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Mario Livio

Brilliant Blunders: From Darwin to Einstein – Colossal Mistakes by Great Scientists That Changed Our Understanding of Life and the Universe

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  • Hittingthespacebarcompartió una citahace 7 años
    “Experience is the name everyone gives to their mistakes.”
  • Юлияcompartió una citahace 10 años
    There is no better way to end a book on blunders than with an important reminder—a plea for humility, if you like—that nobody can express more eloquently than Darwin:

    We must, however, acknowledge, as it seems to me, that man with all his noble qualities, with sympathy which feels for the most debased, with benevolence which extends not only to other men but to the humblest living creature, with his god-like intellect which has penetrated into the movements and constitution of the solar system—with all these exalted powers—Man still bears in his bodily frame the indelible stamp of his lowly origin.
  • Юлияcompartió una citahace 10 años
    Einstein had to find a way to keep the universe described by his equations from collapsing under its own weight. To achieve a static configuration with a uniform distribution of matter, Einstein guessed that there had to be some repulsive force that could balance gravity precisely. Consequently, just a little over a year after he had published his theory of general relativity, Einstein came up with what appeared, at least at first glance, to be a brilliant solution. In a seminal paper entitled “Cosmological Considerations on the General Theory of Relativity,” he introduced a new term into his equations. This term gave rise to a surprising effect: a repulsive gravitational force! The cosmic repulsion was supposed to act throughout the universe, causing every part of space to be pushing on every other part—just the opposite of what matter and energy do. As we shall soon discover, mass and energy warp space-time in such a way that matter falls together. The fresh cosmological term effectively warped space-time in the opposite sense, causing matter to move apart. The value of a new constant that Einstein introduced (on top of the familiar strength of gravity) determined the strength of the repulsion. The Greek letter lambda, Λ, denoted the new constant, now known as the cosmological constant. Einstein demonstrated that he could choose the value of the cosmological constant to precisely balance gravity’s attractive and repulsive forces, resulting in a static, eternal, homogeneous, and unchanging universe of a fixed size. This model later became known as “Einstein’s universe.” Einstein concluded his paper with what turned out to be a pregnant comment: “That term is necessary only [my emphasis] for the purpose of making possible a quasi-static distribution of matter, as required by the fact of the small velocities of the stars.” You’ll notice that Einstein talks here about “velocities of stars” and not of galaxies, since the existence and motions of the latter were still beyond the astronomical horizons at the time.
  • Юлияcompartió una citahace 10 años
    Einstein’s pivotal premise in general relativity was a truly revolutionary idea: What we perceive as the force of gravity is merely a manifestation of the fact that mass and energy cause space-time to warp. In this sense, Einstein was closer, at least in spirit, to the geometrical (rather than dynamical) views of the astronomers of ancient Greece than to Newton and his emphasis on forces. Instead of being a rigid and fixed background, space-time can flex, curve, and stretch in response to the presence of matter and energy, and those warps, in turn, cause matter to move the way it does. As the influential physicist John Archibald Wheeler once put it, “Matter tells space-time how to curve, and space-time tells matter how to move.” Matter and energy become eternal partners to space and time.
    By introducing general relativity, Einstein dazzlingly solved the problem of the faster-than-light propagation of the force of gravity—the predicament that bedeviled Newton’s theory. In general relativity, the speed of transmission boils down to how fast ripples in the fabric of space-time can travel from one point to another. Einstein showed that such warps and swells—the geometrical manifestation of gravity—travel precisely at the speed of light. In other words, changes in the gravitation field cannot be transmitted instantaneously.
  • Юлияcompartió una citahace 10 años
    When I throw my keys up in the air, they reach some maximum height, and then they fall back into my hand. Only for an instant do the keys stay still, as they reach the highest point. Obviously, the gravitational pull of the Earth is responsible for this behavior. If somehow I could propel the keys to a speed exceeding about seven miles per second, they would escape the Earth altogether, as did, for instance, the Pioneer 10 spacecraft, with which communication was lost in 2003, when the probe was at a distance of more than seven billion miles from Earth. However, in the absence of an opposing force, the Earth’s gravity alone does not allow for the keys to float suspended in midair.
    Two scientists showed independently in the 1920s that the behavior of the cosmic space-time is expected to be very similar. Those two researchers, Russian mathematician and meteorologist Aleksandr Friedmann and Belgian priest and cosmologist Georges Lemaître, applied Einstein’s theory of general relativity to the universe as a whole. They soon realized that the gravitational attraction of all the matter and radiation in the universe implies that space-time, Einstein’s combination of space and time, can either stretch or contract, but it cannot stably stand still at a fixed extent. These important findings eventually provided the theoretical background for the discovery by Lemaître and Hubble that our universe is expanding.
  • Юлияcompartió una citahace 10 años
    Hoyle’s blunder was somewhat different from those of Darwin, Kelvin, and Pauling in two important respects. First, there was the issue of the scale of the topic, in the context of which the blunder occurred. Darwin’s blunder involved only one element of his theory (albeit an extremely important one). Kelvin’s blunder concerned an assumption at the basis of a particular calculation (a very meaningful one). Pauling’s blunder affected one specific model (unfortunately for the most crucial molecule). Hoyle’s blunder, on the other hand, concerned no less than an entire theory for the universe as a whole. Second and more important, Hoyle did nothing wrong in proposing the steady state model—unlike Darwin, who did not understand the implications of a faulty biological mechanism; Kelvin, who neglected unforeseen physical processes; and Pauling, who ignored basic rules of chemistry. The theory itself was bold, exceptionally clever, and it matched all the observational facts that existed at the time. Hoyle’s blunder was in his apparently pigheaded, almost infuriating refusal to acknowledge the theory’s demise even as it was being smothered by accumulating contradictory evidence, and in his use of asymmetrical criteria of judgment with respect to the big bang and steady state theories.
  • Юлияcompartió una citahace 10 años
    Physicists sometimes tend to ignore the history of their subject. After all, who cares who discovered what as long as the discoveries are made widely known. Only totalitarian regimes have been obsessed with insisting that all good ideas are homegrown. In an old joke about the Soviet Union, an important visitor is brought to the science museum in Moscow. In the first room, he sees a giant picture of a Russian man he had never heard of. When he asks who that person is, he is told, “This is so-and-so, the inventor of the radio.” In the second room: another giant portrait of a complete stranger. “The inventor of the telephone,” his host informs him. And so it continues for about a dozen rooms. In the final room, there is a picture that dwarfs by comparison all of the other pictures. “Who is this?” the visitor asks in astonishment. The host smiles and answers, “This is the man who invented all of those other men in the previous rooms.”
  • Юлияcompartió una citahace 10 años
    When the boisterous George Gamow came to summarize his own views on Hoyle’s role in the theory of the formation of the elements, he did so by a witty account that he entitled “New Genesis”:

