Why can't we see light?

A peculiar question indeed! You might think it needs complex physics and maths involved to be answered. But no it is not so the answer is quite simple and can be explained by means of simple logic.

Suppose a genius inventor somehow builds a high tech camera capable of shooting at some trillion frames per second and sets it up for an experiment to observe light or supposedly the particles which compose light, the photons.

So, he uses a simple torch as the source of light which he intends to fire up on a screen in front of it and will record the path of light on his camera expecting to see the photons and their interactions in slow motion. He also ensures absolute vacuum conditions between the torch and the screen so that he can get a clear observation of the photons. Finally he turns the room completely dark and fires his torch and records this action on the camera.

Now,he runs towards his camera to watch the less than 1 second footage that was recorded. He runs the footage at the slowest possible rate that the camera is capable of. But, he finds nothing. Nothing but the illuminated screen and the burning torch.

The reason is quite clear. When the torch is turned on, photons are emitted and are scattered to all directions and some of them reach our eye and some of them reach the screen. Our intention is to view the photons that are moving towards the screen. We know that we are only able to see things when the photons reach our retina after bouncing off the thing (actually this is not exactly that happens. This is just an over simplification). So, to view them, they need to reach our eye first of all (or the camera lens in this case). Also as photons are massless they cannot interact with each other. So, one photon cannot also bounce off another photon to enable us to see it.

Thus, we only see the objects that light illuminates (in this case- the screen) or the sources from which it is produced (in this case- the torch) but not light itself. Simply speaking we cannot observe something that that is itself required for observation.

Reasons and Consequences of THEORY of EVERYTHING

Reasons to obtain Theory of Everything

I think that currently there are no formal reasons or necessity for obtaining a Theory of everything. Well, then why should the scientists go through all this labor and pain to obtain it? Won’t it be simply sheer waste of time? Well, the answer is that science is not just to comfort lives of people by its inventions and discoveries. Unlocking the secrets of the universe, the search for reality is also part of the game even if it may not have any possible benefit to mankind. Some might even argue that such absurd fairytale theories are not required in this utilitarian world and the world is happy with what technology has to offer. But they forget that technology has itself originated from science. Pursuit for reality never goes vain and even if reality is absurd, it has to be accepted. Scientists are characterized as people in pursuit of science and ToE is just the pursuit for the ultimate science. Also, applications of a scientific theory cannot be well predicted unless it is itself discovered. Who knows, discovery of a Theory of Everything might have the power to completely change the way of mankind.

Consequences of Theory of Everything

Well, the obvious consequences of discovery of a ToE is that we will be able to completely understand the universe we live in, various scientific debates relating to different topics will finally resolve once and for all.

Apart from these, I think there is another powerful consequence of a ToE. It would be the 'END OF PHYSICS' (which was postulated long before, during the time of Einstein). Because after we understand EVERYTHING, what would be left to discover and understand would be NOTHING. So, it is possible that ToE would be the long-predicted end of physics. 

But in this 21^st century end of physics seems to be nowhere near. So, it is certain that discovery of a Theory of Everything has quite a long way to go.

Happy Republic Day !

I wish a Happy Republic Day to all my Indian friends !

GöDEL's THEOREMS- "the argument against Theory of Everything"

Gödel's incompleteness theorems are two theorems of mathematical logic that establish limitations against completeness or consistency of any physical or arithmetic theory. They were devised by Kurt Gödel in 1931.

Kurt Gödel 

1st INCOMPLETENESS THEOREM-

“For any consistent axiomatic system in arithmetic there always exists a set of arithmetic propositions which can’t be proved by it.”

It means that, a consistent (free from any sort of contradiction) mathematical theory-X that completely covers up certain mathematical topic-x cannot be stated as a complete theory because it is always possible to formulate a statement belonging to topic-X whose validity or invalidity cannot be proved by theory-X.

So, basically, Gödel’s first theorem states that a theory can’t be consistent as well as complete at the same time and therefore there would always exist unprovable statements.

