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Justin Gallagher

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  1. When I first saw this movie, there was one big question I had. Why is the planet Miller not pulled into the Black Hole Gargantua by the gravitational force, and so I did some research and found out some cool stuff. One of the main reasons Planet Miller isn't pulled into the black hole in spite of its proximity is that the adviser, Kip Thorne made sure that Gargantua was a rapidly spinning black hole—and it turns out that the physics of rotating black holes differ from non-rotating ones. The sheer speed of Gargantua's rotation means there is a single stable orbit just outside of Gargantua's event horizon that is very stable. However, Gargantua would have to fill half the sky in order for it to be so close. With spinning black holes, the area where the time dilates as drastically as in the movie is expanded exponentially, which allows for a small area where an object can orbit. Another cool thing about this movie is the the tidal waves on the planet miller. According to The Science of Interstellar by Kip Thorne, Miller's planet is shaped a little like a football, with one end constantly pointing at Gargantua. The waves are literally tidal waves, so it's not the waves coming toward you, it's the planet rotating under you and the fixed waves slamming into you. But because the planet doesn't rotate, the waves wouldn't slam into you. Fortunately, tidally locked planets can rock back and forth, and Thorne used this as a scientifically accurate loophole to explain tidal waves on a tidally locked planet. Also, because the water on Miller is mostly concentrated in the waves, you could have knee-high oceans, like the one shown in the film.
  2. Building a potato (or lemon or apple) battery reveals a bit about the inner workings of electrical circuits. To do this simple science experiment, you insert two different metallic objects often a galvanized (zinc-coated) nail and a copper penny into the potato, and connect wires to each object with alligator clips. These wires can be attached either to the two terminals of a multimeter (which measures a circuit's voltage) or to something like a digital clock or lightbulb. (It may take two or three potatoes wired in series to generate enough voltage to power those devices.) The potato acts like a battery, generating a current of electrons that flow through the wire. This happens because acid in the potato induces a chemical change in the zinc that coats the nail. The acid acts as an "electrolyte," ionizing the zinc atoms by stripping two electrons from each of them and leaving them positively charged. Those electrons are conducted away from the zinc ions through the wire and through whatever devices lie along the circuit and end up at the copper penny. From there, they join up with positive hydrogen ions in the potato starch that have been repelled there by the nearby zinc ions. The movement of these electrons is enough to power a toy clock or light bulb.
  3. The spinning top, a toy found across many of the world's cultures and even among ancient archaeological ruins, lays bare some profound physical principles. The first is the conservation of angular momentum, the law that dictates that, in the absence of external influences, something spinning must keep spinning. Because a top balances upon a tiny point, it experiences a minimal amount of friction with the surface below it, and thus continues spinning for a delightfully long time, demonstrating the law. But as friction eventually slows the top, it becomes unstable and starts to wobble, leading to the demonstration of another principle, called "precession." When the top wobbles, its axis of rotation the invisible line running vertically through its center tips sideways, making an angle with the table. This angle allows the force of gravity to exert a "torque" on the top, putting additional spin on it, and this causes it to swing (or precess) outward in an arc, still spinning as it does so. In an effort to conserve its total angular momentum, the top precesses faster the slower it spins; this explains why tops typically lurch outward just as friction brings their spinning to a stop.
  4. If you run really fast, you gain weight. Not permanently, or it would make a mockery of diet and exercise plans, but momentarily, and only a tiny amount. Light speed is the speed limit of the universe. So if something is travelling close to the speed of light, and you give it a push, it can’t go very much faster. But you've given it extra energy, and that energy has to go somewhere. Where it goes is mass. According to relativity, mass and energy are equivalent. So the more energy you put in, the greater the mass becomes. This is negligible at human speeds – Usain Bolt is not noticeably heavier when running than when still – but once you reach an appreciable fraction of the speed of light, your mass starts to increase rapidly.
