Cosmology

"Consistent, relativistic string theories had already been written down in two, ten or twenty-six dimensions (the last being relevant only to bosonic strings) in the 1970s. A closed string is a loop which replaces a spacetime point. Its quantum oscillations correspond to particles of higher spins and higher masses, which may be arranged in a linear trajectory in a spin-versus-mass ... (Regge) plot. If the slope parameter of this trajectory — the only parameter in the theory — is adjusted to equal the Newtonian constant, one can show, quite miraculously, that in the zeroth order of the closed bosonic string there emerges from the string theory Einstein's gravity in its fullness! (The higher orders give modifications to Einstein's theory, with corrections which have a range of length = 10–33 cm.)"

"The most recent chapter in our new understanding of nonperturbative effects in string theory has been the incorporation of unstable branes and open string tachyons into the overall framework of the theory. It has turned out that an understanding of unstable D-branes is necessary to properly describe all D-branes. This is natural from the point of view of K-theory, where brane configurations which are equivalent under the annihilation of unstable branes are identified ... The long-mysterious tachyon instability of open string theory has finally been given a physical interpretation: it is the instability of the D-brane that supports the existence of open strings. The instability disappears in the tachyon vacuum, in which the D-brane decays. Moreover, the belief that D-branes are solitonic solutions of string theory has been confirmed: starting with the appropriate tachyonic field theory of unstable space-filling branes, one can describe lower dimensional D-branes as solitonic solutions. Lower dimensional D-branes are thereby essentially obtained as solitons of the tachyon field theory, so, in some sense, lower-dimensional D-branes can be thought of as being made of tachyons! It has also been shown that the physics of unstable D-branes is captured by string field theory, thus making it a candidate for a non-perturbative formulation of string theory capable of describing changes of the string background."

"... all of these caveats really work only against the idea that the final theory of nature is a quantum field theory. They leave open the view, which is in fact the point of view of my book, that although you can not argue that relativity plus quantum mechanics plus cluster decomposition necessarily leads only to quantum field theory, it is very likely that any quantum theory that at sufficiently low energy and large distances looks Lorentz invariant and satisfies the cluster decomposition principle will also at sufficiently low energy look like a quantum field theory. Picking up a phrase from Arthur Wightman, I’ll call this a folk theorem. At any rate, this folk theorem is satisfied by string theory, and we don’t know of any counterexamples."

"From the beginning it was clear that, despite its successes, the Standard Model of elementary particles would have to be embedded in a broader theory that would incorporate gravitation as well as the strong and electroweak interactions. There is at present only one plausible candidate for such a theory: it is the theory of strings, which started in the 1960s as a not-very-successful model of hadrons, and only later emerged as a possible theory of all forces."

"It's possible that the true structures in the underlying theory are something quite different — and the obvious candidate is strings. That direction, I think, is certainly worth working on. We don't whether that's the correct direction."

"String theory at its finest is, or should be, a new branch of geometry. ...I, myself, believe rather strongly that the proper setting for string theory will prove to be a suitable elaboration of the geometrical ideas upon which Einstein based general relativity."

"I would expect that a proper elucidation of what string theory really is all about would involve a revolution in our concepts of the basic laws of physics - similar in scope to any that occurred in the past."

"It's been said that string theory is part of the physics of the twenty-first century that fell by chance into the twentieth century. That's a remark that was made by a leading physicist about fifteen years ago. ...String theory was invented essentially by accident in a long series of events, starting with the Veneziano model... No one invented it on purpose, it was invented in a lucky accident. ...By rights, string theory shouldn't have been invented until our knowledge of some of the areas that are prerequisite... had developed to the point that it was possible for us to have the right concept of what it is all about."

"Generally speaking, all the really great ideas of physics are really spin-offs of string theory... Some of them were discovered first, but I consider that a mere accident of the development on planet earth. On planet earth, they were discovered in this order [general relativity, quantum field theory, superstrings, and supersymmetry]... But I don't believe, if there are many civilizations in the universe, that those four ideas were discovered in that order in each civilization."

"I feel that we are so close with string theory that—in my moments of greatest optimism—I imagine that any day, the final form of the theory may drop out of the sky and land in someone's lap. But more realistically, I feel that we are now in the process of constructing a much deeper theory than anything we have had before and that well into the twenty-first century, when I am too old to have any useful thoughts on the subject, younger physicists will have to decide whether we have in fact found the final theory."

"String theory is not like anything else ever discovered. It is an incredible panoply of ideas about math and physics, so vast, so rich you could say almost anything about it."

"Unlike a Feynman graph, which is divided into different lines, which can represent particles of different types with different masses and spins, any part of a string world sheet is equivalent to any other so "there is only one string." Whatever particles there are going to be represent different states of vibration of one basic string. Also there are not any vertices in the string world sheet so we do not have the freedom to tell the string how to interact."

"... almost any inflationary model has the property that it produces not just one big bang but ultimately an infinite number of them, at an exponentially increasing rate — and that's what we we call eternal inflation. It's eternal only into the future — we don't think it's eternal into the past — so the word "eternal" is not quite being used in its dictionary definition ..."

