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  • richardmitnick 7:57 am on April 14, 2016 Permalink | Reply
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    From FNAL’s Don Lincoln on livescience: “Collider Unleashed! The LHC Will Soon Hit Its Stride” 

    Livescience

    April 12, 2016

    FNAL Don Lincoln
    Don Lincoln, Senior Scientist, Fermi National Accelerator Laboratory; Adjunct Professor of Physics, University of Notre Dame

    CERN/LHC Map
    CERN LHC Grand Tunnel
    CERN LHC particles
    LHC at CERN

    If you’re a science groupie and would love nothing better than for a cornerstone scientific theory to be overthrown and replaced with something newer and better, then 2016 might well be your year. The world’s largest particle accelerator, the Large Hadron Collider (LHC), is resuming operations after a pause during the winter months, when the cost for electricity in France is highest.

    So why is it such a big deal that LHC coming back on line? It’s because this is the year the accelerator will operate at something approaching its design specifications. Scientists will smash the gas pedal to the floor, crank the fire hose wide open, spin the amplifier button to eleven or enact whatever metaphor you like. This year is the first real year of full-scale LHC operations.

    A particle smasher reborn

    Now if you actually are a science groupie, you know what the LHC is and have probably heard about some of its accomplishments. You know it smashes together two beams of protons traveling at nearly the speed of light. You know scientists using the LHC found the Higgs boson.

    CERN ATLAS Higgs Event
    CERN ATLAS Higgs Event

    CERN CMS Higgs Event
    CERN CMS Higgs Event

    You know that this marvel is the largest scientific device ever built.

    So what’s different now? Well, let’s go back in time to 2008, when the LHC circulated its first beams. At the time, the world’s premier particle accelerator was the U.S. Department of Energy’s Fermilab Tevatron, which collided beams at a whopping 2 trillion electron volts (TeV) of energy and with a beam brightness of about 2 × 1032 cm-2 s-1.

    FNAL/Tevatron map
    FNAL/Tevatron map

    FNAL/Tevatron CDF
    FNAL/Tevatron CDF detectorFNAL/DZero detector
    FNAL/DZero detector

    The technical term for beam brightness is “instantaneous luminosity,” and basically it’s a density. More precisely, when a beam passes through a target, the instantaneous luminosity (L) is the number of particles per second in a beam that pass a location (ΔNB/Δt) divided by the area of the beam (A), multiplied by the number of targets (NT), L = ΔNB/Δt × (1/A) × NT. (And the target can be another beam.)

    The simplest analogy that will help you understand this quantity is a light source and a magnifying glass. You can increase the “luminosity” of the light by turning up the brightness of the light source or by focusing the light more tightly. It is the same way with a beam. You can increase the instantaneous luminosity by increasing the number of beam or target particles, or by concentrating the beam into a smaller area.

    The LHC was built to replace the Tevatron and trounce that machine’s already-impressive performance numbers.

    [If our USA Congress was not filled with idiots, we would have built in Texas the Superconducting Super Collider and not lost this HEP race.]

    The new accelerator was designed to collide beams at a collision energy of 14 TeV and to have a beam brightness — instantaneous luminosity — of at least 100 × 1032 cm-2 s-1. So the beam energy was to be seven times higher, and the beam brightness would increase 50- to 100-fold.

    Sadly, in 2008, a design flaw was uncovered in the LHC when an electrical short caused severe damage, requiring two years to repair . Further, when the LHC actually did run, in 2010, it operated at half the design energy (7 TeV) and at a beam brightness basically the same as that of the Fermilab Tevatron. The lower energy was to give a large safety margin, as the design flaw had been only patched, not completely reengineered.

    The situation improved in 2011 when the beam brightness got as high as 30 × 1032 cm-2 s-1, although with the same beam energy. In 2012, the beam energy was raised to 8 TeV, and the beam brightness was higher still, peaking at about 65 × 1032 cm-2 s-1.

    The LHC was shut down during 2013 and 2014 to retrofit the accelerator to make it safe to run at closer to design specifications. The retrofits consisted mostly of additional industrial safety measures that allowed for better monitoring of the electrical currents in the LHC. This helps ensure there are no electrical shorts and that there is sufficient venting. The venting guarantees no catastrophic ruptures of the LHC magnets (which steer the beams) in the event that cryogenic liquids — helium and nitrogen — in the magnets warm up and turn into a gas. In 2015, the LHC resumed operations, this time at 13 TeV and with a beam brightness of 40 × 1032 cm-2 s-1.

