Eat My Waste

Toronto is really dirty at the moment. (Well, so it the whole world but Toronto is special now). The city workers have gone on strike and everywhere you look, you either see garbage or you see green stinky lines swirling out to your nose and causing you disgust. As much disgust as it caused me as well, I was thinking about recycling and how ineffective it is. There must be a way to get rid of all our garbage fast and give back to Earth like all grateful organisms should.

The solution lies with those awesome bacteria. Research has gone in to find that bacteria can indeed eat away our garbage and create gases that are useful to us. It's a prospect, but as the "really smart and visionary" businessmen aren't really all jumpy about letting their money making machines go, its developing slowly. But how does it actually work?

It works by accelerating the process of decomposition. Municipals store their garbage and waste in dry "tombs" and let the waste die away. The acceleration occurs by balancing the air-liquid quantities of the containers knows as bioreactors. Three types of bioreactors can be configured:
Aerobic- In an aerobic bioreactor, moisture is removed from one layer and piped to liquidsstorage tanks, and re-circulated into the landfill in a controlled manner. Air is injected into the waste mass, using vertical or horizontal wells, to promote aerobic activity and accelerate waste stabilization.
Anaerobic- In anaerobic bioreactors, moisture is re-circulated to obtain optimal moisture levels. Biodegradation here occurs in the absence of oxygen (anaerobically) and produces mostly methane which can be captured to minimize greenhouse gas emissions and for energy projects.
Hybrid (Aerobic-Anaerobic)- The hybrid bioreactor accelerates waste degradation by employing a sequentially alternating aerobic-anaerobic treatment to rapidly degrade organics in the container and collect gas. This sets off much rapid release of gases as well resulting in better efficiency.

Reference

Even though the technology exists and readily available, municipals are not ready to implement this. Maybe some conspiracy working behind it, as with everything else. So much so, liquids are prohibited in landfills of Ohio (read about it here).

So, the smell in Toronto is not going away any time soon. Nor is the world going to get rid of its waste the smart way. One can only hope municipals see that scientists actually know things better than those with fat bellies and as long as they don't, the can eat their waste themselves, and mine too.
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By Kowsheek Mahmood
Ryerson University, Toronto
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The Aftermath Publications, Issue 4
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OLBERS’ PARADOX!

As theories of the universe evolved from that of Aristotle to that of Galileo, philosophers and scientists continued coming up with ever accurate theories until Isaac Newton (detail identification not necessary for obvious reasons!), came up with his most exact and mathematically sound theory of gravitation that could and can still explain the behaviour of celestial objects with amazing correctness. Newton formulated his theory of the universe according to which the universe was:

1. Static
2. Centre less
3. Infinite
4. Based on mathematical laws of motion and gravitation
5. Infinitely aged

The Newtonian universe is infinite in size and contains an infinite number of stars.




At the first instant, the Newtonian model of the universe seems to provide satisfactory explanations of almost all the celestial phenomena but if closely inspected, the Newtonian model offers some serious flaws!!

One of the consequences of the Newtonian model is that the night sky should have never been dark! According to our observation, the night sky is dark; atleast the spaces between the stars are dark. This is not surprising at the first thought. At night we are on the side of the earth that points away from the sun, it is bound to be dark, isn’t it? Actually it is not as obvious as that. Infact it is very difficult to explain why the sky at night is dark on the basis of the Newtonian model.

If, as par the Newtonian model, we consider that the universe is infinitely sized with infinite stars that maintain a certain distribution pattern, we can easily assign a number, say N, to the number of stars per unit volume of space. The volume of a spherical shell of space centred on the earth is ∆R*4πR2 where R is the distance of a shell of thickness ∆R which is at a distance R from the centre of the earth. If the stars are uniformly distributed, the number of stars in each shell is proportional to R2. The light emitted from a shell is thus proportional to R2. But light obeys inverse square law getting weaker with distance, in proportion to (1/R2). So each shell produces the same intensity of light at the earth. If there are infinite numbers of shells, i.e. if the universe is infinitely large, then the night sky should be infinitely bright!

This seemingly possible yet unobserved phenomenon is often named the OLBERS’ PARADOX.


The resolution to the paradox can be brought about very simply. First of all, it is very difficult to ascertain whether the universe is finite or infinite. Let’s keep this as a query to the best of the minds and proceed with the fact that the universe is infinitely large. Still we can solve the paradox! Until very recently, scientists like Edwin Hubble formulated laws like the Hubble’s law and made it sure that there is a particular age of the universe and thus it is not of infinite age. At any moment we are only receiving light from a finite number of stars. Light from others is still on its way to us (because they are very far from us and since the universe is not infinitely aged, the light from these stars did not get enough time to reach us). The overall effect is that we are continuously seeing light from the equivalent of a spherical shell of stars that is not wide enough to cover the entire sky. This explains why gaps between stars are dark.

More to be found in Hubble’s law is that distant stars recede from the earth at very high speeds than the less distant ones. This causes the energy from these stars to be red shifted sufficiently that by the time they reach the earth, they are no more in the visible range. Hence light from those stars can never be seen. If however, it becomes clear that the universe is finitely sized, it would rather reinforce the arguments put above to prove why the night sky is dark.


These inferences have serious consequences other than resolving Olbers’ paradox. The presence of visually undetected radiations in the universe suggests that there might be radiations reaching the earth’s surface now, that were emitted by stars and galaxies that once existed right after the birth of the universe. These radiations might hold important and intriguing information about the elemental compositions of celestial bodies right after the big bang and might often lead us into knowing why the big bang occurred in the first place!


