. Besides ordinary matter, The Universe contains a lot of “dark matter” which is an unknown substance. What fraction of the mass of the Universe is ordinary matter, like hydrogen and helium?
a. 70 – 80%
b. 30 – 40%
c. 2 – 3%
d. 0 – 0.2%

14. Galaxies are built of many stars. How many stars are in a typical galaxy?
a. 10 Million
b. 1 Billion
c. 100 Billion
d. 100 Trillion

15. The expansion of The Universe was discovered by observing that all galaxies are moving away from us. Who made this discovery?

a. Albert Einstein
b. Fritz Zwicky
c. Edwin Hubble
d. Johannes Kepler


1. What are asteroids?
2. According to the astronomer who gave talk to us, why Pluto is not in our Solar System?
3. Write in your own words, how did Saturn look yesterday? (Be creative)
4. What is a light year?
5. What are Sunspots?
6Do you like geography? Why?
7 Your experiences in geography class.
8 Write your comments on yr experience of Star gazing and other memorable experiences of yesterday's programme.

NOTE: This is a first test. Open only for Don Bosco students of Chitradurga. Send your answers both in blog and my email and same answers in the comment section of my blog.
do check for the photographs

Wednesday, January 21, 2009


* 15billion years ago, there was a cosmic mass. (smaller than the dot)
* It was made up of hot and dense matter.
* A great explosion shattered the cosmic mass into countless tiny pieces.
* This explosion is known as “Big Bang”.
* The Big Bang resulted in the formation of nebulae.
* In the course of millions of years, the temperature and density of nebulae
increased till the nebulae increased till the nebulae collapsed by itself.
* As a result, new stars were born.
* The hydrogen within these stars got converted into helium, sun, star, was born

in this way.

  • On a cloudless night, one can see a cluster of stars forming a narrow band in the sky. This is called MILKY WAY OR AKASH GANGA.It is a galaxy containing as many as 1,00,000 million stars. Sun is a medium sized star in the Milky Way galaxy. There are millions of galaxies in the Universe.


  • Universe is vast in size.
  • Distances between heavenly bodies cannot be expressed in units like kms or miles
  • If you drive on a highway at 60 k.m.s per hour in one hour you may get to Hiriyuru.
    Steady speed!
    If you keep on driving after 4 hours you would reach Bangalore.Steady speed - no stops
  • If we could keep on and on - - ---------
  • If you could drive to the Moon at 70 miles per hour, 230,000 miles or about 400,000 km, it would take you 3400 hours, or 140 days.
  • A light year is the unit adopted for measuring distances in the Universe. A ray of light travels at a speed of 30,000 km per second.
  • Light and heat comes from the Sun.
  • It is a long way away ! 146 million km
    If you could drive to the Sun at 70 miles per hour, it would take over 50 000 days.
    = 150 years
    – longer than we live !
  • Light travels very, very fast!
  • It takes 8 minutes for light to reach us from the Sun!
  • Light travels 300 000 kilometres through space every second!
  • A light year is the distance, which a ray of light would cover in a year’s time.
  • After the Sun, the ALPHA CENTAURI is the nearest star to the earth..
    Also called PROXIMA CENTAURI & 4.3 light years away.


  • Galaxy is a collection of billions of stars, found clustered together due to their own gravity. The arrangement of the stars gives rise to different shapes , consisting of varying numbers of stars.


  • They are cloud like formations containing dust and hot gases. They appear as misty patches of light spanning the sky.
  • They appear as dark patches or bright luminous clouds, depending on the colour of the sky which forms their background


What’s in Our Solar System?

Refers to heavenly bodies which belong to Sun’s family. These heavenly bodies are held in their places by the gravitational force of the Sun. It consists of a central star (the Sun), the nine planets orbiting the sun, moons, asteroids, comets, meteors, interplanetary gas, dust, and all the “space” in between them.

    Sun is the source of light and radiant energy for all heavenly bodies of the Solar system.

    The nine planets of the Solar System are named for Greek and Roman Gods and Goddesses.

