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Information about 'The Universe'
Stars, moons, planets, Earth, space and everything that you see in the sky are on the land are included in the universe. Scientists have different theories about the beginning of the universe. The most popular of these theories is the Big Bang theory. According to the theory, the universe started as a result of a big explosion, or the “Big Bang”. Nobody knows how long ago the Big Bang occurred. In other words, we don’t know the exact age of the universe.
The solar system is the name given to the sun and the nine planets (including our Earth) that move around it. Some of the planets have their own satellites (or moons), and they are also included in the solar system. There are also some free moving asteroids (or tiny particles) that form a ring between Mars and Jupiter, and they too are included in the solar system. Apart from these heavenly bodies (objects existing in space), there are also gases and comets (shooting stars). Scientists usually believe that the solar system came into being around 4.7 billion years ago.
The nine planets of the solar system are listed below according to their distance from the sun:
Named after Mercury, (from Roman Mythology) the messenger of the gods, Mercury is closest to the sun. The average distance from the sun is 58 million kilometers, it completes a circle around the sun much faster than the earth, and the period f the orbit around the sun is 88 Earth days. Its surface temperature is believed to range from -180o to 102o C, and the surface gravity is 0.38 times that of the Earth.
Named after Venus, the Roman god-dess of love and beautiful Venus is the second planed of the solar and is one of the brightest planets in the sky. Its average distance from the sun is 108 million kilometers. The average surface temperature is about 450o C and the surface gravity is 0.91 times that of the Earth. The period of orbit around the sun is 225 Earth days.
Earth is the only planet where life is possible. Its average distance from the sun is 150 million kilometers. The temperature of the surface of the Earth varies from about -89o C to about 58o C. the period of the orbit around the sun is 365 Earth days.
Named after Mars the Roman god of War, It has two moons. It appears like a red star on the night sky. Its average distance from the sun is 228 million kilometers. The surface temperature usually range from about -120o C to about 30o C and the surface gravity is 0.38 times that of the Earth. The period of orbit around the sun is 687 Earth Days.
Named after Jupiter, king of the Roman gods, It has 16 moons revolving around it. It is made up of gases and has no solid surface. Its average distance from the sun is 778 million kilometers. The average temperature is about -140o C and the surface gravity is 2.9 times that of the Earth. The period of orbit around the sun is about 12 Earth years.
Named after Saturn, the roman god of agriculture, It has 18 moons. It is made up of gases and it has rings around it that are even visible from the earth. These rings contain various particles that circle the planet. Its average distance from the sun is 1425 million kilometers. The average temperature is about -170o C and the surface gravity is 1.3 times that of the Earth. The period of orbit around the sun is 29.5 Earth years.
Named after the Roman god Uranus, It has 15 moons and cannot be seen from the earth without a telescope. Its average distance from the sun is 2867 million kilometers. The average temperature is about -184oC and the surface gravity is 0.93 times that of the Earth. The period of orbit the sun is 84 Earth years.
Named after Neptune, the Roman god of seas and navigators, it has 18 moons and cannot be seen from the earth without a telescope. Its average distance from the sun is 4486 million kilometers. The average temperature is about -218oC and the surface gravity is 1.2 times that of the Earth. The period of orbit around the sun is 165 Earth years.
Pluto is the most distant planet from the sun. Its average distance from the sun is 5890 million kilometers and its surface probably consists of frozen water, ammonia and methane. The average temperature is about (-230o C), the period of orbit around the sun 249 Earth years.
Life on Planets
Out of these Planets, Earth is the only one where life is known to exist. In fact Earth is the only planet in the universe with known life. Other planets have very different conditions from Earth and at least the kind of life that exists on Earth is very difficult to imagine there. For instance, Mercury and Venus are too hot, while the other planets are too cold. A day or night lasts 42 years on Uranus, while a year on Pluto is as long as 247 Earth years (plus a few months)!
The sun is about 150 millions kilometers (km) away from the Earth. It is many times larger than all other planets of the solar system combines together. If you imagine the Earth as a pea, then the sun would be a big as a football.
The sun mainly consists of gases. The most important of these is hydrogen, which is used in nuclear reactions that happen on the sun all the time. Around 6 million tones of hydrogen are burnt up every second, but the sun is so huge that it can continue to shine at its present brightness for another 6 billion years.
The burning of gases on the sun gives out enormous heat and light, which has made it possible for life to exist on the Earth. Without the sun there would be no life on our planet.
Like all other planets of the solar system, the Earth also revolves around the sun. The path covered by the Earth while revolving around the sun is called its orbit. The time in which the Earth covers this distance is called year.
While the Earth revolves around the sun, it also rotates around itself. The imaginary line around which the Earth rotates is called axis. The time in which the Earth completes on rotation around axis is called a day.
The moon revolves around the Earth and completes one circle in 29.5 days. It does not have a light of its own, but glows due to the reflection of the sunlight.
You know that the moon circles the Earth. Sometime the moon comes in-between the Earth and the sun. When this happen the shadow of the moon falls on the sun and this is called the solar eclipse. One such eclipse occurred in 1999 and was visible in many areas of South Asia, including Pakistan.
Lunar eclipse, or the eclipse of the moon happens when the Earth is in-between the moon and the sun. If the Earth positioned centrally, then there is a total lunar eclipse, otherwise only partial lunar eclipse occurs.