PHYSICSTime Traveling: The Story of Black Holes and Dr. WhoI remember how much we all used to admire Dr. Who and other time travelers who travel through time and space, face a variety of challenges, defeat enemies and make things right by moving to wherever they want and whenever they want.
Science fiction for the first time introduced us to the idea of ‘Time Travelling’. There is a story ‘By his bootstraps’ by Robert Heinlein, in which the protagonist in the story stumbles on a time travel device brought back to the present by a visitor from the faraway future. He steals it and constantly worries about being found by the old man he stole the time machine from -- until one day, many years later, he realizes that he is now the old man from whom his younger self will steal the time machine. In the summer of 1985 as Carl Sagan was writing his science fiction novel ‘Contact’, he asked Kip Thorne of Caltech to come up with some plausible-sounding scientific explanation of the literary device of a wormhole through space which could enable his characters to travel between the stars. At that time, Thorne and his colleagues first found that there is nothing in the relativity equations to prevent the existence of such wormholes, and then realized that any tunnel through space is also, potentially, a tunnel through time… The laws of physics do not forbid time travel! So let’s start looking at ‘time’ from the very beginning. It was Isaac Newton who gave us the concrete picture of time for the first time. He explained time to be like an arrow, once fired; it went towards its target, doesn’t waver, doesn’t slow down and never comes back. Thus, the common belief was that time is the same everywhere: one second on Earth is the same as one second on Jupiter or elsewhere in the universe. The clock ticks at the same rate everywhere. Then Einstein challenged this intuitive view. To him, time was like a river which could slow down and speed up. According to his Special Theory of Relativity of 1905, you would slow down in time the faster you moved. Hence, a clock orbiting in space would slow down relative to a clock on Earth. An observer on Earth, watching an astronaut's rocket near the speed of light, would see the astronaut moving in slow motion. That leaves us with some important questions: is time travel actually possible? Can we master time? Can we move to the past to see how the universe began or make our way to the future to see how it will end? To understand this, let us first consider time as a fourth dimension. To move in time would then simply mean moving in fourth dimension. We all are fairly familiar with three dimensions that we see all around us. We move in a straight line, that is one dimension. We turn right or left, we add another dimension, and adding some height to it means we are in three dimensional systems. Similarly, considering that everything in this universe from stones to human beings has a specific age, time becomes a fourth dimension. But the question is how on Earth do we travel in time? Wormholes: “Nothing is flat or solid. If you look closely enough at anything you’ll find holes and wrinkles in it. It’s a basic physical principle and it even applies to time.” Stephen Hawking There are holes and tunnels in time also and these are known as ‘worm holes’. These worm holes occur down at the smallest scale, smaller than atom and molecules and they actually link two separate places and two different times. But the problem with these worm holes is that they are unfortunately too small and now the challenge is to enlarge these worm holes so that some human or a spaceship might pass through it. If that is made possible, it would be revolutionary. We can step into distant past maybe stone-age, or even before that. That just sounds awesome. See Figure 1. Grandfather Paradox: The famous paradox of travelling into past is named as ‘Grandfather Paradox’. "What would happen to you if you went back in time and killed your grandfather before he had offspring?"In his past, he has not been born but in the future he exists. In such a case, cause is happening before effect and that leads many scientists to conclude that travelling to past be not possible, though a certain class of Physicists strongly believes in another theory which rules out this paradox. Parallel Universes: Ruling out these paradoxes, we have to look deep into quantum mechanics. There is this idea of ‘parallel universe’ or ‘alternative histories’ which says that there are other universes existing parallel to ours and each of these parallel universes is as real as our own. There is an alternative history for every decision ever made and alternative histories branch out from ‘decision points’ like the branches of a tree. The idea has plenty of supporters, including Oxford’s David Deutsch. [2] A refinement of this theory suggests that if there is some experiment with two possible outcomes, there are always two universes involved each with one possible outcome, but prior to the experiment they are identical in all respects. In general, we would need an infinite number of universes to cover all the possibilities. This of course would be resolved if the universe did indeed turn out to be infinite in size. If you can somehow go back in time and prevent yourself from being born, it really wouldn’t matter because the decision to do so moved you to a whole new alternate universe, where you were never born. However, since you were still born and built your time machine in the first universe, this is no longer paradoxical.