  5. The speed of light in a vacuum is a constant: 300,000km a second. However, light does not always travel through a vacuum. In water, for example, photons travel at around three-quarters that speed. In nuclear reactors, some particles are forced up to very high speeds, often within a fraction of the speed of light. If they are passing through an insulating medium that slows light down, they can actually travel faster than the light around them. When this happens, they cause a blue glow, known as Cherenkov Radiation, which is comparable to a sonic boom but with light. Incidentally, the slowest light has ever been recorded traveling was 17 meters per second – about 38 miles an hour – through rubidium cooled to almost absolute zero, when it forms a strange state of matter called a Bose-Einstein condensate. Scientists at the University of Darmstadt in Germany have stopped light for one minute. For one whole minute, light, which is usually the fastest thing in the known universe and travels at 300 million meters per second, was stopped dead still inside a crystal. This effectively creates light memory, where the image being carried by the light is stored in crystals. Beyond being utterly cool, this breakthrough could lead to the creation of long-range quantum networks — and perhaps, tantalizingly, this research might also give us some clues on accelerating light beyond the universal speed limit. To stop light, the German researchers use a technique called electromagnetically induced transparency (EIT). They start with a cryogenically cooled opaque crystal of yttrium silicate doped with praseodymium. A control laser is fired at the crystal, triggering a complex quantum-level reaction that turns it transparent. A second light source is then beamed into the now-transparent crystal. The control laser is then turned off, turning the crystal opaque. Not only does this leave the light trapped inside, but the opacity means that the light inside can no longer bounce around — the light, in a word, has been stopped. With nowhere to go, the energy from the photons is picked up by atoms within the crystal, and the “data†carried by the photons is converted into atomic spin excitations. To get the light back out of the crystal, the control laser is turned back on, and the spin excitations are emitted at photons. These atomic spins can maintain coherence for around a minute, after which the light pulse/image fizzles. In essence, this entire setup allows the storage and retrieval of data from light memory.
  6. Inflation has become a cosmological buzzword in the 1990s. No self-respecting theory of the Universe is complete without a reference to inflation -- and at the same time there is now a bewildering variety of different versions of inflation to choose from. Clearly, what's needed is a beginner's guide to inflation, where newcomers to cosmology can find out just what this exciting development is all about. The reason why something like inflation was needed in cosmology was highlighted by discussions of two key problems in the 1970s. The first of these is the horizon problem -- the puzzle that the Universe looks the same on opposite sides of the sky (opposite horizons) even though there has not been time since the Big Bang for light (or anything else) to travel across the Universe and back. So how do the opposite horizons "know" how to keep in step with each other? The second puzzle is called the flatness problem This is the puzzle that the spacetime of the Universe is very nearly flat, which means that the Universe sits just on the dividing line between eternal expansion and eventual recollapse. Ever since 1905, when Albert Einstein revealed his special theory of relativity to the world, the speed of light has had a special status in the minds of physicists. In a vacuum, light travels at 299 792 458 meters per second, regardless of the speed of its source. There is no faster way of transmitting information. It is the cosmic speed limit. Our trust in its constancy is reflected by the pivotal role it plays in our standards of measurement. We can measure the speed of light with such accuracy that the standard unit of length is no longer a sacred meter bar kept in Paris but the distance traveled by light in a vacuum during one 299 792 458th of a second. So I ask? Why do opposite sides of the universe look the same? It's a puzzle, you see, because the extremes of today's visible universe should never have been in touch. Even back in the early moments of the big bang, when these areas were much closer together, there wasn't enough time for light - or anything else - to travel from one to another. There was no time for temperature and density to get evened out; and yet they are even. One solution: light used to move much faster. But to make that work could mean a radical overhaul of Einstein's theory of relativity. During inflation the Universe expanded a factor of 1054, so that our horizon now only sees a small piece of what was the total Universe from the Big Bang. The cause of the inflation era was the symmetry breaking at the GUT unification point. At this moment, spacetime and matter separated and a tremendous amount of energy was released. This energy produced an overpressure that was applied not to the particles of matter, but to spacetime itself. Basically, the particles stood still as the space between them expanded at an exponential rate. Note that this inflation was effectively at more than the speed of light, but since the expansion was on the geometry of the Universe itself, and not the matter, then there is no violation of special relativity. Our visible Universe, the part of the Big Bang within our horizon, is effectively a `bubble' on the larger Universe. However, those other bubbles are not physically real since they are outside our horizon. We can only relate to them in an imaginary, theoretical sense. They are outside our horizon and we will never be able to communicate with those other bubble universes. Inflation solves the flatness problem because of the exponential growth. Imagine a highly crumbled piece of paper. This paper represents the Big Bang universe before inflation. Inflation is like zooming in of some very, very small section of the paper. If we zoom in to a small enough scale the paper will appear flat. Our Universe must be exactly flat for the same reason, it is a very small piece of the larger Big Bang universe. The horizon problem is also solved in that our present Universe was simply a small piece of a larger Big Bang universe that was in causal connection before the inflation era. Other bubble universes might have very different constants and evolutionary paths, but our Universe is composed of a small, isotropic slice of the bigger Big Bang universe.