    So what’s expected in 2016?

    The LHC will run at 13 TeV and with a beam brightness that is expected to approach 100 × 1032 cm-2 s-1 and possibly even slightly exceed that mark. Essentially, the LHC will be running at design specifications.

    In addition, there is a technical change in 2016. The protons in the LHC beams will be spread more uniformly around the ring, thus reducing the number of protons colliding simultaneously, resulting in better data that is easier to interpret.

    At a technical level, this is kind of interesting. A particle beam isn’t continuous like a laser beam or water coming out of a hose. Instead, the beam comes in a couple of thousand distinct “bunches.” A bunch looks a little bit like a stick of uncooked spaghetti, except it is about a foot long and much thinner — about 0.3 millimeters, most of the time. These bunches travel in the huge 16-mile-long (27 kilometers) circle that is the LHC, with each bunch separated from the other bunches by a distance that (until now) has been about 50 feet (15 meters).

    The technical change in 2016 is to take the same number of beam protons (roughly 3 × 1014 protons) and split them up into 2,808 bunches, each separated not by 50 feet, but by 25 feet (7.6 m). This doubles the number of bunches, but cuts the number of protons in each bunch in half. (Each bunch contains about 1011 protons.)

    Because the LHC has the same number of protons but separated into more bunches, that means when two bunches cross and collide in the center of the detector, there are fewer collisions per crossing. Since most collisions are boring and low-energy affairs, having a lot of them at the same time that an interesting collision occurs just clutters up the data.

    Ideally, you’d like to have only an interesting collision and no simultaneous boring ones. This change of bunch separation distance from 50 feet to 25 feet brings the data collection closer to ideal.

    Luminous beams

    Another crucial design element is the integrated beam. Beam brightness (instantaneous luminosity) is related to the number of proton collisions per second, while integrated beam (integrated luminosity) is related to the total number of collisions that occur as the two counter-rotating beams continually pass through the detector. Integrated luminosity is something that adds up over the days, months and years.

    The unit of integrated luminosity is a pb-1. This unit is a bit confusing, but not so bad. The “b” in “pb” stands for a barn (more on that in a moment). A barn is 10-24 cm2. A picobarn (pb) is 10-36 cm2. The term “barn” is a unit of area and comes from another particle physics term called a cross section, which is related to how likely it is that two particles will interact and generate a specific outcome. Two objects that have large effective area will interact easily, while objects with a small effective area will interact rarely.

    An object with an area of a barn is a square with a length of 10-12 cm. That’s about the size of the nucleus of a uranium atom.

    During World War II, physicists at Purdue University in Indiana were working with uranium and needed to mask their work for security reasons. So they invented the term “barn,” defining it as an area about the size of a uranium nucleus. Given how big this area is in the eyes of nuclear and particle physicists, the Purdue scientists were co-opting the phrase “as big as a barn.” In the luminosity world, with its units of (1/barn), small numbers mean more luminosity.

    This trend is evident in the integrated luminosity seen in the LHC each year as scientists improved their ability to operate the accelerator. The integrated luminosity in 2010 was 45 pb-1. In 2011 and 2012, it was 6,100 pb-1 and 23,300 pb-1, respectively. As time went on, the accelerator ran more reliably, resulting in far higher numbers of recorded collisions.

    Because the accelerator had been re-configured during the 2013 to 2014 shutdown, the luminosity was lower in 2015, coming in at 4,200 pb-1, although, of course, at the much higher beam energy. The 2016 projection could be as high as 35,000 pb-1. The predicted increase merely reflects the accelerator operators’ increased confidence in their ability to operate the facility.

    This means in 2016, we could actually record eight times as much data as we did in 2015. And it is expected that 2017 will bring even higher performance.

    Illuminating new science

    Let’s think about what these improvements mean. When LHC first collided beams, in 2010, the Higgs boson was still to be observed.

    Higgs Boson Event
    Higgs Boson Event

    On the other hand, the particle was already predicted, and there was good circumstantial evidence to expect that the Higgs would be discovered. And, without a doubt, it must be admitted that the discovery of the Higgs boson was an enormous scientific triumph.

    But confirming previously predicted particles, no matter how impressive, is not why the LHC was built.

    Scientists’ current theory of the particle world is called the Standard Model, and it was developed in the late 1960s, half a century ago.