2nd INCOMPLETENESS THEOREM-

“Any consistent axiomatic system cannot prove its own consistency and if it does so, it is inconsistent.”

So, the 2nd theorem clearly states that any consistent mathematical theory cannot be used to prove itself.

Now, what has Gödel’s theorems got to do with Theory of Everything?

First we must remember that a physical theory is always in form of a mathematical model. So, the Gödel’s theorems hold as good for physics as they do for mathematics. Now, suppose we get a theory that could be claimed as a theory of everything (call it ToE v1.0). For it to be accepted as valid, it is bound to be consistent. So, as it is consistent, by Gödel’s 1st theorem, it will be incomplete or there will always be something that couldn't be explained by it (thus contradicting it from a theory of “EVERYTHING”). Now, even if we construct a even higher theory (call it ToE v2.0) which could explain the thing that was unexplainable by ToE v1.0, Gödel’s 1st theorem would still apply, due to which something else will get formulated which would be unexplainable by ToE v2.0. So, this process of refinement of theories will go on forever but still none of them will succeed to be claimed as a true Theory of Everything.

Suppose we are able to create a satisfying theory of everything disregarding Gödel’s first theorem. Now, this theory by definition would be able to explain everything. And everything includes itself. This is where Gödel’s 2nd theorem will come to play. By Gödel’s 2nd theorem, we know that no theory can prove itself. So, if this theory of everything could explain itself, it will be inconsistent and eventually be invalid.

Therefore Gödel’s incompleteness theorems will deviate any proposed theory of everything from its very definition of being “of EVERYTHING” and will disprove its validity. So, this is how Gödel’s theorems prove to be strong arguments against a theory of everything.

A number of scholars claim that Gödel's incompleteness theorem suggests that any attempt to construct a ToE is bound to fail. Stephen Hawking was originally a believer in the Theory of Everything but, after considering Gödel's Theorem, concluded that one was not obtainable. 

He says In his lecture ‘Gödel and the End of Physics’ -

“Some people will be very disappointed if there is not an ultimate theory that can be formulated as a finite number of principles. I used to belong to that camp, but I have changed my mind. I'm now glad that our search for understanding will never come to an end, and that we will always have the challenge of new discovery. Without it, we would stagnate. Godel’s theorem ensured there would always be a job for mathematicians. I think M theory will do the same for physicists.”

Still many physicists believe that a ToE is possible to formulate. Most physicists believe that Gödel's Theorem does not mean that a ToE cannot exist. They argue that the theory of everything may not refer to a set of underlying rules but to the understanding of how and why the universe exists and how it works. Surely they will leave no stone unturned to get to it.

(To tell the truth I as a lover of physics am quite scared and startled of the consequences of these theorems)

Click Here for Part-3 (Pillars for the Toe)

Click Here for Part-5 (Reasons and Consequences of the ToE)

Pillars for the THEORY OF EVERYTHING

THE FOLLOWING ARE SOME THEORIES SIMILAR OR CLOSE TO THE ToE.

Kaluza–Klein theory-

Kaluza–Klein theory is a model that seeks to unify the two fundamental forces of gravitation and electromagnetism. It says that the world is 5 dimensional and not 4 dimensional (which is the accepted norm), but we can't see the 5th dimension because it is incredibly small. This extra dimension is packed up tightly into a tiny circle of size in order of Planck length and it would contain just one force and just one type of field, the gravitational force or the gravitational field. The ripples or vibrations produced in this gravitational field would seem to the observers like vibrations in an electromagnetic field and a scalar field in the remaining three spatial and one time dimension. So, it states that all other forces are actually derived from the force of gravity which is itself higher dimensional.

David Hilbert

Hilbert's program-

In mathematics, Hilbert’s program, formulated by German mathematician David Hilbert, was a proposed solution to the foundational crisis of mathematics, when early attempts to clarify the foundations of mathematics were found to suffer from paradoxes and inconsistencies. Hilbert proposed to ground all existing theories to a finite, complete set of axioms, and provide a proof that these axioms were consistent. Basically, it is a theory of everything for mathematics.

