Want to travel in universe
The universe is a name that we use to describe the collection of all things that exist in space. It is made of trillions of stars, galaxies, black holes, enormous clouds of gas and many other fascinating things
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“Two things are infinite: the universe and human stupidity; and I'm not sure about the universe.”
The Universe contains billions of galaxies, each containing millions or billions of stars. The space between the stars and galaxies is largely empty. However, even places far from stars and planets contain scattered particles of dust or a few hydrogen atoms per cubic centimeter. Space is also filled with radiation (e.g. light and heat), magnetic fields and high energy particles (e.g. cosmic rays). The Universe is incredibly huge. It would take a modern jet fighter more than a million years to reach the nearest star to the Sun. Travelling at the speed of light (300,000 km per second), it would take 100,000 years to cross our Milky Way galaxy alone. No one knows the exact size of the Universe, because we cannot see the edge – if there is one. All we do know is that the visible Universe is at least 93 billion light years across. (A light year is the distance light travels in one year – about 9 trillion km.) The Universe has not always been the same size. Scientists believe it began in a Big Bang, which took place nearly 14 billion years ago. Since then, the Universe has been expanding outward at very high speed. So the area of space we now see is billions of times bigger than it was when the Universe was very young. The galaxies are also moving further apart as the space between them expands.
“The magic is only in what books say, how they stitched the patches of the universe together into one garment for us.”
Today, scientists are not so sure that life began on or near the Earth's surface. Everywhere we look, there seems to be life – even several kilometres underground. It may be that life began at the bottom of the oceans, where hot springs provided energy instead of sunlight. Another idea is that life – or at least the chemical building blocks – came from space. Many comets were crashing into Earth early in its history. Comets are rich in carbon-based chemicals from which life could have started. It is also possible that life could transfer from one planet to another. It seems that life is tough enough to survive a long journey through space. A large comet or meteorite crashing into the Earth could throw large numbers of rocks into space. Any bacteria that are riding as passengers on these rocks could eventually land on another planet. In the same way, a meteorite from Mars could carry Martian life (if it existed) to Earth. In 1996, scientists told the world that they had found just such a Martian rock in Antarctica. However, other scientists question their research.
“ 'THE BIG-BANG' We are an impossibility in an impossible universe.”
Most astronomers believe the Universe began in a Big Bang about 14 billion years ago. At that time, the entire Universe was inside a bubble that was thousands of times smaller than a pinhead. It was hotter and denser than anything we can imagine. Then it suddenly exploded. The Universe that we know was born. Time, space and matter all began with the Big Bang. In a fraction of a second, the Universe grew from smaller than a single atom to bigger than a galaxy. And it kept on growing at a fantastic rate. It is still expanding today. As the Universe expanded and cooled, energy changed into particles of matter and antimatter. These two opposite types of particles largely destroyed each other. But some matter survived. More stable particles called protons and neutrons started to form when the Universe was one second old. Over the next three minutes, the temperature dropped below 1 billion degrees Celsius. It was now cool enough for the protons and neutrons to come together, forming hydrogen and helium nuclei. After 300 000 years, the Universe had cooled to about 3000 degrees. Atomic nuclei could finally capture electrons to form atoms. The Universe filled with clouds of hydrogen and helium gas.
