First Light – CMBR

IYL-unesco
Celebrating IYL 2015

     If you look at the modern periodic table you will find hundred and eighteen elements listed in it. Out of this, ninety four elements occur naturally.  All these elements can be found on Earth (exceptions are there).  Elements are building block of things that you see around you.  Whether it’s a human, animal, tree, building, roads, bridges, monuments, mountains, etc, everything is made up of elements.  But the question that comes to our mind is who brought all these elements on the Earth?  How are they formed?  The answer is… all these elements are formed inside a star.  Yes, in a sense, everything that you see around is cooked inside a star!  Richard Feynman, a famous physicist once said that, the stuff which we are made was once cooked in a star and spit out.

      The entire universe comprises trillions of trillions stars which cooks the matter that we see around us.  The next question that arises is how do these stars form?  Well, these kinds of questions will go on….. it’s a never ending process. But then, where do we begin?

Yes, we begin at the beginning.
We begin at the Big Bang!

Big Bang
Artist view of Big Bang before the explosion.

     The universe which includes stars, galaxies, nebulae etc. is expanding for billions of years.  If you look back, somewhere in the past there must exist a time where the entire universe is concentrated in a point of high density (infinite density).  According to the accepted theory, this high density state of a point, exploded violently, creating the universe that we see today.  This is the Big Bang theory proposed by Edwin Hubble in the year 1929.  The explosion that we consider in Big Bang is not at all a violent explosion, in fact it is one of the silent explosions that you can ever think of and it is neither big nor bang!  This is just a name given to the theory.  The reason is this, the space, time, sound, matter, elements and more importantly the light that we feel and experience today was created after Big Bang!  Big Bang is just an expansion of a point of infinite density, nothing more that.  But then, how do we verify this theory?

     If this kind of an expansion has happened in the past, then we must be able to detect, outer surface of the expanding sphere which contains the information of big bang in the form of light.  According to the theory, this sphere of light should uniformly exist all over the space. In a sense we have to detect the first light from the big bang.  This is called background radiation of the Big Bang.  If we succeed, it confirms the theory Big Bang.

   In the year, 1960 two astrophysics namely Dickey and Pebbles were working on the challenge of finding background radiation of the Big Bang.  They came to the conclusion that, since universe is expanding from billions of years, the energy of the photons of background radiation must be less because of the expansion in space.  (Expanding Universe:  The space and time fabric between the galaxies expand.  The light or the photon which travels in this fabric also expands.  When it expands the energy of the photon becomes less – this is predicted by Einstein’s General Theory of Relativity) When they did the calculation by using Wien’s Displacement law, they found that photon’s energy lies in the microwave region of light.
Few miles away from this group of scientist there were two more researchers from Bell Laboratory namely Penzias and Wilson designing the Horn antenna for radio astronomy.  They were trying to remove the background noise in the antenna which is detected by the detector.  No matter how much they tried they were unable to remove the background noise even-though they replaced the detector for many times.  Interestingly the detector was detecting the noise in all the direction and at all times of the day.  After their unsuccessful attempt of trying to remove this noise, they come to the conclusion that, this signal is not a noise, it is actually coming from outer space.

     Later it turned out that the noise of Penzias and Wilson’s horn antennae was actually the background radiation of Big Bang that Dickey and Pebbles were searching for!  Yes, it was an accidental discovery by two researchers from Bell Laboratory who have no idea about background radiation.  All they did was they tuned their antennae to receive a microwave radiation.  The detector was detecting first light from the Big Bang but Penzias and Wilson thought it was noise!!  The temperature of the background radiation was 3 kelvin and it was in perfect agreement with the measured value from the theory.  This is famously called as 3 kelvin black body radiation curve or 3 K curve.   Both of them were awarded noble price in physics in the year 1978 for their accidental discovery of Background Radiation.  Press Release from Bell Labs can be seen here. This observation confirms Big Bang theory.  (Big Bang theory is still a debatable theory for other reasons).