    The path along which each planet revolves round the Sun is called its ORBIT.

    Farthest planet from sun is Pluto (????) – distance about 5900 million km from the sun. (now it is considered as dwarf planet.)

  • Without sun, there would be no solar system. The sun provides not only energy required for life, but also provides gravitational force to hold the planets in the orbit.
  • The Sun is the most massive body in the Solar System, containing 98% of the mass of the Solar System. The Sun is more than 330,000 times more massive than the Earth. The Sun is also the Solar System's largest body, with a diameter of 1,391,900 kilometers, over 109 times that of Earth's.
  • The Sun is layered, and can effectively be divided into three regions, the core, the radiative zone, and the convective zone. The "surface" of the Sun that we see is the photosphere, above which lies the chromosphere and the outlying corona.


The Sun is hot gaseous body. The Sun’s age is about 5 billion years. Its energy comes from nuclear fusion (where hydrogen is converted to helium) within its core. This energy is released from the Sun in the form of heat and light.

  • Stars are the only solar bodies that generate their own light. Very bright planets, such as Venus and our moon, appear bright because they are reflecting sunlight.
  • Remember: Stars produce light. Planets reflect light.
  • Our sun is classified as a yellow main sequence star. A star’s temperature determines its “color.” The coldest stars are red. The hottest stars are blue.
  • The sun is the biggest, brightest, and hottest object in the solar system. It has a radius of 5900 million km. The sun is an ordinary star. It is made of about 70% hydrogen and 28% helium. The surface temperature of Sun is 6000 degree C. The core of the sun has temperature of 2,00,00,000 degree C.
  • It rotates on its axis every 27 days approximately.-Not uniform since it is a big ball of gas and not a solid.
  • Sun exudes tremendous energy by a process similar to the explosion of a hydrogen bomb. Within the sun, this process is continuous.
  • The Earth intercepts only a small faction of this energy- provides warmth, light and even rain required for life on earth.


Sunspots reside in the photosphere, and are large dark regions of strong local magnetism. The magnetic field of a sunspot prevents the escape of energy from below, and consequently sunspots have lower temperatures than the rest of the photosphere. However, sunspots only appear dark when viewed against the hotter, brighter surroundings. If you took

a sunspot off the Sun and placed it in the night sky, it would shine very brightly. Galileo first discovered the Sunspots and from them he deduced that Sun rotates on its axis.

Under Sun’s gravitational force each planet follows an elliptical orbit around the Sun.
All planets rotate in an anti-clockwise direction except Venus and Uranus.

Uranus and Venus rotate clockwise direction, i.e. east to west.

The8 Planets of the Solar System

Mercury, Venus,Earth, Mars, Jupiter, Saturn, Uranus and Neptune are 8 planets . Pluto is considered as dwarf planet.

  • Planets are classified on basis of their distances from the Sun.
  • Mercury and Venus are called Inferior Planets, as their orbits lie within the orbit of the earth. Farther planets from Mars to Neptune, are called Superior Planets.


Planets are also classified on the basis of their physical properties.

  • Mercury, Venus, Earth & Mars – inner planets – small in size – made of rocky substances and have a high density – hotter than Outer planets – also called Terrestrial Planets.


INNER PLANETS onsist of Mercury, Venus, Earth, Mars and OUTER PLANETS consist of Jupiter, Saturn, Uranus, Neptune.
Inner planets are closer to the Sun whereas outer planets are far away from the Sun.
Inner Planets have a solid surface made of dense metallic minerals. They are called rock-type planets. Outer Planets' surface is not solid but made up of hot gases, mainly hydrogen & helium. They are called gas-type planets.
Inner Plaets travel faster and have shorter period of revolution. Outer Planets travel more slowly and have a longer period of revolution.
Inner Planets are much smaller.Our earth which is the largest in size is a quarter of Neptune. Outer Planets are extremely large. Jupiter is the largest and others put together would not be equal to half its volume.

