What we are going to dis-cuss in this article, is one of the breaking theories which shook the world of science and these ideas were created and developed by many scientists all through the history of science. After spending a lot of time reading what these people have said, I herewith am throwing some interesting facts and questions, which you can read, debate and understand.

The main aim of this article is to kindle the scientist in each of you, however tiny they may be and arouse the curiosity in you, to think of this beautiful mysterious universe, as we discuss the theory of relativity. You may not have all the answers when you finish reading this article, but my wish is that you start asking more questions than you have been doing about science.

     I wish students (and every one) today know the art of searching for answers, because if you master that art, you may uncover a lot of diamonds in your life. You can think for answers, use your own imagination, ask your friends, ask your teachers, discuss and debate with your friends and teachers, read books from your library, make experiments of your own, visit scientist friends to share their views and browse the internet, where you may have clues to almost everything that is available in this world.

Wish you all the best!

THE BASICS

What is Light?
Light helps our eyes to identify things. In the absence of light, we can’t see.

But can we see Light?

Yeah, when I look at the sun, the tubelight, I can see bright spots, which strain my eyes. So light is visible. But when I look at my room door, the door is visible, but the light which helps my eyes to locate the door... is it visible? I see the door, but I don’t get to see the light, which is between my eyes and the door...

So is light invisible? or transparent?
So can I say, light is visible at the source and not visible as it is seen in the source, when it is outside the source?

Is Light always travelling?
When I look at the church in my village, it is always stationary. It doesn't move. Every day, when I walk by that road, it remains there. So I can say church is stationary or the speed of the church is zero.
When I look at the minute hand of the church clock, it is always moving at the same speed. It makes one full round, in one hour. It doesn't stop, as far as I can see. So can I say that the clock’s minute hand is dynamic and as it is always moving in the same speed, the speed of the minute hand is one round/1 hour or say constant, as it does not change, as far as I can notice.
If I start to think about Light in these lines, is it a moving body like the minute hand of the clock or is it a stationary object like the church?
Is Light Moving? Yeah it is... if not how can I see the morning sun? The light from the sun has moved into my room. So light is moving... So I can call it dynamic.

What is the speed of light?
Okay... If light moves, what is its speed? Can we measure it? How can we measure the speed of light?
How do we measure the speed of a car? We have a speedometer fixed in it, which reads the speed for us. Can we fix a speedometer in light? But we are not sure whether Light is a visible or an invisible entity. So this is not easy. How do we measure the speed of athletes in 100 metre running race? We calculate the time taken by them to complete running 100 metres, say 10 seconds. The speed is 100 metres/10 secs... that is. . 10 metres/sec... that is 600 metres/ 60 sec or 600 metres/1 minute... that is... 36000 metres/60 minutes or 36000 metres/1 hr. or 36 Km/hr., which means if an athlete runs for 10 seconds, he may cover 100 metres. If he runs for 60 seconds, he may cover 600 metres and one hour means 36000 metres which is 36 kms. But can an athlete run with the same speed of 36km/hr, for one hour is a question?

Nowadays, when we watch a cricket match, we see the speed of the ball bowled immediately displayed, as soon as the bowler has bowled the ball. How is this possible? Can you think of it? The clues are "radar gun" / "doppler effect"... think...

I think the same principle is also used in identifying the overspeeding cars on the road, where there is no policeman! Interesting... isn’t it?
Now let’s come back to our question of measuring the speed of light...

This is not the first time obviously, that we discuss measuring the speed of light. Possibly the first experiment, as far as I know, to measure the speed of light was conducted in the 16th Century, by an Italian astronomer called Galileo. I don’t know, if you all know, he was the man who invented the thermometer, in 1593.

The process of understanding and learning science is very simple and its mysteries open up one by one, as we start thinking creatively, on our own. First time, when Galileo tried to measure the speed of light using a simple experiment, he did not succeed in his attempt.
In a dark night, Galileo sent his assistant to a distant hill with a lantern. When Galileo flashed his lantern, the assistant was instructed to flash his lantern back. By measuring the time interval between when Galileo initially flashed his lantern and when he saw the light return from the assistant's lantern, he thought he could determine the amount of time it took for the light to travel to the distant hill and back.

