Gravitational Force

          It all started when a 22 year old boy who returned home from his college discovered most of the understood fundamental of physics while dealing out with the force of attraction between the two bodies. Gravitation has been defined as the force experienced by any two bodies in the universe by virtue of their mass. The gravitational force was first experienced by the great scientist Issac Newton. When an apple fell on his head he realized that the Earth pulls everybody towards itself. Later, he concluded that everybody in the universe attracts each other which he named as gravitational force.

Black Holes

        Space is dark and also empty. In it also exists, dark and dense bodies known as “Black Holes”. These are places or objects where force of gravity is so large that it does not allow even light to escape. Black holes may be stationery or moving but the unusual property is regarding space and time. Time is dilated as we go near a black hole and vanishes inside it. 

Depending upon the mass of black hole it is basically classified into the following- 

• Miniature black hole 
• Siellar 
• Supermassive 

     Black holes cannot have charge owing to the fact that due to high gravitational force it will attract the charges of opposite polarity and neutralize them. It is very difficult to predict what is there inside the black holes as the communication is ceased due to trapping of signals by the strong gravitational force. 

       Black holes are born due to gravitational collapse i.e. when the celestial bodies cannot withstand their own compressing force of gravity. They grow in size by capturing/trapping other bodies coming close to them. When two black holes collide, they form a large black hole which is another main cause of their growth. 

      Previously it was thought that death of black hole was impossible since nothing, even light cannot escape from it. But the eminent scientist Stephen Hawking theorized black holes emit some radiation and at some point of time it will disappear.

BY: Molla Ramizur Rahman

Dark Matter

      For years the physicists struggled for creating an image of the outer space through computers but failed to develop a stable model. The model was being developed in order to see whether the data that we collected is accurate or not. Also the purpose was to discover a black hole. A Black Hole cannot be detected by using instruments in space. Every time the outer space was simulated, every time it fell apart. There was something that was missing, but what was that ? The answer was The Dark Matter.

     What is this new thing? Is it an element or planet or a star? This new thing has been defined as matter but its type is still undefined. A matter is defined to have mass and volume; so does dark matter. Dark Matter constitutes a large amount of the total mass of the universe. This matter cannot be seen, then how can it be detected? The only known way today is by weighing the matter. When values were substituted with dark matter in mind, it gave astonishing result, a stable space. But what was in this matter that we were not able to achieve a stable universe? Using the laws of conservation, the mass of celestial bodies was calculated and equated for analysis, but due to lack of sufficient strength to hold the bodies together in the system, the space was tearing apart again and again which is not true. To resolve this missing mass, the concept of dark matter was introduced.

Teleportation

             Ever since the invention of wheel more than 5000 years ago, human desire to reach a place faster has lead to numerous inventions. From chariot to bicycle to automobile to airplane and rocket, all have been created with a single motive to travel faster. But all these inventions share the same flaw; it requires us to travel the physical distance. With development in the field of paranormal physics, scientists have been trying to combine the properties of telecommunication and transportation to achieve “teleportation”.

         Teleportation involves transfer of matter from one place to another without physical traversing the space between them. It deals with dematerializing an object at one point, sending the details of the precise atomic configuration at another location where it will be reconstructed. With the tremendous potential being embedded on this invention it would explore the possibilities of travelling without physically crossing the space. The idea of teleportation moved out of the realm of science fiction into the world of theoretical possibility in 1933. Physicist Charles Bennett with a team of researchers at IBM confirmed that quantum teleportation is possible, but only if the object being transported was destroyed. Since then, experiments using photons has proven that quantum teleportation is in fact possible.

          In 1998, physicists at Caltech successfully teleported a photon by reading its exact atomic structure, sending the information across 1 meter of coaxial cable and creating a replica of photon.  As predicted, the original photon was destroyed once the replica was made. In the event of teleporting objects larger than photon the main hurdle in the path is “Heisenberg Uncertainty Principle”. The principle states that determining the momentum and location of a particle simultaneously is not possible. If you cannot determine the location of a particle then how can you teleport it? The photon experiment was carried out by using a phenomenon called entanglement. For a person to be transported, a machine would have to be built that can pinpoint and analyze all of the  atoms that make up the human body. That's more than a trillion trillion atoms. The machine would then have to send this information to another location, where the person's body would be reconstructed with exact precision. Molecules couldn't be even a millimeter out of place, lest the person arrive with some severe neurological or physiological defect. The laws of physics may even make it impossible to create a transporter that enables a person to be sent instantaneously to another location, which would require travel at the speed of light. The availability of this technology tough looks bleak in the near future.