QUESTION 1: Name the Inferior and Superior Planets.
ANSWER :Mercury and Venus – Inferior
Mars to Pluto – SUPERIOR

QUESTION 2: Which planets are called Outer Planets?
ANSWER Jupiter, Saturn, Uranus, Neptune.


Mercury sweeps through its orbit at nearly 50km per second, faster than any other planet. It has a revolution period of 88 days. A revolution period is time it takes for a planet to complete one full orbit around the sun. This is also called a year. It has extreme temperature fluctuations, ranging from 800°F (daytime) to -270°F (nighttime). Even though it is the closest planet to the sun, recent radar info suggests there is ICE on Mercury! Scientists believe the ice is protected from the sun’s heat by crater shadows. It is covered with meteorite impacts and barely has a trace of an atmosphere.

Mercury is solid and is covered with craters. It has almost no atmosphere. It is the eighth largest planet.
It is located at mean distance of 57.9 million km from Sun. It completes one rotation in about 59 days.
It rotates very slowly.

    The surface of Mercury rough and pockmarked with craters.


Named after goddess of love & beauty
•Known as morning star when high in eastern sky
•Evening star when visible in the western night sky

Venus is the brightest object in the sky after the sun and moon because its atmosphere reflects sunlight so well. People often mistake it for a star.
The atmosphere of Venus has a large amount of carbon dioxide gas. Carbon dioxide traps heat in Venus’s atmosphere, causing the surface temperatures to increase greatly. We call this effect the Greenhouse Effect. Venus’s Greenhouse Effect is so strong that its temperature about 470 degree C .

Venus has no moons. It has thick yellowish clouds composed of sulfuric acid driven by fast winds. Its surface is dry and dusty with craters, mountains, and volcanoes.

Venus is the sixth largest planet. It’s about three-fourths the size of earth.

The surface is rocky and very hot. The atmosphere completely hides the surface and traps the heat.

Located at a mean distance of 108 million km from the Sun.

It takes longest period -243 days to complete one rotation.
It rotates from east to west.

It completes one revolution around the Sun in a shorter period of only 223 days . So a day on Venus is longer than its year.

Unlike earth, it is covered with a very thick blanket of clouds which reflects 75% of the light reaching.

The clouds have never parted enough to allowa view of the surface through the telescope and so Venus presents an unchanging view-a white planet with no visible markings on it.

It is called as ‘Veiled Planet’.


Jupiter is the largest and most massive planet: it’s diameter is 11 times bigger than that of the Earth’s. Overall, Jupiter is about 318 times the size of Earth. Jupiter is composed almost entirely of hydrogen and helium.
Because Jupiter rotates so quickly, it’s clouds form belts (low-lying, relatively warm cloud layers) and zones (bright, high-altitude, cooler cloud layers) that encircle the planet.
Jupiter’s characteristic Great Red Spot is an enormous storm, consisting of a spiraling column of clouds big enough to contain three Earths. The clouds are colder than the surrounding areas, and so the Great Red Spot sits about five miles above the upper cloud layer.

Jupiter has 16 moons.


The Great Red Spot, a huge storm of swirling gas that has lasted for hundreds of years.
Jupiter does not have a solid surface. The planet is a ball of liquid surrounded by gas.

Voyager 1 took this photo of the planet Jupiter on January 24, 1979 while still more than 40 million km away.


Jupiter has four large Galilean moons, twelve smaller named moons and twenty-three more recently discovered but not named moons.
We’ll take a look at the four large Galilean moons which were first observed by Galileo in 1610.

Jupiter's moon Io floats above the planet's cloudtops in an image recorded by Cassini on January 1, 2001, two days after the probe's closest approach to Jupiter[NASA JPL]


Saturn is the second largest planet and the sixth from the sun.
It is made of materials that are lighter than water. If you could fit Saturn in a lake, it would float!

It, like Jupiter, is composed almost entirely of hydrogen and helium. Saturn is the least dense of all the planets. In fact, Saturn’s density is less than that of water.
It has many rings composed primarily of ice with some ice-coated rocky particles. Saturn’s rings are very wide (they extend outward to about 260,000 miles from the surface) but very thin (less than 1 mile thick).
It has 18 known moons, some of which orbit inside the rings!