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By Mahmud Hasan
The Aftermath Publications.
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The Aftermath Publications, Issue 4
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Dance of the Spirits

For many years “Dance of the Spirits" has been mesmerizing millions of people. Yes, I am talking about the famous Aurora borealis, which is more frequently known as “Northern lights”. It is a very common phenomenon for Northern Hemisphere region as the chance of visibility increasing with proximity to the North Magnetic Pole, which is currently in the arctic islands of northern Canada.
But what exactly are northern lights? Or more precisely why does it occur?
Fusion reactions in the sun and the other solar lead to the production of charged particles (mostly electrons and sometimes protons). These charged particles usually have kinetic energy of the order of 100s of keV. This energy originates entirely from the fusion energy inside the sun and provides the particle with sufficient energy to overcome the magnetic field of the sun. When these particles come in vicinity of the earth, they become subjected to the earth’s magnetic field. The intrinsic magnetic field with the particles and the earth’s magnetic filed combine to produce an unbalance force on the particle, causing them to move from one pole to the other with high velocities. In the process they collide with atoms present in the earth’s atmosphere, raising them to higher energy levels. The high energy atoms in turn give out electromagnetic radiation in the visible range which is manifested in the form of the northern lights.

A magnificent view of the aurora

The aurora--a woodcut by Fridtjof Nansen

What does it look like? Most often, you see greenish white ribbons stretching across the sky, roughly from east to west, usually with waves in them. In Fairbanks they could be overhead, in northern Norway or Sweden too, sometimes even in Winnipeg. Further south those ribbons tend to be near the northern horizon. And if you look closely at them, you will note that they contain many parallel rays, running across their width (see picture beside).
Anyone who has ever used a compass knows that the Earth is a giant magnet. The needle of the compass usually points towards one of two points, the magnetic poles of the Earth, located near the geographic poles. But because the compass needle is mounted horizontally, it does not show everything. Actually, the magnetic force points not just northward but also slants down into the Earth. Compass needles carefully balanced on a horizontal axis ("dip needles") point in that slanting direction, when allowed to swing in a north-south vertical plane. In fact, the angle gets steeper the closer one gets to the magnetic pole. At the pole the force is vertical. The rays of the aurora faithfully follow that slanting direction.

What connects the pattern of the aurora to the region of the Earth's magnetic forces--the "magnetic field" of the Earth, as that region is known? For such a region, extending far into space, a convenient method is needed to describe it there. Such a method is provided by magnetic field lines, or as they were once called, "magnetic lines of force."
Chances are you have seen a drawing of the fieldlines of a bar magnet. They fan out from one pole, bend around in big curves, and then converge on the other pole. The magnetic pattern near Earth is like that, too--it is as if the Earth had a small (but oh so powerful!) bar magnet in its center: the lines fan out from the region near the south magnetic pole, reach their greatest distances above the equator, then converge again near the north magnetic pole.
To define field lines more exactly, imagine you had a compass needle hanging in space, able to tell us the exact direction of the magnetic force, in 3 dimensions. Such a needle will always point in the direction of the magnetic field line at its location. North of the equator such lines converge towards the region near the north magnetic pole, just like those of a bar magnet.

Back to the aurora. Between 1895 and 1907 the Norwegian physicist Kristian Birkeland tried to study its behavior in a lab. Inside a glass vacuum chamber he mounted a sphere with a magnet inside--he called it "terrella," Latin for "little Earth"-- and directed towards it a beam of electrons. To his surprise and gratification, the magnet steered the beam right to a patch around the magnetic poles of his small sphere, producing there, as it hit, a visible glow. He probably thought-- aha, so that is how it is done!
It turned out that negative electrons and positive ions alike are guided in space by magnetic field lines. They tend spiral around them, meanwhile sliding along them, like beads on a wire. Because Birkeland's field lines reached the terrella near its magnetic poles, that is where his electrons came down. Similarly magnetic field lines of the Earth guide electrons of the aurora to come down in the auroral zone. No wonder the rays of the aurora pointed along such lines! Each was produced by a ray of electrons, riding its own field line down to the atmosphere.
Understanding northern lights is a very small purchase, where the huge parlor of beauty and charisma is still to be discovered. Nature is still playing its own game of wonder. There is no ending of learning. Isn’t it? As the great man said “Learn to be unlearned” – Richard Feynman

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By Mohammad Atif Bin Shafi
East West Univesity, Dhaka, Bangladesh.
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The Aftermath Publications, Issue 4
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Dark matter : science or fiction

As scientists began to unravel more information about our galaxies they were intrigued by more questions than answers. One of the many questions was that of the eluding Dark matter. It so happens that as scientists began studying about the rotation of galaxies and their temperature distribution they were able to predict the amount of material present in particular parts of space and that is what they exactly did. But Scientists were stunned with what they had found. Amazingly it turned out that there was 5 times more material in clusters of galaxies than they had expected by observing the hot gases. Thus it led scientists to believe that most of the stuff in clusters of galaxies is invisible and, since these are the largest structures in the Universe held together by gravity, scientists then concluded that most of the matter in the entire Universe is invisible. This invisible stuff is aptly called 'dark matter’. Scientist use the term to describe any matter that is not detectable by our usual x-ray, optical or even satellite telescopes.Dark matter does not reveal its presence by emitting any type of electromagnetic radiation. It emits no infrared radiation, nor does it give off radio waves, ultraviolet radiation, X-rays or gamma rays. It is truly "dark." leading Cosmologists to believe that we can only see about 10 percent of the matter in the universe.Until they can accurately determine the mass of the universe, they will not know for sure whether it is expanding infinitely or will stop expanding at some point and collapse. So, how in the world do scientists know that dark matter really exists?

