DESTINATION MOON

Free Web Hosting Provider - Web Hosting - E-commerce - High Speed Internet - Free Web Page

No celestial object fascinated the human mind more than this bright white disc in the sky- the moon. Ancient people thought the moon was an object of power and divinity. The ancient Romans called their moon Diana, she used moon crescent as bow and moon rays as arrows. In olden days Greeks, Egyptians worshipped moon as god with different names.

The appearance of the Moon in fact made human being to imagine figures resembling objects on the Earth. The Japanese felt it was like a rabbit making rice cakes. Some Europeans visualised it as a woman’s face and some others as a crab

Let us first of all see how astronomers define direction. We all know that earth rotates from west to east. Hence all the stars, our sun and moon rise in the east and set in the west. So, if we stand such that our right hand is towards the east and left hand towards west, then our face will be towards north and our back towards south.

Now we are seeing the moon among myriads of stars. Our ancestors have envisioned some pattern among these stars resembling some terrestrial or imaginative objects, which are called constellations. Presently the International Astronomical Union has divided the sky into eighty-eight areas as distinct constellations. Horizontal and vertical arcs bound these areas. Among them twelve are classically granted more importance and they are called the Zodiacal constellations. The remaining seventy-six constellations are called non -zodiacal constellations. Sun is the source of energy for earth and all the eight other planets revolving around sun. The sun supplies all energy needed to support life on Earth. Relative to Earth the Sun appears to move in the sky in a circular path annually, which the Astronomers call Ecliptic. This circle is divided into twelve equal parts called zodiacal signs. The constellations falling majorly in a zodiacal sign is the corresponding zodiacal constellation.

Look up there. The moon is near those stars in the form of; well you have guessed it SCORPION or the VRISCHIC rashi. This is seen in night sky during the months of May to September from India. Now see that star. It is actually a red supergiant star. It is called Antares. It is three hundred times the diameter of Sun. In fact our sun would also become a red giant star. Then it would become so large that it would be swallowing our Earth in the process. Oh ! Don’t worry. It will take five billion years.

Earth’s axis of rotation changes its orientation with respect to the fixed stars in the sky. Hence that star, there, which is our pole star or North Star will not remain as our pole star in future.

Moon is the only natural satellite of earth. Similarly, many other planets also have their own natural satellites. For example, The largest planet in our solar system, Jupiter has seventeen satellites and Saturn has more than twenty-two satellites.

We have developed space vehicles to transport us to moon. Let us imagine that we have boarded one such space vehicle for a journey to moon. Are you Ready for the trip?

But don’t think that we can directly aim a rocket to moon. In this way we will not reach moon because by the time we reach there, the moon would have shifted to a new position, as moon is revolving around earth and the earth is revolving around sun.

Now look at those stars in the form of an archer or may be you can guess it in the form of a teapot. That’s the lid, the body of the pot, the handle and the outlet. This is the constellation of Sagittarius. This is seen in the night sky during the months of July to November from India. Can you observe that white patch near Sagittarius? This is the dense region of our Milky Way galaxy. If you visit Calicut planetarium’s sky observation programme, when this Milky Way is visible, ask to focus the telescope in this patch. You would be observing millions of stars. But don’t think that they are tightly packed. Take any two stars. The distance between these two stars is something like twenty five million million kilometers.

Residing in Calicut, which is bounded on one side by the Arabian Sea, you can never miss to observe the occurrence of tides. If you were a regular visitor of Calicut beach, you would have seen the changes in the level of water along the shores in the course of a month. Ask a fisherman about tides and he would answer you that it occurs four times a day, two high tides and two low tide.

You may be curious to know how moon radiates light. Further you have observed that the illuminated face of the moon changes with time. Does moon produce its own energy? Does the production of energy vary with time? The fact is, the moon actually reflects suns light falling on it. But as moon moves around Earth, just in the same way as Earth and other planets moves around Sun, different fraction of illuminated portions are visible from the surface of Earth depending on the location of the observer. These are called phases of moon. A full moon is about ten to twenty times brighter than a half moon.

When the total circular disc is visible, it’s called the full moon. But when fully dark, its called new moon. Further the moon revolves round the earth in an elliptical path with the earth located in one of the off centered point called focus. Hence the distance between earth and moon continually varies. The point at which the moon is furthest to earth is called apogee and the nearest is called perigee. A lunar month is twenty-nine and half days, roughly two days more than the revolution period of moon around earth. This is due to the fact that by the time the moon completes one revolution around earth, the earth will make a journey of twenty-seven degrees around sun. The moon goes around earth in a little more than twenty-seven days. The entire path around earth is divided into twenty-seven regions called Lunar Houses or Nakshatras, according to ancient Indian astronomy. Each lunar house consists of a little more than thirteen degrees, and they are named after the important stars situated in that region like Aswani, Bariny, Krithika and so on. A person born on the day when moon is located in Aswini is said to be born in Aswini Nakshatra as practised by Astrologers.

