The possibility of extraterrestrial life is a subject that has fascinated Hawking very much and on and off he speculates its possibility in a vigorous way. In fact he holds such a possibility quite firmly, perhaps more as a matter of a scientist’s faith than anything based on observed or observable facts. In one of his lectures he says: “Meeting a more advanced civilisation, at our present stage, might be a bit like the original inhabitants of America meeting Columbus. I don’t think they were better off for it.” But that will hardly be of any consequence when it comes to the procedural aspects of scientific observations and conclusions. ~ RYD   more »

John A. Wheeler, a visionary physicist and teacher who helped invent the theory of nuclear fission, gave black holes their name and argued about the nature of reality with Albert Einstein and Niels Bohr, died Sunday morning at his home in Hightstown, N.J. He was 96...

As a professor at Princeton and then at the University of Texas in Austin, Dr. Wheeler set the agenda for generations of theoretical physicists, using metaphor as effectively as calculus to capture the imaginations of his students and colleagues and to pose questions that would send them, minds blazing, to the barricades to confront nature. ...   more »

Imho, this is an important article about the pluses and minuses of religion, an interview with a former nun who has had many deep experiences of what she writes. Highly recommended. ~ ronjon

Karen Armstrong is a one-woman publishing industry, the author of nearly 20 books on religion. When her breakthrough book "A History of God" appeared in 1993, this British writer quickly became known as one of the world's leading historians of spiritual matters. Her work displays a wide-ranging knowledge of religious traditions -- from the monotheistic religions to Buddhism. What's most remarkable is how she carved out this career for herself after rejecting a life in the church.

At 17, Armstrong became a Catholic nun. She left the convent after seven years of torment. "I had failed to make a gift of myself to God," she wrote in her recent memoir, "The Spiral Staircase." While she despaired over never managing to feel the presence of God, Armstrong also bristled at the restrictive life imposed by the convent, which she described in her first book, "Through the Narrow Gate." When she left in 1969, she had never heard of the Beatles or the Vietnam War, and she'd lost her faith in God. ...   more »

...In 1964, Peter Higgs, a shy scientist in Edinburgh, added his name to that list by coming up with an ingenious theory that gave scientists the tools to explain how two classes of particles, which now appear to be different, were once one and the same. His theory proposes the existence of a single particle responsible for imparting mass to all things — a speck so precious it has come to be known as the "God particle." The scientific term for it is the Higgs boson, and to find it physicists are counting on the most powerful particle accelerator ever constructed: the Large Hadron Collider (LHC) at the CERN laboratory in Geneva, a 17-mile underground circuit that took 25 years to plan and $6 billion to build.

The LHC won't begin operation until this summer, but when Higgs, 78, made his first visit there on April 5, it was, in the nomenclature of particle physics, "an event." ...   more »

4) Here are the final letters by Leonard Susskind' and Lee Smolin in their email debate re the Anthropic Principle.

Smolin: ... My main point is that string theory will have much more explanatory power if the dominant mode of reproduction is through black holes, as is the case in the original version of CNS. This is the key point I would hope to convince Susskind and his colleagues about, because I am sure that the case they want to make is very much weakened if they rely on the Anthropic Principle (AP) and eternal inflation. ...

Susskind: ... Finally let me quote a remark of Smolin's that I find revealing. He says "It was worry about the possibility that string theory would lead to the present situation, which Susskind has so ably described in his recent papers, that led me to invent the Cosmological Natural Selection (CNS) idea and to write my first book. My motive, then as now, is to prevent a split in the community of theoretical physicists in which different groups of smart people believe different things, with no recourse to come to consensus by rational argument from the evidence." First of all, preventing a "split in the community of theoretical physicists" is an absurdly ridiculous reason for putting forward a scientific hypothesis.

But what I find especially mystifying is Smolin's tendency to set himself up as an arbiter of good and bad science. Among the people who feel that the anthropic principle deserves to be taken seriously, are some very famous physicists and cosmologists with extraordinary histories of scientific accomplishment. They include Steven Weinberg [2], Joseph Polchinski [3], Andrei Linde [4], and Sir Martin Rees [5]. These people are not fools, nor do they need to be told what constitutes good science. ...    more »

The Hubble Space Telescope has discovered the first organic molecule on a planet that's not in our solar system. According to NASA, this breakthrough could be a major step toward discovering life on other planets. Scientists believe that the organic compound detected, methane, can be an integral part in the chemical reactions considered necessary to form life as we know it. ...   more »

3) Here's Leonard Susskind's #2 to Lee Smolin #2:

...The issue here is not whether the usual phenomenological inflation was of the eternal kind although that is relevant. Eternal inflation taking place in any false vacuum minimum on the landscape would favor [in Smolin's sense] the maximum cosmological constant. But for the sake of argument I will agree to ignore eternal inflation as a reproduction mechanism.