Horn Antenna
Penzias and Wilson in front of Horn Antenna

     Today we have some of the sophisticated scientific instruments in the on-board satellites which are revolving around the Earth.  WMAP (Wilkinson Microwave Anisotropy Probe) has mapped the background radiation.  The first light from the Big Bang is here….

cmbr_planck_960
CMBR – Cosmic Microwave Background Radiation by WMAP

The Light which is the sole responsible for life on earth was actually began its journey 13.5 billion years ago.

Through light on some atoms for billions of years, eventually you have life!

Image Details:
First Image: International Year of Light and Light Based Applications – 2015 Logo
Second Image: S. Harris Cartoon
http://www.sciencecartoonsplus.com/gallery/physics/index.php
Third Image : Bell Labs
https://www.bell-labs.com/about/stories-changed-world/Cosmic-Microwave-Background-Discovery/
Fourth Image:
http://apod.nasa.gov/apod/ap130325.html
APOD Images, March 25, 2013
—–
Year 2015 is celebrated as International Year of Light and Light Based Technology by UN as a global event.  This year mark the 150th anniversary of Maxwell’s Equations by James Clerk Maxwell, the man who unfolded the secret of nature and answered what light is made up of. 

More Information about IYL 2015
UN Anniversaries
http://www.un.org/en/sections/observances/international-years/index.html
IYL – 2015 Home Page
http://www.light2015.org/Home.html
IYL – 2015 Blog
http://light2015blog.org/


Upcoming Topics for IYL 2015

  • Elusive Particles of the Universe
  • Biological Industry – Photosynthesis
  • Principe, Africa – 1919 TSE
  • Copy of Earth – Extraterrestrial Planet
  • ದೀಪವು ನಿನ್ನದೆ ಗಾಳಿಯು ನಿನ್ನದೆ ಆರದಿರಲಿ ಬೆಳಕು
  • Let there be light – Newton, Maxwell, Hertz and Einstein


Viswa Keerthy S

 

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Maxwell and his ‘c’

     If you ever type “Maxwell Equations” in ‘Google Images’ you get many images, like the one mentioned below.

God Said Maxwell Equation

     Have you ever thought why it is been shown like this.  What is so important about these equations.  If you want to know, read this article

     If you ask me about these equations, I will say these are the greatest equations in the history of physics.  These equations may not look beautiful to a common man.  But truly, it looks beautiful for a physicist.  I am writing this article not to tell you the mathematics or the physics behind these equations.  But to tell you the beauty of nature, which is hidden in these equations!

    Let me first tell you this,

  • E= Electric Field
  • B= Magnetic Field
  •  ρ = Charge Density
  •  ɛ = Permittivity of free space (Property of medium)
  •  μ = Permeability of free space (Property of medium)
  • J = Current Density
  • Inverted triangle symbol is called ‘del’ It is just a differential operator

(read ɛ and μ as “epsilon not” and “mu not”)

That’s all about these equations.

     Before Maxwell, Electricity and Magnetism are two separate theories in physics.  They were independent of each other.  But this person called “Maxwell” unified these two theories as a single theory, called “Electromagnetic Theory”.  He said, a moving charge produces a magnetic field, and a change in magnetic field produces current in a wire!  True, this looks obvious to us now.  But during Maxwell time (year 1865) this is a remarkable achievement in the field of Physics.  Later it said that, this is the second Greatest Unification Theory in the History of Physics since “Newton’s Universal Law of Gravitation”.  Einstein once remarked on Maxwell theory that “Most profound, most truthful that physics has experienced since the time of Newton”.  Believe it or not all his work on “Electromagnetic Theory” stands on the above four equations!  If you exploit each equation, hidden natures beauty will unfolds to you.  If you ask me what these equations means, in a crude language I will say, disturbance of Electric and Magnetic fields travel in space (medium/vacuum) as Electromagnetic Waves obeying above equations.

     As I mentioned in the first paragraph, I want to show one such hidden beauty from these equations.  Before that let me introduce you to a “Wave Equations”.  It is just a mathematical equation which governs the propagation of wave in space.  And the equation is…

Wave Equation

     Here, Ѱ is a wave, V= Velocity of the wave.  Don’t worry about the differentiation; just see the form of equation.  We will come back to this equation later on.

