The phases of moon

Do we know?. why does the moon changes its shape?

The moon, which causes high and low tides on the Earth, is a sphere. It does not changes its shape; only our view of it changes. The reason is that unlike the stars, the moon does not produce light, but only reflects the light of the sun. Since the moon goes around the Earth once in a month, the orientation of the moon, the sun, and the Earth respective to one another changes. For this reason, the illuminated part of the moon cannot always be seen clearly from the Earth. Sometimes we see it full, sometimes half, and sometimes not at all. The side of the moon that faces us remains the same. We can see the craters and dark spots on the moon, which are known as 'mares'.

We always see the same side of the moon.

It happens because of the moon rotates once on its axis during the time it complete one revolution around the Earth -which is 27 days, 7 hours, and 43 minutes. The mutual attraction between the Earth and the moon has tuned these two movements in this way. In fact,we did not know for a long time how the moon looked 'from behind'. In 1959, a Russian probe sent pictures of the unseen side of the moon to the Earth. The Apollo spaceship landed on the visible side of the moon because a radio connection cloud not be established with the other side.

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The lifecycle of stars

Do we really know about a star? Stars are heavenly bodies, which shine like our sun. Many shine brightly, the others have a dim glow. Some are red while others are blue. Stars are giant balls of gas made of hydrogen, bound together by their own force of gravity. The energy that makes them shine comes from a kind of power plant in their interior, where atomic nuclei of hydrogen atoms are fused together to form helium atoms. The stars do not live forever and ;die' at some point. Many simply get extinguished, while very heavy stars expand and explode. Their remains become either a neutron star of a 'black hole'. The cradle of a star is a cloud of hydrogen and dust. There are numerous such clouds in the universe. By the action of external forces -such as the explosion of a star -this cloud gets compressed and keeps pulling itself together due to the increasing force of attraction among the particles. After a few hundreds of thousands of years, it begins to ...

How many plant species are there?

Today, scientists are aware of around 320,000-500,000 different species of plants, but they estimate this number to be much higher. Many of the known trees and flowers come from Asia, while other species of plants thrive in the tropical rain forests. Some plants have adapted to live in or below water, whereas some have adapted to live in the desert areas. Algae, lichen, and moss also belong to the plant kingdom. Lichen: Many lichens grow in inhospitable terrain; for instance, in the rocky highlands and cold Arctic. They also grow on the walls of the houses in big cities. The growth rate of lichens very slow -a few species grow less than one millimetre in a year. If you step on them, you may destroy in seconds a plant that took hundreds of years to grow. Since lichens are very sensitive to air pollution, they are often used as pollution indicators. The cleaner the air the more lichen will grow. ...

How are animals becoming extinct?

Since the animals have evolved species continue to become extinct. The most well-known example of extinct species is that of the dinosaurs. Often the species cannot adjust fast enough to the changing environmental conditions, or new species arise and displace the existing ones. Today, many species are becoming extinct because of the actions of humans. Elephants, big cats, and rhinos are hunted ruthlessly, forest areas are cleared, and the grey whales are endangered. These are only a few of the species mentioned in the ' Red List'. Do you know about 'Red List'? 'Red List' comes under organization IUCN (The International Union for Conservation of Nature). The list of endangered species is known as the Red List. It lists all those plant and animal species that are facing the threat of extinction worldwide. The list is revised every 2 years. For the year 2006, the list contained around 16,000 species of plants and animals; 530 species more than t...

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