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

by Livio, Mario

  This was a genuine tour de force. The massive, 108-page paper started with a romantic touch: two contradictory quotes from Shakespeare about the question of whether the stars govern humanity’s fate. The first, from King Lear, reads: “It is the stars, the stars above us, govern our conditions.” This is followed by the words “but perhaps” preceding the second quote, from Julius Caesar: “The fault, dear Brutus, is not in our stars, but in ourselves.” The paper ended with a call to observers to make every possible effort to determine the relative abundances of different isotopes in stars, since those could truly be used to test the different nuclear reaction schemes. Figure 22 shows a picture taken at the Institute of Theoretical Astronomy in Cambridge in 1967. Fred Hoyle is in the middle of the second row, with Margaret Burbidge to his left. Willy Fowler is in the middle of the front row, with Geoff Burbidge to his right.

  Figure 22

  There was one thing that the B2FH paper did not achieve. No matter how hard they tried, Hoyle and his collaborators did not manage to account for the abundances of the lightest elements by forming them inside stars. Deuterium, lithium, beryllium, and boron were just too fragile—the heat in stellar interiors was sufficient for these elements to be destroyed by nuclear reactions, rather than created. Helium, the second most abundant element in the cosmos, proved to be problematic too. This may sound surprising, since stars are clearly forming helium. After all, isn’t the fusion of four hydrogens into helium the main source of power for most Sun-like stars? The difficulty turned out to be not at all with synthesizing helium in general, but with synthesizing enough of it. Detailed calculations have shown that nucleosynthesis in stars would predict for helium a cosmic abundance of only about 1 percent to 4 percent, while the observed value is about 24 percent. This left the big bang as the lone source for the lightest elements, just as Gamow and Alpher had suggested.

  You may have noticed that the story of the genesis of the elements—the “history of matter,” as Hoyle called it—contains in it some sort of “cosmic compromise.” Gamow wanted all the elements to have been created within a few minutes following the big bang (“in less time than it takes to cook a dish of duck and roast potatoes”). Hoyle wanted all the elements to be forged inside stars during the long process of stellar evolution. Nature chose a give-and-take: Light elements such as deuterium, helium, and lithium were indeed synthesized in the big bang, but all the heavier elements, and in particular those essential for life, were cooked in stellar interiors.

  Hoyle got a chance to present his version of the history of matter even at the Vatican. Just a few months before the B2FH paper appeared in print, the Pontifical Academy of Sciences and the Vatican Observatory organized a scientific meeting on “Stellar Populations” at the Vatican. The two dozen invitees included some of the most distinguished scientists in astronomy and astrophysics at the time. Both Fowler and Hoyle presented their results on the synthesis of the elements, and Hoyle was also asked to give a summary of the entire meeting from a physical point of view. The Dutch astronomer Jan Oort summarized from an astronomical perspective. At the opening of the meeting, on May 20, 1957, the participants met Pope Pius XII. Figure 23 shows Hoyle shaking the Pope’s hand. Willy Fowler (with his back to us) stands to Hoyle’s right, and Walter Baade (facing us) is to the Pope’s right.

  The rest, as they say, is history. The experimental and theoretical program at Kellogg Lab became, under Willy Fowler’s dynamic leadership, the hub for nuclear astrophysics. Fowler went on to win the Nobel Prize in physics in 1983 (together with astrophysicist Subramanyan Chandrasekhar). Many people, including Fowler himself, felt that Hoyle should have also shared the prize. In 2008 Geoffrey Burbidge went so far as to say, “The theory of stellar nucleosynthesis is attributable to Fred Hoyle alone, as shown by his papers in 1946 and 1954 and the collaborative work of B2FH. In writing up B2FH, all of us incorporated the earlier work of Hoyle.”

  Figure 23

  Why then wasn’t the Nobel Prize awarded to Hoyle? Opinions vary. Geoff Burbidge concluded, based on private correspondence, that a major reason for the exclusion was a perception (which he insisted was unjustified) that Fowler was the leader of B2FH. Hoyle himself apparently thought that he was denied the prize because of his criticism of the Nobel committee when it decided to award the Nobel Prize for the discovery of pulsars to Antony Hewish instead of to his graduate student Jocelyn Bell, who actually made the discovery. Others thought that Hoyle’s insistence on unorthodox views concerning the big bang, which we shall discuss in detail in the next chapter, might have played a role in his not getting the prize.

  What were those dissenting views? What was the background for Hoyle’s opposition to the big bang?

  During the years of World War II, Hoyle found himself working at the Admiralty Signals Establishment in Witley, Surrey. There he befriended two of his younger colleagues, Hermann Bondi and Thomas “Tommy” Gold, both of them Austrian-born Jews who’d escaped to England following the rise of Nazism. Ironically, prior to their work for the navy at Witley, the British government had interned the two men as enemy aliens because of their Austrian roots.

