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?