Well we have to hand it to our scientists they have found a way to detect dark matter too. The key to detect dark matter lies in the ever so reliable gravitational forces. The most obvious of these gravitational effects has to be the rotation of galaxies. This begs us to ask the question of how that is to be done. No worries to study galactic rotation, astronomers look at the emission line spectra of stars in each part of the galaxy. When the light from a star is observed using a diffraction grating or a prism, the starlight is separated into its true colors, in much the same way ordinary sunlight is separated by rain drops during the formation of a rainbow.The true colors constituting starlight separate into a series of light and dark lines in the visible spectrum, with each colored line corresponding to a specific wavelength of light. The specific wavelengths at which these lines occur are characteristic of the elements the stars Thus, they can be used as an elemental "fingerprint" to identify a star's composition.When a star emitting these line spectra is moving away from us, all of the wavelengths of the spectral lines are shifted to higher values than they would have been were the star stationary or moving side to side (neither towards nor away from us). All of the spectral lines are thus shifted towards the long wavelength part of the spectrum, or to the red end of the spectrum.

Similarly if the galaxies are moving towards us they spectral lines would shift to the short wavelength part of the spectrum, or to the blue end. These phenomenons are respectively called the ‘red shift’ and the ‘blue shift’. By measuring the shift in wavelength, researchers can calculate the precise speed of a star, either towards us or away from us.

When a galaxy is rotating, the starlight from stars on the side of the galaxy that is moving towards are blueshifted, while the starlight from the stars on the other side of the galaxy are redshifted. Thus, we can tell how fast and in what direction each individual star in the galaxy is orbiting about the center of the galaxy.
When stars orbit the center of a galaxy, their orbital speed is determined by the distribution of the mass contained within the galaxy. A graph showing the orbital speeds of the stars versus their distances from the center of the galaxy is known as the "rotation curve" for the stars in the galaxy. If one takes all the luminous matter that can be seen in the galaxy (stars, gas and dust) and predicts the rotation curve using the well-known laws of gravitational physics discovered by Newton, the speed of stars should decrease in a predictable manner the father away they are from the center of the galaxy. Scientists however noticed some hair raising data from the curves. They saw that the rotational speed didn’t fall off with distance as expected. Instead, the curves level off, and star far away from the center of the galaxy move faster than expected. The only way to account for this observation is that a large quantity of matter which cannot be seen--dark matter--exists in the galaxies. To explain the astronomical observations, this dark matter must surround the spherical distribution known as a galactic halo.Theoretical candidates for dark matter have been divided into two groups, dubbed MACHOs and WIMPs. The existence of MACHOs (Massive Astrophysical Compact Halo Objects) has been confirmed experimentally--recently in our own Milky Way galaxy. The nature and origin of MACHOs are currently a matter of great speculation and debate, but their masses and distributions have been measured by their gravitational effects. Proposals for candidate MACHOs include primordial black holes, as well as some types of new, exotic astrophysical objects whose properties have yet to be properly described.WIMPs (Weakly Interacting Massive Particles) are exotic, massive elementary particles that do not interact strongly with matter. (Hence they have not been interacting with our detectors so we have not detected them yet). Because WIMPs do have mass, and there would be great numbers of them, their individually weak but collectively strong gravitational effects account for part of the impact that dark matter has on the rotation curves of galaxies.Dark matter is known to exist through the gravitational effect it exerts on visible matter in the universe. Scientists have made discoveries that point very strongly to their presence. But even than a lot more work still needs to be done if we truly are to understand more about dark matter and how it behaves.
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By Tahsin Uddin Mullick
North South University, Dhaka, Bangladesh.
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The Aftermath Publications, Issue 4
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Infinity

It's natural for us to see things from a start to and end. The concept of eternity is a mystery for the human mind and it has crept in to mathematics as well. Infinity, as we know, is endless; not an enormous number but a representation of an eternal number.

According to definition of infinity, it's simpler than most things which have a definite beginning and ending because infinity just is and can not be measured. It's use in mathematics has been narrowed down since it can behave like a real number but does not follow the properties of a real number. In fact infinities lie beyond the boundaries of real numbers, - ∞ < x < ∞ where x is a real number.

Some properties that infinity follows are:
∞ + ∞ = ∞
-∞ + -∞ = -∞

∞ × ∞ = ∞
-∞ × -∞ = ∞
-∞ × ∞ = -∞

x + ∞ = ∞
x + (-∞) = -∞
x - ∞ = -∞
x - (-∞) = ∞

x × ∞ = ∞, x > 0
x × (-∞) = -∞, x > 0

x × ∞ = -∞, x < 0
x × (-∞) = ∞, x < 0

Functions never are able to reach infinity, since it's endless, but only reach towards and is known as approaching it's limit.

Problems involving finding limits, as it is well know, is not enjoyable and can mess with one's brain. L'Hopitals's rule attempts to make it easier. The process in l'Hopital's rule involves finding the derivatives of functions which tend to zero or infinity. And generally the derivative of a function is a measurement of it's rate, so it can be assumed that the derivative helps find the rate at which each function in consideration is reaching zero or infinity. When they are being divided, as l'Hopital's rule imposes, the ratio of the rates is being found. At times this rule can cause the problem to go in circles, but with interruptions of the rule the limit can be found.