    The Standard Model of elementary particles , with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth.
    The Standard Model of elementary particles , with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth

    While it is an incredibly successful theory, it is known to have holes. Although it explains why particles have mass, it doesn’t explain why some particles have more mass than others. It doesn’t explain why there are so many fundamental particles, given that only a handful of them are needed to constitute the ordinary matter of atoms and puppies and pizzas. It doesn’t explain why the universe is composed solely of matter, when the theory predicts that matter and antimatter should exist in equal quantities. It doesn’t identify dark matter, which is five times more prevalent than ordinary matter and is necessary to explain why galaxies rotate in a stately manner and don’t rip themselves apart.

    When you get right down to it, there is a lot the Standard Model doesn’t explain. And while there are tons of ideas about new and improved theories that could replace it, ideas are cheap. The trick is to find out which idea is right.

    That’s where the LHC comes in. The LHC can explore what happens if we expose matter to more and more severe conditions. Using Einstein’s equation E = mc2, we can see how the high-collision energies only achievable in the LHC are converted into forms of matter never before seen. We can sift through the LHC data to find clues that point us in the right direction to hopefully figure out the next bigger and more effective theory. We can take another step toward our ultimate goal of finding a theory of everything.

    With the LHC now operating at essentially design spec, we can finally use the machine to do what we built it for: to explore new realms, to investigate phenomena never before seen and, stealing a line from my favorite television show, “to boldly go where no one has gone before.” We scientists are excited. We’re giddy. We’re pumped. In fact, there can be but one way to express how we view this upcoming year:

    See the full article here .

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  • richardmitnick 7:14 pm on March 30, 2016 Permalink | Reply
    Tags: , Don Lincoln, , , Quantum electrodynamics   

    From Don Lincoln at FNAL: “Quantum electrodynamics: theory” video 

    FNAL II photo

    Fermilab is an enduring source of strength for the US contribution to scientific research world wide.

    FNAL Don Lincoln
    Don Lincoln

    The Standard Model of particle physics is composed of several theories that are added together.

    The Standard Model of elementary particles , with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth.
    The Standard Model of elementary particles , with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth.

    The most precise component theory is the theory of quantum electrodynamics or QED. In this video, Fermilab’s Dr. Don Lincoln explains how theoretical QED calculations can be done. This video links to other videos, giving the viewer a deep understanding of the process.


    Access mp4 video here .

    Watch, enjoy, learn.

    See the full article here .

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    Fermilab Campus

    Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a US Department of Energy national laboratory specializing in high-energy particle physics. Fermilab is America’s premier laboratory for particle physics and accelerator research, funded by the U.S. Department of Energy. Thousands of scientists from universities and laboratories around the world
    collaborate at Fermilab on experiments at the frontiers of discovery.

     
  • richardmitnick 10:32 am on March 25, 2016 Permalink | Reply
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    From Don Lincoln of FNAL: “Theoretical physics: insider’s tricks “ 

    FNAL II photo

    Fermilab is an enduring source of strength for the US contribution to scientific research world wide.

    Mar 24, 2016

    FNAL Don Lincoln
    Don Lincoln

    Theoretical particle physics employs very difficult mathematics, so difficult in fact that it is impossible to solve the equations. In order to make progress, scientists employ a mathematical technique called perturbation theory. This method makes it possible to solve very difficult problems with very good precision. In this video, Fermilab’s Dr. Don Lincoln shows just how easy it is to understand this powerful technique.


    Access mp4 video here.

    Watch, enjoy, learn.

    See the full article here .

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    Fermilab Campus

    Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a US Department of Energy national laboratory specializing in high-energy particle physics. Fermilab is America’s premier laboratory for particle physics and accelerator research, funded by the U.S. Department of Energy. Thousands of scientists from universities and laboratories around the world
    collaborate at Fermilab on experiments at the frontiers of discovery.

     
  • richardmitnick 2:48 pm on February 2, 2016 Permalink | Reply
    Tags: , Don Lincoln, ,   

    From FNAL: “Quantum Gravity” video with Don Lincoln 

    FNAL II photo

    Fermilab is an enduring source of strength for the US contribution to scientific research world wide.

    2.2.16
    FNAL Don Lincoln
    Don Lincoln

    While there are many challenges facing modern particle physics, perhaps the ultimate one (and certainly among the most difficult) is to describe the nature of gravity in the quantum realm. Despite a century of effort, scientists have had only the most cursory of success. In this video, Fermilab’s Dr. Don Lincoln talks about the idea of quantum gravity and sketches out the need for this difficult advance.


    Download the mp4 video here .

    Watch, enjoy, learn.

    See the full article here .