  7. For many years, we believed that the Earth was flat and that one could eventually fall off of the globe. We also believed that the Earth was the center of the universe (some people still do). And several ancient civilizations even used to use mercury as a medicine. Fortunately, we tested these ideas and came up with better ones. Since Sir Isaac Newton described gravity in his publication, "Principia." in 1687, to John Michell conjectured that there might be an object massive enough to have an escape velocity greater than the speed of light, to 1970 when Stephen Hawking defined modern theory of black holes, which describes the final fate of black holes, we have always been fascinated about the nature of black holes. But what if I tell you that’s not it. You don't believe me? Well that’s okay. To those that do not believe me, leave now or just shut up and don't comment. To those that are interested, prepare to have your mind blown. Gravastar: What is it? This is an unconventional idea that is as interesting as it is odd. This hypothesis was originally put forward by Mazur and Mottola in 2004. Gravastar literally means “Gravitational Vacuum Condensate Star,†which is (in theory) an extension of theBose-Einstein Condensate and put forward as a part of gravitational systems. Ultimately, it is meant to stand as an alternative to black holes. One of the benefits of the Gravastar over that if an ordinary black hole is that of entropy, the current accepted models of black holes have them having a very large entropy value. Gravastars, on the other hand, have quite a low entropy. The theory goes that, as a star collapses further [past the point of neutron degeneracy] the particles fall into a Bose-Einstein state where the entire star [all of the collapsing material] nears absolute zero and is able to get very compact. As a result, it acts as a giant atom composed of bosons. The interior of these Gravastars is thought that it might be within a de Sitter Spacetime, which means that it has a positive vacuum energy which could give rise to an internal negative pressure. Most of the math that goes into explaining this new model for a black hole is extremely complex. It suffices to say that this theoretical model consists of 5 different layers that construct the Gravastar, with de sitter spacetime effectively creating the negative pressure that keeps the Gravastar from collapsing along with some other mathematical constructs. Instead of using the Einstein field equations to calculate the event horizon of a black hole, Mazur & Mottola put forward that the event horizon (as we know it) is actually the outer shell of the Bose-Einstein matter, anything that comes in contact with it becomes a part of it–similar to matter hitting a neutron star and being broken down into neutrons due to the environment. Over the past few years this model has been getting more and more attention as a contender of the current black hole model; however, it still only has a small “following†in the grand scheme of things.
  8. The Grand Unified Theory is a vision of a physics theory that can combine three of the four fundamental forces into one single equation. The four forces are the Strong Nuclear Force, the Weak Nuclear Force, the Electro-Magnetic Force, and the Gravitational Force. The EM and Weak forces were initially thought to be two separate forces until scientists discovered one theory (the Electro Weak theory) to explain both of them and then went on to observe this unified force in action (much like Maxwell unified the electric and magnetic forces into the Electro-Magnetic Force). If a Grand Unification of all the interactions is possible, then all the interactions we observe are all different aspects of the same, unified interaction. However, how can this be the case if strong and weak and electromagnetic interactions are so different in strength and effect? Strangely enough, current data and theory suggests that these varied forces merge into one force when the particles being affected are at a high enough energy. The grand unification energy is the energy level above which, it is believed, the electromagnetic force, weak force, and strong force become equal in strength and unify to one force governed by asimple Lie group. Specific Grand unified theories can predict the grand unification energy but, usually, with large uncertainties due to model dependent details such as the choice of the gauge group, the Higgs sector, the matter content or further free parameters. Furthermore, at the moment it seems fair to state that there is no agreed minimal GUT. The unification of the electroweak forces and the strong force with the gravitational force in a so-called "Theory of Everything" requires an even higher energy level which is generally assumed to be close to the Planck Scale. In theory, at such short distances, gravity becomes comparable in strength to the other three forces of nature known to date. This statement is modified if there exist additional dimensions of space at intermediate scales. In this case, the strength of gravitational interactions increases faster at smaller distances, and the energy scale at which all known forces of nature unify, can be considerably lower. This effect is exploited in models of large extra dimensions. The exact value of the grand unification energy (if grand unification is indeed realized in nature) depends on the precise physics present at shorter distance scales not yet explored by experiments. If one assumes the Desert and supersymmetry, it is at around 1016 GeV. The most powerful collider to date, the LHC, is designed to reach a center of mass energy of 1.4x104 GeV in proton-proton collisions. The scale 1016 GeV is only a few orders of magnitude below the Planck scale, and thus not within reach of man-made earth bound colliders at the current moment.