           But like all technologies, scientists are sure to continue to improve upon the ideas of teleportation to the point that we may one day be able to avoid such harsh methods. One day, one of your descendants could finish up a work day at a space office above some far away planet in a galaxy many light years from Earth, tell his or her wristwatch that it's time to beam home for dinner on planet X below and sit down at the dinner table as soon as the words leave his mouth.


By: Ankit Jain

Galilean Relativity: Volume-3

Inertial Frames

Inertial Frame of Reference

    Physicists generally have a tendency to mention the frame of reference and its type, such as inertial or non-inertial. The importance of the frame of reference lies in the fact that the Law of Inertia is valid in it. Law of Inertia is also known by the name Newton's First Law of Motion which states that a body will tend to continue in its state of rest or uniform motion unless and until acted upon by an external force. Referring back to the cabin of ship described in Galilean Relativity: Volume-1 all the objects inside the cabin will follow the law of inertia till the time it is an inertial frame.

          An inertial frame is defined as a frame which is at rest or moves with a uniform velocity i.e. not gaining speed. Any reference frame with a constant relative velocity to an inertial frame is also considered as an inertial frame. A frame which is accelerating is known as an Accelerating Frame and consequently the law of inertia is not valid in it. When analyzing the behavior of an object in accelerating frame, the results seem to be absurd. To account for the acceleration of the frame a pseudo force is employed or simply an acceleration of same numerical value but in opposite direction. Similarly, the Galilean Relativity is implemented using inertial frames or using pseudo force or negative acceleration for accelerating frames.

Galilean Relativity: Volume-2

Galilean Transformation

Galileo Galilei

The theories that deals with relativity are mainly -

• Special Theory of Relativity (1905)
• General Theory of Relativity (1915)

Yet these two theories draw their foundation from the Galilean Relativity. The concept that is borrowed by Einstein is the principle of Inertial Frame.

          The Galilean Transformation deals with the relative motion of the two bodies that move with a velocity negligible to that of light (assigned a value c). To analyze this consider a situation wherein two bodies, let us say two trains, are moving in the same direction (say, towards geographical north). For our analysis, let the velocity of train A be 30 mph and of train B be 20 mph. Now by the Galilean Transformation the relative velocity of train A with respect to train B is 10 mph (30 mph - 20 mph) towards geographical north while the relative velocity of train B with respect to train A is 10 mph (20 mph - 30 mph) towards geographical south.

          Let us say in a subsequent situation, that a man in train A gets up from his seat and moves in the direction of motion of the train i.e. geographical north, with a velocity of 32 mph with respect to the ground. In this case the relative velocity of the man with respect to train B will be 12 mph (32 mph - 20 mph) towards geographical north while with respect to train A it will be 2 mph (32 mph - 30 mph).

          Now in the same situation let us consider the man to walk in a direction opposite to that of the train's motion and with a velocity of 32 mph. This time the relative velocity of the man with respect to train B will be 52 mph (32 mph + 20 mph) however with respect to train A it is 62 mph (32 mph + 30 mph).

Note: It may seem weird that the relative velocity of man with respect to the ground is 32 mph which is greater than the velocity of either of the trains but this is perfectly alright because the man is in contact (sitting) with the train so his velocity with respect to the ground is already 30 mph, an additional walk lets say of 2 mph will result in the mentioned value, 32 mph.

Galilean Relativity: Volume-1

Galileo Galilei

     In the world it is possible that a particular event is viewed differently by different people. Depending upon the frame of reference, an event may seem to be different to viewers but in all the cases the laws of physics are never violated. Galilean Relativity is a reference frame based phenomena. With reference to this concept, let us consider two simple situations. 