It's rings are not solid; they are composed of small countless particles.
The rings are very thin. Though they’re 250,000km or more in diameter, they’re less than one kilometer thick.

1,25,000 rings in saturn. Ring consists of Dust and gaseous particles.there are gaps between the rings. Has 32 natural satellites. Believed that there may be life in Titon, satellite of Saturn.


Uranus is tilted on its axis at 98°. Because of its strongly tilted axis of rotation, Uranus essentially spins on its side as it orbits the sun.
It has 11 dark rings surrounding it. These rings contain some of the darkest matter in our solar system.
It has 15 known moons, and scientists suspect more lurk within its rings.
It is the third largest planet and the seventh from the sun.
It is one of the giant gas planets. Uranus is blue-green because of the methane in its atmosphere


Neptune has the fastest winds on the solar system: up to 2000 km/hr.
It is also blue in color due to methane gas in its atmosphere.
It has a Great Dark Spot in its atmosphere. The Great Dark Spot is a huge storm the size of Earth.

Neptune is the fourth largest planet and the eight from the sun.

Because of the orbits, from 1979 to 1999, Neptune was the ninth planet.Like Uranus, the methane gives Neptune its color.


Based on current data, scientists believe it is a small, rocky planet.It seems to lie on its side: its equator points straight up, and one of its poles points directly at the sun.It was located and named in 1930.

Pluto: The First Dwarf Planet-It is actually smaller than one of Neptune's moons, Triton is the second-largest known dwarf planet in the Solar System and the tenth-largest body observed directly orbiting the Sun.

For many years, Pluto was thought of as the farthest known planet from the Sun.
It has a very unusual orbit. Once every 248 Earth years, Pluto swings inside the orbit of Neptune. It stays there for twenty years.
During those twenty years, Pluto is closer to the Sun than Neptune.
While it is closer to the Sun, Pluto has an atmosphere. The methane and nitrogen frozen at the poles thaw out, rise, and temporarily form an atmosphere.
As it moves toward its farthest point from the Sun, Pluto's atmosphere freezes and falls back on the surface of the planet.
Since the year 2000, astronomers realized that Pluto was not like the other eight planets but very much like a new group of objects found in the outer solar system. In 2006, astronomers re-classified Pluto to be a dwarf planet .
Pluto has three moons. It's largest moon, Charon, is half the size of Pluto.
In 2005, astronomers observed two more moons of Pluto. The moons were named Nix and Hydra.

Name Pluto was suggested by an 11 year old schoolgirl – Venetia BurneyGave name because the name of Roman God of the underworld was suitable for the planet so far from the Sun

Facts about Pluto

Average Solar Distance : 6 billion km

Revolution Period: 248 Earth years

Rotation Period: 6.4 Earth days

Equatorial diameter: 2400 km Earth

Natural Satellites 1+2



Asteroids are rocky bodies, which revolve round the Sun in the big gap of about 550 million kms between orbits of Mars & Jupiter.
There have been countless references to them as "space debris" or "vermin of the skies". Otherwise they are overlooked as they are small, dull, inert and lack an atmosphere. However, for the last three or four thousand million years asteroids have been the most important agent of surface modification on a great many bodies including Mercury and our very own Moon.

There are over 8000 large asteroids, and many more which are too small to detect easily. Only 26 asteroids are known to have a diameter greater than 200 kilometers, and it is likely that all asteroids above 100 kilometers in size have been detected. However, not many of the smaller asteroids have been discovered - there may be over a million asteroids with a size of 1 kilometer.
The largest asteroid is 1 Ceres with a diameter of 974 kilometers. This one asteroid contains about a quarter of the mass of all the asteroids. In terms of size, Ceres is followed by 2 Pallas, 4 Vesta and 10 Hygiea. These asteroids are between 400 and 538 kilometers in diameter. All other known asteroids are less than 350 kilometers across.