 

The experiment.. failed can you think & discuss why?

The same experiment, is today adopted by some US universities to measure the speed of sound successfully. Why? It is given as an exercise for the students, to give them a real experience of research.

It is later found that the speed of light is 186,000 miles (or 300,000,000 metres) per second. It is also found that electricity also travels in the same speed.That is why computers are so fast. Within the tiny chip, electricity has to flow only a couple of millimetres, and, within an entire computer, only a few feet.

You know, the light takes 8 minutes to travel from sun to earth. Now can you calculate the distance between the Sun and the Earth?

The speed of light is found to be approximately 3,00,000,000 metres per second...that is 3,00,000 km per second. ..that is 1,80,00,000 km per minute...10,80,000,000 km per hour... Can we think of how much this speed is in reality?

My school bus during my school days travelled at 60 km per hour speed. My car travels at 100 km per hour speed. I can see race cars speed at 300-350 km/hr.
Ships travel at a speed of 40-50 km per hour. Titanic, the famous Ship which sunk, was travelling at a speed of approximately 42 km/hr, when it collided with Iceberg.
Modern Jet Planes travel at 900 Km/hr. Tsunamis, like the one that hit our coastal areas last December, travel at a speed of 750 - 1000 km/Hr.
The Speed of Sound is 1215 km per hour. The Concordes which have been withdrawn from service travelled more than double the speed of sound, which is more than 2450 km/hr.
How much is 2450 kms? The distance between Delhi and Chennai is roughly about 2000 kms.
Now, comparing all these with the speed of light, which is 3,00,000 km per second, can you imagine how much speed that is?

If your school is situated in Sun, and if you travel in your school bus, can you tell me how long it will take for you to reach the school?

    I mean... can light be brought to a halt, like the church in our village? Can light be stationary?

In Dec 2003, there was an article in New Scientist stating that scientist Mikhail Lukin and colleagues at Harvard University in Cambridge, Massachusetts managed to stop light by firing a short burst of red laser light into a gas of hot rubidium atoms.
"Frozen, stationary pulses of light mark a new chapter in quantum optics," comments Marlan Scully at Princeton University, New Jersey, in the famous science magazine called Nature.
From this shall we go on to discuss time?

What is Time?
Don’t look at your watch to say what the time is now? There is another question in that question... Read it again.
This is one of the very difficult questions that science is struggling to answer today... and again a number of scientists have come up with different ideas at different points of time (again time!)
The American Heritage Dictionary defines time as "A nonspatial continuum in which events occur in apparently irreversible succession from the past through the present to the future".

What is the difference between time and the clock?

Clock is a device used to measure time, as we have set it to measure time. If you have a watch in which you say one minute is 60 moves of the second hand, I can also make a watch in which the second hand can make 70 moves per minute.Minutes, Hours, Days, Weeks, Years... all mean time.

The time in India is different from the time in USA or UK. There are 24 hours in a day, but at the same time, the clock would show different timings in UK and India. Is it due to the rotation of the earth? Think and discuss?
     Then, what is time?
Think ...
In the earth one day is 24 hours. In the Moon, one Earth 'day' is about 18 hours long (instead of our 24 hour day). What is time, then?

Here the number of hours varies..? Can time be fast or slow? Then what is the speed of time? can time also be brought to rest, like light? If time stops what happens?

If time becomes faster, will we grow old faster? If time becomes slower, will we remain young for a longer time? If time stops, will we all live for ever, because we may not grow older??

Einstein gave some brilliant insights about time during his time and they are still being discussed and debated, in our times.

Light so bright!
Where do you come from?

A new rush of fresh energy!
Every morning with a Good Morning!!

You fill up all my room and
even slip into my closed eyes!!

Where do you come from?
Is the sun your home?

In night sky, you are so far!
Scattered with the stars!!

So colorful! So Beautiful!
Every night a wonderful sight!!

Where do you come from?
Are stars your home?

I switch on my bedroom light!
What a wonder! You come out of that!

