Why were the Pyramids built?

The Pyramids were built as tombs for the pharaohs of ancient Egypt.

The early kings, or pharaohs, were buried in tombs inside roughly built stepped pyramids. The greatest pyramids came later. The largest is that of the pharaoh Khufu (also called Cheops) at Giza. Over two million blocks of stone were needed, each dragged into place by hundreds of slaves.

Inside the burial chamber, the pharaoh's body, preserved as a mummy wrapped in cloth, was buried in a stone tomb. Around him were food, clothes, weapons: everything that he might need in the next world.

Why cannot I fly?

You cannot fly because the force of gravity pulls you down. In order to fly, the force of gravity has to be overcome. Birds, bats and insects can fly because they can overcome gravity.

Why do we say that the optical telscope drew a new picture of the Universe?

The telescope was a very important discovery in astronomy, and astronomers discovered that if more light reached the eyepiece of a telescope, the image would be much brighter. So, they made the lenses and mirrors of their telescopes bigger, so as to capture as much light as possible, and focus it on a single point.

Optical telescopes have lenses in them that collect light from objects in the sky. These lenses focus the light, by either bending it or reflecting it to form an image. There are two different designs of optical telescopes - refracting telescopes and reflector telescopes. An optical telescope forms images of faint stars and other objects that are very far away, so as to give the observer a clearer picture of the Universe. This type of telescope can gather many times the amount of light that your eye can.

Why did Copernicus revolutionize concepts about the Universe?

Copernicus is said to be the founder of modern astronomy. His investigations were carried on quietly and alone, without help or consultation.

He made his celestial observations from a turret situated on the protective wall around a cathedral. His observations were with just his eyes, as a hundred more years were to pass before the invention of the telescope.

In 1543, Copernicus published a book about a new idea he had. Most people in his day thought that the Earth was at the centre of the Universe. They thought that the stars were little holes in a glass ball that surrounded the Earth. But, Copernicus disagreed. According to him, the Universe is not centred around the Earth, but that the Earth is actually a planet circling the Sun. Not many people liked his book or his ideas, for they went against the philosophical & religious beliefs that had been held during the medieval times. Copernicus died in 1543, and was never  to know what a stir his work had caused. Of course, we know today that Copernicus was right!

Why did ancient astronomers observe the sky?

Beginning around 600 BC, ancient philosophers and scientists developed a number of important astronomical ideas by simply observing the sky, since they didn't have any modern tools or instruments to tell the time, location of a place or the nature of the Universe.

The ancient Greeks were able to figure out the shape and size of the Earth by calculating the height of the Sun or the stars. About 230 BC, Eratosthenes estimated the size of the Earth by using the Sun as a reference point. The sundial was another simple tool that depended on the Sun to let people know what time it was.

Sailors at sea used the stars above to guide them. In fact, Many early tribes of Polynesia and New Zealand have sailed great distances using the stars for navigation. The sun's position in the sky also allowed sailors to determine the latitude at which they were sailing. Another instrument called the 'qiblah' used the sun to find the direction of Mecca, so that Muslims could face in that direction for their daily prayers. So, you see ancient astronomers had many good reasons, to watch the sky, the Sun, stars and the Moon, day and night.

How did the ancient astronomers pictured the Universe?

The ancient astronomers pictured the Universe from the point of view of an observer on Earth. In fact, to them, the Earth was the centre of the Universe, and they believed that above it was a shining dome that was sprinkled with thousands of shining little lights that were the Sun, the Moon and the stars.

Later, the Greek astronomer Pythagoras suggested that the Earth might be a sphere, but he still thought that it was the centre of the Universe. It was only in 1543 that an astronomer named Copernicus suggested that the Sun might be the centre of the Universe. It was with the discovery of the telescope that Man finally developed a better picture of what the Universe is really like.

Why did astronomy spread and grow?