You may be wondering, how much time would it take to travel to moon. Well, if it were possible to fly to moon in an aeroplane it would take around two and half weeks. However if you board a spaceship it takes around four days. Light takes one point three seconds to reach earth from the moon.

It is interesting to know that we can accommodate nearly fifty moons inside earth. Further if we keep thirty earths side by side, then we can reach the moon from earth.

Let us see about how moon originated. There are different classical models regarding the origin of moon, each having its own drawbacks.

The hypothesis of fission supposes that moon is a piece of earth’s mantle which detached itself. However, notable difference in chemical composition between the moon and the earth completely invalidates this model.

The second hypothesis of the double planet envisages the accretion of the two bodies, namely the earth and the moon in the neighborhood of each other. This hypothesis is also contradicted by the lunar chemistry.

The hypothesis of capture supposes that moon initially in solar orbit, was captured by the earth. However the capture should have occurred very early and it could have taken place before the crystallization of the earth crust, nearly four billion years ago, because the variation in energy caused by such a capture would have led to reheating and total melting of moon.

A recently proposed theory suggests that the earth and moon system formed by the collision of two large planetesimals. The differentiated body formed a single large object that became the high-density iron rich earth. Ejected mantle material condensed to form the low-density iron poor moon.

Moonquakes occur similar to earthquakes. Most of them originate at a depth between eight hundred to nine hundred and fifty kilometers, whereas quakes of the earth occur within ninety-five kilometers of the surface.

The earth rocks have been exposed to free oxygen, where moon rocks are not. Also compared to earth rocks, lunar rocks generally contain elements, which have high melting point such as calcium, alumunium and titanium.

The moon’s orbit and the apparent sun’s annual path, which are inclined at an angle of about five degrees, intersect at two points called the nodes. Indian astronomers called them by the names of RAHU and KETU, the celestial demon’s head and its body. When the moon is at one of its nodes and between the earth and sun, the shadow of moon may hit a portion of our earth’s surface and a solar eclipse is observed there.

Any shadow formed by a large source consists of two parts, namely the dark central portion called the umbra and the semi dark portion called the penumbra. Whenever the dark portion hits a section of earth,; a total solar eclipse is observed there, and if penumbra hits a portion, a partial solar eclipse is observed.

Similarly when ever earth comes between moon and sun, with the precondition that moon is at one of its nodes, lunar eclipse occurs. The longest observed lunar eclipse was on July 6, 1982 for three hours and fifty-six minutes.

It is interesting to know that the spherical shape of earth got proved from the observation of lunar eclipse.

The maximum duration of a solar eclipse is nearly seven and half minutes. Two Solar eclipses in the same calendar month of a year is very rare. For example, solar eclipse occurred twice in December 1880. This will be taking place in July 2000 and for a repeate one has to wait till December 2206.

Occultation is a phenomenon, which takes place when a nearby body such as the moon, hides the view of a farther object such as a star as seen from earth. The occultation of the stars along the ecliptic by the moon is a common phenomenon. Due to the five degrees tilt between the ecliptic along the moon’s obit around the earth, the moon occults stars within a belt of ten degrees from the ecliptic.

Look at that bright star in the constellation of Taurus. It is observed in the night sky during the months of November to April from India. It is called Aldebaran or Brahmarishi in Sanskrit. It is a red giant star. In future our sun is also going to become a red giant star. Now look at those stars in the form of a lion. That particular star is called Regulus or Magha, and the constellation is called Leo or Simha. It is seen in the night sky during the months of February to September from India. Now look at those stars in the form of a Virgin. It is called Virgo or Kanya. It is seen in the night sky during the months of March to August from India. That star in this constellation is called spica or chitra. These stars are frequently occulted by moon.

Many incidents and discoveries are connected with occultations. One of them is the occultation of a star by Uranus, Seventh planet in our solar system, on March 10,1977.This was a very significant one. This was observed from India and the Southern Hemisphere, notably from the South Africa and Australia. Kuiper Airborne observatory was pressed into service. J C Bhattacharya and K Kuppuswamy , both from Indian Institute of Astrophysics, Bangalore, observed the event from India. The star winked several times before going behind the planet. The star winked again as it came from behind Uranus. This indicated the presence of some unknown obstacle around Uranus. A detailed mathematical analysis unveiled rings around Uranus.