[1] TRAVELLING TO THE FUTURE Let’s come to the question of travelling into future and look into the possible ways of doing that. Using a Black Hole: The idea was proposed by Einstein some hundred years ago. In some cases time slows down, in others it’s beaten up. Einstein realized that matter drags on time, slows it down like the slow part of the river. The heavier the object, the more it drags and that gives us a hint on how to travel to the future. We need a much more massive object for traveling to future in significant time. Black holes, according to relativity theory, warp space-time with their enormously powerful gravitation field. The effect of this gravitational field is that if an astronaut were to cross the event horizon of a black hole, time would slow down on board. Actually, time slows down in proportion to speed, the faster our astronaut travels the slower time runs. The closer the astronaut travels to the speed of light the more time slows, until at the speed of light, time would stop. So, the black hole can serve the purpose of a natural time machine. Imagine a spaceship which somehow manages to attain right trajectory and right speed such that it is not pulled inside the black hole. If the space ship starts rotating around the black hole, the persons inside the spaceship are travelling in time. Now for people on earth spaceship completes its orbit around black hole in 16 minutes, but people in spaceship experience 8 minutes of time in every orbit. Time in spaceship would be slow down by half. The more orbits the spaceships take, the more it travels in time. Let’s say spaceship come back on earth after 10 years then everyone on earth would have aged by 20 years. “Physicists further suggest that a simple black hole won’t be that effective. It would simply swallow up anything that comes near to it. At the heart of such a black hole, there is a point known as singularity, where space and time cease to exist and matter is crushed to infinite density. Roger Penrose, at Oxford, proved that something which falls into a black hole must be drawn in by its gravitational pull and be obliterated. However, also in the 1960s, Roy Kerr found that if the black hole is rotating, matters are quite different. A singularity still forms, but like the mint with a hole. In principle, it would be possible to dive into such a black hole and through the ring, to emerge in another place and another time. This "Kerr solution" was the first mathematical example of a time machine. The Kerr solution only became interesting and was only developed after astronomers discovered what seem to be real black holes.”[2] “Frank Tipler published a possibility in the… journal Physical Review in 1974 …which involved making a singularity that is not concealed from view behind the event horizon of a black hole. To make a naked singularity involves rotating a singularity extremely rapidly and if rotated fast enough it would fling away the event horizon and expose the singularity. We know that space-time is extremely distorted by the singularity's strong gravitational field and the effect of this rotation would be to twist space-time, and tip it over so that one of the dimensions of the space dimensions is replaced by the time dimension. A carefully piloted spaceship taken close to the singularity would enter the time dimension and journey through time instead of space. When the spaceship moved away from the distorted area around the singularity, it would be in a different time from when they had entered the area. “ [3] See Figure 2. Using a Super Fast Train: Let us just use the fact that time dilates for the speeds really close to the speed of light and make a track around earth for a superfast train, a train whose speed approaches speed of light. If the train circles the earth 7 times a second, it approaches the speed of light and at that instant time starts moving slowly inside the train. With such a high speed the laws of nature automatically prevent the speed limit by slowing down the time. If this train circles around the earth for one week, one hundred years would have been passed on earth. So, yes, we do need a lot of technology to put into practice for that train to be built and functional but once we do that, we would be able to step into future. See Figure 3. Using Light Instead of Massive Objects - Time-wrapping theory: There is a U Conn Physics Professor Mallett who considered an alternative to these time travel methods. “Einstein showed that mass and energy are the same thing,” said Mallett, who published his first research