  9. Experiment after experiment has tried to find flaws in the Standard Model's predictions, but so far all the experimental evidence supports it. Nevertheless, scientists do not believe that the Standard Model provides complete answers to all our questions about matter. It describes everything we see in the laboratory. Aside from leaving gravity out, it's a complete theory of what we see in nature. But it's not an entirely satisfactory theory, because it has a number of arbitrary elements. For example, there are a lot of numbers in this standard model that appear in the equations, and they just have to be put in to make the theory fit the observation. For example, the mass of the electron, the masses of the different quarks, the charge of the electron. If you ask, "Why are those numbers what they are? Why, for example, is the top quark, which is the heaviest known elementary particle, something like 300,000 times heavier than the electron?" The answer is, "We don't know. That's what fits experiment." That's not a very satisfactory picture. When you look even closer there are many things wrong with this model. Some of these include: Gravity: Most important of all. Where the hell's gravity? A theory of quantum gravitation, or more formally quantum geometrodynamics, does not yet exist. Incorporating gravity into particle physics looks to be a horrendous challenge. Arbitrary parameters (like the mass of the electron) Planck Limits: The Standard Model describes quite accurately physics near the electroweak symmetry breaking scale (246 GeV). But the Standard Model is only a "low energy" approximation to a more fundamental theory. The Standard Model cannot be valid at energies above the Planck scale (~1019 GeV), where gravity can no longer be ignored. Cosmology: dark matter and dark energy. Cosmological observations tell us the standard model explains about 5% of the energy present in the Universe. About 26% should be dark matter, which would behave just like other matter, but which only interacts weakly (if at all) with the Standard Model fields. Yet, the Standard Model does not supply any fundamental particles that are good dark matter candidates. The rest (69%) should be dark energy, a constant energy density for the vacuum. Attempts to explain dark energy in terms of vacuum energy of the standard model lead to a mismatch of 120 orders of magnitude. Matter-antimatter asymmetry: the Universe is made out of mostly matter. However, the standard model predicts that matter and antimatter should have been created in (almost) equal amounts if the initial conditions of the Universe did not involve disproportionate matter relative to antimatter. Yet, no mechanism sufficient to explain this asymmetry exists in the Standard Model. Once we decide to tackle gravity, the Standard Model as we know it transforms beyond recognition and an ultimate Theory of Everything becomes possible. We could then say that physics has reached its end.