Through a remote sensing camera inside our space ship let us scan the lunar surface. It’s so uneven, consisting of highlands, plains and lowlands. The lowlands are called craters. The darker lava filled basins was named Maria by Gallelio, which means seas in Latin. The highlands called terrae are recognizable by their bright colour and mountainous nature. They cover nearly eighty percent of the surface of the moon. The craters are formed mainly by the impact of meteors from outer space. Further there is no atmosphere above the surface of moon because of its low value of the velocity needed to escape from its gravitation field. For this reason we have been provided with oxygen cylinders to be carried with us during our movement in the moon. Due to the lower mass of the moon the gravitation on the surface of the moon is one sixth that of earth. Further as there is no atmosphere, the atmospheric pressure on the moon surface is nill .For adding mass to our body to overcome low gravitational field and the absence of atmosphere, we are provided with specially designed suit on the surface of moon.

We shall be landing near mare tranquilities where the first human, Neil Armstrong landed on July 20; 1969. We can observe from this space ship that apart from few recent impacts, the craters and the ejecta of the highlands are severely defaced.

The Maria’s are the prominent features on the surface of moon. In fact they are large plains composed of dark materials that are only slightly cratered. Studies show that Maria was formed from a molten liquid that fills the low-lying areas with layers of very fluid lava.

Further, analyzing the data transmitted by Lunar Prospector, a space ship sent by NASA for studying moon, scientists have found evidences of water in the form of ice crystals on the moon’s polar surface. They have also mapped precisely the variation in the gravitation pull of the moon over its surface. Also, recently in late 1999,this spacecraft crashed on the lunar polar region and dispersed the ashes of the astronomer Shoemaker, who had a dream of going to moon which never got fulfilled.

Finally we are approaching our destination. Here we land. Getting down the ladder we can first observe the American flag erected by Armstrong. The footprints of Armstrong are present intact. They will remain here for millions of years. Eventually, tiny hits from small meteoroids will cause the footprint to fade. We can observe our home, Earth. Due to synchronization between the rotation and revolution of the moon the earth is fixed in the lunar sky. For the same reason we can only observe one particular face of the moon from earth. Further unlike the daytime sky of earth, here the sky is always black with sun and stars. The blue sky on the earth is formed due to the scattering of light by dust particles in our atmosphere and moon has no atmosphere, so the moon’s sky is black. Here we find that the surface is completely covered by a layer of dust, some five to ten meters – the regolith. In 1959 Lunar 3 revealed that the hidden side of the moon is much different from the other visible part.

Further by measuring the time it takes for a laser beam to return to the earth from the reflectors installed on the surface of the moon, very accurate measurements of distance can be made. It has been estimated that the moon moves a little farther away from the earth every year. Precise measurements show that the moon is receding from the earth at a rate of three centimeters per year.

Could human colonize moon? The moon is a dead world – There is no air to breathe, no water to drink, no grass, no trees and no life of any kind. The temperature on the surface varies between one thirty degree Celsius during day to minus one twenty nine degree Celsius during the two week long lunar night. The two week long lunar night is due to the synchronous rotation of moon about its axis and its revolution around earth. Yet ambitious plans are being developed for the construction of permanent bases on our nearest celestial neighbour. Some day there may be an entire city on the moon where thousands of people can live in comfort and safety.

Now its time to return to earth. As we do so lets imagine our earth without moon. What would happen if the earth lose its natural satellite? First of all, it would affect the beauty of night; there would be no cool and transparent moonlight, no silvery paths on water. There would be no more moon tides, to be left only with solar tides. But the sun being at such a great distance away, its tides would be far weaker than moon's tide.

The absence of moon would make astronomical observation easier. We would discover more comets, see possible smaller planets in our solar system, and so on.

The moon is indispensable in the development of space travel because many essential operations involved in space navigation are tried out in the vicinity of the moon.

Further, the confirmation of Newton’s law of universal gravitation came from studies of moon’s revolution around earth. Again, the same observation first prompted the idea of creating artificial earth satellites. The moon was the first mirror in space, which helped to develop the methods of astronomical radiolocations. The experiments with radio waves reflected from the lunar surface were the basis for designing special instruments to locate many of the planets in the solar system.

Further, one of the natural units of time that is from new moon to new moon or from full moon to full moon, which is approximately a little more than twenty-nine and half days would be lost.

The Moon is still enigmatic despite its closeness to our home, Earth. The complete mystery is not known, neither it can be revealed in a single sitting.

Ladies and gentlemen, as you leave this planetarium you would be realizing how important is our earth’s natural satellite to us.