The Standard Model-

It is the theory of particle physics concerning the electromagnetic, weak, and strong nuclear interactions which govern the motion and interactions of the sub atomic or elementary particles. The standard model is also referred as the set of all elementary particles known till date (can be considered as a 'periodic table' for particle physics) It includes the force carriers- the gluons, photons, W bosons, Z bosons which are underneath any force or interaction between big and small bodies. The standard model also has the mass carrier- the Higgs boson which are believed to be the fundamental particles that provide mass to any object. The standard model is sometimes referred as "theory of almost everything"due to its inability to incorporate gravity and its foundations being based on simplifying assumptions. Still, it is a quite successful and well tested theory in physics.

Grand Unified theory-

A Grand Unified Theory is a model in particle physics which attempts to merge the electromagnetic, weak, and strong interactions into one single interaction.

Loop Quantum gravity-

Loop quantum gravity is a theory that attempts to describe the 

quantum properties of gravity. It proposes that the structure of space is granular and has a certain critical density of matter that can be contained within it, thus contradicting general relativity (which proposes that space can be stretched infinitely).  Area and volume of any portion of space are quantized.

Granular Structure of Space as proposed by Loop Quantum Gravity

These theories are not ToE but are close to it and will certainly form the FOUNDATIONAL PILLARS of ToE if such a theory would ever be possible to construct.

Click Here for Part-2 (String Theory & E8 Theory)

Click Here for Part-4 (Godel's Theorems)

Two candidates for the ULTIMATE THEORY

String Theory

Projection of a Calabi-Yau Manifold,
one of the ways of compactifying the 
extra dimensions as proposed by 
string theory

String theory is a powerful theory which attempts to solve the ToE. It originated around  1960 and is currently one of the major topics of research in theoretical physics. String theorists believe that in the most fundamental level of matter there is nothing but vibrating strings. These strings are believed to be one dimensional objects present at the heart of all matter and that their vibration produces different particles. This theory proposes that just like musician can produce numerous tunes from a violin string, different types of elementary particles are produced from different vibrations of the strings and these elementary particles form all the matter in the universe. And as there are infinitely many types of vibrations, there are infinitely many types of particles proposed by the string theory. It also predicts that these strings resonate in a mind boggling 10 dimensions. So, as string theory describes the “Standard Model” (the set of all elementary particles observed) as well as naturally incorporates gravity, it is considered as candidate for a ToE by many physicists and string theorists like Michio Kaku, Stephen Hawking and Edward Witten. According to Hawking in particular, "M-theory is the only candidate for a complete theory of the universe."(M-theory is an extension of string theory that predicts existence of 11 dimensions). 

Michio Kaku (leading String Theorist)

The E8 Theory

Antony Garrett Lisi

The E8 theory (as it is popularly known as) is another unified theory which was revealed in November 2007 in a paper known as “An Exceptionally Simple Theory of Everything”. The physicist behind this theory is Antony Garrett Lisi, who is an independent researcher without any academic position. It is based on an 8 dimensional mathematical pattern known as the E8. According to Lisi’s theory of everything, the universe looks like this E8 structure. Lisi says "I think our universe is this beautiful shape." Lisi found a way to put all the elementary particles discovered into the 248 points of the E8 and found 20 points remaining. So, his theory predicts that there must be another 20 elementary particles to complete the standard model. It is basically a geometric unified theory of the universe which effectively combines gravity and particle physics. It is considered to be very promising because it can work within 4 dimensions and does not require any hypothetical higher dimensions as string theory does. Also unlike string theory, the E8 theory is believed to be verifiable by using current technology.  Despite not being a widely accepted theory, this theory has attracted many physicists from round the world who have took it on for further research onto it. But, it is still an incomplete and young theory as described by Lisi and requires time to evolve into a stronger one.