  10. The Higgs boson or Higgs particle is an elementary particle in the Standard Model of particle physics. Its main relevance is that it allows scientists to explore the Higgs field – a fundamental field first suspected to exist in the 1960s that unlike the more familiar electromagnetic field cannot be "turned off", but instead takes a non-zero constant value almost everywhere. For a subatomic particle that remained hidden for nearly 50 years, the Higgs boson is turning out to be remarkably well behaved. Yet more evidence from the world's largest particle accelerator, the Large Hadron Collider (LHC) in Switzerland, confirms that the Higgs boson particle, thought to explain why other particles have mass, acts just as predicted by the Standard Model, the dominant physics theory that describes the menagerie of subatomic particles that make up the universe. The new results show that the Higgs boson decays into subatomic particles that carry matter called fermions — in particular, it decays into a heavier brother particle of the electron called a tau lepton. This decay has been predicted by the Standard Model. Even so, the findings are a bit of a disappointment for physicists who were hoping for hints of completely new physics. On July 4th, 2012, the discovery of a new particle with a mass between 125 and 127 GeV/c2 was announced; physicists suspected that it was the Higgs boson, an elusive particle first proposed 50 years ago by English physicist Peter Higgs. In Higgs' conception, in the blink after the Big Bang, an energy field, now dubbed the Higgs field, emerged that imparts mass to the subatomic particles that trawl through it. Particles that are "stickier" and slow down more while traversing the field become heavier. Because subatomic particles are either matter carriers called fermions, such as electrons and protons, or force-carrying particles called bosons, such as photons and gluons, the existence of the Higgs field implied an associated force-carrying particle, called the Higgs boson, which is like a ripple in that field. The 2012 discovery left little doubt that the Higgs boson exists, however, there were still many unanswered questions. Is there one Higgs boson or multiple? If there are multiple, what are their masses? And just how do these different-flavored Higgs behave? To answer those questions, physicists still had to pore over tons of data from the LHC, which accelerates protons to just below the speed of light, then smashes them together, creating a shower of subatomic particles. When the LHC collaborators analyzed those Higgs events, they found about 6 percent of the elusive particles decayed into tau leptons. And though not unexpected, the new results show no hint of additional Higgs bosons that would lend credence to alternate theories such as supersymmetry, which predicts that every particle currently known has a "superpartner" with slightly different properties. The idea of the Higgs decaying to tau leptons was somewhat tacked onto the Standard Model after its creation, yet this addition to the Standard model turns out to be how nature does it. But there are still a few pieces left to complete the picture predicted by the Standard Model.
  11. While I visited the Rochester Institute of technology over the break, I talked to a Junior who was majoring in Physics. He was explaining to me what he was working on and theorized. He was currently working on the Grand Unified Theory. This interested me quite a bit so I did some research into this subject. It all starts with the Fundamental forces and their Interactions. There are 4 fundamental forces that have been identified. In our present Universe they have rather different properties. Properties of the Fundamental Forces: The Strong Nuclear Force is very strong, but very short-ranged. It acts only over ranges of order 10-13 centimeters and is responsible for holding the nuclei of atoms together. Since the protons and neutrons which make up the nucleus are themselves considered to be made up of quarks, and the quarks are considered to be held together by the color force, the strong force between nucleons may be considered to be a residual color force. In the standard model, therefore, the basic exchange particle is the gluon which mediates the forces between quarks. Since the individual gluons and quarks are contained within the proton or neutron, the masses attributed to them cannot be used in the range relationship to predict the range of the force. When something is viewed as emerging from a proton or neutron, then it must be at least a quark-antiquark pair, so it is then plausible that the pion as the lightest meson should serve as a predictor of the maximum range of the strong force between nucleons. The Electromagnetic Force manifests itself through the forces between charges (Coulomb's Law) and the magnetic force, both of which are summarized in the Lorentz force law. Fundamentally, both magnetic and electric forces are manifestations of an exchange force involving the exchange of photons . The electromagnetic force holds atoms and molecules together. In fact, the forces of electric attraction and repulsion of electric charges are so dominant over the other three fundamental forces that they can be considered to be negligible as determiners of atomic and molecular structure. Even magnetic effects are usually apparent only at high resolutions, and as small corrections. The Role of the Weak Nuclear Force in the transmutation of quarks makes it the interaction involved in many decays of nuclear particles which require a change of a quark from one flavor to another. It was in radioactive decay such as beta decay that the existence of the weak interaction was first revealed. The weak interaction is the only process in which a quark can change to another quark, or a lepton to another lepton - the so-called "flavor changes". The Gravitational Force is weak, but very long ranged. It is by far the weakest of the four interactions. The weakness of gravity can easily be demonstrated by suspending a pin using a simple magnet (such as a refrigerator magnet). The magnet is able to hold the pin against the gravitational pull of the entire Earth. Yet gravitation is very important for macroscopic objects and over macroscopic distances. It is the only interaction that acts on all particles having mass; it has an infinite range, like electromagnetism but unlike strong and weak interaction; it cannot be absorbed, transformed, or shielded against and it always attracts and never repels.
