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  • feedwordpress 09:01:38 on 2019/01/15 Permalink
    Tags: , , , , , , , string theory, ,   

    “The Universe is under no obligation to make sense to you”*… 


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    bubble

    Uppsala University researchers have devised a new model for the Universe – one that may solve the enigma of dark energy. Their new article, published in Physical Review Letters, proposes a new structural concept, including dark energy, for a universe that rides on an expanding bubble in an additional dimension.

    We have known for the past 20 years that the Universe is expanding at an ever accelerating rate. The explanation is the “dark energy” that permeates it throughout, pushing it to expand. Understanding the nature of this dark energy is one of the paramount enigmas of fundamental physics.

    It has long been hoped that string theory will provide the answer. According to string theory, all matter consists of tiny, vibrating “stringlike” entities. The theory also requires there to be more spatial dimensions than the three that are already part of everyday knowledge. For 15 years, there have been models in string theory that have been thought to give rise to dark energy. However, these have come in for increasingly harsh criticism, and several researchers are now asserting that none of the models proposed to date are workable.

    In their article, the scientists propose a new model with dark energy and our Universe riding on an expanding bubble in an extra dimension. The whole Universe is accommodated on the edge of this expanding bubble. All existing matter in the Universe corresponds to the ends of strings that extend out into the extra dimension. The researchers also show that expanding bubbles of this kind can come into existence within the framework of string theory. It is conceivable that there are more bubbles than ours, corresponding to other universes.

    The Uppsala scientists’ model provides a new, different picture of the creation and future fate of the Universe, while it may also pave the way for methods of testing string theory…

    Via AAAS Eureka Alerts

    (For a different emerging new theory– that may or may not be contradictory– see “Our universe has antimatter partner on the other side of the Big Bang.”)

    * Neil deGrasse Tyson

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    As we fumble with the fundamentals, we might send carefully-deduced birthday greetings to Richard Bevan Braithwaite; he was born on this date in 1900.  A Cambridge philosopher who specialized in the philosophy of science, he focused on the logical features common to all sciences.  Braithwaite was concerned with the impact of science on our beliefs about the world and the appropriate responses to that impact.  He was especially interested in probability (and its applications in decision theory and games theory) and in the statistical sciences.  He was president of the Aristotelian Society from 1946 to 1947, and was a Fellow of the British Academy.

    It was Braithwaite’s poker that Ludwig Wittgenstein reportedly brandished at Karl Popper during their confrontation at a Moral Sciences Club meeting in Braithwaite’s rooms in King’s. The implement subsequently disappeared. (See here.)

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  • feedwordpress 08:01:14 on 2018/07/09 Permalink
    Tags: , , , , Mysterium cosmographicum, , , string theory,   

    “The truth is not always beautiful, nor beautiful words the truth.”*… 


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    Does anyone who follows physics doubt it is in trouble? When I say physics, I don’t mean applied physics, material science or what Murray-Gell-Mann called “squalid-state physics.” I mean physics at its grandest, the effort to figure out reality. Where did the universe come from? What is it made of? What laws govern its behavior? And how probable is the universe? Are we here through sheer luck, or was our existence somehow inevitable?

    In the 1980s Stephen Hawking and other big shots claimed that physics was on the verge of a “final theory,” or “theory of everything,” that could answer these big questions and solve the riddle of reality. I became a science writer in part because I believed their claims, but by the early 1990s I had become a skeptic. The leading contender for a theory of everything held that all of nature’s particles and forces, including gravity, stem from infinitesimal, stringy particles wriggling in nine or more dimensions.

    The problem is that no conceivable experiment can detect the strings or extra dimensions…

    John Horgan examines physicist Sabine Hossenfelder‘s claim that desire for beauty and other subjective biases have led physicists astray: “How Physics Lost Its Way.”

    * Lao Tzu, Tao Te Ching

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    As we contemplate certainty, we might recall that it was on this date in 1595 that Johann Kepler (and here) published Mysterium cosmographicum (Mystery of the Cosmos), in which he described an invisible underlying structure determining the six known planets in their orbits.  Kepler thought as a mathematician, devising a structure based on only five convex regular solids; the path of each planet lay on a sphere separated from its neighbors by touching an inscribed polyhedron.

    It was a beautiful, an elegant model– and one that fit the orbital data available at the time.  It was, nonetheless, wrong.

    Detailed view of Kepler’s inner sphere

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  • feedwordpress 09:01:24 on 2018/01/16 Permalink
    Tags: , generator, , , , , , string theory, , Van de Graaff   

    “Doubtless we cannot see that other higher Spaceland now, because we have no eye in our stomachs”*… 


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    An ” Amplituhedron“, an illustration of multi-dimensional spacetime

    Our architecture, our education and our dictionaries tell us that space is three-dimensional. The OED defines it as ‘a continuous area or expanse which is free, available or unoccupied … The dimensions of height, depth and width, within which all things exist and move.’ In the 18th century, Immanuel Kant argued that three-dimensional Euclidean space is an a priori necessity and, saturated as we are now in computer-generated imagery and video games, we are constantly subjected to representations of a seemingly axiomatic Cartesian grid. From the perspective of the 21st century, this seems almost self-evident.

    Yet the notion that we inhabit a space with any mathematical structure is a radical innovation of Western culture, necessitating an overthrow of long-held beliefs about the nature of reality. Although the birth of modern science is often discussed as a transition to a mechanistic account of nature, arguably more important – and certainly more enduring – is the transformation it entrained in our conception of space as a geometrical construct.

    Over the past century, the quest to describe the geometry of space has become a major project in theoretical physics, with experts from Albert Einstein onwards attempting to explain all the fundamental forces of nature as byproducts of the shape of space itself. While on the local level we are trained to think of space as having three dimensions, general relativity paints a picture of a four-dimensional universe, and string theory says it has 10 dimensions – or 11 if you take an extended version known as M-Theory. There are variations of the theory in 26 dimensions, and recently pure mathematicians have been electrified by a version describing spaces of 24 dimensions. But what are these ‘dimensions’? And what does it mean to talk about a 10-dimensional space of being?…

    Experience says we live in three dimensions; relativity says four; string theory says it’s 10– or more… What are “dimensions” and how do they affect reality? Margaret Wertheim offers a guide: “Radical dimensions.”

    * Edwin A. Abbott, Flatland: A Romance of Many Dimensions

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    As we tax our senses, we might spare a thought for Robert Jemison Van de Graaff; he died on this date in 1967.  A physicist and engineer, he is best remembered for his creation of the Van de Graaff Generator, an electrostatic generator that creates very high electric potentials– very high voltage direct current (DC) electricity (up to 5 megavolts) at low current levels.  A tabletop version can produce on the order of 100,000 volts and can store enough energy to produce a visible spark. Such small Van de Graaff machines are used in physics education to teach electrostatics; larger ones are displayed in some science museums.

    Boy touching Van de Graaff generator at The Magic House, St. Louis Children’s Museum. Charged with electricity, his hair strands repel each other and stand out from his head.

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