  This is how Gold described his initial impression of Hoyle: “He seemed so strange; he seemed never to listen when people were talking to him, and his broad North Country accent seemed quite out of place.” Very quickly, however, his opinion changed:

  I also discovered that I had misinterpreted Hoyle’s attitude of apparently not listening. In fact, he listened very carefully and had an extremely good memory, as I would find out later when he frequently had remembered what I had said much better than myself. I think he put on this air not to say, “I am not listening,” but instead “don’t try to influence me, I am going to make up my own mind.”

  In their spare moments at the naval radar research facility, the trio of Hoyle, Bondi, and Gold started to discuss astrophysics, and these collaborative exchanges continued after the war. In 1945 all three returned to Cambridge, and until 1949 they spent a few hours together every day at Bondi’s place. It was during that period that they started thinking about cosmology—the study of the entire observable universe, all treated as one entity. The Royal Astronomical Society asked Bondi to write what was then called a note, which was really a review article that would bring together an extensive body of knowledge. Hoyle suggested cosmology as the topic, since in his view “the subject had been in abeyance for a long time.” To bring himself up to speed on the subject, Bondi immersed himself in the existing literature, including a sweeping 1933 article entitled “Relativistic Cosmology” by physicist Howard Percy Robertson. Hoyle, who had previously read the article, also decided to go through it again in more detail. They both realized that the almost encyclopedic essay rather dispassionately covered various possibilities for cosmic evolution without offering an opinion. In his typical nonconformist fashion, Hoyle immediately started thinking, “Has he [Robertson] really thrown his net wide enough? Are there any other possibilities?” At the same time, Gold was thrusting himself into more philosophical ideas about the universe. These were the seeds for the theory of steady state cosmology, which was put forward in 1948. As we shall soon discover, the theory had been a serious contender to the big bang for more than fifteen years before it became the focus of often-acrimonious controversy.

  CHAPTER 9

  THE SAME THROUGHOUT ETERNITY?

  Bold ideas, unjustified anticipations, and speculative thought are our only means of interpreting nature . . . Those among us who are unwilling to expose their ideas to the hazard of refutation do not take part in the scientific game.

  —KARL POPPER

  Fred Hoyle’s most enduring works were in the areas of nuclear astrophysics and stellar evolution. Yet most of those who remember him from his popular books and prominent radio programs know him as a cosmologist and co-originator of the idea of a steady state universe. What does being a cosmologist really mean?

  The question “How close is the nearest planet to Earth?” is not a que
stion in modern cosmology. Even a question on a larger scale, such as “What is the distance from the Milky Way to its nearest galaxy neighbor?” is not considered to be a question in cosmology. Cosmology deals with the average properties of our observable universe—the ones you obtain once you smooth out, over the range that our most powerful telescopes can reach. Even though galaxies tend to reside in small groups or in rich clusters, both held together by the force of gravity, once we sample large enough volumes, the universe appears to be very homogeneous and isotropic. In other words, there is no privileged position in the universe, and things look the same in all directions. Statistically speaking, any cosmic cube with a side of five hundred million light-years or larger would look roughly the same in terms of its contents, irrespective of its location in the universe. (One light-year is the distance light travels in one year, or about six trillion miles.) This broad-brush homogeneity becomes increasingly more accurate the larger the scale, up to the “horizon” of our telescopes. Cosmology deals with precisely those questions that would yield the same answer independent of the galaxy we happen to be in or the direction in which we happen to point our telescope.

  Einstein had introduced the assumption of the large-scale homogeneity and isotropy of space in 1917, but this simplifying conjecture was elevated to the status of a fundamental principle in a paper published in 1933 by the English astrophysicist Edward Arthur Milne. Milne called his principle the “extended principle of relativity,” requiring that “not only the laws of nature but also the events occurring in nature, the world itself, must appear the same to all observers, wherever they be.” Today the stipulation of homogeneity and isotropy is known as the cosmological principle (a name coined by the German astronomer Erwin Finlay-Freundlich), and the most powerful direct evidence for its validity comes from observations of the “afterglow of creation”: the cosmic microwave background radiation. This radiation is a relic of the primeval hot, dense, and opaque fireball. It comes from all directions and is isotropic to better than one part in ten thousand. (In the words of astronomer Bob Kirshner: “much smoother than a baby’s bottom.)” Large-scale galaxy surveys also indicate a high degree of homogeneity. In all surveys that encompass a large enough slice of the cosmos to constitute a “fair sample,” even the most conspicuous structural features are dwarfed and smoothed out.

  Since the cosmological principle has proven to be so effective when applied to different positions in space, it was only natural to wonder whether it could be extended to apply to time as well. That is, could one argue that the universe is unchanging in its large-scale appearance as well as in its physical laws? This was the big question raised by Hoyle, Bondi, and Gold in 1948. Amusingly enough, the illustrious trio may have been inspired to ask this question by a British horror film called Dead of Night. (Figure 24 shows the original poster of the film.) Here is how Hoyle himself described the sequence of events:

  Figure 24

  In a sense, the steady-state theory may be said to have begun on the night that Bondi, Gold, and I patronized one of the cinemas in Cambridge . . . It [the film Dead of Night] was a sequence of four ghost stories, seemingly disconnected as told by the several characters in the film, but with the interesting property that the end of the fourth story connected unexpectedly with the beginning of the first, thereby setting-up the potential for a never-ending cycle.