The question of how many black holes are formed is somewhat ambiguous. What if two black holes coalesce to form a single one. Does that count as one black hole or two? Strictly speaking, given that black holes are defined by the global geometry, it is only one black hole. What happens if all the stars in the galaxy eventually fall into the central black hole? That severely diminishes the counting. So we better assume that the bigger the black hole, the more babies it will have. Perhaps one huge black hole spawns more offspring than 10^22 stellar black holes.

That raises the question of what exactly is a black hole? One of the deepest lessons that we have learned over the past decade is that there is no fundamental difference between elementary particles and black holes. As repeatedly emphasized by 't Hooft [10][11][12], black holes are the natural extension of the elementary particle spectrum. This is especially clear in string theory where black holes are simply highly excited string states. Does that mean that we should count every particle as a black hole? ...   more »

...if antimatter is, from a physics standpoint, the mirror image of matter, why is there so little antimatter in the universe? What happened early in the universe’s history to favor—if by only a small amount—the creation of matter instead of antimatter?

Particle physics has, like other scientific fields, its own lexicon that can be baffling to outsiders, and while reading 'The Mystery of the Missing Antimatter' one runs the risk of getting lost among terms like CP violation, J/psi particles, and leptogenesis. The authors do their best, though, to explain non-intuitive physics with plain language and analogies... For those curious about why the universe is the way it is, this book is a reminder of how much we have learned about physics at its smallest and largest scales, but also how much more we have yet to understand. ...   more »

It’s easy to forget that until recently cosmology was largely a theoretical science. Thanks in particular to the Wilkinson Microwave Anisotropy Probe (WMAP), which was launched by NASA in 2001 to study the cosmic microwave background, researchers are now able to talk about the first instants of the universe with the kind of certainty normally associated with a bench-top experiment.

With the analysis of two further years of WMAP data announced last week, that view of the early universe has just got even more detailed. As well as placing tighter constraints on parameters such as the age and content of the universe, the five-year WMAP data provide new, independent evidence for a cosmic neutrino background. The detection of such low-energy neutrinos, wrote Steven Weinberg in 1977 in his famous book The First Three Minutes, “would provide the most dramatic possible confirmation of the standard model of the early universe” — yet at the time no-one knew how to detect such a signal.   more »

Faced with the difficulty of observing Hawking radiation from astrophysical black holes, some physicists have attempted to make artificial ones in the lab that have a higher characteristic temperature. Clearly, generating huge amounts of gravity is both dangerous and next to impossible. But artificial black holes could be based on an analogous system in which the curved space–time of a gravitational field is enacted by another varying parameter that affects the propagation of a wave. “We cannot change the laws of gravity at our will,” Ulf Leonhardt at the University of St Andrews in the UK tells physicsworld.com. “But we can change analogous parameters in a condensed-matter system.” Leonhardt’s group at St Andrews is the first to create an artificial black-hole system in which Hawking radiation could be detected (Science 319 1367). ...   more »

Mysteriously, four spacecraft that flew past the Earth have each displayed unexpected anomalies in their motions. -- These newfound enigmas join the so-called "Pioneer anomaly" as hints that unexplained forces may appear to act on spacecraft.

A decade ago, after rigorous analyses, anomalies were seen with the identical Pioneer 10 and 11 spacecraft as they hurtled out of the solar system. Both seemed to experience a tiny but unexplained constant acceleration toward the sun. -- A host of explanations have been bandied about for the Pioneer anomaly. At times these are rooted in conventional science — perhaps leaks from the spacecraft have affected their trajectories. At times these are rooted in more speculative physics — maybe the law of gravity itself needs to be modified.

Now Jet Propulsion Laboratory astronomer John Anderson and his colleagues — who originally helped uncover the Pioneer anomaly — have discovered that four spacecraft each raced either a tiny bit faster or slower than expected when they flew past the Earth en route to other parts of the solar system. ...   more »

2) And here's Lee Smolin's #2 to Leonard Susskind #1:

I am grateful to Lenny for taking the time to respond to my paper. I will be as brief as I can in replying, especially as the key points are already presented in detail in my paper hep-th/0407213 ["Scientific alternatives to the anthropic principle"] or in my book, Life of the Cosmos or previous papers on the subject. -- For clarity I had in section 5.1.6 identified two arguments in Weinberg's papers. The first is the one I criticized in the summary. Susskind reponds, reasonably, by agreeing, and then raising the second argument. This argument is also criticized in detail in my paper, and it was perhaps a mistake not to include this in the summary I sent to Susskind.

This second argument is based on a version of the AP called the "Principle of Mediocrity" by Garriga and Vilenkin, who have done the most to develop it. Their version states that, "...our civilization is typical in the ensemble of all civilizations in the universe." -- This argument is discussed in full in sections 5.1.5 and 5.1.6. There I argue that the mediocrity principle cannot yield falsifiable predictions because it depends on the definition of the ensemble within which our civilization is taken to be typical as well as on assumptions about the probability distribution. I establish this by general argument as well as by reference to specific examples including Weinberg's use of it.