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    Fermilab Campus

    Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a US Department of Energy national laboratory specializing in high-energy particle physics. Fermilab is America’s premier laboratory for particle physics and accelerator research, funded by the U.S. Department of Energy. Thousands of scientists from universities and laboratories around the world
    collaborate at Fermilab on experiments at the frontiers of discovery.

     
  • richardmitnick 7:56 pm on January 15, 2016 Permalink | Reply
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    From FNAL: Don Lincoln on Quantum Field Theory 

    FNAL II photo

    Fermilab is an enduring source of strength for the US contribution to scientific research world wide.

    The subatomic world has long been known to be truly mind-bending, with particles that are waves and vice versa. Cats are alive and dead and everything is governed by probability.

    While this remains true, science has progressed since the invention of quantum mechanics and scientists currently use an extended form of quantum mechanics called quantum field theory or QFT. QFT teaches us that all particles are waves that interact with one another. If you thought the quantum world was weird before, modern ideas can give you a headache. In this video, Fermilab’s Dr. Don Lincoln tells us all about it.

    Watch, enjoy, learn.

    See the full article here .

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    Fermilab Campus

    Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a US Department of Energy national laboratory specializing in high-energy particle physics. Fermilab is America’s premier laboratory for particle physics and accelerator research, funded by the U.S. Department of Energy. Thousands of scientists from universities and laboratories around the world
    collaborate at Fermilab on experiments at the frontiers of discovery.

     
  • richardmitnick 5:05 pm on November 25, 2015 Permalink | Reply
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    From Don Lincoln at FNAL: “What good is particle physics?” 

    FNAL II photo

    Fermilab is an enduring source of strength for the US contribution to scientific research world wide.

    FNAL Don Lincoln
    Don Lincoln

    Most particle physics research is publicly funded, so it is fair that society asks if this is a good use of taxpayers’ money. In this video, Fermilab’s Dr. Don Lincoln explains how this research attempts to answer questions that have bothered humanity since time immemorial. And, for those with a more practical bent, he explains how this research is an excellent investment with a high rate of return for society.

    See the full article here .

    Please help promote STEM in your local schools.

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    Stem Education Coalition

    Fermilab Campus

    Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a US Department of Energy national laboratory specializing in high-energy particle physics. Fermilab is America’s premier laboratory for particle physics and accelerator research, funded by the U.S. Department of Energy. Thousands of scientists from universities and laboratories around the world
    collaborate at Fermilab on experiments at the frontiers of discovery.

     
  • richardmitnick 11:54 am on November 20, 2015 Permalink | Reply
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    From FNAL- “Frontier Science Result: CMS Lead bottom” 

    FNAL II photo

    Fermilab is an enduring source of strength for the US contribution to scientific research world wide.

    Nov. 20, 2015
    FNAL Don Lincoln
    Don Lincoln

    1
    Today’s article describes what happens when you collide individual protons into lead nuclei. This result helps understand an exciting new state of matter called a quark gluon plasma. Image: CERN

    The nice thing about the LHC research program is that it allows scientists to investigate many phenomena.

    CERN LHC Map
    CERN LHC Grand Tunnel
    CERN LHC particles
    LHC

    All are exotic, with some pushing the very frontier of knowledge, while some investigate complex phenomena as a means to understand even more complex phenomena.

    When two heavy atomic nuclei are slammed together at very high energy, a peculiar thing occurs. The temperatures in these collisions are so high that the protons and neutrons in the nuclei literally melt, and the quarks and gluons that are normally inside the protons and neutrons can move around freely. We call this state of matter a quark-gluon plasma.

    In addition, the high collision energy can convert into matter-antimatter pairs, as suggested by Einstein’s equation E=mc2. If you want to study what occurs in the collision, you look for types of matter that don’t exist as ordinary matter. One example of this more exotic type of matter is bottom quarks. Since they don’t generally exist inside the nuclei of atoms, if you see bottom quarks, you know that they were made from the energy of the collision.

    Scientists have lots of experience making bottom quarks by colliding two protons together. This is the way we run the LHC for most of the time, and we have made (although not recorded) many billions of bottom quarks. The process is pretty well-understood.

    We also can make bottom quarks by colliding two lead nuclei together. We do this at the LHC about one month per year. In these collisions, a total of 416 protons and neutrons are smashed together. Naively, you’d expect that all the protons and neutrons can participate in the collision and that the number of bottom quarks that are made can be easily calculated from the well-understood proton-proton scattering process.

    However, we see fewer bottom quarks than we’d expect from lead-lead collisions. The usual explanation is that these bottom quarks have to push their way through the hot quark-gluon plasma. They become tired and slow down, so they don’t escape the collision.