As much as infinity and bothers us, I believe it's one of the most amazing concepts understood by humans. Because as much as everyone believes in the end of the Universe, I believe the Universe will go on forever and (until we have discovered otherwise) the Big Crunch will not take place.
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By Kowsheek Mahmood
Ryerson University, Toronto, Canada
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The Aftermath Publications, Issue 3
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The Man Every Physicist Wants to Get Married To - Einstein

We all know a thing or two about Einstein’s great works that lofted physics into great heights. But unfortunately we no almost nothing of his life apart form his works. Albert Einstein was born on March 14th 1879, of Jewish parents. He was a shy and curious child.
He attended a rigorous Munich elementary school where he showed an interest in science and math but did poorly in other areas of study. He finished high school and technical college in Switzerland. At the age of 22 he became a Swiss citizen. In 1903 he married
Mileva Marec. They had two sons but were later divorced. He later married his widowed cousin Esla in 1919. Around 1902 Einstein became an examiner in the Swiss patent office at Bern. In 1905 at the age of 26 he published five major research papers in an important German physics journal. He received a doctorate for the first paper. The next four papers that he published changed view of whole of mankind about our universe.

Einstein,Gezin,Mileva

Esla and Einstein

The first paper provided a theory explaining Brownian motion, the zigzag motion of microscopic particles in suspension. Einstein suggested that the movement was caused by the random motion of molecules of the suspension medium as they bounced against the suspended particles.

The second paper laid the foundation for the photon, or Quantum theory of light. In it he proposed that light is composed of separate packets of energy called quanta or photons that had both particle and wave nature. This very paper redefined the theory of light.
A third paper which began with an essay Einstein had written at the age of 16 contained the “Special theory of relativity”. The last of the four papers, the fourth paper was a mathematical addition to the special theory of relativity where he presented his most famous equation E = mc2. These papers established Einstein’s status among the most respected physicists in Europe.




Albert Einstein and Rabindranath Tagore in Berlin, Germany, 14th July, 1930

Einstein and Plank

In 1916 Einstein published his general theory of relativity. In it he proposed that gravity is not a force, a previously accepted theory, but a curved field in the space-time continuum that is created by the presence of mass. Between 1909 and 1914 Einstein taught theoretical physics in Switzerland and Germany. Worldwide fame came to him in 1919 when the Royal Society of London that predictions made in his General theory had been confirmed. He was awarded the Nobel Prize for physics two years later for his work in theoretical physics. When the Nazis came to power in 1933, they denounced his ideas, seized his property and burned his books. That year he moved to USA and in 1940 became an American citizen. His later years would mainly pass by in trying to establish a formula that would explain of the properties of matter and energy. Einstein died in Princeton in April 1955. This was the story of Einstein’s life.
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By Tahsin Uddin Mullick
North South University, Dhaka, Bangladesh
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The Aftermath Publications, Issue 3
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An Ode to CD

The CD (compact disc) a familiar name to us all, the device that gave us music, video and data storage capacity unparallel to any other previous recording device seen before.
Didn’t it bring us the tears of joy? As history would have it the CD was the combined work of two great warriors of the tech industry. One was Philips and the other was Sony. Each company had introduced a working model of an optical disc in separate dates but later collaborated to produce the master piece we have become so acquainted to.

The basic design of a CD is some what like the diagram below.

 A. A polycarbonate disc layer has the data encoded by using bumps.
 B. A reflective layer reflects the laser back.
 C. A lacquer layer is used to prevent oxidation
 D. Artwork is screen printed on the top of the disc.
 E. A laser beam reads the polycarbonate disc, is reflected back, and read by the player.

The polycarbonate layer contains bumps as a single, continuous, extremely long spiral track of data. The reflective layer usually aluminum helps in reflecting the laser back. The aluminum is protected by a layer of lacquer to avoid chances of oxidation. At last the lacquer is covered by a design. The CD spirals start at the center and spread outwards.
This when taken into consideration allows CD’s to be smaller than 4.8 inches. The track is made by elongated bumps 0.5 microns wide a minimum of 0.83 microns long and 125 nanometers high and also each track is separated from one another by 1.6 microns. The picture below is a microscopic view of CD bumps.

To read data in such tiny scale requires high degree of precision. Looks like a job for laser man. The drive has three basic jobs to perform , first of is the spinning of the CD which is carried out by the drive motor . The drive motor rotates the disc at 200 to 500 rpm. The second task at hand is that of the laser and a lens system which is to focus and read the data of those very tiny bumps. The third job rests with the tracking mechanism that rotates the laser to mimic the spiral track. The tracking system has to be able to move the laser at micron resolutions.

When a CD is being read, a laser is shown through the polycarbonate layer and reflected off of the reflective material. The reflected laser light is in turn detected by an optical sensor which converts the received laser signal into electricity. Depending on whether the laser was focused on a bump or not, the electrical signal will be different because the reflected laser light will be different. The difference in the electrical signals is how a computer can read data off of the CD. This is how the CD works.Till the next time stay tuned.
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By Tahsin Uddin Mullic
North South University, Dhaka, Bangladesh
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The Aftermath Publications, Issue 3
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A Short History of Astronomy

Astronomy is one of the oldest subjects ever ventured into by ancient scholars and philosophers. Astronomical study was probably first made by the Mayans and the Aztecs either as apart of astrology where the ancients strove to predict the future, or more scientifically in knowing when to sow crops, or as a navigational aid.

Although it is often claimed that the prime scholars and philosophers who studied astronomy had their roots in Babylonian and Egyptian cultures, there is strong evidence to show that the present day astronomy started with the Greek civilization.