on time travel in 2000 in Physics Letters. “The time machine we’ve designed uses light in the form of circulating lasers to warp or loop time instead of using massive objects.” To determine if time loops exist, Mallett is designing a desktop-sized device that will test his time-warping theory. By arranging mirrors, Mallett can make a circulating light beam which should warp surrounding space. Because some subatomic particles have extremely short lifetimes, Mallett hopes that he will observe these particles to exist for a longer time than expected when placed in the vicinity of the circulating light beam. A longer lifetime means that the particles must have flowed through a time loop into the future. “Say you have a cup of coffee and a spoon,” Mallett explained. “The coffee is empty space, and the spoon is the circulating light beam. When you stir the coffee with the spoon, the coffee – or the empty space – gets twisted. Suppose you drop a sugar cube in the coffee. If empty space were twisting, you’d be able to detect it by observing a subatomic particle moving around in the space.” And according to Einstein, whenever you do something to space, you also affect time. Twisting space causes time to be twisted, meaning you could theoretically walk through time as you walk through space. [4] “As physicists, our experiments deal with subatomic particles,” said Mallett. “How soon humans will be able to time travel depends largely on the success of these experiments, which will take the better part of a decade. And depending on breakthroughs, technology, and funding, I believe that human time travel could happen this century.” [5] The interesting thing is that according to the equations of Albert Einstein's general theory of relativity (the best theory of time and space we have), there is nothing in the laws of physics to prevent time travel. So the saying goes, if nothing is prohibited, it must happen at some point and the events happening in Geneva are pointing towards the way. TIME TRAVEL HAPPENING IN REAL LIFE: “Time travel is actually happening all around us. If we hold out our hand every second a dozen or so tiny nuclear particles called cosmic ray muons will pass through us. These particles are so small to feel and the damage they make is repaired by the body itself. Cosmic Ray muons are the debris from collisions high in the atmosphere. Stable nuclear particles from the sun and the stars collide with the atmosphere 20 km above the Earth. Traveling at the speed of light, about 300,000 kilometers per second, it should take these muons around seven millionths of a second to reach a person on Earth. The only problem is that muons only live for two millionths of a second and so should never reach someone standing on the ground. But Einstein's special theory of relativity claims that the muons travel through time to get to reach us.” [6] AT LHC in CERN, there are particles accelerated to nearly speed of light. And at that speed they time travel. Pi mesons are the particles which are extremely short lived. Normally they live for 25 billion of a second and then disintegrate but in LHC they are observed to remain stable 30 times longer. They are examples of real time travel. In the 24 November 2003 issue of Scientific American, Michio Kaku summarizes the realities of time travel succinctly: “It would take a civilization far more advanced than ours, unbelievably advanced, to begin to manipulate negative energy to create gateways to the past. But if you could obtain large quantities of negative energy -- and that's a big "if" -- then you could create a time machine that apparently obeys Einstein's equation and perhaps the laws of quantum theory.” [7] Footnotes:
[1] Brian Greene The Elegant Universe [2] John and Mary Gribbin http://www.bibliotecapleyades.net/ciencia/time_travel/esp_ciencia_timetravel06.htm [3] http://www.thekeyboard.org.uk/Is%20time%20travel%20possible.htm [4] Quoted and paraphrased from http://www.ufodigest.com/mallett.html [5] http://www.physorg.com/news63371210.html [6] http://www.firstscience.com/home/articles/big-theories/is-time-travel-possible-page-1-1_1741.html [7] Michio Kaku Scientific American Nov. 24, 2003 Rabia Aslam Digging it Deep: The Fundamental Idiosyncrasies of the UniverseI remember when I first studied the simplest atomic model, the one that consists of electrons orbiting around the nucleus, I made the analogy of the atom being a state. In that state, the nucleus was the palace and it accommodated neutrons and protons where Proton was King and the Neutron was Queen - The charge on the proton making him King, of course. And the electrons were the servants or soldiers orbiting the palace for security waiting for orders. With a comparatively much smaller mass compared to the nucleus, for electrons to be of a low rank made sense. The wars between soldiers of different states were the chemical reactions and the atom which gained an electron won over the one who lost it. The transferred electron was supposed to be the slave in the other state and my story continued.