The earliest atronomers were priests and holy men, studying the movement of celestial bodies to chart celebrations and planting cycle. Their knowledge and theories of the Universe spread through two routes - trade and war. As great empires expanded, their gods, cultures, and learning influenced other cultures as well.

The ancient Babylonians were amongst the first to start developing theories about the design of the Universe. The Greeks and Romans later adopted the Babylonian system, replacing the names with the names of their own Gods. The earliest astronomical records are in the form of clay tablets that have been discovered in what was once Mesopotamia.

Early observers of the heavens realized that the repeated motions of the Sun, Moon and stars could be fashioned into a clock to tell the time of the day, and a calendar to mark the progression of the seasons. Many of the ancient monuments, in fact, show some of the features of an astronomical observatory.

Did you know that the earliest observatory to have survived is in Korea? It is a simple beehive structure with a hole in the roof.

Why is the astronomy called the first science?

Astronomy, or the study of the stars, began as a science only about 2,500 years ago, though people have been gazing at the heavens for millions of years. In the beginning, Man had only a few crude hand tools. Using these tools, and some mathematical calculations, he tried to find some explanation for the changing seasons, the floods, the droughts, sunrise, sunset, and all the other mysteries of nature.

Some of these explanations were very primitive and strange. But they are important, because they made people think and ask, and it is this spirit of curiosity that replaced imaginations with scientific observation and reasoning. This is why astronomy is called the first science.

Why are there many myths about the creation of the Universe?

Haven't you often wondered how this Earth and our Universe began? Well, this question has fascinated Man for millions of years, and different cultures and civilizations developed their own myths to answer this question. The ancient Egyptians, for example, believed that the Universe was created when the God Atum uttered his own name. Next, he vomited up his brother and sister, and they had two children together called Geb, who was the Earth, and Nut, who was the sky.

The Chinese believed that the Universe began with a huge egg, and within it, two forces known as ying and yang created the God Phan Ku, who in turn became the Universe.

The Hindus have several creation myths. One of these myths states that Universe began when the ocean gave birth to a golden egg from which Brahma, the creator of the Universe emerged.

The Aztecs of Mexico had a rather violent myth. They believed that the Universe was created when a goddess was ripped apart by two other gods creating the Earth and the sky!

According to the Christians, God created the Universe in six days, and rested on the seventh day. Today, of course, science has other explanations for the origin of the Universe, but you must admit that the old myths are really fascinating.

What are cosmic rays?

Cosmic rays are tiny particles that slam into the Earth's atmosphere at various levels of energy. Billions of cosmic rays are slamming into the Earth every second, most of them with a quite low energy. Although they are called 'cosmic rays', it should be noted that cosmic rays are point-like atomic particles. They are called cosmic rays because they are found everywhere in the Universe.

Astronomers believe that cosmic rays reach their high speeds because of the action of magnetic forces in space. There are two types of cosmic rays - primary and secondary. Their study provides scientists with information about the structure, operation, and history of the galaxy and of the Universe.

What is the relationshipe between matter and energy?

Matter is the material which makes up all things on Earth. Energy is simply the capacity for doing work. Matter comes in three states - solids, liquids and gases, and energy comes in many forms too. The most common forms of energy are kinetic energy and potential energy. Kinetic Energy is energy due to motion, and potential energy is the energy that is stored in an object that can be converted into kinetic energy.

Scientists now think that matter is formed as a result of the 'freezing' of energy. They believe that the particles that make up matter began to form out of some of the energy, when the Universe became cooler, after the 'birth' of the Universe.

What is the Theory of Relativity?

You've probably all heard of Albert Einstein and his Theory of Relativity before. It is this theory that helped scientists to answer to the mysteries of the Universe. So, what is this theory?

Well, to put it simply, one of Einstein's great insights was to realize that the movement of an object is a relative one. For example, suppose you are travelling in a car with your father. As you see things moving away, you can say you are moving. But, for your father, you are not moving at all. That means if you are moving along with a body, you cannot feel the motion. In other words, motion is relative. Again, Einstein observed that the fastest thing in the Universe is light, and that light travels at a constant speed any where in the Universe.