EGYPTIANS PLACED TOMBS IN PLACES WITH ASTROLOGICAL SIGNIFICANCE

Early thoughts in Greek astronomy originated from renowned philosophers like Plato or Eudoxus of Cnidus, the ideas of whom were concretely established later by Aristotle (384BC-322BC). Aristotle was one of the most eminent thinkers. He developed a geocentric model of the universe with the earth at its centre and the Heavens above.

ARISTOTLE’S GEOCENTRIC MODEL OF THE UNIVERSE

Astronomical research then remained suspended for many years, due to its religious obligations until in around AD140, Ptolemy, another Greek resident took the earth centered Aristotle model and endeavored to account for the varying speeds and occasional retrograde motion of the planets. According to Ptolemy, each planet moved in a small circle (epicycle) whose centre moved on a bigger circle (the deferent).
Most of Ptolemy’s work was gathered into a book known by its Arabic title, The Almagest, which means, The Greatest. With Ptolemy’s death, classical western astronomy was slipping into the dark ages.

The Ptolemic model of the universe was not superseded until the arrival of Nikolaus Copernicus (1473-1543), the son of a rich Polish merchant. Copernicus developed a revolutionary model for the universe that was unique in its true sense. He is the one who first established the heliocentric model in which the planets travelled around the sun in circular orbits. Copernican model awakened astronomy form its dark age. All of Copernicus’s ideas were published in a book titles De Revolutionibus Orbium Coelestium (on the revolutions of the celestial spheres). The years following Copernicus’s death were to be a golden era for astronomy as it was only within a thirty year period, three major figures in the field of cosmology and astronomy were born.

A SIMPLIFIED VERSION OF THE COPERNICAN MODEL

Tycho Brahe (1546-1601), a Danish nobleman, made important contributions to observational astronomy by many amazing inventions. His wit and talent was enough to impress the then King Frederick II of Denmark who funded him for his research. Tycho Brahe built the very first observatories and made instruments like the quadrant which could measure the position of stars with remarkable accuracy. Tycho Brahe’s work was further carried on by his student Johannes Kepler.

MANY OF TYCHO BRAHE’S INVENTIONS

Kepler deduced three, very important and immensely useful laws which hold true even today!
The laws were mainly based on observation and had no mathematical basis.
1.The orbit of a planet about the sun is an ellipse with the sun at one focus.
2.The line joining a planet and the sun sweeps out equal areas in equal times.
3.A planet’s orbital period squared is proportional to its average distance from the sun cubed.

Can you prove the Third Law using laws of Gravitation and Circular Motion?

Galileo Galilei was born shortly before the birth of Kepler in 1564 in Pisa, Italy. He investigated many aspects of physics and was probably the first astronomer to use telescopes for systematic astronomical observations. Galileo’s contribution to astronomy mainly comprised of early attempts of unifying astronomy with material sciences and inventions of more accurate astronomical devices.
Isaac Newton made astronomy a truly scientific subject. Physics and astronomy were used to be considered as separate disciplines until the time of Newton. Newton was the first philosopher or scientists who attempted for the first unification of celestial objects with that of terrestrial objects. He was successful into showing that it was not separate theories but the same, governing the behavior of objects in the universe. While trying to explain what forces cause the motions of planets, he discovered gravity, an attractive force exerted by all masses on all other masses in the universe. His ideas greatly helped in reducing anomalies and complexities in astronomy.

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By Mahmud Hasan

The Aftermath Publications

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The Aftermath Publications, Issue 3

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Laser

LASER. At the first instant the name reminds me of my childhood days when I used to fancy about sci-fi robots, extra-terrestrials and heroes with mighty powers. I still remember watching numerous shows like Startrek or Galactica back in the 90s. An integral part of all those shows was the “Laser” which was used either in the form of weapons of mass destruction by perilous space beings or even in the form of “teleporters”.

Little did I know that the laser had even more important and mind boggling applications in our daily lives than in amusing but apocryphal science fictions. From checking out the shopping at the supermarket to precision hospital surgery, from printing our homework to communicating along thin strands of glass---laser is all around us.

SPECTACULAR LASER SHOWS ARE A COMMON PUBLIC ATTRACTION TODAY

LASER is an acronym for Light Amplification by Stimulated Emission of Radiation. Most lasers share the following components:

1. A lasing medium
2. An energy source
3. A resonator

Conventional lasing mediums consist of mixtures of helium and neon gases. In normal conditions the atoms of the gases are all in their ground states. The lasing medium is enclosed within a discharge tube with highly reflecting mirrors at two ends of the tube along with arrangements for the application of high voltages.

This high voltage arrangement acts as an energy source. When a high voltage is applied across the ends of the tube containing the gas, an electric current is caused to flow through it, thereby exciting the electrons in the atoms of the lasing medium to higher energy levels---a situation termed as Population Inversion.

When the excited atoms decay to the ground state, they emit photons of light spontaneously. However, if this photon of light then meets another excited atom, it stimulates the excited atom to drop to its ground state. In this process, another photon of light is emitted (by stimulated emission).

THE SCHEMATIC DIAGRAM SHOWS: 1. LASING MEDIUM

2. ENERGY SOURCE; 3,4. MIRROR RESONATORS; 5. EMERGENT LASER LIGHT

Einstein showed in his papers that both the stimulating and the stimulated photons have:
The same wavelength
The same phase
The same direction of travel

The emitted photons can be allowed to bounce back and forth along the axis of the tube by means of highly reflecting mirrors which act as resonators. This avalanche effect produces more and more photons until a beam of monochromatic laser light is allowed to emerge from any one end of the discharge tube.
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By Mahmud Hasan
The Aftermath Publications
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The Aftermath Publications, Issue 3
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Mentos and Diet Coke: The Truth Revealed!