Humans have been trying to find the smallest entity in the universe since the very beginning. The very first concept of the atom came from the Greeks who regarded it as the smallest indivisible particle that was the fundamental unit of everything in the Universe. The idea was fascinating: humans had finally discovered what nature was all about, only that it was wrong. Eventually, Rutherford bombarded atoms with alpha particles and a whole new story of the nucleus, protons and neutrons was revealed. Rutherford himself was shocked after his experiment because for a long period of time almost all scientists were sure that atom was the smallest particle and was indivisible. “…It was quite the most incredible event that ever happened to me in my life. It was almost as incredible as if you fired a 15.inch shell at a piece of tissue paper and it came back and it you...”Rutherford, 1936 So, discoveries led to the idea that atom was divisible with nucleus at the centre and negative charges revolving around and then protons, electrons and neutrons were considered to be the fundamental particles of the atom. We spent an age believing this: In 1963, Gell-Mann and American physicist George Zweig independently postulated the existence of the quark- an even more fundamental elementary particle with a fractional electric charge. Quarks are confined in protons, neutrons, and other particles by forces associated with the exchange of gluons. It was discovered that protons and neutrons were not dimensionless fundamental points rather they were fuzzy ball like objects having some internal structure. Deep inelastic scattering experiment showed that protons contained smaller point like objects. In this experiment, electrons were fired at protons and neutrons in atomic nuclei. When an electron emerged from the nucleus its trajectory and velocity was detected. It was found out that baryons had three points of deflection and mesons had two (once baryons and mesons were considered to be elementary. Baryon is a generic name for particles composed of three quarks, whereas mesons are a family of particles composed of one quark and one antiquark). Richard Feynman called this fundamental particle Parton and Gell-Mann named it Quark later on. Quarks were termed as the elementary particles of every substance with no size no structure. Gell-Mann and others later constructed the quantum field theory of quarks and gluons called quantum chromo dynamics (QCD). There have been discovered 6 quarks (up, down, strange, charm, top and bottom) and 6 leptons (electrons, muon, tau, electron-neutrino, muon-neutrino and tau-neutrino) and there are anti particles for all of them. So all in all there are 12 quarks and 12 leptons (quarks and leptons being different in the sense that leptons are not affected by the strong force while quarks experience all four fundamental forces of nature namely gravitation, electromagnetic force, the strong force and the weak force) making 24 particles in total that are considered to be the elementary structure of the universe, the building blocks of matter and hence, the basis of universal existence. These quarks and leptons in different combinations make all the particles. Now, we believe that everything in the Universe is to be made from twenty four basic building blocks called fundamental particles, governed by four fundamental forces. After this discovery maybe the search for the fundamental particle of the universe is complete. Or maybe like Rutherford we again come across a completely shocking experiment and it turns out that quarks and leptons are even composed of smaller particles, then how do we know if that’s the end of it: How can we ever be sure that we have found out the smallest particle of the universe? How do we know that this might not be an infinite regression? Maybe this search is never going to have an end. Maybe the journey we started from atoms and moved to nucleons and then to quarks will go on forever. Essentially, can we ever be certain that we have finally discovered the true smallest element? Rabia Aslam
For a downloadable version of this essay, right click and save the file in the column. Chaos and ButterfliesI’m going by start by quoting James Gleick who inspired me to overcome my laziness and write something. In Chaos: Making of a New Science, he writes:“Theoretical physics has strayed far from human intuition about the world. Whether this will prove to be fruitful heresy or just plain heresy, no one knows.” This essay will elaborate on Chaos Theory and why it has changed the game of Theoretical Physics.