He also said that, matter and energy are different forms of the same thing. Matter or mass can be turned into energy, and energy into mass. According to Einstein, you multiply the mass, say m, by the square of the speed of light (c), which is constant, to get the amount of energy, that is E. It is written as E=mc(2). This is a rough idea of the Theory of Relativity.

What is light?

Throughout human history, light has been something Man has taken for granted. We know that it comes out of the Sun or a lamp, let us see things, and makes us warm. But what is it?

Light is a form of energy. It consists of photons that move in waves. The size of a wave is measured as its wavelength. Light can move through a vacuum, and its speed can be measured.

The white light that we see it not white at all. It is actually a mixture of all colours. The band of this mixture is known as a spectrum. The different colours in the spectrum have different wavelengths. So, we know many things about light, but it is still difficult to define it exactly!

Will the Universe end?

It is difficult to think that the Universe might end some day. But cosmologists, the people who study the Universe, are sure it will. They think it will stop expanding outwards, and start shrinking back to nothing. They call this event the 'Big Crunch'. The stars will burn out gradually, and finally, there will be just lumps of rock and dust floating around. However, don't worry too much about it. All this is billions, and possibly trillions of years from now. Moreover, there are still some scientists who think that this won't happen at all, and that the Universe will go on forever. They figure that gravity won't allow the Universe to stop expanding, and so it will just keep getting bigger and bigger!

Where are we in the Universe?

The Earth is the third planet of eight (or nine, if you still count Pluto as a planet) from the Sun in the solar system, at an average distance of about 149,668992 kms. The solar system itself is on the inner rim of one of the arms of the Milky Way galaxy. It is about 6,500 light years from the next arm!

The Milky Way galaxy is millions of light years from what we believe to be the centre of the Universe. It is only one of more than probably billions of galaxies in the Universe! In fact, there are about 1.8 million, million stars for every human being alive on the Earth today. Awesome isn't it? It makes us realize what a tiny, tiny role our planet plays in the Universe.

Why is it possible for us to study the Universe?

The most basic way to study the Universe is simply to look at it. Even with just the naked eye, it is possible to make observations. Many astronomical objects are easy to see, such as the planets like Venus, Jupiter, Mars, and Saturn, and meteors, comets, and even teh distant stars.

A simple telescope helps us to see much more of our Universe, or at least our solar system. For example, the rings around Saturn become visible if you look at the planet through a telescope. Some telescopes let you see features on the planet's surface as well. More complicated telescopes give us more detailed information.

Telescopes that use mirrors have the distinct advantage of allowing much larger lenses, and the larger the lens, the further it can see. Telescopes like the Hubble Space Telescope are placed in space, to get clear images of the Universe.

Special instruments called spectrometers study the light coming from the stars, and break it up into its components or spectrum. Scientists use this information to figure out the features of a star, like its temperature, composition, and whether it is moving or not. Radio telescopes detect a wide range of radio frequencies given off by celestial objects, and this can be used to study stars.

Some objects are so far away that we cannot see any light that they emit, even with the most powerful telescope. However, they do emit heat. Studying infrared light with the help of special instruments can be extremely useful for detecting heat radiated by objects, and dust in space.

We can also learn about the Universe by studying the x-rays and gamma rays given off by the stars.

What is Parsec?

Parsec is another unit of distance. It was introduced when people started measuring the distance to nearby stars using the parallex method. It corresponds to the distance at which the mean radius of the Earth's orbit stretched an angle of one second of arc. One parsec is equal to about 3.258 light years. It is used to measure distances in astronomy since it is a convenient size to measure such large distances.