      In first situation, imagine two humans inside the cabin of a ship which is at rest. The cabin contains some of the decorative items like an aquarium with some fishes in it, paintings, etc. Also let us bound the outside view from inside the cabin. Let us say that one of the friend 'A' throws a ball towards his friend 'B' inside the cabin. Since the ship is at rest, the relative velocity of the objects inside the cabin including the humans will be zero. In this situation the people inside cannot tell whether they are moving or not as there is no relative motion between the objects inside the cabin.

      In the second situation, imagine that the ship is moving with certain but constant velocity in a particular direction. Now let us say hat the velocity is v. The velocity of each and every object inside the cabin will be v with respect to the ground or the shore. This means that the relative velocity of objects with respect to each other is zero. Suppose the friend 'A' again throws the ball towards his friend 'B'. Since the outside view is bounded & the relative velocity is zero the people inside will not be able to tell whether the ship is in motion or not.

       It is clear from the above exercise that the velocity of ship has no impact on the event taking place inside & so even though the ship is in motion, none of the humans or intelligent species can tell whether the ship is in motion or not. This is the basic idea of 'Galilean Relativity'.

What is Matter?

Definition of Matter

     Matter, generally defined as anything that has mass and occupies space is classified to exist in four of the known states viz. solid, liquid, gas and plasma. Matter has been proved to exhibit wave nature as well as particle nature. With the development of the 'String Theory', the definition of matter has witnessed a drastic change for now the fundamental particles were not atoms or molecules, not even proton, electron and neutron. Now the fundamental particle in nature was defined to be a string. A question that arises in mind is that how is matter related to fundamental particle? The answer follows by the relation that anything and everything in the world is a singular or a combination set of the fundamental particle(s). Lately the matter is defined as the different modes of vibrations of the fundamental particle, string (based on String Theory). Defining precisely matter consists of particles that are themselves different modes of vibration of the fundamental particle - string.

Milkyway's End

        Everything that has a start has an end too. The final state or the destiny or the future of a living organism, star, galaxy and the universe has, is to die as all involves life. The end in many cases can be predicted but its accuracy is proved only by time. With great efforts combined by the masters of Physics throughout the world, a picture of how our MILKYWAY galaxy, which is also known as AKASHGANGA will end in the time frame yielding a new galaxy.

        With the advancement in technology, we have figured out the answer to our galaxy's end. As per the experiments, physicists believe that our galaxy would die due to its collision with another galaxy heading towards it. The collision will not take place in a day or a year, rather it will be a process of many centuries. It is predicted that the galaxies would cross each other by side many times and will eventually form a new galaxy with a new black hole at its center. The velocity with which milkyway is heading is nearly 4,00,000 Km/hr yet its collision time is a lot ahead; somewhere around 5 to 6 billion years. Fortunately we will not see our galaxy dieing in front of our eyes and we being getting shrunk in the distance.

Big Bang Confirmation

Big Bang ?

        The Big Bang Theory was introduced by Einstein as a solution to the most baffling question about the origin of the universe. According to this theory the universe was born as a result of a huge explosion that occurred 10 to 20 billion years ago. Earlier to that the universe was a very small dense ball of matter which was unstable causing a massive explosion now known as "THE BIG BANG". Though the theory was a huge success, it failed to explain why the universe was unstable in that state. 

Big Bang Confirmation !!

         It was somewhere in 1940's when the Russian physicist George Gamow stood firmly with the statement that the radiations left over after the Big Bang shall still be moving around in the universe despite of the fact that the temperature has drastically fallen down. Gamow and his collaborators - Ralph Alpher and Robert Herman, in 1948 even calculated the temperature of the universe as 5 degree Kelvin. The Theory of Big Bang was confirmed in 1965, when two scientists - Arno Penzias and Robert Wilson while working in Bell Laboratories for satellite communication discovered that the antennae picked up a disturbing signal in the microwave range. At first the scientists failed to recognise the signals as the left over radiation from Big Bang and struggled to eliminate the signal by not only checking up the instruments but cleaning the antennae to the best possible way. They also tried picking up signals in different directions and from certain height from the ground using jet planes and balloons, but couldn't eliminate the disturbance. Rather the higher we went, stronger the signal became. After careful study when the scientists plotted the relationship between the intensity of radiation and the frequency, they found the curve resembling to the one predicted by Gamow nearly two decades back. Even the temperature of the cosmic fire ball (universe) was found to be 3 degree Kelvin, very much close to the one predicted by Gamow. This background interference is also called as the 'echo' of the Big Bang and is a proof of its occurrence.

