Books, Brochures, and Chapters>Book:  Hawking , Stephen W. and Mlodinow , Leonard (2011-09-01), The Grand Design, Bantam, Retrieved on 2011-12-12
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  • Folksonomies: science quantum physics m-theory

    Memes

    12 DEC 2011

     Ionian Science

    According to legend, the first mathematical formulation of what we might today call a law of nature dates back to an Ionian named Pythagoras (ca. 580 BC-ca. 490 bc), famous for the theorem named after him: that the square of the hypotenuse (longest side) of a right triangle equals the sum of the squares of the other two sides. Pythagoras is said to have discovered the numerical relationship between the length of the strings used in musical instruments and the harmonic combinations of the soun...
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    Stephen Hawking provides a fascinating summary of what the ancient Ionians knew about the natural world.

    12 DEC 2011

     What is a "Law of Nature"?

    Our modern understanding of the term "law of nature" is an issue philosophers argue at length, and it is a more subde question than one may at first think. For example, the philosopher John W. Carroll compared the statement "All gold spheres are less than a mile in diameter" to a statement like "All uranium-23 spheres are less than a mile in diameter." Our observations of the world tell us that there are no gold spheres larger than a mile wide, and we can be pretty confident there never will ...
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    Many laws of nature are conclusions drawn from the larger "interconnected system of laws."

    12 DEC 2011

     Human Behavior is Dictated by Laws of Nature, but Too Com...

    While conceding that human behavior is indeed determined by the laws of nature, it also seems reasonable to conclude that the outcome is determined in such a complicated way and with so many variables as to make it impossible in practice to predict. For that one would need a knowledge of the initial state of each of the thousand trillion trillion molecules in the human body and to solve something like that number of equations. That would take a few billion years, which would be a bit late to ...
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    So the hypothesis that we have freewill is convenient, and the Economic model that we act in our best interests helpful, but not always correct.

    12 DEC 2011

     The Brain Creates Models of the World

    We make models in science, but we also make them in everyday life. Model-dependent realism applies not only to scientific models but also to the conscious and subconscious mental models we all create in order to interpret and understand the everyday world. There is no way to remove the observer—us—from our perception of the world, which is created through our sensory processing and through the way we think and reason. Our perception—and hence the observations upon which our theories are...
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    Using the eye as an example, Hawking describes how our brains model the outside world and builds theories about it.

    12 DEC 2011

     Earth's Curve, Flat Maps, and the Fastest Route Between T...

    Imagine, say, that you wanted to travel from New York to Madrid, two cities that are at almost the same latitude. If the earth were flat, the shortest route would be to head straight east. If you did that, you would arrive in Madrid after traveling 3,707 miles. But due to the earth's curvature, there is a path that on a flat map looks curved and hence longer, but which is actually shorter. You can get there in 3,605 miles if you follow the great-circle route. which is to first head northeast,...
    Folksonomies: geometry models maps
    Folksonomies: geometry models maps
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    Because the Earth is a sphere and maps are flat, the fastest route between two points on a map is actually a curved line and airlines take this into account when plotting flight paths.

    12 DEC 2011

     The Four Forces of Nature

    1. Gravity. This is the weakest of the four, but it is a long-range force and acts on everything in the universe as an attraction. This means that for large bodies the gravitational forces all add up and can dominate over all other forces. 2. Electromagnetism. This is also long-range and is much stronger than gravity, but it acts only on particles with an electric charge. being repulsive between charges of the same sign and attractive between charges of the opposite sign. This means the ele...
    Folksonomies: physics laws laws of nature
    Folksonomies: physics laws laws of nature
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    Gravity, Electromagnetism, the Strong and Weak Nuclear Forces with brief descriptions.

    12 DEC 2011

     QED Explained

    Feynman's graphical method provides a way of visualizing each term in the sum over histories. Those pictures, called Feynman diagrams, are one of the most important tools of modern physics. In QED the sum over all possible histories can be represented as a sum over Feynman diagrams like those below, which represent some of the ways it is possible for two electrons to scatter off each other through the electromagnetic force. In these diagrams the solid lines represent the electrons and the wav...
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    A good description of the Feynman Diagrams from QED and how the infinite possibilities must be accounted for in mathematics dealing with them.

    12 DEC 2011

     Implications of M-Theory

    Whether M-theory exists as a single formulation or only as a network, we do know some of its properties. First, M-theory has eleven space-time dimensions, not ten. String theorists had long suspected that the prediction often dimensions might have to be adjusted, and recent work showed that one dimension had indeed been overlooked. Also, M-theory can contain not just vibrating strings but also point particles, two-dimensional membranes. three-dimensional blobs, and other objects that are more...
    Folksonomies: quantum physics m-theory
    Folksonomies: quantum physics m-theory
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    M-Theory allows for multiple Universes and 11 dimensions.