Some universal facts

• Far Far Far Away!
  The galaxy named Abell 1835 IR 1916 is the most distant object in the Universe, according to the European Southern Observatory, in Chile. It is about 13,230 million light years away from us.
• The Big Eye!
  The NASA Hubble Space Telescope, which weighs 11 tonnes, is the largest space telescope. It is 13.1 metres long with a reflector of 240 centimetres in diameter. It was placed in the orbit, on April 24, 1990 by the space shuttle Discovery. Did you know that it cost around 2.1 billion dollars to NASA to make this telescope?
• The Largest!
  The twin Keck Telescopes, situated on the summit of a dormant volcano in Hawaii are the largest optical and infrared telescopes all over the world.
  

What is a radio telescope?

Almost all objects in the Universe emit radiation at radio wavelengths. A radio telescope is an instrument that is able to receive and record radio waves from space. The record of the signal is then analysed by astronomers, using sophisticated software. In order to collect incoming radio waves, the instrument is equipped with one or more antennas. Karl Jansky accidently built the first radio telescope while working at Bell Telephone Laboratories.

Why is it now possible to measure distances from the stars?

Scientists cannot stretch a measuring tape from the Earth to a nearby star, so how do they know how far away they are? It's always been known that the stars are very remote, but it was not until 1838, that the first star distance was measured, using the method of parallax, by F W Bessel. A star, viewed from different points in the Earth's orbit will shift against its background of more distant stars. The deviation in the angle can be used to calculate the distance.

Today, scientists use special cameras to calculate distances. Special types of telescopes are used to photograph large areas of the sky. Scientists also use instruments like a spectroscope, radio telescope, etc. to determine how far is a star from our Earth.

Light years are the unit of distances in space. This sounds like a unit of time, but a light year is actually the distance that light travels in one year. Light travels 299,792 kilometres per second. So, a light year is about 9,460,700,000,000 kms long.

It has been calculated that the nearest galaxy is the Andromeda, which is at a distance of 2.2 million light years, from Earth.

Did you know that the Sun is positioned only 8 light minutes away from Earth?

Why is it difficult to say how big the Universe is?

It is difficult to say how big the Universe is, because we can't even imagine how big it might be. Our Earth is only a tiny, tiny part of our solar system, and our solar system a tiny part of another system called the 'galaxy'. Beyond our own galaxy lies a vast expanse of galaxies. There are billions of galaxies, the most distant of which are so far away that the light arriving from them on Earth today set out from the galaxies billions of years ago! Perhaps, all these billions of galaxies put together are still only a tiny part of a larger system. So, we know that the Universe is bigger than what any one can imagine, but how much bigger is a question that Man has been asking himself since the beginning of time. The answer is still beyond our grasp, especially as scientists believe that the Universe is still expanding!

Why is it not easy to describe the Universe?

When you hear the word 'Universe', what do you think of? You think of a large and unimaginable expanse of dust, gas, stars, clouds, galaxies, and life. It is difficult to describe it exactly, because no one knows what it actually consists of. There may be many distant worlds in the Universe about which we know nothing. Even every empty space is part of the Universe, and so are matter, time, and energy. Some scientists say that if you could look at the entire universe at once, it would look like a giant spider web, made up of billions of galaxies, and trillions and trillions of stars. If you find this a bit too much to grasp, don't worry! Even the greatest scientists have not yet solved the mystery of Universe!

The Worlds Beyond

Since time immemorial, people have been fascinated by what they saw in the sky. They mapped the sky, scaled the time, and prepared calendars based on the study of celestial bodies to develop the oldest branch of science - astronomy. Later, Greek, Babylonian, Egyptian, Indian, Chinese, and many other civilizations all over the world contributed to it. Today, we know a lot more about our Universe, thanks to the great leaps in knowledge and technological advances. Now, 2009 is being celebrated as the years of astronomy, as a commemoration of the 400th anniversary of the first recorded astronomical observations with a telescope by Galileo, and the publication of Kepler's book 'Astronomia Nova'. The aim of this celebration is to create interest among young people, in astronomy and science under the central theme, 'The Universe, Yours to Discover'. In this blog, you can read about the past, present, and future of the Universe, and the unimaginable phenomena taking place in it. Welcome to the stunning worlds beyond.