THE E8 PLANE

Click Here for Part-1 (ToE overview)

Click Here for Part-3 (Pillars for the Toe)

Theory of Everything

The theory of everything (ToE) is the final theory or the master theory that can explain every interaction, every force and the origin of all mass in the universe or simply, a theory to explain everything in the universe as we know it. In other words, it refers to a theory which can explain the origin and existence of the universe and describe its operation in the domain of a single mathematical equation. ToE is one of the major unsolved problems in physics. Not actually an unsolved problem, but an unfulfilled pursuit for the ultimate science. It is currently an active field of research in theoretical physics.

Well, the possibility of discovery of the ToE rests on the two fundamental pillars of modern physics- General Relativity and Quantum Mechanics. Let’s have a brief insight about these two theories.

General Relativity-

It is a theory of gravitation given by Einstein. Modern physics formally came into existence due to the idea of general relativity and therefore Einstein is considered as the father of modern physics. It was indeed a remarkable breakthrough which took physics to a completely different and bizarre path. Well, this theory states that two massive bodies face gravitational attraction towards each other or gravity occurs due to distortions in spacetime caused by massive bodies. It is the current and the most accurate description of gravity in modern physics. General relativity generalizes special relativity and Newton's law of universal gravitation, providing a unified description of gravity as a geometric property of spacetime. So, general relativity explains the nature and cause of gravity which is one of the four fundamental forces of nature.

High-precision test of general relativity by theCassini space probe (artist's impression): radiosignals sent between the Earth and the probe (green wave) are delayed by the warping ofspacetime (blue lines) due to the Sun's mass.
(Source-http://en.wikipedia.org/wiki/File:Cassini-science-br.jpg)

Quantum Mechanics-

It is the branch of physics which investigates what happens in the microscopic levels, where the action is on the order of the Planck Constant. In brief, quantum mechanics is the world of the very small. It helps to predict the interactions elementary particles like electrons on the atomic scale. As quantum mechanics deals with tiny particles and interactions at the atomic scale, it explains the three other fundamental forces of nature other than gravity- electromagnetic, weak nuclear and strong nuclear. 

The Standard Model of Elementary Particles

(Source- http://en.wikipedia.org/wiki/File:Standard_Model_of_Elementary_Particles.svg)

The Problem-

Now, for a unified theory of all forces, the four fundamental forces of nature have to be unified into a single force. In other words, we have to unify quantum mechanics and general relativity in order to get a higher theory that can explain all the forces and interactions existing in nature which may prove as the key to the ultimate ToE. But this is where the problem arises. The world of the tiny is not the same as the world of the large. According to quantum mechanics The atomic world is chaotic and nondeterministic. But the world of the large bodies where general relativity comes into play, the situation is drastically different. It is quite deterministic and harmonical with very definite and rigid laws governing their motions. So, the theories of general relativity and quantum mechanics are quite different from each other. And therefore they couldn't have been combined yet. But if there is any hope of finding a ToE, this job has to be done first. Why the quantum world is so different from the world governed by general relativity? Is there any way we can combine both theories to get a satisfying higher theory that is applicable in both scenarios? We can proceed in the hunt for ToE only if these questions are answered. So, rigorous research is currently going on in the field of quantum gravity. Quantum gravity is a field of theoretical physics that seeks to describe the force of gravity according to the principles of quantum mechanics that even gravity can be incorporated into quantum mechanics.

So, if research on quantum gravity can help overcome its limitations and make it a stronger theory, it may be possible that finally we will be able to combine quantum mechanics and general relativity which might give us the key to unlocking the mystery of the universe.

Albert Einstien (Father of Modern Physics)

Max Plank (Father of Quantum Mechanics)

Click Here for Part-2 (String Theory & E8 Theory)

Dimensions (in Physics)

Well, dimension broadly means measurement. In mathematics a dimension of a space or object is understood as the minimum number of coordinates required to specify the position of a point within it. The term, dimension of course has mathematical origins. It is quite fundamental in mathematics. But, in physics dimension is a much wider concept. In physics, dimension is perceived as the means by which we can precisely describe a body’s position and structure in the space it occupies (although the natural definition of dimension is the same as provided by mathematics). It is of great importance to physicists, especially cosmologists.

