An old man’s tale.

 

15th July 2013

“Keep your eyes on my lantern.  As soon as you see the light, you will be enlightened.” He said with a glint of wickedness in his tone.

I laughed inwardly at his remark. I knew what I had to do.  Uncle and I had practised for days.  He kept emphasizing on how important it was to get the timing right.  All I had to do was open the shutter of my lantern as soon as I saw the light from his lantern.  Uncle would then note down the time lapse between the two events.  We would repeat the experiment (uncle preferred the word duel) switching our roles. This would go on until we achieved consistent values.

We waited for dusk before we set out to the country side.  For our duel to work successfully we had to avoid interference from other artificial sources of light. Uncle left no stone unturned in trying to recreate Galileo’s experiment of the 17th century. We looked like we had stepped out of a time machine; wearing long robes and holding lanterns.  Uncle insisted on walking instead of taking the bus and speaking in Latin, of which I knew not a word.   Suddenly I regretted asking the question. If only Ms.  Darya had answered it instead of brushing it aside with her usual taunts.

28th June 2013

“How could someone, living in the 17th century with no technology available to us today, calculate the speed of light?” I asked.

“You are too young to understand the answer, Varvara,” Ms. Darya replied.

Uncle would never dismiss my questions.  On the contrary he would get excited about all the different ways he could play around with the answer.  This time he outdid himself with the re-enactment. I remember the last time we did one of his re-enactments. It was a fun exercise.  A fact I dare not openly admit to him. Father said any form of praise would breed his insanity.

An excerpt from 13th May 2009

‘’I was hoping that I would give these books to my daughter one day.  But you are just like my daughter, Varvara. I want you to keep them,” uncle said as he kept a dusty box in front of me.

I looked inside to find seven books.  The mystical number 7. 

“Once you finish reading the entire Harry Potter series, I will answer your question of what light consists of.  You will see why I need you to read these books first.”

According to uncle, Galileo was one of a kind.  A man who thought outside the box.  Prominent scientists during his time believed light had infinite speed but Galileo wanted to test whether it was true.  He believed light had a finite speed. However his experiment failed to prove so; a piece of information I was not privy to until the end of the duel.

Back in the laboratory

“Then why did we do it?  What purpose does it serve to re-enact a failed experiment?” I asked dejectedly.

Uncle nodded his head and looked at me with a crooked smile, showing his prominent dimples.

“Simple ideas lead to great discoveries. Take the example of Armand Fizeau, a French scientist who learnt about Galileo’s failure.  It prompted him to devise an improved experiment that successfully found the velocity of light within ten percent level of accuracy.  Over the years, Fizeau’s experiment has been improvised in order to achieve greater precision and accuracy.” He continued.

“You might fail sometimes but never think your failures are insignificant in the face of your success. You will only be able to connect the dots looking backwards.  Only then will you appreciate the role failures played in moulding your character.”

Uncle reached out for a sheet of paper and pen.  I sat next to him, keeping my hands as far as I could from his table.

“Write down a basic speed equation for me.” uncle said handing over the pen and paper to me.

Speed = Distance/time …

He took the paper from my hand and started drawing an experimental set-up. 

speed of light 2

  1. A source of light; a candle. No fancy laser beams in the 17th century.
  2. A semi-reflective mirror tilted at an angle to allow only a fraction of the light to pass through.
  3. A toothed wheel rotating to either allow or block light to an almost perfectly reflective mirror placed 8.63kms (in Fizeau’s experiment) away from the toothed wheel.
  4. The ‘eye’ of the experiment to represent the observer.

 

Uncle disappeared to his room of doom, or as I called it, Schrodinger’s room only to reappear with a box full of coloured markers.  He took out a green marker and started colouring the eye.  He then took out the black marker and started drawing long dense eyelashes under the eye.  Father was right.  Uncle was insane. 

 “Now I want you to observe the toothed wheel.  Why do you think Fizeau used it?” he asked me.

 I nodded, clueless about what the answer could be.

 “The toothed wheel, as you can see, has gaps in between the teeth.  If you picture it rotating it will serve to “chop” up the light coming from the mirror into short pulses which are, in turn, reflected by the mirror 8.63 kilometers away. One of two things can happen to the light when it is reflected back to the toothed wheel. It can EITHER pass through a gap of the toothed wheel OR it can be blocked by a tooth.  Fizeau adjusted the angular speed of the wheel such that the incoming pulse was blocked by the tooth adjacent to the gap through which the pulse had passed through to begin with.” Uncle continued as he reached for his pen.

 “Now I will show you the math to make it clearer.  The unknown variable in this experiment is the speed of light, which we now know, is in fact a constant. We know the distance the light has to travel…”

 “I know!  On doubling 8.63 kilometers we get the distance the light travels since it had to make a roundabout trip in the measured time.”  I answered excitedly.

 He smiled before he continued.

 “Since you seem to have understood the experiment so well, answer this question. How did Fizeau measure time then?”

 “He must have used a pendulum.” I answered confidently.

 “Why do you think Galileo failed to find the speed of light?  Even Galileo had a pendulum,” He paused to let the question sink in.

 He looked at me acutely before arriving at an appropriate conclusion that I had no answer to his question.  I asked him to continue.

 “The time it takes for light to travel is not appreciably noticeable.  That is why Fizeau gained an advantage over Galileo when he decided to use a wheel.  Since angular velocity was known to him he could find the frequency.  Time and frequency are inversely related to each other.”

 f = 1/T (s) …

 “We have everything we need to plug into the speed equation. Do you have any other questions?”  He asked looking with great anticipation towards me.

 “What was the value of the angular velocity he chose in order to block the incoming light?” I asked.

 “Varvara, there are books and papers for that.  You cannot expect me to remember precise experimental values.  Ponder over what you learnt today and come back to me if you have any further questions.”  He said before he disappeared into Schrodinger’s room.  I dare not follow him.

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