Today, theoretical physics has reached a point approaching exhaustion. We have discovered the great laws governing nature like Newtonian mechanics, Quantum Mechanics, Special Relativity, General Relativity and so on. We now can predict the outcome of experiments with extreme accuracy because we know all the basic particles - quarks, gluons etc. – and how they interact. So with the experimental data available till now, we have sufficient theories to explain the laws of nature. One may assume that with the knowledge of all the laws and how everything interacts, we can then model the laws into equations and start to predict. All we require, thus, is infinite computational power to predict how any natural system would work or evolve in time. We can, for instance, with this knowledge predict how the weather would change for months. We just need brute force to make enormous calculations. So we gather up some supercomputers and start simulating a very simplified and idealized weather. We program all the equations of pressure change, wind flow, Eddie currents etc. This then begins to provide us with simulations. But when we try to simulate it again with the same initial conditions it gives us a totally different output - Refer to Fig. 1 Aha! I know what you are thinking - there must be some sort of glitch in the program. However, this is in fact popularly known as the ‘Butterfly Effect’: A small flutter from a butterfly here could cause a tornado in another part of the world. The idea of the butterfly’s flutter is ascribed to Lorentz who, in a December 1972 meeting of the American Association for the Advancement of Science in Washington D.C., asked: Does the Flap of a Butterfly's Wings in Brazil set off a Tornado in Texas? So now I try to explain this whole phenomenon. The way this is carried out is by taking approximate measurements: if, for instance, an astronomer has to predict the trajectory of the meteor, he would tend to neglect the gravitational pull of a far off star because it introduces only a very small error - the error would stay small for millions of year and with this assumption the astronomer would essentially calculate the right answer. Thus, a tiny error in fixing the positions will cause a tiny error in predicting the trajectory. The philosophy of science, according to Gleick, as we study it is: “Very small influences can be neglected. There’s a convergence in the way things work, and arbitrarily small influences don’t blow up to have arbitrarily large effects” Simply put, approximately accurate input gives approximately accurate output. But here’s the catch: in non linear-dynamical systems like the weather and most other things a very small change completely changes the output. A simple example of such a system is friction: without friction, we have a simple linear equation. The more force I exert the more acceleration the object will obtain. But in actuality, friction depends on speed. Speed, in turn, depends on the friction. This twisted changeability makes nonlinearity hard to calculate. Most of the systems around us, which look really simple, are non linear and this is in essence the issue. I like to think of this as the act of playing the game changing the rules itself. Hence, what happens in such systems is that a small error cascades up towards the system and changes the outcome leading to complete disorder, noise and chaos much like the butterfly. This is known as “Chaos Theory” and it blows the concepts of Newtonian determinism. Simple systems like a convection current in water, the flow of a liquid, the cooling of a tea cup, the movement of a water wheel, even cloud patterns - all are totally unpredictable and chaotic thanks to Chaos theory. One can further make sense if one considers that as the universe expands, entropy increases leading to greater disorder. The question however is: how then is there so much order in the world around us? What you have read till now is just bad news. I’ve been trying to tell you that there is too much disorder, everything just goes into randomness and becomes noise. Now, here you may think I am going crazy but aha! - There is order in this disorder. This is where Lorentz comes in. Lorentz saw patterns in random noise and provided us with Lorentz’s systems – essentially, a plot of non linear or chaotic systems. In other words, Lorentz saw order masquerading as randomness. Normally, a simple system would have a path that leads to one place and stops (the system is settling to a steady state) or it may form a loop (the system is settling into a pattern of behavior that repeats itself periodically). But Lorentz’ system does neither. Instead, it displays a kind of infinite complexity. It always stays within certain bound but never repeats and traces a strange distinctive shape like a butterfly. The shape signals pure disorder, since no point or pattern of points ever recurs. Yet it signals a new kind of order - Refer to Fig. 2. Chaos Theory lies at the heart of everything from fluid dynamics to population growths, from noise in circuits to weather forecasts. Using current laws we can predict exactly what particles, dark matter, will result if we collide two particles in a particle accelerator but not what the temperature of my teacup in the next minute because of the complexity and disorder involved. However, with Chaos Theory, we can find patterns in the randomness and noise and solve what seem like the simplest of problems but are exceedingly complicated. Chaos Theory could be the way out, the intuition which has gone missing from theoretical physics of late. In other words, it could bring Theoretical Physics back from particle accelerators to simple toys. To know more, refer to James Gleick’s In Chaos: Making of a New Science. If, however, you wish to see the bungled applications of Chaos Theory, you could instead watch “The Butterfly Effect”: a fictitious take of how this effect plays a role in time travel. Ali Raza
For a downloadable version of this essay, right click and save the file in the column. This is like Falling and Falling is like this *
Source: http://www.tenthdimension.com