     Now, What Maxwell did is, he took two of his last equation, that is…

Last Two Equation

     And his aim was to write down the final equation, which “looks like” wave equation, the one I showed you in the above paragraph.  He did some mathematical manipulation to his equation, and finally arrived what he wanted.  His final equation was this…

Final Equation

     One for Electric Field, another for Magnetic Field.

     Here, if you compare these two equations to the wave equations.  You can identify E and B are Electric and Magnetic Wave respectively.  But notice that, these two equations don’t have the v term in it.  Instead, it has some other terms.  If you equate these two terms, you get…

V square

V final

     So, you (he) finally got the velocity in which Electric and Magnetic Wave travel in space.  Alright, until now everything was fair enough.  But the beauty lies after this.  Let me tell you, we have…

V final

     I said, in the first paragraph that  ɛ and  μ are the properties of medium in which wave is travelling.  And it’s a constant number for a given medium.

For instance, if you consider medium as vacuum.

Constants

(Ignore the units)

If you substitute and calculate the velocity you get…

V

This happens to be precisely the velocity of “Light”!

     Before Maxwell people had did experiment and found velocity of light.

c

     But Maxwell did not even think of light, he took electricity and magnetic theory, combined these two theories to get “Electromagnetic Theory”.  And said the disturbance of electric and magnetic field will travel as “Electromagnetic Wave”.  And now he has calculated the velocity of “Electromagnetic Wave”, it turns out that it will travel at a velocity, precisely equal to the velocity of light.  This means, “Light is also an Electromagnetic Wave”!

     Up to Maxwell time, Mankind did not know, what constitute the light, which was the most abounded form of the energy right through human civilization.  Maxwell unfolded this greatest mystery of nature by saying “Light is a wave made up of electric and magnetic field and they are called as Electromagnetic Wave”.  Truly a remarkable achievement by Maxwell!

     It doesn’t stop here, there is another beautiful thing which is hidden in this formula.  Let me again tell you.  Now we can safely write, Velocity of light is…

C formula

     Again, as I said ɛ and μ are constant for a given medium, and they are the properties of medium itself.

     Isn’t it strikes you that just a properties of a medium tells you the velocity of light, which is the ultimate speed in our universe!  And, what is also interesting is, experiment involving measurement of  ɛ and μ has nothing to do with ‘c’.  But yet their combination gives rise to ‘c’!  Velocity of light is controlled by the properties of medium!  Amazing result.  The same kind of argument can be seen in connection with velocity of sound. That is, you can write velocity of sound in terms of bulk modulus (property of medium) of the medium in which sound is travelling.  But in light, the bulk modulus turned out to be ɛ and μ of the medium.  Nature works same everywhere, and Maxwell showed us the beauty of nature through his equations.  I don’t have many words to say about these things, but this is truly amazing!  Let me remind you, Maxwell did not studied light, he just wrote down his equations on Electric and Magnetic field.  But all these things are just hidden in his equations; he himself did not know about these things.  But his results showed everything, about the hidden quantities.  He himself was surprised!  I have just showed you one example.  You can find many of them, if you exploit the equations.  Truly they are beautiful equations of Nature.

     Now, I hope you got to know why people write Maxwell equations like the one which I showed you at the beginning.  Light is all about Maxwell’s equations.  I personally believe, existence of God is zero. But, if he is there, and if he controls the nature, then surely he must have said this!  Because that is how nature is working.  And this genius Maxwell unfolded the God’s secret to Mankind!

     450px-James_Clerk_Maxwell_statue_in_George_Street,_EdinburghJames Clerk Maxwell (13 June 1831- 05 Nov 1879) was a Scottish man, and one of the greatest physicist during 19th century.  Apart from his “Electromagnetic Theory” he also worked on “Maxwell-Boltzmann Distribution” which is statistical way of describing “Kinetic Theory of Gases”.

Right: Maxwell Statue at Edinburgh. (Image from wikipedia)

-Viswa Keerthy S (29-06-2013)