Death of Earth

        One of the exciting questions of the ancient times was about the death of our own planet Earth. Scientists all over the world struggled long enough to gather information to predict the fate of Earth. Given a choice between two- Death of Earth in ice or fire, scientists bantered each other with their theories and research work. Many theories were tossed out. The plausible answer to this question appears to be death of Earth in fire.
        It is now known that the source of energy of a star is the fission or fusion process taking place continuously. In our sun, fusion takes place in the core. It is believed that once our sun has used up its available hydrogen, then the sun will use the unburned helium which will expand into a red giant star. The size of this giant star is presumed to be as large as the orbit of Mars by Sir Michio Kaku. Consequently, the Earth is supposed to be vaporised by this event and hence will be the fate of our planet. But we need not worry about its end as we won't be there to witness the disaster.

The S-Matrix (Scattering Matrix)

What is S-Matrix ?

        The 's' in S-Matrix stands for 'scattering'. The scattering matrix was formulated for point particles. It is helpful to predict what will happen when particles collide. On collision, how many particles will scatter at an angle with what amount of energy, is predicted by the elements of this matrix. The matrix is significant only if it has finite elements.


Why is Sky Blue ?

        When we look at the sky, what we see is actually the light that has been bounced off by the air molecules in the atmosphere. It is a general misconception that the light we see in the sky is the direct sunlight. Had it been the direct sunlight we would have seen the sky in white colour, as it is a blend of all seven fundamental components of colour found in nature. When the sunlight travels through the atmosphere it collides with molecules in the air (This shows the particle nature of light and hence justifies the use of S-Matrix). Since it is a case of particle collision, it is definite that the energy of both the particles will witness a change in the energy depending on the coefficient of restitution. The intensity with which the collision takes place is the answer for sky to be blue.


Why is Sun seen Red at Sunset ?
     The sun is seen red at the time of sunset due to a opposite effect. Sky is seen blue because of scattered blue component whereas sun is seen red because of non-scattered red component. At the time of sunset, the sun is near the horizon because of which the distance that light has to travel is larger. While travelling the particles of light collide with the particles of air. The number of collision increases due to increase in the path of light. As the light reaches its destiny- us, its components are scattered and only the red component is left.

Heisenberg Uncertainty Principle

 

   Diving into the world of sub atomic particles we come across the most important concept of the "Uncertainty" introduced by WERNER HEISENBERG, one of the founders of the "Quantum Mechanics" in the year 1927. He proposed that the exact position and the velocity of  an object cannot be known simultaneously. The equation describes a relation between the position and velocity/momentum of a microscopic body such as an electron.

        
   Heisenberg said that when the precision of measuring one quantity increases then, the precision of measuring the other quantity decreases. Consequently it can be seen that if we try to measure the position of an electron then we cannot precisely find its velocity. It is because of the fact that to make any measurement we need to see the particle for which we need light, that is a quanta (photon) is required to be aimed at the specimen particle. When the photon hits the particle then it bounces the particle out of its orbit hence changing its position/location. One may argue that we may someday overcome this problem with advanced technology in measuring instruments. But it may be here emphasised that the limitation of uncertainty is not due to the limitation of the present day technology, rather a limitation in nature as we need light (photon) to see. It seems as if nature itself has limited us with the power and conceals some of its secrets.

Time as Curled Dimension

        Today we understand that time is a necessary dimension in our universe to define the state of an object completely. Unlike the 3 other dimensions, time cannot be visualised as an axis.(Note: The graph we plot against time axis is only a form of representation to study variation of other quantities with time. Time is never an axis.) Then where is the time dimension? It might seem absurd if it is proposed that time is a dimension curled with other 3 dimensions, but it can be proved.