Found in all shapes & sizes – rotate on their axis every 5 to 20 hrs depending on their sizes.
2 main groups – Trojan asteroids in the orbit of Jupiter &

Chiron asteroids between Saturn and Uranus .

What are asteroids?
Asteroids are rocky bodies, which revolve round the Sun in the big gap of about 550 million kms between orbits of Mars & Jupiter.

________ largest asteroid.

50,000 asteroids between jupiter and mars. They also revolve around sun and sometimes they crash in to others and fall into other planets. Doesn’t fallin earth due to atmosphere which burns the asteroids before it lands into the earth.


Among the most brilliant, and most rare objects in the night sky. These soaring beacons with their beautiful tails come from the outer realms of the Solar System.

What are comets?
Comets are very small bodies consisting of frozen gases and grains of dust and rock. It is when comets approach the inner Solar System and become subjected to the Sun's heat, that they develop a tail millions of kilometers long and thus become very large objects.
Comets have head called coma and a long tail.Their size range from a few hundred meters to a few hundred kilometers in diameter.

It takes them hudreds and sometimes even thousand of years to complete one revolution around the sun.
When their path passes ear Sun, we are able to see them.
Their tails are turned away from the sun.
Many comets do not have tails.
Appear as small luminary objects moving across sky.


1.PERIODICAL COMETS: have regular orbits round the sun and occur at fixed intervals.
Halley’s comet – due next in 2062
Seen at interval of 76 years.

Seen very rarely and not sighted at regular intervals
Comets are visible only when they travel close to the sun.
Ice melts and gas and dust are swept back to form the tail.
Tail always points away from the sun.
They are small bodies which rotate on their axes & revolve round the planets.
Satellite = a follower and they follow the planets in their paths round the Sun.
They are opaque bodies like the planets and shine by reflecting the sunlight falling on them. All planets do not have satellites .


They are small planetary particles, which are attracted by Earth’s gravitational force when they pass near the Earth.
They are seen as rapidly moving bright objects in the sky lasting for a few seconds.
They are known as shooting stars.
Millions of such meteor-like particles are found scattered in space.
When they enter the Earth’s atmosphere, they get burnt due to friction and appear as bright objects.

image showing meteor of Leonid Meteor shower taken from space


Some meteors are of large size.
Only a part of their mass gets burnt. The remaining mass falls on the Earth as a large boulder.These are called meteorites .

Some of these meteorites are quite large and weigh more than 50 tonnes.
Their impact on earth’s surface has resulted in the formation of craters

Star : A self-luminous ball of gas
Planet : A rocky or gaseous mass that revolves round a star.
Satellite : A body that revolves round a planet.
Galaxy : Large cluster of stars.
Asteroids :Small rocky bodies
Meteorite : a large rocky body entering the earth's atmosphere.
Terrestrial : Earth-like.

Saturday, January 17, 2009



In old days, earth was considered to be a flat disc with steep edges.
All heavenly bodies revolved around the Earth.

Babylonians thought- earth was circular in shape & surrounded by river Okeanos .

Ancient Indians – earth was flat with a huge mountain in the middle.
Aryabhatta , famous Indian astronomer, believed Earth was spherical in shape and rotated on its axis.
In Europe, Greek philosopher Pythagoras and Aristotle were first to state that Earth was spherical in shape. Considerable opposition to this view.
Now we have convincing evidence from man’s landing on the Moon that the Earth is spherical in shape, the evolution of this idea may be considered briefly.


The earth casts a shadow on the moon during a lunar eclipse. This shadow is always semi-circular in shape .

SUNRISE AND SUNSET: The fact that the time of sunrise varies from place to place on the Earth proves that the Earth is not a flat disc.
If the earth was flat, all places on the earth would have sunrise and sunset at the same time.


If we travel around the earth without changing the direction, we arrive at the place we started from.
As the earth is spherical in shape, it is possible to circumnavigate the earth.
Magellan’s crew was first to go round the earth in a ship and complete the voyage without encountering a sharp edge.
Now aircrafts make many trips round the world on scheduled flights.