I do my home work.
You are also awake until I am awake!

How did you travel in those thin wires?
Is tube light your home?

When electricity goes off,
The whole house becomes dark!

My mum lights a candle!
and you come out of that!!!

Where do you come from???
Is fire your home?

Oh Light!

Where do you come from?
Where do you go back?

You are a mystery!
You are a magic!!

You are Light!!!
Are you God?
                                                                                                        - Ashok

I wish you all had a reading about Light & Time, in the last article and before I take up to discuss about the next important entity of Relativity, which is Space, let us look at some more interesting discussions..The first one on Speed of Light Vs. Speed of Sound.

SPEED OF LIGHT Vs. SPEED OF SOUND

You all know that the speed of light is 3,00,000 km/sec approximately.

The speed of sound is 335 m/sec or 0.3 Km/Sec.

Then, how come, when you say hello in your telephone call to London, the next second, it gets heard by your friend in London. If sound can travel only 0.3 km/sec, how is this possible?

When Tendulkar hits a sixer, the very next second, all over the world, the sound of the bat hitting the ball is heard and how is this?

If sound travels only 0.3 Km/sec, it may take around 10 seconds to travel 3 km, but how come, a sound from Calcutta Cricket stadium travels to your Television in your home at Chennai, in a second, where the distance is more than 2000 Km?

Points to Ponder :
In fibre-optic cables a voice on the telephone becomes coded as flashes of laser light. These pulse millions of times per second. Light travels more efficiently in long cables than electricity.
What happens when sound travels from a radio station to a radio? There is no laser light in that.

The speed of light is said to be constant, while speed of sound is not a constant.

What does that mean?
Will sound have the same speed, when it travels through any medium..say…Water, Air, Vaccum? (Does Sound travel through Vaccum?)
Will Light have the same speed. When it travels through any medium say…Water, Air, Vaccum? (What is refractive index, then?)
If you have ever half submerged a straight stick into water, you have probably noticed that the stick appears bent at the point it enters the water. Why is it so?
If speed of light varies according to the medium (air, water, solid, etc..), then why do we call it a constant?

 

Points to Ponder:
Does Light travels through Vaccum…Yes, Light does travel in vaccum, while sound does not travel in vaccum? (Why? Discuss)

Astronauts at the moon cannot communicate directly to each other. They can only speak to each other by radio. This is because the moon has no air.

Jupiter-like planets found for the first time, some 500 light years away!!

I saw this interesting news in Google, when I had been writing this article.
Detecting “extra-solar planets,” in Outer Space began 10 years ago when the first such planet was found. Since then, about 150 have been discovered.

This is the first time that we have come to directly observe planets revolving around stars in the universe, which means, the 150 planets which was discovered in the last 10 years, were actually discovered without seeing it ? How ?

Points to Ponder
When a planet moves around a star, star may undergo a “wobble” as it gets impacted by the planet’s gravity and sometimes star’s light dimmed slightly as the orbiting planet passed in front of it.

Astronomers have caught their first direct glimpse of these planets orbiting nearby stars, detecting infrared light from two “hot Jupiters” with the help of NASA’s infrared Spitzer Space Telescope.

What is the difference between Normal Space Telescope & Infrared Space Telescope?

 

What is the difference between Normal Telescope & Space Telescope?

Points to Ponder
The stars outshine a planet in visible light by a factor of 10,000, making them impossible to see. In infrared light, however, a star is only 400 times as bright, and astronomers can separate a planet from its host.
NASA’S Infrared Spitzer Space Telescope was launched into space in 2003, is able to ascertain precise variations in the star’s and planet’s heat signatures without distortions from Earth’s atmosphere.

Carnegie Institution astrophysicist Alan Boss, comments “ We have entered a New Regime. Hot Jupiters are interesting, but we want to find warm Earths, as well”, from the NASA Head Quarters in USA

The planet HD 209458b, orbiting a star in the constellation Pegasus, is found to be 153 light-years away and the other planet TrES-1 in the constellation Lyra, 500 light-years away.