    But there might be other explanations. Maybe the fact that the colliding protons and neutrons are bound in nuclei (rather that floating freely) influences how their component quarks and gluons are distributed inside them.

    To work out this ambiguity, CMS scientists decided to smash together a beam of protons into a beam of lead nuclei.

    CERN CMS Detector
    CMS

    If the lower-than-expected number of bottom quarks in lead-lead collisions was due to the way bottom quarks plow through quark-gluon plasma you’d expect to see no reduction in the production of bottom quarks from these lead-proton collisions, since the quark-gluon plasma is not made in these kinds of collisions. If the effect was due to the moving around of energy inside nuclei, you’d expect to see behavior midway between the proton-proton and lead-lead scattering.

    As it happens, scientists observed no reduction in the production of bottom quarks. This strongly suggests that the reduction seen in collisions between two lead nuclei originates in the bottom quarks trying to punch through the quark gluon plasma. Thus this measurement validates our understanding of the behavior of matter hot enough to melt protons and neutrons.

    See the full article here .

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    Fermilab Campus

    Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a US Department of Energy national laboratory specializing in high-energy particle physics. Fermilab is America’s premier laboratory for particle physics and accelerator research, funded by the U.S. Department of Energy. Thousands of scientists from universities and laboratories around the world
    collaborate at Fermilab on experiments at the frontiers of discovery.

     
  • richardmitnick 7:43 pm on November 19, 2015 Permalink | Reply
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    From SPACE.com: “Einstein’s Unfinished Dream: Marrying Relativity to the Quantum World” 

    space-dot-com logo

    SPACE.com

    November 18, 2015
    FNAL Don Lincoln
    Don Lincoln, Senior Scientist, Fermi National Accelerator Laboratory; Adjunct Professor of Physics, University of Notre Dame

    1
    This artist’s illustration depicts how the foamy structure of space-time may appear, showing tiny bubbles quadrillions of times smaller than the nucleus of an atom that are constantly fluctuating and last for only infinitesimal fractions of a second. Credit: NASA/CXC/M.Weiss

    This November marks the centennial of Albert Einstein’s theory of general relativity. This theory was the crowning achievement of Einstein’s extraordinary scientific life. It taught us that space itself is malleable, bending and stretching under the influence of matter and energy. His ideas revolutionized humanity’s vision of the universe and added such mind-blowing concepts as black holes and wormholes to our imagination.

    Einstein’s theory of general relativity describes a broad range of phenomena, from nearly the moment of creation to the end of time, and even a journey spiraling from the deepest space down into a ravenous black hole, passing through the point of no return of the event horizon, down, down, down, to nearly the center, where the singularity lurks.

    Deep into a quantum world

    If you were reading that last paragraph carefully, you’ll note that I used the word “nearly” twice. And that wasn’t an accident. Einstein’s theory has been brilliantly demonstrated at large size scales. It deftly explains the behavior of orbiting binary pulsars and the orbit of Mercury. It is a crucial component of the GPS system that helps many of us navigate in our cars every day.

    But the beginning of the universe and the region near the center of a black hole are very different worlds — quantum worlds. The size scales involved in those environments are subatomic. And that’s where the trouble starts.

    Einstein’s heyday coincided with the birth of quantum mechanics, and the stories of his debates with physicist Niels Bohr over the theory’s counterintuitive and probabilistic predictions are legendary. “God does not play dice with the universe,” he is famously reported to have said.

    However, regardless of his disdain for the theory of quantum mechanics, Einstein was well aware of the need to understand the quantum realm. And, in his quest to understand and explain general relativity, he sought to understand how of gravity performed in his epic theory when it was applied to the world of the supersmall. The result can be summarized in three words: It failed badly.


    download the mp4 video here.

    Bridging the quantum world to relativity

    Einstein spent the rest of his life, without success, pursuing ways to integrate his theory of general relativity with quantum mechanics. While it is tempting to describe the history of this attempt, the effort is of interest primarily to historians. After all, he didn’t succeed, nor did anyone in the decades that followed.

    Instead, it is more interesting to get a sense of the fundamental problems associated with wedding these two pivotal theories of the early 20th century. The initial issue was a systemic one: General relativity uses a set of differential equations that describe what mathematicians call a smooth and differentiable space. In layman’s terms, this means that the mathematics of general relativity is smooth, without any sharp edges.

    In contrast, quantum mechanics describes a quantized world, e.g. a world in which matter comes in discrete chunks. This means that there is an object here, but not there. Sharp edges abound.