    13 DEC 2011

     Origins of the Big Bang Theory and Evidence For It

    That the universe is expanding was news to Einstein. But the possibility that the galaxies are moving away from each other had been proposed a few years before Hubble's papers on theoretical grounds arising from Einstein's own equations. In 1922, Russian physicist and mathematician Alexander Friedmann investigated what would happen in a model universe based upon two assumptions that greatly simplified the mathematics: that the universe looks identical in every direction, and that it looks tha...
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    The logical conclusion drawn by a Catholic Priest and the Cosmic Background Radiation (CMBR) we see left over from the event.

    13 DEC 2011

     The Weak Anthropic Principle

    Our very existence imposes rules determining from where and at what time it is possible for us to observe the universe. That is, the fact of our being restricts the characteristics of the kind of environment in which we find ourselves. That principle is called the weak anthropic principle. (We'll see shortly why the adjective weak" is attached.) A better term than "anthropic principle" would have been "selection principle," because the principle refers to how our own knowledge of our existenc...
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    A quick definition and explanation of this theory of why we live in a universe where we could emerge.

    13 DEC 2011

     The Strong Anthropic Principle

    The weak anthropic principle is not very controversial. But there is a stronger form that we will argue for here, although it is regarded with disdain among some physicists. The strong anthropic principle suggests that the fact that we exist imposes constraints not just on our environment but on the possible form and content of the laws of nature themselves. The idea arose because it is not only the peculiar characteristics of our solar system that seem oddly conducive to the development of h...
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    Our existence puts constraints on the very laws of nature.

    13 DEC 2011

     Carbon VS Silicon Life

    Though one might imagine "living" organisms such as intelligent computers produced from other elements, such as silicon, it is doubtful that life could have spontaneously evolved in the absence of carbon. The reasons for that are technical but have to do with the unique manner in which carbon bonds with other elements. Carbon dioxide, for example, is gaseous at room temperature, and biologically very useful. Since silicon is the element directly below carbon on the periodic table, it has simi...
    Folksonomies: life alien life xenobiology
    Folksonomies: life alien life xenobiology
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    While we can imagine living computers, it is hard to imagine silicon life spontaneously forming in the universe.

    13 DEC 2011

     M-Theory Describes a Universe That Creates Itself

    If the total energy of the universe must always remain zero, and it costs energy to create a body, how can a whole universe be created from nothing. That is why there must be a law like gravity. Because gravity is attractive, gravitational energy is negative: One has to do work to separate a gravitationally bound system. such as the earth and moon. This negative energy can balance the positive energy needed to create matter, but it's not quite that simple. The negative gravitational energy of...
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    How it does this, I don't fully understand from this passage.

    13 DEC 2011

     The Precarious Laws of Nature

    By examining the model universes we generate when the theories of physics are altered in certain ways, one can study the effect of changes to physical law in a methodical manner. It turns out that it is not only the strengths of the strong nuclear force and the electromagnetic force that are made to order for our existence. Most of the fundamental constants in our theories appear fine tuned in the sense that if they were altered by only modest amounts, the universe would be qualitatively diff...
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    If the laws of nature were different by a very small amount, the Universe would not work in such a way as to produce life.

    13 DEC 2011

     Stable Orbits are Impossible in More Than Three Dimensions

    If one assumes that a few hundred million years in stable orbit are necessary for planetary life to evolve, the number of space dimensions is also fixed by our existence. That is because, according to the laws of gravity, it is only in three dimensions that stable elliptical orbits are possible. Circular orbits are possible in other dimensions, but those, as Newton feared, are unstable. In any but three dimensions even a small disturbance, such as that produced by the pull of the other planet...
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    The force of gravity gets weaker the more dimensions you add to the Universe, making stable planetary orbits impossible.

    13 DEC 2011

     The Creation of Carbon in Stars

    The first step occurs when older stars start to accumulate helium, which is produced when two hydrogen nuclei collide and fuse with each other. This fusion is how stars create the energy that warms us. Two helium atoms can in turn collide to form beryllium, an atom whose nucleus contains four protons. Once beryllium is formed, it could in principle fuse with a third helium nucleus to form carbon. But that doesn't happen, because the isotope of beryllium that is formed decays almost immediatel...
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    Requires a very delicate balance of natural laws. If the strong nuclear force were to change by as little as 0.5 percent, there would be no carbon or oxygen in the Universe.

    12 DEC 2011

     M-Theory is a Map

    M-theory is not a theory in the usual sense. It is a whole family of different theories, each of which is a good description of observations only in some range of physical situations. It is a bit like a map. As is weU known, one cannot show the whole of the earth's surface on a single map. The usual Mercator projection used for maps of the world makes areas appear larger and larger in the far north and south and doesn't cover the North and South Poles. To faithfully map the entire earth, one ...
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    Just as there is no single flat map that can describe the Earth's surface, M-Theory is a collection of models that describe the laws of our Universe.