The title of this article has probably already made you come to the conclusion that it is going to be like any of those highly sought for forum articles or frequently viewed YouTube videos. Yes, videos and articles which feature “Do It Yourself” formulas of making an exploding mix of Mentos and Diet Coke. But I guarantee that this article discusses something little different though related.

By now, many of you have already come to know about the Mentos-Diet Coke explosion phenomenon. It has been the topic of discussion for quite a long time and the visual splendor of Coke shooting from two liter bottles to extraordinary heights has attracted so much attention in the past few months that the topic even made its way to famous programs like the Mythbusters or Timewarp aired on the Discovery channel.

Each and every video I watched and writing I read about this famous topic emphasized on how an eruption could be made to produce a “Coke Geyser”. Many of you might still have the formula in your mind:

4 Mentos + 2 Liter Diet Coke = Kabooooom!

Typical Coke Geysers

But I was really curious to find out why actually the phenomenon occurred. With a little help from my friends, teachers and the internet, I tried my best to piece together the moments just before an eruption occurs when Mentos is dropped into Diet Coke and this is what this article is all about.
The reaction between Mentos and Diet Coke is more of a physical reaction than chemical. Coke is mainly water with dissolved carbon dioxide, flavorings, and sweeteners. In most liquids, there is some dissolved gas. In high surface tension liquids like water, it is tough for bubbles to form because water molecules tend to be next to each other due to capillary forces. In order to form a new bubble or even to expand a bubble that has already formed, water molecules must be pushed away from each other. It takes extra energy to break this tight mesh of linked water molecules.

Surface Tension Leads To the Formation of Stable Liquid Drops

When Mentos candy is dropped into Diet Coke, the gelatin and Gum Arabic in the coating of the candy act as efficient surfactants. They lower the surface tension of the Coke and reduce the work done to produce bubbles. In Diet Coke, artificial sweeteners instead of sugars are used which are better surfactants. Also, the rate of reaction between Mentos and Coke with artificial sweeteners (i.e. Diet Coke) is very fast than that with conventional Coke.
The surface of Mentos is very rough. When magnified, the surface of Mentos can be seen to have numerous pits. These pits act as nucleation sites encouraging formation of bubbles on them. Though nucleation site theory is not yet clearly understood, but some scientists argue that at the nucleation sites, the curvature of bubbles get reduced and hence the surface energy is also small there. Thus at those sites, bubbles are preferentially formed. Some others argue that at the nucleation sites, the pattern of electrical forces between solvent molecules change which allow solute molecules to break free and escape (in the form of bubbles if the solute is a gas). It is based on this nucleation phenomenon, radiation detectors like Bubble chambers and Cloud chambers work.

Nucleation of carbon dioxide Around a Finger

Mentos candies are relatively heavy and thus they sink to the bottom as soon as they are added to Coke. The sinking Mentos undergoes a rapid physical reaction with the Coke. This coupled with the low surface tension of the Coke and the introduction of numerous nucleation sites leads to the formation of a large number of bubbles in a very short time. These evolving bubbles ascend and push all the liquid Coke above them with great force to cause an impressive eruption. This produces the characteristic “Coke Geyser”.
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By Mahmud Hasan
The Aftermath Publications
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The Aftermath Publications, Issue 2

Stars: Birth to Death

It does not take an expert eye to discover the magnificence of the night sky. It has so much to offer, in the form of its pitch black darkness adorned by equally bright dazzling dots what we more commonly know as stars. Stars are probably the most amazing celestial creations. They embellish the vast emptiness of the sky with their charming hues and brightness so efficiently that they still remain the centers of attraction to astrologers, scientists and philosophers.

Early philosophers believed that stars are gods, who constantly show up in the night skies to impose their presence by brilliance and to inspire people do good deeds for the next day. This is of course not a valid proposition anymore on scientific grounds. So what actually a star is?

Stars Dominate the Night Sky

Astrophysicists use observations to suggest theories of how stars come into being. Interstellar space is not a perfect vacuum as you might expect. Rather it is a low density mixture of atoms, molecules and microscopic specks of dust. In places these form greater concentrations, which appear as large gas clouds.

Interstellar Gas Clouds

A close look at the night sky with a telescope reveals the existence of the gas clouds along with stars and planets. The most available element in these clouds is hydrogen. The most plausible theory is that stars begin as clouds of hydrogen.

Despite the extreme tenuousness of these clouds, gravitational force is predominant force that acts on the particles of the cloud. This pulls the particles together and they accelerate inwards. They collide increasingly frequently sharing their energy. The temperature of the gas thus rises. Therefore gravitational energy is converted to thermal energy. When the gas cloud collapses sufficiently it becomes hot enough to emit infrared radiation. This causes electrons to be stripped off the hydrogen atoms and the atoms eventually become hydrogen nuclei (i.e. protons). This causes the whole mass of the cloud to be converted into a mixture of positive ions and negative electrons called Plasma. At this stage the gas cloud can be called: a Protostar.

Collisions between particles become increasingly energetic as the gravitational contraction continues. If the mass of the cloud is high enough, eventually an ignition temperature of about 10 million Kelvin is reached, which gives the hydrogen nuclei sufficient energy to overcome electrostatic repulsion and join together to start the process of nuclear fusion. This process releases a large amount of energy owing to decrease in potential energy due to strong nuclear force. This maintains or increases the core temperature of the gas clouds so that fusion reactions continue. At the ignition temperature, the hydrogen nuclei fuse to form stable helium. The overall reaction involves four hydrogen nuclei fusing together to form a single helium.
As soon as the nuclear fusion process initiates, the gas cloud can be termed as a star. The core of a star is a fusion reactor. Iron is the largest nucleus that can release energy on formation in this way. When the helium in the core of the stars is used up to form heavier elements, the star collapses on itself to become a white dwarf star. This can be marked as the death of the star.

