Journey to the Moon

The three manned Apollo-11, which had enough space for astronauts to not only move about but also to stand erect within it, set out on a journey to the moon on July 16, 1969. The special feature of Apollo’s landing on the moon was that its two astronauts could touch the surface of the moon with the help of the four legged lunar module Eagle.

At 10.56 pm on July 20, 1969. Neil Armstrong set his foot on the surface of the moon. He was the first human being to put his foot on the moon.

            In his radio communication sent to the earth Neil Armstrong described it as one small step for (a) man, one giant leap for mankind. Therefore, Edwin Aldrin stepped out on the moons surface. Michael Collins remained aboard the Apollo 11 command module in orbit. The two astronauts spent around 2 hours 30 minutes on the moon. During this period, they collected samples of moon’s rocks and soil weighing over 20 kg.

            The total estimated expenditure on this US space programme at sending men to the moon, with Apollo 17 was around 2,554.1 million dollars. With a view to reduce expenditure space shuttle was invented by the US scientists. Space shuttle is a reusable manned space vehicle with a speed of about 28,000 km. per hour. The first space shuttle Columbia was launched on April 12, 1981. The USSR launched a similar space vehicle named buran in September 1988 which returned to the earth safely after successfully completing the mission.

            After the success of this mission, the following persons made journey to the moon under the Apollo programme. They brought with them rocks and soil weighing 3,800 kg.

Apollo 12        : Conrad, Bean, Gordon November 14,     1969

Apollo 14        : Shepard, Mitchell, Roosa January 31, 1971

Apollo 15        : Scott, Irwin, Worden July 26, 1971

Apollo 16        : young, Duke, Mattingly II april 16, 1972

Apollo 17        : Cernan, Schmitt, Evans December 7, 1972

 

Apollo-11 Moon Landing

 Apollo 11 Lunar Module

Neil Armstrong set his foot on the Moon on July 20, 1969

Surface of the Moon

Our Universe - The Sun

            The sun is one of the stars in the Milky Way. It looks bigger than other stars because it is the closest star to the earth. However, it is smaller than some other stars. Betelgeuse, a red giant star, is 800 times bigger than the sun.

The sun is a huge mass of gases

            The sun lies about 150 million km. from the earth. Its diameter is about 1,40,000 km. i.e., 109 times the earth’s diameter. Its gravitation is 28 times more than the gravitation of the earth.

Parts of the Sun

            The sun lies at a distance of about 32,000 light years form the centre of the galaxy. It takes the sun about 225 million years to complete one revolution around the center of the galaxy with a speed of 250 km. per second. This period is called cosmic year. The sun, like the earth, and, therefore, can rotate at varying speeds at different latitudes. It rotates once on its axis in 24-25 days at the poles and in 34-37 days at the equator.

            The sun is composed of about 75% hydrogen and almost 25% helium. It may be called a big hydrogen bomb because it release huge amount of heat and light as a result of nuclear fusion. The sun is directly

Responsible for all life on earth. It provides the earth with all of its light, heat and energy.

            The glowing surface of the sun which we see is called photosphere. It has a temperature of about 6000 degree centigrade while the temperature of the core is 15,000,000 centigrade Celsius.

            The glowing flames constantly arising from the photosphere are called solar prominences which rise up to a height of 1,000,000 km.

            The dark spots noticed on the surface of the sun are called sunspots. They are cooler than the surrounding area. The life span of sunspots varies from a few hours to many weeks. Larger sunspots may have temperatures up to 4000-5000 degree Celsius. Some of them are made of many folded layers larger than our earth’s size.

            When sunspots persist for longer periods, they cause solar flares and high solar prominences which create upheavals in the ionosphere resulting with disturbances in our radio communications.

The Earth’s Force of Gravity

What is the earth’s force of gravity?

            According to science, the earth attracts everything towards its centre. It is for this reason that fruits from trees or a ball thrown up into the air, all fall to the earth surface. This invisible force of attraction between the earth and any other body is called the force of gravity.

Gravitational pull keeps the moon revolving around the earth

            The centre of gravity of the earth lies in this center. Imagine what would happen if a hole is drilled in the earth form one side to the other, passing through its centre and a ball is dropped in this hole. The ball, in fact, will stop at the centre of the earth; it will not come out form the other side. The weight of a body will be more, if it is nearer the centre of the earth.

            Similarly, the weight will be less if the body is away from it. This is why a body weighs more at the poles than at the equator, since the poles are nearer to the centre than the equator.

            Not only the earth, but all other planets have this force of gravity. As a matter of fact, every body in this Universe attracts the other body with its force of gravitations, and it is this force that keeps all the planets and stars in their places in the sky. It is this gravitational pull that keeps the moon revolving around the earth, and the earth revolving around the sun.

            Naturally, the moon also attracts the earth; tides in the seas are mainly due to the gravitational pull of the moon.