    The water analogy

    In order to clarify these different mathematical formulations, one need think a bit more deeply than usual about a very familiar substance we know quite well: liquid water. Without knowing it, you already hold two different ideas about water that illustrate the tension between differential equations and discrete mathematics.

    For example, when you think of the familiar experience of running your hand through water, you think of water as a continuous substance. The water near your hand is similar to the water a foot away. That distant water might be hotter or colder or moving at a different speed, but the essence of water is the same. As you consider different volumes of water that get closer and closer to your hand, your experience is the same. Even if you think about two volumes of water separated by just a millimeter or half a millimeter, the space between them consists of more water. In fact, the mathematics of fluid flow and turbulence assumes that there is no smallest, indivisible bit of water. Between any two arbitrarily-close distances, there will be water. The mathematics that describes this situation is differential equations. Digging down to its very essence, you find that differential equations assume that there is no smallest distance.

    But you also know that this isn’t true. You know about water molecules. If you consider distances smaller than about three angstroms (the size of a water molecule), everything changes. You can’t get smaller than that, because when you probe even smaller distances, water is no longer a sensible concept. At that point, you’re beginning to probe the empty space inside atoms, in which electrons swirl around a small and dense nucleus. In fact, quantum mechanics is built around the idea that there are smallest objects and discrete distances and energies. This is the reason that a heated gas emits light at specific wavelengths: the electrons orbit at specific energies, with no orbits between the prescribed few.

    Thus a proper quantum theory of water has to take into account the fact that there are individual molecules. There is a smallest distance for which the idea of “water” has any meaning.

    Thus, at the very core, the mathematics of the two theories (e.g. the differential equations of general relativity and the discrete mathematics of quantum mechanics) are fundamentally at odds.


    download the mp4 video here.

    Can the theories merge?

    This is not, in and of itself, an insurmountable difficulty. After all, parts of quantum mechanics are well described by differential equations. But a related problem is that when one tries to merge the two theories, infinities abound; and when an infinity arises in a calculation, this is a red flag that you have somehow done something wrong.

    As an example, suppose you treat an electron as a classical object with no size and calculate how much energy it takes to bring two electrons together. If you did that, you’d find that the energy is infinite. And infinite to a mathematician is a serious business. That’s more energy than all of the energy emitted by all of the stars in the visible universe. While that energy is mind-boggling in its scale, it isn’t infinite. Imagining the energy of the entire universe concentrated in a single point is just unbelievable, and infinite energy is much more than that.

    Therefore, infinities in real calculations are a clear sign that you’ve pushed your model beyond the realm of applicability and you need to start looking to find some new physical principles that you’ve overlooked in your simplified model.

    In the modern day, scientists have tried to solve the same conundrum that so flummoxed Einstein. And the reason is simple: The goal of science is to explain all of physical reality, from the smallest possible objects to the grand vista of the cosmos.

    The hope is to show that all matter originates from a small number of building blocks (perhaps only one) and a single underlying force from which the forces we currently recognize originates. Of the four known fundamental forces of nature, we have been able to devise quantum theories of three: electromagnetism, the strong nuclear force, and the weak nuclear forces. However, a quantum theory of gravity has eluded us.

    General relativity is no doubt an important advance, but until we can devise a quantum theory of gravity, there is no hope of devising a unified theory of everything. While there is no consensus in the scientific community on the right direction in which to proceed, there have been some ideas that have had limited success.

    Superstring theory

    The best-known theory that can describe gravity in the microworld is called superstring theory. In this theory, the smallest known particles should not be thought of as little balls, but rather tiny strings, kind of like an incredibly small stick of uncooked spaghetti or a micro-miniature Hula-Hoop. The basic idea is that these tiny strings (which are smaller compared to a proton than a proton is compared to you) vibrate, and each vibration presents a different fundamental particle.

    Employing a musical metaphor, an electron might be an A-sharp, while a photon could be a D-flat. In the same way that a single violin string can have many overtones, the vibrations of a single superstring can be different particles. The beauty of superstring theory is that it allows for one of the vibrations to be a graviton, which is a particle that has never been discovered but is thought to be the particle that causes gravity.

    It should be noted that superstring theory is not generally accepted, and indeed, some in the scientific community don’t even consider it to be a scientific theory at all. The reason is that, in order for a theory to be scientific, it must be able to be tested, and have the potential to be proven wrong. However, the very small scale of these theoretical strings makes it difficult to imagine any tests that could be done in the foreseeable future. And, some say, if you can’t realistically do a test, it isn’t science.