*Ani DiFranco - Falling is like this Its crazy how the entire earth is pulling the little magnet behind the fish down and the fish still manages to stay stuck to your fridge. How do things like magnets or “static charged balloons” attract or repel other materials. One theory says that objects are like people throwing basketballs at each other. Some people like to take steps forward to catch the ball while others have a tendency to step back while catching. It all depends on who is throwing and who is catching, two guys acting macho will keep stepping back so that they can throw the ball harder, further (repulsive forces) while you really don't want to chuck the ball over your girlfriends head so that she has to run back to catch it and you might just have to run forward to catch her throw. Gravity is mediated by a mass less small basketball called the ‘graviton’. Masses throw gravitons at each other and they step forward to catch it. Magnets throw photons at each other. So why does the fish magnet win and the earth lose? Well put simply there are more photons being tossed than gravitons. We don't have enough gravitons to throw. So where do all the gravitons go? No problem. Adding extra dimensions explains everything up till now. Or rather it helps work out the math. At this level everything has to be written out mathematically. So what does a dimension mean in math? To a mathematician, nothing extraordinary at all. To him a circle and a sphere really are the same thing. All the points equally far away from a central point. They call the circle a 1-sphere and an actual sphere a 2-sphere. They don’t really care much about 3-spheres or what they would look like but have more fun messing around with n-spheres (In general, an n-sphere of radius 1 is described by the equation {x Rn+1 | d(x,0) = 1}) Imagine 2 dimensional people, like the king of hearts on a playing card. For one, he can't have a digestive tract because that would split his body into half. Now suppose that his two dimensional world, the playing card exists in a 3 dimensional space. The king can interact with the higher third dimension but only the part of which exists on the surface of his world. If, for example a balloon was to go through his card he would initially see a point which expanded into a circle, reduced again to a point which would then disappear. All he knows about the balloon the is intersection, the cross section of the balloon and his card. If we were to pass through his card he would see cross sections of our internal organs as we pass through the card. That's what it feels like to be a 2 dimensional creature suspended in 3d space. Things popping in and out of space, and the only information we have about them is the portion of them that is present on our card. Eerie? Not really, we have a very similar form of existence. We happen to be 3 dimensional creatures existing in 4 dimensional space, the fourth dimension being time. The knowledge we have of the fourth dimension is only that which currently intersects with our 3d world. Could higher dimensional creatures travel back and forth in time? Perhaps, but just as the king can't leave his card and wander into the 3d space, we are trapped as well. And so as our card moves through time, the cross section that we can see ages, and like the balloon eventually pops out of existence. The abstract time dimension does not help with solving our gravity problem but it is probably the easiest understood higher dimension. A theory that attempts to solve our problem goes as follows; our universe is actually a three dimensional brane suspended on four dimensional bulk. Gravitons are the only particles that are allowed to pass through the brane into the bulk, hence the shortage of gravitons in our daily lives. So what is a brane? Well you live on a brane. The brane is like a membrane, like the thin skin that forms on your soup when it gets cold. The peel on an apple. It is part of the whole but one dimension less. The brane rests on the 4 dimensional super massively bulky, bulk (think soup/apple). Now that we can sort of grasp what is meant by extra dimensions let us look at another view of the universe. Well we need more dimensions to make the math work. So why not have normal three dimensional space with six-dimensional Calabi Yau manifolds at every point in space? Sure, but what is a Calabi Yau manifold? Lets start simple again. What is a Mobius strip? Take a long strip of paper. Twist it once from the middle and tape the edges. [See Fig. 2] Now is this two-dimensional or three (half?) dimensional? If an ant starts walking on it, it will go all around and come back to where it started. If we take two mobius strips and join them together we get a Klein bottle [See Fig. 3]. Ofcourse, it won't be real Klein bottle because they are 4 dimensional creatures and can't exist in our world. It comes close though. A real Klein bottle wouldnt have a nexus, which is the place where the bottle intersects itself giving a handle. Again Klein bottles have only one side and therefore zero volume. The water is outside the bottle. A Calabi Yau manifold is something like this [See Fig. 4]. If you were in one it would probably look like a house of mirrors. You could see yourself in front of you. If you tossed a ball at your image in front of you it would take a roller coaster ride through the manifold and hit you in the back. So why haven't you ever seen a Calabi Yau thing? Well get another ant out here. Now you and the ant are walking on a tightrope. You can only go forward or backwards (and so perceive only one dimension). The ant can go forward backwards and left or right! These other dimensions are so small that we can't feel them in our day to day activities. Calabi Yau is theorized as beginning to occur at perhaps 1/1000000000000000 of a meter. What we can do is build a 27 kilometer long, 2.6 billion pound particle accelerator and smash tiny particles together and study their remains. The English have equalized this to smashing up a grandfather clock to study its pieces. The data collected from these high energy collisions suggest that under the presence of high energies space and time are bent around each other, and not the 3+1 that we experience everyday. CERN to the world on the Large Hadron Collider: "This machine will not create a black hole that will blow up the universe." If ofcourse, we go smaller, to 1/100000000000000000000 of s the scale of a Calabi Yau manifold, classical physics breaks down entirely and we enter the quantum realm. Hassan Bukhari Faith in the Rolled One: On Quantum Indeterminacy
We’ve all had our passions, tastes or choices questioned at one point or another. I remember being asked multiple times what it is about Mathematics that I like – with my response invariably delving into it’s transparency: how the pieces fit together so elegantly even before you’ve got to any solution; how everything just makes sense leaving no ambiguity or microscopic phenomenon for you to ponder upon. In other words, it’s the satisfaction that you get out of knowing there is an explanation - something that can more or less be extended across all scientific disciplines.