A White Dwarf (Left)

Stars continue shocking us as we explore and understand more plausible theories that unveil secrets of their origin, evolution and death. Our knowledge of celestial objects is still at its infancy. Until we get the exact and most accurate information that define the existence of all celestial bodies from black holes, planets to stars correctly, I suppose it is safe to sing-

      “Twinkle twinkle little star;
How I wonder what you are?”

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By Mahmud Hasan
Aftermath Publications
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The Aftermath Publications, Issue 2
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How to Get the Perfect Date?

No folks Aftermath hasn’t entered the matchmaking business but remains your ever so humble science e-magazine. This article is actually based on the ingenious method that tells you the age of a host of things from a mummy to a dinosaur bone or perhaps the age of the antique clay pot on your display shelf. This scientific process is known as radiometric / radioactive dating. There are number of types of dating from uranium dating to C-14 dating. They are categorized by the time period to which they can reliably confirm dates of objects, formation of geological features or even bodies of ancient people. The C-14 dating was the first convincing dating procedures that worked on matter which was once living. The method was developed immediately following World War II by Willard F. Libby and coworkers, and has provided age determinations in archaeology, geology, geophysics and other branches of science. Radiocarbon determinations can be obtained on wood; charcoal; marine and fresh-water shell; bone and antler; peat and organic-bearing sediments, carbonate deposits such as tufa, caliche, and marl; and dissolved carbon dioxide and carbonates in ocean, lake and ground-water sources.
C-14 is created when cosmic rays from the far reaches of space strike nuclei to produce neutrons; these in turn bombard nitrogen atoms to produce C-14. This C-14 is radio active in nature and combines with oxygen in the atmosphere to form CO2 and thus enter our living cycle.

Archaeologists and scientists use this radioactive quality to their advantage by measuring the activity from the sample substance and
comparing it to the equilibrium level of living things  they can determine the time that has passed. Since all life on Earth is made of organic molecules that contain carbon atoms derived from the atmosphere, all living things have about the same ratio of C-14 atoms to other carbon atoms in their tissues.
Once an organism dies it stops taking in carbon in any form, and the C-14 already present begins to decay. Over time the amount of C-14 present in the material decreases, and the ratio of C-14 to other carbon atoms declines. In terms of radio carbon dating the fewer C-14 atoms in the sample the older the sample is. The rate of decay of C-14 is pretty steady.

The half life of C-14 is 5730 years. What this means is that half of the C-14 has decayed after 5730 years. Then half of the remaining C-14 or one fourth of the original amount decays in the next 5730 years. After about 50,000 years the amount of C-14 still present in the sample becomes immeasurable. Carbon-14 decays with a half life of about 5730 years by the emission of an electron of energy 0.016 MeV. This changes the atomic number of the nucleus to 7, producing a nucleus of nitrogen-14. At equilibrium with the atmosphere, a gram of carbon shows an activity of about 15 decays per minute.
The low activity of the carbon-14 limits age determinations to the order of 50,000 years by counting techniques. That can be extended to perhaps 100,000 years by accelerator techniques for counting the carbon-14 concentration.

The accelerator technique works with the help of a cyclotron  accelerator working in unison with mass spectrometers .

While radiocarbon dating is a good method of dating fairly recent prehistoric objects, other techniques must be used to date materials older than 50,000 years. These methods include other absolute dating techniques that are similar to C-14 dating methods. Elements other than C-14 can be used in absolute dating techniques.

In this list of radioactive dating processes are:


Samarium-neodymium dating method
This involves the Alpha-decay of 147Sm to 143Nd with a half life of 1.06 x 10^11 years. Accuracy levels of less than twenty million years in two-and-a-half billion years are achievable.

Potassium-argon dating method
This involves electron capture or positron decay of potassium-40 to argon-40. Potassium-40 has a half-life of 1.3 billion years, and so this method is applicable to the oldest rocks. Radioactive potassium-40 is common in micas, feldspars, and hornblendes, though the blocking temperature is fairly low in these materials, about 125°C (mica) to 450°C (hornblende).

Rubidium-strontium dating method
This is based on the beta decay of rubidium-87 to strontium-87, with a half-life of 50 billion years. This scheme is used to date old igneous and metamorphic rocks, and has also been used to date lunar samples. Blocking temperatures are so high that they are not a concern. Rubidium-strontium dating is not as precise as the uranium-lead method, with errors of 30 to 50 million years for a 3-billion-year-old sample.

Uranium-thorium dating method
A relatively short-range dating technique is based on the decay of uranium-238 into thorium-230, a substance with a half-life of about 80,000 years. It is accompanied by a sister process, in which uranium-235 decays into protactinium-231, which has a half-life of 34,300 years.
While uranium is water-soluble, thorium and protactinium are not, and so they are selectively precipitated into ocean-floor sediments, from which their ratios are measured. The scheme has a range of several hundred thousand years.

These dating techniques can’t exactly pinpoint the date an event occurred. But they can give us a close approximation as to when the event might have taken place. So now u too have learnt the way to get the perfect date.
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By Tahsin Uddin Mullick
North South University, Dhaka, Bangladesh
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The Aftermath Publications, Issue 2
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O Radio, O Radio, What Art Thou?