        Let us analyse this situation. Let there be a particle of mass 'm' (take any value for mass here, as it would not affect our analysis). Whenever we encounter an equation describing the motion of a particle, it is generally of the form s=ax+by+cz but not of the form s=ax+by+cz+dt (here dt is not a differential, d is a constant). Rather it is of the form s=axt+byt+czt+dzt. Suppose a particle moves in space such that its coordinates change from P(x1,y1,z1) at t1 time to Q(x2,y2,z2) at t2 time. If we do not associate time dimension with x,y and z then we would surely describe the equation to be s=ax+by+cz+dt1, but how do we visualise the fourth term? Moreover, we can see that the particle has moved in all dimensions. The movement of the particle in space is x,y,z but in space-time continuum it is xt,yt,zt. Lets say that at t1 the position of particle is s1=x+y+z+t1 and at t2 it is s2=x+y+z+t2 (Taking the constants a=b=c=d=1 for sake of simplicity). Analysing this we find that the positions are separated in time but not it space, implying that the position of the particle has not changed even though we have considered the particle to be motion. This is actually not possible. Since the particle has moved in space and in time with time being  a parameter to measure the position in every dimension it is concluded that the time is a curled dimension.

Schrödinger's Cat

INTRODUCTION

Erwin Schrödinger

Schrödinger's Cat is a thought experiment which was devised by the Austrian physicist ERWIN SCHRÖDINGER in 1935. The thought experiment presents a cat that might be alive or dead, depending on an earlier random event.


PURPOSE
The above experiment illustrates the problem of the Copenhagen Interpretation of quantum mechanics when applied to everyday objects.


CONSTRUCTION
A cat along with a flask filled with a poison and a radioactive source is placed in a sealed box. A Geiger Counter is placed inside the box to detect radiation. The flask shatters when the radiation is detected. Due to the breaking of flask the poison is released in the box thereby killing the cat. Standing with Copenhagen Interpretation of the quantum mechanics implies that after a while, the cat is simultaneously alive & dead, contradicting the common experience.


EXPLANATION

Superposition of
two states

In common observation, a person defines or describes only one state of a system which is well-defined by a wave function associated with the system. As an example imagine a tree in a forest. Whether the tree in forest is standing or has fallen, either of two can be associated but not both. At particular instant of time, a system has only one state.


In Copenhagen Interpretation of quantum mechanics, a system stops being a superposition of two states and becomes either of two when an observation is made. This clearly shows that the wave function collapses to a single value whenever a conscious observation is made. Copenhagen Interpretation is an observer induced collapse.
When the cat is sealed inside the box, it is alive. Now after a while, there are two states that can be associated to the system(containing cat & flask)-"decayed nucleus/dead cat" or "undecayed nucleus/alive cat". The decay of the radioactive substance is small, may be one atom per hour. Now, when the box is opened, i.e. an observation is made, so the wave function of two states for a single system collapses into one state. If the atom has not decayed, then the cat is alive and if the atom has decayed, the cat is dead.

Collapse of the Wave Function

Another Video : http://www.youtube.com/watch?v=HCOE__N6v4o

Space Time Continuum

A general misunderstanding of common people is that we live in a world that has significantly only three dimensions- length, breadth and height. For a longer time the physicists thought that the universe is in three dimension (3D). It was Einstein who proved that our universe has one more dimension- time. The fourth cannot be represented as an axis on a paper (for better understanding only, in many areas time is represented as an axis). He suggested that our universe is a space time continuum. The dimensions originated for the purpose of defining the state of an object at any instant of time completely.

To understand it in a better way, lets try out a simple exercise. Let us assume that time is not the fourth dimension. Now with three dimensions we will try to define the state of an object at a certain difference of time. Consider a person A who is at point P(x1,y1,z1) at a time say t1. Say at this instant your friend makes a phone call. Now the person moves from point P and reaches point Q(x2,y2,z2) at time say t2. Now if your friend asks you "Where is A ?", you answer him Point Q. Alternatively if he asks "Where was A when I made a phone call ?". The answer will be point P. This shows that if we do not use time as the fourth dimension, the sense of 'when' i.e. the time of occurrence is lost and we would be unable to define the state of an object completely.