            Till the end of the 15^th century, it was assumed that if two bodies were simultaneously dropped from the same height in vacuum, the heavier body would hit the ground first.

            But this assumption was found to be baseless. The famous scientist Galileo Galilei was the first to prove that irrespective of their masses, all the objects dropped simultaneously form the same point in vacuum will reach the ground at the same time. He dropped one ball weighing 100 pounds and another of just half pound at the same time from the learning tower of Pisa, and demonstrated in the presence of thousands of people that both the balls hit the ground at the same time.

            Subsequently, Newton propounded the law of gravitation. According to this law, the force of attraction between two bodies is directly proportional to the product of their masses ad inversely proportional to the square of distance between them. It follows form this that the force of attraction will be doubled if the mass of one of the two bodies is doubled.

            On the other hand, if the distance between them is doubled, the force will be reduced to one-fourth of the initial value. The velocity of a freely falling body towards the earth increases by 9.8 meters or 32 feet every second. This is called acceleration due to gravity.

Geodesy

What is geodesy?

            Geodesy is the science of measuring the circumference of earth. When people came to know that the earth was round, they made use of geometry related to circles and angles. Nowadays, geodimeters can measure long distances very accurately by using light rays.

The traditional method used  by eratosthenes to calculate the circumstance of Earth

            The diagram shows how, in about 250 B.C., Eratosthenes measured the earth’s circumference. At noon in midsummer, the sun shone straight down a well at Syene, near Aswan in Egypt. At the same time in Alexandria, monument showed that the sun made an angle of 72 degrees.

            Using geometry, Eratosthenes knew that the angle at the centre of the earth would be the same. He calculated that the earth’s circumference was 46,300 kilometers.

            Eratosthenes was not very inaccurate in his measurements. In fact, the distance around the equator is 40,076 kilometers.

            Geodimeters are very useful and accurate devices for taking earth measurements.

Measure the Mass of the Earth

How do we measure the mass of the earth?

            When we wish to know the mass of an object, we weight it in a balance. The size of the balance varies with the size of the object to be weighed. The earth is a giant body and to think of a balance for weighting it, is almost impossible. Then, what is the way of measuring the mass of the earth?

            Scientists use Newton’s law of gravitation to determine earth’s mass. According to this law, there exists a force of attraction between any two bodies in the universe and this is dependent on the masses of the two bodies as well as on the distance between them. The force of attraction is directly proportional to the product of the masses of the two bodies, and inversely proportional to the square of the distance between them.

            An experiment is performed to determine earth’s mass with the help of the above mentioned law. In this experiment, a small metallic ball is suspended with the help of a thin thread. The position of this ball is accurately determined. Now a big lead ball weighing a ton is brought near this ball. The small ball is attracted towards the big ball due to the gravitational pull and as such it is slightly displaced form its initial position with respect to the big ball. The change in the position of the small ball is even less than one-tenth of an inch. This displacement is very accurately measured with the help of precision instruments. Using with the help of displacement in a formula of physics, the mass of the earth is calculated. The mass of the earth has been found to be 598x10¹⁹ (5980, 000,000,000,000,000,000) tones. 

Steps of Earth Formation

How was the earth formed?

            Have you ever wondered how earth came in to existence? This unique planet came into existence around 4.6 billion years ago. Earth is the third planet forms the sun and the only planet on which life exists. Like the sun and the other planets, it was also formed out of dust clouds and gases. Would you believe that before taking its present shape, earth was a fireball? Earlier, earth revolved around the sun in the form of a hot spherical body. Thousands of years later, it gradually started moving away from the sun but still kept revolving around it. S it moved farther ad farther form the sun, the temperature of earth kept decreasing. As it started cooling, its outer layer changed into a crust. With the hardening of this crust, cracks developed in it and molten material from inside started coming out. Over a period of millions of years, this molten material gave birth to mountains and valleys.

Earth is 4.6 billion years ago

Earth is 1500 millions of years ago

Earth is 200 million years ago

Earth is Today

            As time passed, the thick layer of hot gases enveloping the earth started cooling and turned into clouds. These clouds rained on the earth continuously for a long time. Rainwater accumulated in the low-lying areas of the earth and these areas became the oceans as we know the today. With the passage of time, there were upheavals due to which its surface was raised high, or pressed down. This resulted in many volcanoes. Slowly, earth became calm and the seas and mountains took their definite shapes.

            Subsequently, around 570 million years ago, micro-organisms started developing on the earth. In the first 345 million years of earth’s existence, marine aquatic animals came into existence. As time passed, the aquatic animals also underwent changes.

            In the next phase of evolution, the great reptiles came into existence. And finally, around a million ears ago, man gradually evolved form lower two-legged species. Today, earth has the most favorable climate among all the nine planets, which is required for the sustenance of life. Had there been no atmosphere around the earth, human life would not have existed.