Can this be right if, as Susskind claims, Weinberg's prediction was found to hold? In fact, Weinberg's prediction did not work all that well. In the form that he made it, it led to an expectation of a cosmological constant larger than the observed value. Depending on the ensemble chosen and the assumptions made about the probability distribution, the probability that Lambda be as small as observed ranges between about 10 % and a few parts in ten thousand. In fact, the less probable values are the more reasonable, as they come from an ensemble where Q, the scale of the density fluctuations, is allowed to vary. While I am not an expert here, it appears from a reading of the literature [references in the paper] that to make the probability for the present value as large as 10% one has to assume that Q is frozen and fixed by fundamental theory. It is hard to imagine a theory where the parameters vary but Q does not, as it depends on parameters in the inflation potential. ...   more »

1) Here's Leonard Susskind's answer to Lee Smolin's first email:

Yesterday I received an email message from Lee Smolin asking for my comments about a paper he had posted the previous day [1]. Having not had a chance to read the paper I asked if he would summarize the arguments. He was kind enough to do so in an admirably concise and clear summary. (See above). -- I took a quick look at the paper just to make sure that there was not more that I might have missed in the summary. -- I noticed that in the paper Smolin quotes the philosopher, Karl Popper. Personally I don't think these are deep philosophical issues requiring a heavyweight like Popper. Weinberg was just using good old fashioned common sense.

Weinberg's argument, which is clearly stated in his general audience book Dreams of a Final Theory is not that the cosmological constant has to be smaller than the limit from galaxy formation. If it were, then Smolin would be correct: the Anthropic Principle doesn't add much to the observed fact that galaxies exist. What Weinberg argued was that if the Anthropic Principle is correct, then the cosmological constant will probably not be much smaller than the galaxy formation limit. Weinberg was just expressing the common sense opinion that if anthropics is the only reason the cosmological constant is small, then it is unlikely that it will be orders of magnitude smaller than the anthropic limit. -- Was it a prediction that could be proved wrong? Most people thought so. Just about everyone I know was certain that the cosmological constant was exactly zero.

Smolin's next argument involves what he calls a scientific alternative to the Anthropic Principle. He argues for a Darwinian natural selection principle. Smolin believes, as I do, that universes can reproduce and give rise to mutated offspring that differ in the values of the constants of nature. He believes the mechanism involves black holes while I believe it involves eternal inflation and Coleman de Luccia bubble nucleation. But either will do. ...   more »

Introduction

Recently, I received a copy of an email sent by Leonard Susskind to a group of physicists which included an attached file entitled "Answer to Smolin". This was the opening salvo of an intense email exchange between Susskind and Smolin concerning Smolin's argument that "the Anthropic Principle (AP) cannot yield any falsifiable predictions, and therefore cannot be a part of science".

After reading several postings by each of the physicists, I asked each if (a) they would consider posting the comments on Edge, and (b) if they would write a new, and final "letter". -- Both agreed, but only after a negotiation: (1) No more than 1 letter each; (2) Neither sees the other's letter in advance; (3) No changes after the fact. A physics shoot-out.
While this is a conversation written by physicists for physicists, it should nonetheless be of interest for Edge readers as it's in the context of previous Edge features with the authors, it's instructive as to how science is done, and it's a debate that clarifies, not detracts. And finally it's a good example of what Edge is all about, where contributors share the boundaries of their knowledge and experience with each other and respond to challenges, comments, criticisms, and insights. The constant shifting of metaphors, the intensity with which we advance our ideas to each other — this is what intellectuals do. Edge draws attention to the larger context of intellectual life. ...   more »

"How inflation happened a split second after the Big Bang." "Identify the exact sources of these cosmic rays and how they accelerate particles." Two different Nobel Laureates raised these two unrelated queries in cosmology publicly in November and December 2007. The timing of these queries is close to the fourth anniversary of a postmodern Big Bang cosmology theory published Dec. 15, 2003, in a cosmology book, "How Dark Matter Created Dark Energy and the Sun," authored by Jerome Drexler.

There is the possibility that plausible answers or helpful responses to both of these queries can be derived from a recent cosmology paper utilizing Drexler's dark matter theory and Big Bang cosmology... The paper argues that the Big Bang, which occurred at the beginning of time, must have satisfied the Second Law of Thermodynamics. Thus, immediately after the Big Bang the entropy of the universe would be at the lowest level it would reach throughout all time. Therefore, the Big Bang should not be characterized, as it has been for over 40 years, as a chaotic fireball explosion associated with a high level of disorder and high entropy.

The very low entropy could be achieved by the Big Bang firing out, in all directions, high-velocity ultra-high-energy (UHE) relativistic protons and helium nuclei in the well-known ratio of 12 to 1. A very high percentage of their energies would be available to do work since their entropy, a measure of the percentage of their energy unavailable to do work, would be very low. Such a Big Bang, characterized by a dispersion of UHE relativistic nuclei, would be highly efficient and could create very high usable energy and very low entropy, and might be designated a Relativistic Big Bang. This concept is fundamental to Drexler's dark matter theory and his postmodern Big Bang cosmology. ...   more »