CHANDRAYAN – I
India’s First Mission to Moon

India is gearing up to launch it’s first Moon Mission CHANDRAYAN - I during 2007-2008. The ISRO Website says that CHANDRAYAN – I is devoted to high-resolution remote sensing of the lunar surface features in visible, near infrared, X-ray and low energy gamma ray regions and it opts to study the following areas, in this mission.

Specific areas of study

• High resolution mineralogical and chemical imaging of permanently shadowed north and south polar regions

• Search for surface or sub-surface water-ice on the moon, specially at lunar pole

• Identification of chemical end members of lunar high land rocks

• Chemical stratigraphy of lunar crust by remote sensing of central upland of large lunar craters, South Pole Aitken Region (SPAR) etc., where interior material may be expected

• To map the height variation of the lunar surface features along the satellite track

• Observation of X-ray spectrum greater than 10 keV and stereographic coverage of most of the moon’s surface with 5 m resolution, to provide new insights in understanding the moon’s origin and evolution

Let me give you some interesting questions.

Every day, when you walk from your home to school, you find that the distance between your school and home is 2 km and my question is, is that 2 km, constant?

If we measure the distance between your home and school every day, will we record the same distance of 2km every day?

If we go one step further and think a little more in depth, School is not moving. Home is not moving. Road is not moving. So logically, it should be 2km every day, but we have one more entity, the road, the school and the home all are on earth, which is moving.

Do you know at what speed Earth is moving?

The Earth is orbiting around the Sun. Earth is moving through the space at a speed of 29.8 km per second, which means all of us on earth including you and me, are already traveling at a speed of 29.8 km/second through the space.

The speed of light in a vacuum is exactly 299,792,458 m/s, which is 299792 km per second.

So light is traveling 10,000 times faster than us.

and now the question that we were discussing is …Does the distance between the School and Home remain the same every day?

And another question that I would like to recollect from the last article is “ Can Time be fast or slow?

The first question is
“ Does Space remains constant or does it keep changing?”
The second question is
“Does Time remains constant or does it keep changing?”

Think and Discuss !!
Many believed that Space and Time were constant for many many centuries, till the 19th Century, When Einstein’s Theory of Relativity made its entry into this world, which we will discuss in the next article.

WHAT IS LIGHT YEAR?

A Light Year, abbreviated ly, is the distance light travels in one year. It is roughly 9,460,730,472,580,800 m. Units related to the light year are the light minute and light second, the distance light travels in a vacuum in one minute and one second, respectively. A light minute is equal to 17,987,547,480 m. Since light travels 299,792,458 m in one second, a light second is 299,792,458 m in length.

These units are primarily used to measure the distance between stars and planets in the Universe and now can you think of how far away it means for the newly seen planet, if it is 500 light years away?

It takes 8.3 minutes for light to travel from the Sun to the Earth.

Thus, we are about 8.3 light minutes from the Sun.

The nearest known star, Proxima Centauri is 4.22 light years away.

How far away is the recently found “Hot Jupiter – like” planets in the Universe from earth?

A QUIZ ON EINSTEIN’S LIFE :

1. Which magazine named Einstein as“Person of the Century” in 1999?
A. Forbes Magazine
B. Times Magazine

2. How many years before did Einstein publish his first paper on “The Special Theory of Relativity”?
A. 120 Years
B. 100 Years

3. Which organization commemorated the year 2005 as the “World Year Of Physics”
A. International Union of Pure and Applied Physics (IUPAP)
B. International Union of Pure and Applied Science (IUPAS)

4. …………….. is more important than Knowledge – What did Einstein say?
A. Wisdom
B. Imagination

5. Einstein was a
A. Violinist
B. Scientist

6. Einstein graduated in the Year
A. 1905
B. 1900

7. Einstein published the paper on “Photo Electric Effect” in
A. 1905
B. 1900

8. In 1921, Einstein won the Noble Prize for his work on
A. Photo Electric Effect
B. Theory of Relativity

9. General Theory of Relativity was actually confirmed in the year
A. 1921
B. 1919

10. How many years did Einstein wait to get the Noble Prize after he published the paper on Photo Electric Effect?
A. 16 Years
B. 15 Years