When a ship approaches the shore, a person standing on the shore can see the smoke at first and then the chimney and then the ship as a whole.


The photographs of the earth & other planets sent by the artificial satellites prove that the earth is round.Aerial photographs from space show earth spherical. Astronauts have taken pictures of earth from moon showing its spherical shape

Now – not a perfect sphere.
Flattened at the poles & bulging at the equator
Named ‘geoid’.
At equator diameter measures 12,756 km
Poles the diameter is 12,714 k.m. giving a difference of 42km.

Earth is geoid in shape


Average diameter is about 12,735 km.
Four planets – Mercury, Venus, Mars and Pluto (?) are smaller than the Earth.
Others are larger
Early attempt made to estimate the size in 3rd century BC by Greek philosopher called Eratosthanes.



New Moon
Waxing Crescent
First Quarter or Half Moon
Waxing Gibbous
Full Moon
Waning Gibbous
Last Quarter or Half Moon
Waning Cresce

The moon is not visible from Earth. The moon is between the Sun and the Earth.
The dark side is facing us.
This phase lasts one night.

Waxing Crescent

Waxing means that the bright side is increasing. The right side is the bright side.
Less than one half of the moon is illuminated.
This phase includes any visible moon from a small sliver to almost half.

First Quarter or Half Moon

The entire right side of the moon is illuminated.
The moon looks like a half circle.
The illuminated side is increasing.
This phase only lasts one night

Waxing Gibbous

Gibbous means that more than one half is visible, but it is not quite full.
This phase includes the night after the first quarter to the night before the full moon.

Full Moon

The moon is full and bright. It looks like a large circle.
The illuminated side is facing us.
Only happens one night per lunation.

Waning Gibbous

The moon appears more than half but not quite full.
Waning means that the illuminated side is decreasing.
The left side is the bright side.

Last Quarter or Half Moon

Left Half of the moon is illuminated.
The illuminated side is decreasing.
This phase also only lasts for one night.


Less than one half of the moon is illuminated.
The moon will continue to become smaller and smaller.


Why is only one side of the moon visible from the earth?
We always see the same side of the moon. The Moon always keeps the same side pointing towards us so we can never see the 'back' of the Moon from the Earth.

The moon revolves or orbits the Earth once every 29 days.
We all ways see the same side of the moon because the moon rotates and revolves at about the same speed.
The opposite side of the moon is hidden from our view.

The Moon is not a light source, it does not make its own light. The moon reflects light from the sun. We can see the Moon because light from the Sun bounces off it back to the Earth. If the Sun wasn't there, we wouldn't be able to see it.
The Sun always lights up (illuminates) half of the Moon at one time.
The Moon appears to change shape but what we are actually seeing is the Moon lit up by the light from the Sun in different ways on different days.

Why does the moon have phases?
The revolution of the Moon around the Earth causes the Moon to appear to have phases.

Few questions for you to revise:

1. Describe the phases of the moon.
2. What are eclipses?
3. What causes Solar Eclipse?
4. What are the Waxing and Waning phases of the Moon?
5. Which eclipse, Solar or the Lunar, gives evidence that the Earth is a sphere?


"Here lie the bodies of Ho and Hi,Whose fate, though sad, is risible;Being slain because they could not spyTh' eclipse which was invisible."
Author unknown: Said to refer to the Chinese
eclipse of 2136 BC or 2159 BC.

"If the Sun at its rising is like a crescent and wears a crown like the Moon: the king wll capture his enemy's land; evil will leave the land, and (the land) will experience good . . . "
Refers to a solar eclipse of 27 May 669 BC.Rasil the older, Babylonian scribe to the king.Quoted in Historical Eclipses and Earth's Rotation, by F Richard Stephenson, Cambridge University Press, 1997, page 125.

"Nothing can be surprising any more or impossible or miraculous, now that Zeus, father of the Olympians has made night out of noonday, hiding the bright sunlight, and . . . fear has come upon mankind. After this, men can believe anything, expect anything. Don't any of you be surprised in future if land beasts change places with dolphins and go to live in their salty pastures, and get to like the sounding waves of the sea more than the land, while the dolphins prefer the mountains."