But what about disciplines of science where such satisfaction is evasive; where the complete picture does not consist of pieces falling into place neatly, but instead is an incredibly dynamic scenario with pieces vanishing, appearing and ‘rolling’ at random? Is the inherent elegance of science still preserved in such cases? Can ‘not knowing’ ever make sense to someone whose only pleasure lies in figuring everything out? On that note, let me tell me you a little bit about a theory that exemplifies ‘not knowing’ like no other - Quantum Physics. Richard Feynman, credited with the mean feat of popularizing theoretical physics, once said in an interview: “I don't have to know an answer. I don't feel frightened by not knowing things; by being lost in a mysterious universe without any purpose — which is the way it really is, as far as I can tell, possibly. It doesn't frighten me.” I wonder if this is reflective of the satisfaction pervading the lot of physicists throughout the world who have learnt to breathe with the ‘fact’ that they can never definitely know if it ‘will be’- all they have is the privilege of saying is that ‘it might be’. Simply put, if you ask someone not ‘quantized’ enough whether you’re actually sitting where you are, the most likely response is “Duh!” Ask a Physicist and the response would go something like this, “Assuming that you’re a point particle (indeed, scientists love assumptions that dumb down lesser mortals), I can say that the wave-function in real space transformed from your associated de Broglie wave has a maximum amplitude at x = ‘here’, which implies that there is a high non-zero probability that you are actually here. However, depending on your exact waveform you’re also likely to exist a few meters off from here. Just out of curiosity, any chance you’ve got a Gaussian distribution?” All this possibly portrays Quantum Physics as disturbingly unpredictable – almost completely shattering the classical physicist’s image of a completely deterministic universe. Einstein himself (despite his own contribution to the development of quantum theory) was not comfortable with the idea of a world where one couldn’t predict the definite state of a system knowing its current state, thus his famous “God does not play dice with the universe”. Ask why and you hit what Stephen Hawking terms as ‘a fundamental, inescapable property of the world’- Heisenberg’s uncertainty principle. It’s a simple but profound formulation in which the whole of quantum mechanics is grounded today. In other words: find a way to evade Heisenberg and you would have to rewrite all books on theoretical physics. Oh wait! To evade him you need to know where he is and how fast he’s moving, right? And that’s where he gets you. Twiddle. Plainly put, the uncertainty principle says that you can never measure both the position and the momentum of a particle accurately. There is always an uncertainty in the measurement of the particle’s position and an uncertainty in the particle’s momentum; and the product of the two uncertainties is always greater than a certain quantity related to Planck’s constant. Bypassing the Mathematics behind the principle, many authors have tried explaining it in different ways - amongst which Hawking is perhaps the most reader-friendly: “In order to predict the future position and velocity of a particle, one has to be able to measure its present position and velocity accurately. The obvious way to do this is to shine light on the particle… However, one will not be able to determine the position of the particle more accurately than the distance between the wave crests of light, so one needs to use light of a short wavelength…. This quantum(of light) will disturb the particle and change its velocity in a way that cannot be predicted… the more accurately one measures the position, the shorter the wavelength of the light that one needs and hence the higher the energy of a single quantum. So the velocity of the particle will be disturbed by a larger amount. In other words, the more accurately you try to measure the position of the particle, the less accurately you can measure its speed, and vice versa.” Simple. But is it satisfying enough? Probably not. My own first reaction was, “So it’s the experimenter silly enough not to come up with a better way of measuring stuff: how does his inability transform into a fundamental principle?” But long before picking up Feynman’s Lectures on Physics I had done my own thought experiment to answer the above question. Thought experiments, incidentally, I was later surprised to learn, are the methodology of choice of most Physicists to explore various concepts that deal with such fundamental