  12. In 1889, inspired by a famous astronomical drawing that had been circulating in Europe for four decades, Vincent van Gogh painted his iconic masterpiece “The Starry Night,†one of the most recognized and reproduced images in the history of art. At the peak of his lifelong struggle with mental illness, he created the legendary painting while staying at the mental asylum into which he had voluntarily checked himself after mutilating his own ear. But more than a masterwork of art, Van Gogh’s painting turns out to hold astounding clues to understanding some of the most mysterious workings of science. This fascinating short animation from TED-Ed and Natalya St. Clair, author of The Art of Mental Calculation, explores how “The Starry Night†sheds light on the concept of turbulent flow in fluid dynamics, one of the most complex ideas to explain mathematically and among the hardest for the human mind to grasp. From why the brain’s perception of light and motion makes us see Impressionist works as flickering, to how a Russian mathematician’s theory explains Jupiter’s bright red spot, to what the Hubble Space Telescope has to do with Van Gogh’s psychotic episodes, this mind-bending tour de force ties art, science, and mental health together through the astonishing interplay between physical and psychic turbulence.
  13. Hopefully you have read the Quantum Foam, blog, if not, that is fine. Commence the melting of your brains. Are ya ready? In physics, a spinfoam or spin foam is a topological structure made out of two-dimensional faces that represents one of the configurations that must be summed to obtain a Feynman's path integral (functional integration) description of quantum gravity. It is closely related to loop quantum gravity. Loop Quantum Gravity has a covariant formulation that, at present, provides the best formulation of the dynamics of the theory of Quantum Gravity. This is a Quantum Field Theory where the invariance under diffeomorphisms of general relativity is implemented. The resulting path integral represents a sum over all the possible configuration of the geometry, coded in the spinfoam. A spin network is defined as a diagram (like the Feynman diagram) that makes a basis of connections between the elements of a differentiable manifold for the Hilbert spaces defined over them. Spin networks provide a representation for computations of amplitudes between two different hypersurfaces of the manifold. Any evolution of spin network provides a spin foam over a manifold of one dimension higher than the dimensions of the corresponding spin network. A.K.A. Spin foam may be viewed as a quantum history. Spin networks provide a language to describe quantum geometry of space. Spin foam does the same job on spacetime. A spin network is a one-dimensional graph, together with labels on its vertices and edges which encodes aspects of a spatial geometry. Spacetime is considered as a superposition of spin foams, which is a generalized Feynman diagram where instead of a graph we use a higher-dimensional complex. In topology this sort of space is called a 2-complex. A spin foam is a particular type of 2-complex, together with labels for vertices, edges and faces. The boundary of a spin foam is a spin network, just as in the theory of manifolds, where the boundary of an n-manifold is an (n-1)-manifold. In Loop Quantum Gravity, the present Spinfoam Theory has been inspired by the work of Ponzano-Regge model. The concept of a spin foam, although not called that at the time, was introduced in the paper "A Step Toward Pregeometry I: Ponzano-Regge Spin Networks and the Origin of Spacetime Structure in Four Dimensions" by Norman J. LaFave. In this paper, the concept of creating sandwiches of 4-geometry (and local time scale) from spin networks is described, along with the connection of these spin 4-geometry sandwiches to form paths of spin networks connecting given spin network boundaries (spin foams). Quantization of the structure leads to a generalized Feynman path integral over connected paths of spin networks between spin network boundaries. This paper goes beyond much of the later work by showing how 4-geometry is already present in the seemingly three dimensional spin networks, how local time scales occur, and how the field equations and conservation laws are generated by simple consistency requirements. The partition function for a spin foam model is, in general...