May refer to a total solar eclipse of 6 April 648 BC. Archilochus, Greek poet (c680-640 BC) Quoted in Historical Eclipses and Earth's Rotation, by F Richard Stephenson, Cambridge University Press, 1997, page 338. Partly quoted in Encyclopaedia Britannica CD 98.

"On the day of the new moon, in the month of Hiyar, the Sun was put to shame, and went down in the daytime, with Mars in attendance."
One of the earliest written records of an eclipse of the Sun, on 3 May 1375 BC, found in the city of Ugarit in Mesopotamia.(Reprinted, from Chasing the Shadow, copyright 1994 by Joel K Harris and Richard L Talcott, by permission of Kalmbach Publishing Co.

Friday, January 16, 2009



* An eclipse is the darkening of a heavenly body when the shadow of one object in space falls on another object.
* Eclipses occur when the Sun or the Moon is hidden from our view for a short period.
* Greek word – eclipse = failing to appear
Possible only when Sun, Moon and Earth are in a straight line
Planet farther away from Sun is then in shadow of the nearer body
The darker side of the shadow is called umbra and the partial shadow surrounding the image is called penumbra.


During a solar eclipse, the moon passes directly between the Earth and the sun, blocking out the sun as seen from Earth. A path of totality is formed where the moon blocks out the entire sun and observers can see a total eclipse. Outside the path of totality, only a partial eclipse can be viewed.

Every total eclipse begins with a series of partial phases which may last an hour or more. However, the total phase or “totality” never lasts more than 7.5 minutes.
This time series photo shows an entire total solar eclipse, from start to finish over a period of over two hours.

In the last seconds before totality begins, the remaining bit of Sun resembles a dazzling jewel as the ring-like corona appears.

The Sun, the Moon, and two photographers all lined up last month in Antarctica during an unusual total eclipse of the Sun. Even given the extreme location, a group of enthusiastic eclipse chasers ventured near the bottom of the world to experience the surreal momentary disappearance of the Sun behind the Moon. One of the treasures collected was the above picture -- a composite of four separate images digitally combined to realistically simulate how the adaptive human eye saw the eclipse. As the image was taken, both the Moon and the Sun peaked together over an Antarctic ridge. In the sudden darkness, the magnificent corona of the Sun became visible around the Moon. Quite by accident, another photographer was caught in one of the images checking his video camera. Visible to his left are an equipment bag and a collapsible chair.
(APOD: 2003 December 8 - An Antarctic Total Solar Eclipse )

Partial Eclipse of Oct. 14, 2004 (Hawaii)
Partial eclipses are visible over a much larger part of Earth than total eclipses. So they are seen by many more people.

A lunar eclipse occurs when the Earth is between Sun and the moon – sun, earth and moon arein a straight line with the earth in-between the sun and moon.
Shadow of the earth falls on the moon .
Usually happens on Full Moon days and is more frequent than solar eclipses.

Lunar eclipse do not occur on every full moon night because the moon’s orbit is inclined to the Earth’s orbital path.
A lunar eclipse may be partial or total.
1.PARTIAL LUNAR ECLIPSE: When a part of Moon is hidden by the Earth’s shadow, it is called Partial Lunar Eclipse.
2.. TOTAL LUNAR ECLIPSE: When the entire Moon is hidden from view, it is called a Total Lunar Eclipse.
* Only certain portions of the Earth experience each eclipse for a short period because the Earth and the Moon are moving along their orbits.

In a lunar eclipse, the Earth moves between the sun and the moon and casts a shadow on the moon. Lunar eclipses can come in a variety of colors from deep black to rich shades of red. The red coloring comes from light from the sun that is filtered as it passes through the Earth’s atmosphere and is bent toward the moon. That light reflects off the surface of the moon and into our eyes on Earth. Lunar eclipses are only evident when the moon is passing through the Earth’s umbral shadow.

Bajpe slideshow