    In the beginning God created radiation and ylem. And ylem was without shape or number, and the nucleons were rushing madly over the face of the deep. And God said: “Let there be mass two.” And there was mass two. And God saw deuterium, and it was good. And God said: “Let there be mass three.” And God saw tritium and tralphium [Gamow’s nickname for the isotope of helium 3He] and they were good. And God continued to call number after number until He came to the transuranium elements. But when He looked back on his work He found that it was not good. In the excitement of counting, He missed calling for mass five and so, naturally, no heavier elements could have been formed. God was very much disappointed, and wanted first to contract the universe again, and to start all over from the beginning. But it would be much too simple. Thus being almighty, God decided to correct His mistake in a most impossible way.

    And God said: “Let there be Hoyle.” And there was Hoyle. And God looked at Hoyle . . . and told him to make heavy elements in any way he pleased. And Hoyle decided to make heavy elements in stars, and to spread them around by supernovae explosions. But in doing so he had to obtain the same abundance curve which would have resulted from nucleosynthesis in ylem, if God would not have forgotten to call for mass five. And so, with the help of God, Hoyle made heavy elements in this way, but it was so complicated that nowadays neither Hoyle, nor God, nor anybody else can figure out exactly how it was done.
  • Юлияcompartió una citahace 10 años
    To continue the story of the formation of the elements, we need to remind ourselves of some of the very basic properties of atoms. Here is an extraordinarily brief refresher. All ordinary matter is composed of atoms, and all atoms have at their centers tiny nuclei (the atomic radius is more than 10,000 times the nuclear radius), around which electrons move in orbital clouds. The constituents of the nucleus are protons and neutrons, which are very similar in mass (a neutron is slightly heavier than a proton), each of them being about 1,840 times more massive than an electron. While neutrons bound in stable nuclei are stable, a free neutron is unstable—it decays with a mean lifetime of about fifteen minutes into a proton, an electron, and a virtually invisible, very light, electrically neutral particle called an antineutrino. Neutrons in unstable nuclei can decay in the same fashion.
    The simplest and lightest atom that exists is the hydrogen atom. It consists of a nucleus that contains only one proton. A single electron revolves around this proton in orbits the probability for which can be calculated using quantum mechanics. Hydrogen is also the most abundant element in the universe, constituting about 74 percent of all the ordinary (known as baryonic) matter. Baryonic matter is the stuff that makes up stars, planets, and human beings.
  • Юлияcompartió una citahace 10 años
    Eddington was one of the strongest champions of Einstein’s theory of relativity (especially general relativity). On one occasion, physicist Ludwik Silberstein approached Eddington and told him that people believed that only three scientists in the entire world understood general relativity, Eddington being one of them. When Eddington didn’t answer for a while, Silberstein encouraged him, “Don’t be so modest,” to which Eddington replied, “On the contrary. I’m just wondering who the third might be.”
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