  14. Yeah you heard that right. I just said Quantum Foam. And the best part, it is an actual science term. It's time to blow up some minds. Like I said In my "The imposible Conundrum" blogs, how things can be created from nothing, this is what happens down at the quantum level of this idea. Quantum foam (also referred to as space-time foam) is a concept in quantum mechanics devised by John Wheeler in 1955. The foam is supposed to be conceptualized as the foundation of the fabric of the universe. Additionally, quantum foam can be used as a qualitative description of subatomic space-time turbulence at extremely small distances (on the order of the Planck length). At such small scales of time and space, the Heisenberg uncertainty principle allows energy to briefly decay into particles and antiparticles and then annihilate without violating physical conservation laws. As the scale of time and space being discussed shrinks, the energy of the virtual particles increases. According to Einstein's theory of general relativity, energy curves space-time. This suggests that—at sufficiently small scales—the energy of these fluctuations would be large enough to cause significant departures from the smooth space-time seen at larger scales, giving space-time a "foamy" character. This relates to other theories in many ways. In the "The Impossible Conundrum" Blogs, the arising then annihilating cause "vacuum fluctuations" which affect the properties of the vacuum, giving it a nonzero energy known as vacuum energy, itself a type of zero-point energy. However, physicists are uncertain about the magnitude of this form of energy. The Casimir effect can also be understood in terms of the behavior of virtual particles in the empty space between two parallel plates. Ordinarily, quantum field theory does not deal with virtual particles of sufficient energy to curve spacetime significantly, so quantum foam is a speculative extension of these concepts which imagines the consequences of such high-energy virtual particles at very short distances and times. Spin foam theory is a modern attempt to make Wheeler's idea quantitative. Tune in next time as I talk about Spin Foam.
  15. To really sum everything up is quite simple. According to the strong anthropic principle, there are either many different universes or many different regions of a single universe, each with its own initial configuration and, perhaps, with its own set of laws of science. In most of these universes the conditions would not be right for the development of complicated organisms; only in the few universes that are like ours would intelligent beings develop and ask the question: "Why is the universe the way we see it?" The answer is then simple: If it had been different, we would not be here! There are something like ten million million million million million million million million million million million million million million (1 with eighty zeroes after it) particles in the region of the universe that we can observe. Where did they all come from? The answer is that, in quantum theory, particles can be created out of energy in the form of particle/antiparticle parts. But that just raises the question of where the energy came from. The answer is that the total energy of the universe is exactly zero. The matter in the universe is made out of positive energy. However, the matter is all attracting itself by gravity. Two pieces of matter that are close to each other have less energy than the same two pieces a long way apart, because you have to expend energy to separate them against the gravitational force that is pulling them together. Thus in a sense, the gravitational field has negative energy. In the case of a universe that is approximately uniform in space, one can show that this negative gravitational energy exactly cancels the positive energy represented by the matter. So the total energy of the universe is zero. Now twice zero is also zero. Thus the universe can double the amount of positive matter energy and also double the negative gravitational energy without violation of the conservation of energy. One could say: "The boundary condition of the universe is that it has no boundary." The universe would be completely self-contained and not affected by anything outside itself. It would neither be created nor destroyed. It would just BE. The idea that space and time may form a closed surface without boundary also has profound implications for the role of God in the affairs of the universe. With the success of scientific theories in describing events, most people have come to believe that God allows the universe to evolve according to a set of laws and does not intervene in the universe to break these laws. However, the laws do not tell us what the universe should have looked like when it started - it would still be up to God to wind up the clockwork and choose how to start it off. So long as the universe had a beginning, we could suppose it had a creator. But if the universe is really completely self-contained, having no boundaries or edge, it would have neither beginning nor end: it would simply be. Like the south pole on the earth. What is south of the south pole? When you understand what I am saying, then as yourself: What place, then, for a creator? So when people ask if a God created the universe, I tell them that the question itself makes no sense. Time didn't exist before the big bang, so there is no time for God to make a universe. It's like asking for directions to the edge of the earth. In early history, the answer would simply be travel in any direction and you will eventually get there. But eventually one person came along and asked for proof and found everything about the earth having an edge was wrong. The earth is a sphere. It doesn't have an edge, so looking for it is a futile exercise. We are each free to believe what we want, yet it is my view that is the only one that has evidence. The one that is always the simplest explanation: There is no god. No one created the universe and no one directs our fate. There is no meaning to life. We are here by the tweaking of laws over an infinite number of time. This leads me to a profound realization. There is probably no heaven or hell, and no afterlife either. We have this one life to appreciate the grand design of the universe, and for that, I am extremely grateful.

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