shifts in classical thought: Einstein, for instance, made extensive use of such experiments during his formulation of Special Relativity. For now, let’s just walk into my lab. Do pardon the austerity; I am too busy with Physics to decorate it. Let’s begin. I start by using the shortest possible wavelength of light to measure the position of an electron as accurately as possible. Now the goal is to obtain the momentum of the electron as I measure its position at lets say x. To do that, allow the electron to go on and collide with another particle of much smaller mass so that all of the electron’s momentum is transferred to the particle at rest. Measure this momentum (let’s call it Mehr-Momentum just for kicks) and we will know what the momentum of the electron was after it was disturbed by the light used to measure the position. Now, knowing the wavelength of the photons initially used and hence their momentum, I could again use the law of conservation of momentum to determine what themomentum of the electron was before it went ahead and collided. And now I have the two quantities: momentum and position at x, with the uncertainty in them not necessarily being greater than that defined by the principle. So, what’s the problem? Look again. I was able to obtain both the position and momentum of the particle simultaneously for a certain point in space, except for a fatal glitch: the particle was not at x anymore when I obtained its momentum for x. It had moved on. That leaves quantum physics laughing in my face saying, “Any monkey can make calculations about the past. We’re talking about predictions here.” Again, twiddle. So yes, predict is the key here. The central dogma of determinism demands that we know the present - not the past - in order to predict the future state of a system. One is therefore compelled to accept that the uncertainty principle is not a consequence of our experimental limitations but a direct result of the fact that the act of observation itself cannot be separated from the system. This very postulate about the ‘observer’s interference in the universe’ barring an objective formulation of theories about the universe, is what Einstein and other proponents of a “hidden variables interpretation” of quantum mechanics are not comfortable with. The mainstream (the Copenhagen) interpretation builds upon the uncertainty principle and claims that all the information you can ever get about a particle is contained in its wave-function as obtained by the solution of the Schrödinger’s equation. Einstein, on the other hand, favored an interpretation with hidden variables that contained information responsible for the randomness. With some scientists themselves being in a state of skepticism, it’s not hard to understand the layman’s discomfort with Quantum Mechanics. Questions such as, “But how can you not know?”, “How is it a wave and particle at the same time?” are perhaps natural, considering that we live in a world where Newtonian mechanics makes sense. One has to move away from the dimensions of everyday life and be immersed in those of atoms and molecules to see classical Physics break down. And therein emerges the theory of Quantum Mechanics: something even more bizarre than the observations it tries explain. But when what appears to be a bizarre amalgam of conjectures and messy Mathematics goes on well beyond experiment to prove itself in your computers and space missions, its high time you appreciate its postulates and recognize it as one of the most intricately beautiful theories ever. In hindisight, there is of course no shutting your eyes to alternative possibilities; provided those possibilities are ready to face the adjudicator called experiment. For instance, there are predictions about using the hypothetical gravitons to ‘see’ particles and defying the uncertainty principle. That possibility, however, does not falsify what we now hold to be true. It would be the same as saying, that if we discover a certain ‘lambda virus’ tomorrow all our theories about the causes of a certain disease can be proved wrong - even if those theories have helped us treat a million patients. So be it. Bring on the lambda and experiment will judge. My lab is open. Mehr Un Nisa Shahid For a downloadable version of this essay, right click and save the file in the column. |
References and Figures for Time Traveling:
Is Time Travel Possible? For essay, click here. For FirstScience.com entry click here.
Physorg.com: On Ronald Mallet, the physicist who predicted time travel. Click here. Figures for Digging it Deep:
Figures for Chaos and Butterflies: Downloadable Articles:
Figures for This is like Falling and Falling is like this: |