That’s right this time around I will look into our friend in solitude our life saver in desperate times, the “Radio”. The radio is like the nitro that speeded up the telecommunication industry and allowed us to get rid of those hideous wires.
The story is some what like this, after the discovery of radio waves in 1888 an Italian genius named Marconi got a bright idea. The idea was to use radio waves to communicate .This made Marconi one of the pioneers in wireless radio communications. Marconi was successful in introducing radiotelegraph to the world. The importance of the radiotelegraph became more evident when operators from Marconi’s company were the ones to signal in for help which saved around 700 lives during the Titanic wreck. The radiotelegraph didn’t look anything like the radio sets of today. The telegraph was far away from commercial purpose radios as it was able to only communicate in Morse code.

But soon enough Morse code was replaced by speech and music with the introduction of the crystal radio sets around the early 1900s. The credits for this invention goes to an array of scientists as they combined their magical ideas to give us the first radio sets that were able to receive music and speech. The crystal radio sets didn’t require any kind of power supply the radio waves were enough to power up these babies.

1922 Crystal Radio

The crystal radios contained crystals of galena or pyrites which acted as detectors much like the diodes of today. The crystal radios did give sound but quality of the sound needed some fixing up. That’s when the thermionicvlave entered the picture. The thermionicvalves were also known as vacuum tubes. The valves emitted electron after being heated up. They allowed inventors to switch amplify or modify electrical signal by controlling the electron flow and replaced solid state diodes.

Though the valve radios gave quality sound they didn’t appease the users because of their heavy and ugly looking bodies. It was around 1930s that companies like Marconi-phone started building radios that complemented the furniture. This fashionable trend took off from that time onwards with radios. New models of radios had press buttons to preset channels and wooden or metallic exteriors were replaced by bakelite exterior. No the radio wasn’t ugly any more but had changed into a work of art.

A Two Valve Radio 1924

However, the biggest break through in the industry came with the advent of transistors. Using transistors instead of valves in radios reduced power consumption and allowed the use of lighter batteries. In electronics, a transistor is a semiconductor device commonly used to amplify or switch electronic signals. A transistor is made of a solid piece of a semiconductor material, with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's terminals changes the current flowing through another pair of terminals. Because the controlled (output) power can be much larger than the controlling (input) power, the transistor provides amplification of a signal. The transistor is the fundamental building block of modern electronic devices like the radio. Transistors paved the way for portable radios which hit the market with a bang and the people, well they just fell in love with the cute radio sets.

The first commercially successful transistor radio was the Sony TR-55 (as shown in the picture on the right), introduced in 1955.

The radios after this just kept coming in all different sizes and designs. In 1933 Trevor Baylis was watching a program about AIDS in Africa, and realized that many people in developing countries had no radio (and so had limited access to health information) because they had no mains electricity.

He developed the wind-up radio. Windup radio is a radio that is powered by human muscle power rather than batteries or the electrical grid. In the most common arrangement, an internal electrical generator is run by a mainspring, which is wound by a hand crank on the case. Turning the crank winds the spring, and a full winding will allow several hours of operation. The wind-up radio was succeeded by the digital radio that received signals as digital code ensuring clearer sound Because of the way in which the signal can be compressed, more radio stations can be transmitted using the same range of frequencies (‘bandwidth’).

The digital signal includes information about the channel, making it easier to ‘tune in’ (there is no need to remember the frequency). A display on the radio can show the program, the name of the track currently being played, email addresses, up to the minute sports results or competition details, making it more informative.

The development of IC circuits was like a blessing from GOD as it allowed the development of smaller and cheaper and well designed radios. The ICs of today can hold a number of transistors, resistors capacitors all in a tiny amount of space. Thus people know can enjoy the radio even in the poorest parts of the world. The development of the radio was truly amazing from the huge radiotelegraphs to the modern day handheld digital radios. Thanks to a large number of scientific discoveries and scientists who combined to give us our pal in sunshine or rain the Radio set.
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By By Tahsin Uddin Mullick
North South University, Dhaka, Bangladesh
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The Aftermath Publications, Issue 2
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The Fifth Force

The work of a Hungarian scientist Roland von E'otv'os in the early 20th century involved testing the principle of equivalence, a postulate of Einstein's which stated that gravity affecting an object is independent of their composition. This principal is one of the fundamental assumptions of Einstein's General Theory of Relativity and naturally, could not be wrong, E'otv'os declared a null experiment since he discovered an error in his calculation.

And as almost everything in Physics is discovered from “mistakes”, Dr. Ephraim Fishbach and his fellow Physicists at Purdue University set out to prove the existence of a fifth force, related to hypercharge, opposing the force of gravity. The range of this force, they figure is from a few millimeters to cosmic lengths. Even though it's not infinite as gravity, it's as weak as gravity. And thus it is difficult to experiment with. Nonetheless, working with E'otv'os results and re-performing his “mistaken” experiment Fishbach and friends seek to find the effect of this illusive force. So much so that the Physicists have to perform their experiments a kilometer below the surface to find minimal traces of it.

A solid proof of the this force seems to be nowhere in sight and many predict that the effect of its discovery would not be more than causing publishers to release new editions (which they are always happy to) so that students may learn of a new force along with the existing four and find it harder to tell which is which on tests and exams.

It's also unlikely that this fifth force would disprove General Theory of Relativity because it seems to be so insignificant, but I could not help but hope it does. I mean, have YOU read that theory? It's mind blowing, and I am no Einstein.
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By Kowsheek Mahmood
Ryerson University, Toronto, Canada
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The Aftermath Publications, Issue 2
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