Conventionally, we deal with three dimensions in our daily lives. Those are length, breadth and height. These are what required to describe the 3-dimensional structure of our beautiful surroundings. These are known as the spatial dimensions. Almost all study related to dimensions in maths is confined to these three dimensions. But, these three spatial dimensions can only define the structure of the 3-dimensional bodies. What about its duration? Thus, physics has attached an additional dimension to the conventional 3-dimensional objects. It is the temporal dimension or the time dimension. Time is often referred to as the fourth dimension for this reason, but that is not to imply that it is a spatial dimension. It defines the time duration of a body or its position in the passage of time. It is perceived differently from the three spatial dimensions as there is only one of it, and we cannot move freely in time but subjectively move in one direction. Thus, these four dimensions are required to describe the structure of spacetime. The term spacetime has originated from the special theory of relativity formulated by Albert Einstein.  It is the accepted physical theory regarding the relationship between space and time. It proved that space and time are not two different things. But, they are combined into a single interwoven continuum.

To describe ‘dimensionless’ there is even a zero dimension. It is represented by a point which has no dimensions. This dimensionless object is the base of the other higher spatial dimensions (length, breadth & height). 

Now, let’s see how we can visualize the spatial first four dimensions. 

Well, the 1^st dimension can be represented by a line or a line segment which just has a length (infinite in case of a line and finite in case of a line segment). A line can be seen as a collection of parallel points.

The 2^nd dimension which consists of both length and breadth can be represented in the simplest way as a square (where length and breadth are finite) or in a broad sense, a plane (where length and breadth are infinite). Two parallel lines when connected form a square.

The 3^rd dimension which consists of length, breadth and height can be represented in the simplest way as a cube. Two parallel squares when connected by their corresponding vertices form a cube.

Then comes the 4^th dimension. It is represented by a tesseract which is theoretically formed when two parallel cubes are connected by their corresponding vertices. According to the Oxford English Dictionary, the word tesseract was coined and first used in 1888 by Charles Howard Hinton in his book,”A New Era of Thought”. A tesseract, also known as a hypercube, is a hypothetical object which cannot be shown on a plane surface or even in form of a 3-D model as it is a higher dimensional object. The tesseract and even higher dimensional hypercubes can only be shown through computer simulations.

A Tesseract

                                                        (I got these nice pics from Wikipedia)

Higher Dimensions

In physics 3-dimensional space and one time dimension is the accepted norm. And our visible universe consists of this 3+1 dimensional subspace. But there are attempts to unify the four fundamental forces in physics (or to formulate a theory of everything) by introducing higher dimensions. The string theory or the M-theory is a modern higher dimensional theory proposed by physicists which predicts the existence of up to 11 dimensions! This 11-dimensional M-theory is considered as a valid and the most reliable candidate for “the theory of everything” although till date there is no experimental evidence confirming existence of these additional higher dimensions.

Where do these dimensions exist? The observable universe is 3+1 dimensional but the mutiverses (theory of existence of multiple universes) are expected to be higher dimensional (although there is no experimental evidence for multiverses as well). It is also predicted that the maximum number of dimensions that can exist in any universe other than ours is 11, because beyond that the universe becomes unstable and immediately collapses into a 11-dimensional form.

Now, if higher dimensions are predicted to exist, why can’t we see them or gather evidence about them? Physicists till now can’t predict what exactly the higher dimensions would look like. Simply speaking, we don’t exactly know what we are looking for. The world around us including us is 3-dimensional and thus we can calibrate our scientific instruments up to 3 dimensions only. The dark matter and dark energy that is predicted to consume most of our universe is expected to be higher dimensional stuff as we can see their effects but we can’t see them. It is also a possibility that the higher dimensional multiverses may be hovering right below our noses, but we can’t detect them or get a slightest hint of them because our world is functioning is a 3-dimensional system.