    Personally, I think that is an extreme opinion, as one can imagine doing such a test when technology advances. But that time will be far in the future.

    Another idea for explaining quantum gravity is called loop quantum gravity. This theory actually quantizes space-time itself. In other words, this model says that there is a smallest bit of space and a shortest time. This provocative idea suggests, among other things, that the speed of light might be different for different wavelengths. However, this effect, if it exists, is small and requires that light travel for great distances before such differences could be observed. Toward that end, scientists are looking at gamma-ray bursts, explosions so bright that they can be seen across billions of light-years — an example of the cosmic helping scientists study the microscopic.

    The simple fact is that we don’t yet have a good and generally accepted theory of quantum gravity. The question is simply just too difficult, for now. The microworld of the quantum and the macroworld of gravity have long resisted a life of wedded bliss and, at least for the moment, they continue to resist. However, scientists continue to find the linkage that blends the two. In the meantime, a theory of quantum gravity remains one of the most ambitious goals of modern science — the hope that we will one day fulfill Einstein’s unfinished dream.

    See the full article here .

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  • richardmitnick 12:00 pm on October 19, 2015 Permalink | Reply
    Tags: , Don Lincoln, ,   

    From Don Lincoln at FNAL: “What the heck is a Multiverse? ” Video 

    FNAL II photo

    Fermilab is an enduring source of strength for the US contribution to scientific research world wide.

    10.16.15

    The idea of a multiverse (short for multiple universes) can seem absurd. After all, the definition of universe means everything, so what does it mean to have multiple universes? In this video, Fermilab’s Dr. Don Lincoln lists a couple possible definitions for a multiverse. The reality in which we live might indeed be a very strange place.

    Watch, enjoy, learn.

    See the full article here .

    Please help promote STEM in your local schools.

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    Fermilab Campus

    Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a US Department of Energy national laboratory specializing in high-energy particle physics. Fermilab is America’s premier laboratory for particle physics and accelerator research, funded by the U.S. Department of Energy. Thousands of scientists from universities and laboratories around the world
    collaborate at Fermilab on experiments at the frontiers of discovery.

     
  • richardmitnick 4:18 pm on October 7, 2015 Permalink | Reply
    Tags: , Don Lincoln, , ,   

    From DON Lincoln (FNAL) for NOVA: “Neutrino Physicists win Nobel, but Neutrino Mysteries Remain” 

    PBS NOVA

    NOVA

    07 Oct 2015
    FNAL Don Lincoln
    Don Lincoln

    Neutrinos are the most enigmatic of the subatomic fundamental particles. Ghosts of the quantum world, neutrinos interact so weakly with ordinary matter that it would take a wall of solid lead five light-years deep to stop the neutrinos generated by the sun. In awarding this year’s Nobel Prize in physics to Takaaki Kajita (Super-Kamiokande Collaboration/University of Tokyo) and Arthur McDonald (Sudbury Neutrino Observatory Collaboration/Queen’s University, Canada) for their neutrino research, the Nobel committee affirmed just how much these “ghost particles” can teach us about fundamental physics. And we still have much more to learn about neutrinos.

    Super-Kamiokande experiment Japan
    Super-Kamiokande experiment Japan

    Sudbury Neutrino Observatory
    Sudbury Neutrino Observatory

    1
    View from the bottom of the SNO acrylic vessel and photomultiplier tube array with a fish-eye lens. This photo was taken immediately before the final, bottom-most panel of photomultiplier tubes was installed. Photo courtesy of Ernest Orlando, Lawrence Berkeley National Laboratory.

    Neutrinos are quantum chameleons, able to change their identity between the three known species (called electron-, muon– and tau-neutrinos). It’s as if a duck could change itself into a goose and then a swan and back into a duck again. Takaaki Kajita and Arthur B. McDonald received the Nobel for finding the first conclusive proof of this identity-bending behavior.

    In 1970, chemist Ray Davis built a large experiment designed to detect neutrinos from the sun. This detector was made up of a 100,000-gallon tank filled with a chlorine-containing compound. When a neutrino hit a chlorine nucleus, it would convert it into argon. In spite of a flux of about 100,000 trillion solar neutrinos per second, neutrinos interact so rarely that he expected to see only about a couple dozen argon atoms after a week’s running.

    But the experiment found even fewer argon atoms than predicted, and Davis concluded that the flux of electron-type neutrinos hitting his detector was only about a third of that emitted by the sun. This was an incredible scientific achievement and, for it, Davis was awarded a part of the 2002 Nobel Prize in physics.