  When the three colleagues returned to Trinity College, Gold asked suddenly, “What if the universe is like that?” meaning that the universe could be eternally circling on itself without a beginning or an end. The idea was certainly intriguing, except that at first blush it appeared to be at odds with the discovery by the Belgian priest and cosmologist Georges Lemaître and astronomer Edwin Hubble that the universe was expanding. The cosmic expansion seemed to be pointing rather to a linear evolution, starting from a dense and hot beginning (the big bang) and indicating a clear direction for the arrow of time. Hoyle, Bondi, and Gold were fully aware of these findings, since Hubble’s discovery and its potential implications had already featured frequently in the discussions of the trio. In an interview in 1978, Gold reminisced about those intense analyses:

  What happened was that there was a period when Hoyle and I would sit around in Bondi’s rooms in college a substantial amount of the time and discuss, as Hoyle always insisted, what does the Hubble thing really mean? . . . all those galaxies, all this flying apart, would the space be terribly empty afterwards? Has it been very dense in the past?

  All of those contemplations had led to an unexpected outcome: Hoyle, Bondi, and Gold started to think seriously about the problem of whether the observed cosmic expansion could somehow be accommodated in the context of a theory of an unchanging universe.

  But before delving into that fascinating topic, let’s go back to the 1920s for a moment. The discovery of the expanding universe is not only the greatest astronomical discovery of the twentieth century, it plays such a crucial role both in Hoyle’s blunder and Einstein’s that it would be instructive to take a short detour to review the history of this breakthrough. This story is especially pertinent, since a new, very intriguing twist in the chronicle of events created a huge buzz in the astronomical and history of science communities in 2011.

  Cosmic Expansion: Lost (in Translation) and Found

  When cosmologists say that our universe is expanding, they base this statement primarily on evidence that comes from the apparent motion of galaxies. A highly simplified, oft-used example can help visualize the concept.

  Imagine a two-dimensional world that exists only on the surface of a rubber sphere (figure 25). That is, galaxies in this world are simply small, round chads (like those created with a hole punch) glued on the surface. Neither the inside of the sphere nor the space outside it exists for the inhabitants of this world; their entire universe is just the surface. Note that this world has no center; no chad on the surface is different from any other chad. (Remember that the center of the sphere itself is not a part of this world.) This universe also has no boundary or edge. If a point were to move in a certain direction on the spherical surface, it would never reach an edge.

  Figure 25

  Now, what would happen if this sphere were being inflated? Irrespective of which chad on the surface you happen to belong to, you will see all the other chads receding and rushing away from you. Moreover, chads that are more distant will be receding faster: A chad that is twice as far as another will be moving twice as fast (since it will cover twice the distance during the same period of time). In other words, the speed of recession will be proportional to the distance. Einstein’s theory of general relativity articulates that the fabric of space-time (the combination of space and time into a single continuum) in our universe behaves in such a way that we can turn around this simplified example. That is, the discovery that all the distant galaxies are receding from us, combined with the fact that the speed of recession is proportional to the distance, imply that space in our universe is stretching. (We shall return to this topic in chapter 10.) Note that the expansion of the universe cannot be compared with an exploding hand grenade. In the latter case, the explosion occurs within a preexisting space, and it has a definite center (and an edge). In the universe, the receding motion arises because the fabric of space itself is stretching. No galaxy is any different from any other galaxy; from every location, you will see all the other galaxies rushing away in all directions.

  The key figure with whom the discovery of cosmic expansion is usually associated is astronomer Edwin Hubble, after whom the Hubble Space Telescope was named. Hubble is commonly credited with having measured (in collaboration with his assistant, Milton Humason) the distances and recession velocities to a few dozen galaxies, and having established, in a paper published in 1929, the law that bears his name, stating that galaxies recede from us at speeds that are proportional to their distance. From that “Hubble’s law,” Hubble and Humason derived an overall current expansion rate suggesting that with every 3.26 million light-years
of distance, the recession speed of the galaxies increases by about 500 kilometers per second, or about 311 miles per second.

  Given the relatively small-distance range of Hubble’s original observations, it would have been a real leap of faith to infer from them a universal expansion were it not for some supporting theoretical ideas, a few of which had even preceded the observations. In fact, as early as 1922, the Russian mathematician Aleksandr Friedmann showed that general relativity allowed for an expanding, matter-filled, unbounded universe. While few took notice of Friedmann’s results (other than Einstein himself, who eventually acknowledged their mathematical correctness but dismissed them, since he thought that “a physical significance can hardly be ascribed to them”), the notion of a dynamical universe was starting to gain influence during the 1920s. Consequently, the interpretation of Hubble’s observations in terms of an expanding universe became popular fairly fast.

  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.”