Scary! Isn’t it? But don’t worry it is just a speculation.

Everything is Physics

Well we all know what physics is but few of us understand what physics really means and what is its real significance. Physics by definition is the branch of science which deals with the nature and properties of matter, motion, space-time and energy. But I would argue that physics is in fact the only science. Lets see if this statement can be proved or not.

Chemistry is all about chemicals and chemical reactions. Two fundamental topics that we read in chemistry are atomic structure and chemical bonding. Broadly, chemistry is the study of matter (especially chemicals) in atomic or molecular levels and the reactions or interactions occurring between those atoms or molecules. Thus, these two topics indeed form the base of chemistry. Now, you must have heard about the quantum model of atom. It is currently the accepted theory of atomic structure. Quantum mechanics, which is a part of modern physics is the base of this theory. Previously many physicists like J.J. Thompson, Ernest Rutherford and Niels Bohr have tried to explain the atomic structure by using classical mechanics. (But those theories were discarded due to the limitations and contradictions that accompany them) Through this quantum model of atom, scientists were also able to give a more satisfying theory of chemical bonding that is, orbital overlapping. Thus we see that theoretical chemistry is in fact physics. But what about the rest of chemistry? They have the least relation to physics. But the other theories and phenomenon in chemistry could be explained only because of the accurateness of the atomic theory that only quantum physics could provide. Thus we can say that existence and explanation of chemistry is possible only due to existence of physics.

Now it's turn of biology. When we hear biology, we think about proteins, DNA, RNA, amino acids, etc. These are few of the different types of chemicals that make up a functional human body. In fact, every living body is made up of chemicals. And for sustainment of a biological system, chemical reactions continuously take place at microscopic and macroscopic levels. For example, in the process of digestion numerous reactions take place on the food as it passes through the alimentary canal until it is finally broken down into simple molecules absorbable by the body or simply until its complete digestion. Thus, biology is very closely linked with chemistry and as chemistry is related to physics, chemistry acts as the link between biology and physics. So, existence of biology is also dependent (though indirectly) on existence of physics.

After physics,chemistry and biology what is left in natural sciences is earth sciences. Well, it is quite clear that earth sciences is just a correlation of physical sciences(physics and chemistry) and life sciences(biology). The areas that earth sciences cover like geology, geography, ecology, hydrology, oceanography, climatology, paleontology, etc can be completely explained by using physics, chemistry and biology. Thus, its ultimate relation to physics is quite obvious.

Apart from natural sciences there are also social sciences like law, criminology, history, political science, etc. these sciences have been created by human minds. Human minds are result of brains. Brains are explained by biology. Thus, as biology exists due to physics, social sciences do also exist due to physics.

It can be argued that formal sciences (logic and maths) do also exist and there existence is in any way not dependent on physics. Well, maths cant be considered as an actual science because the test of it's validity is not experiment. Instead, it is actually the language of science, specifically physics as physics can be explained in the most simplest and meaningful way only in terms of mathematics. And talking of logic, it is the base of mathematics.

So I think this is done here. Even I am writing this blog be cause I belong to this universe, I live in this universe because the universe has itself originated somewhere, someplace sometime. And the origin of the cosmos can be explained by physics. So, I am here due to physics. 

Just kidding! But this is the point. The point is that if we look backwards we will ultimately find that the master governance of everything lies in the laws of physics. And therefore, everything is physics.

The picture above sums up all.

Hello World !

Hi there visitor ! (Although i do not expect any visitor on the first day of my blog). And I wish you a very happy new year. This is the first day of 2014 and i thought to spend it in a more productive way than my last year. So I created this blog. Well, through this blog I intend to share some cool stuff which might interest you if you are interested in physics and technology.


B3R55HFRN9DX