    Explaining how these neutrinos got “lost” in their journey to Earth would take nearly three decades. The correct answer was put forth by the Italian-born physicist Bruno Pontecorvo, who hypothesized that the electron-type neutrinos emitted by the sun were morphing, or “oscillating,” into muon-type neutrinos. (Note that the tau-type neutrino was postulated in 1975 and observed in 2000; Pontecorvo was unaware of its existence.) This also meant that neutrinos must have mass—a surprise, since even in the Standard Model of particle physics, our most modern theory of the behavior of subatomic particles, neutrinos are treated as massless.

    3
    The Standard Model of elementary particles (more schematic depiction), with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth.

    So, if neutrinos could really oscillate, we would know that our current theory is wrong, at least in part.

    In 1998, a team of physicists led by Takaaki Kajita was using the Super Kamiokande (SuperK) experiment in Japan to study neutrinos created when cosmic rays from space hit the Earth’s atmosphere. SuperK was an enormous cavern, filled with 50,000 tons of water and surrounded by 11,000 light-detecting devices called phototubes. When a neutrino collided with a water molecule, the resulting debris from the interaction would fly off in the direction that the incident neutrino was traveling. This debris would emit a form of light called Cerenkov radiation and scientists could therefore determine the direction the neutrino was traveling.

    4
    Cherenkov radiation glowing in the core of the Advanced Test Reactor [Idaho National Laboratory].

    By comparing the neutrinos created overhead, about 12 miles from the detector, to those created on the other side of the Earth, about 8,000 miles away, the researchers were able to demonstrate that muon-type neutrinos created in the atmosphere were disappearing, and that the rate of disappearance was related to the distance that the neutrinos traveled before being detected. This was clear evidence for neutrino oscillations.

    Just a few years later, in 2001, the Sudbury Neutrino Observatory (SNO) experiment, led by Arthur B. McDonald, was looking at neutrinos originating in the sun. Unlike previous experiments, the SNO could identify all three neutrino species, thanks to its giant tank of heavy water (i.e. D2O, two deuterium atoms combined with oxygen). SNO first used ordinary water to measure the flux of electron-type neutrinos and then heavy water to observe all three types. The SNO team was able to demonstrate that the neutrino flux of all three types of neutrinos agreed exactly with those emitted by the sun, but that the flux of electron-type was lower than would be expected in a no-oscillation scenario. This experiment was a definitive demonstration of the oscillation of solar neutrinos.

    With the achievements of both the SuperK and SNO experiments, it is entirely fitting that Kajita and McDonald share the 2015 Nobel Prize in physics. They demonstrated that neutrinos oscillate and, therefore, that neutrinos have mass. This is a clear crack in the impressive façade of the Standard Model of particle physics and may well lead to a better and more complete theory.

    The neutrino story didn’t end there, though. To understand the phenomenon in greater detail, physicists are now generating beams of neutrinos at many sites over the world, including Fermilab, Brookhaven, CERN and the KEK laboratory in Japan. Combined with studies of neutrinos emitted by nuclear reactors, significant progress has been made in understanding the nature of neutrino oscillation.

    Real mysteries remain. Our measurements have shown that the mass of each neutrino species is different. That’s why we know that some must have mass: if they are different, they can’t all be zero. However, we don’t know the absolute mass of the neutrino species—just the mass differences. We don’t even know which species is the heaviest and which is the lightest.

    The biggest question in neutrino oscillation physics, though, is whether neutrinos and antimatter neutrinos oscillate the same way. If they don’t, this could explain why our universe is composed solely of matter even while we believe that matter and antimatter existed in equal quantities right after the Big Bang.

    Accordingly, Fermilab, America’s premier particle physics laboratory, has launched a multi-decade effort to build the world’s most intense beam of neutrinos, aimed at a distant detector located 800 miles away in South Dakota.

    Sanford Underground Research Facility Interior
    Sanford Underground Research Facility

    Named the Deep Underground Neutrino Experiment (DUNE), it will dominate the neutrino frontier for the foreseeable future.
    FNAL DUNE
    FNAL Dune & LBNF
    LBNF/DUNE

    This year’s Nobel Prize acknowledged a great step forward in our understanding of these ghostly, subatomic chameleons, but their entire story hasn’t been told. The next few decades will be a very interesting time.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    NOVA is the highest rated science series on television and the most watched documentary series on public television. It is also one of television’s most acclaimed series, having won every major television award, most of them many times over.

     
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