"As for inflation, scientists believe it occurred in the early universe at a temperature far above the energy of particle accelerators and relatively close to the energy at which quantum gravity becomes important. We do not yet have a convincing, detailed model of how and why inflation transpired because the models of particle physics that we have are not adequate at the huge energies of inflation. Understanding inflation requires a much better knowledge of particle physics than we have now, and possibly a full knowledge of string theory and quantum gravity."

"The theory of cosmic inflation offers an attractive resolution of some of the great paradoxes in cosmology: why the universe is so large, flat and uniform on large scales, and how density variations arose. Inflation has rightly dominated cosmological thinking for the past two decades, helping stimulate the development of high-precision observational programmes. The survival of simple inflationary models in the face of an impressive observational onslaught has been interpreted as convincing evidence of the correctness of the basic idea. In this paper, I review inflation, but highlight its weaknesses, explaining my reasons for believing that a more complete theory may supersede inflation without necessarily incorporating it."

"I think inflation is too flexible of an idea for that to make sense."

"The definition of inflation is extraordinarily simple: it is any period of the Universe's evolution during which the scale factor, describing the size of the Universe, is accelerating. This leads to a very rapid expansion of the Universe, though perhaps a better way of thinking of this is that the characteristic scale of the Universe, given by the Hubble length, is shrinking relative to any fixed scale caught up in the rapid expansion. In that sense, inflation is actually akin to zooming in on a small part of the initial Universe."

"Our point is that we should be talking about the contemporary version of inflation, warts and all, not some defunct relic. Logically, if the outcome of inflation is highly sensitive to initial conditions that are not yet understood, as the respondents concede, the outcome cannot be determined. And if inflation produces a multiverse in which, to quote a previous statement from one of the responding authors (Guth), “anything that can happen will happen”—it makes no sense whatsoever to talk about predictions. Unlike the Standard Model, even after fixing all the parameters, any inflationary model gives an infinite diversity of outcomes with none preferred over any other. This makes inflation immune from any observational test."

"I say looking at the next 100 years that there are two trends in the world today. The first trend is toward what we call a type one civilization, a planetary civilization... The danger is the transition between type zero and type one and that’s where we are today. We are a type zero civilization. We get our energy from dead plants, oil and coal. But if you get a calculator you can calculate when we will attain type one status. The answer is: in about 100 years we will become planetary. We’ll be able to harness all the energy output of the planet earth. We’ll play with the weather, earthquakes, volcanoes. Anything planetary we will play with. The danger period is now, because we still have the savagery. We still have all the passions. We have all the sectarian, fundamentalist ideas circulating around, but we also have nuclear weapons. ...capable of wiping out life on earth. So I see two trends in the world today. The first trend is toward a multicultural, scientific, tolerant society and everywhere I go I see aspects of that birth. For example, what is the Internet? Many people have written about the Internet. Billions and billions of words written about the Internet, but to me as a physicist the Internet is the beginning of a type one telephone system, a planetary telephone system. So we’re privileged to be alive to witness the birth of type one technology... And what is the European Union? The European Union is the beginning of a type one economy. And how come these European countries, which have slaughtered each other ever since the ice melted 10,000 years ago, how come they have banded together, put aside their differences to create the European Union? ...so we’re beginning to see the beginning of a type one economy as well..."

"This is the moment of the homogenization of the world, when the diversities of societies are eroding, when a global civilization is emerging. There are no exotic places left on Earth to dream about. And for this reason there remains an even greater and more poignant need today for a vehicle, a device, to get us somewhere else. Not all of us; only a few – to the deserts of the Moon, the ancient seacoasts of Mars, the forests of the sky. There is something comforting in the idea that one day a few representatives of our little terrestrial village might venture to the great galactic cities."

"Since, in the long run, every planetary society will be endangered by impacts from space, every surviving civilization is obliged to become spacefaring — not because of exploratory or romantic zeal, but for the most practical reason imaginable: staying alive."

"This Voyager spacecraft was constructed by the United States of America. We are a community of 240 million human beings among the more than 4 billion who inhabit the planet Earth. We human beings are still divided into nation states, but these states are rapidly becoming a single global civilization. We cast this message into the cosmos. It is likely to survive a billion years into our future, when our civilization is profoundly altered and the surface of the Earth may be vastly changed. Of the 200 billion stars in the Milky Way galaxy, some - perhaps many - may have inhabited planets and spacefaring civilizations. If one such civilization intercepts Voyager and can understand these recorded contents, here is our message: This is a present from a small distant world, a token of our sounds, our science, our images, our music, our thoughts, and our feelings. We are attempting to survive our time so we may live into yours. We hope someday, having solved the problems we face, to join a community of galactic civilizations. This record represents our hope and our determination, and our good will in a vast and awesome universe."

"Hydra-Centaurus Supercluster, which contains the Great Attractor, the Laniakea central gravitational point,"

"We have finally established the contours that define the supercluster of galaxies we can call home … This is not unlike finding out for the first time that your hometown is actually part of much larger country that borders other nations."

"It’s like water dividing at a watershed, where it flows either to the left or right of a height of land."

"For the first time, astronomers have outlined and named the network of galaxies that includes the Milky Way, adding a line to our cosmic address and further defining our place in the universe. They call it Laniakea, which is Hawaiian for “immense heaven.”"

"This week, scientists add a new line to our planetary coordinates: the Laniakea galaxy supercluster. Do not bother googling the name. It really is brand new, coined by an international group of astronomers … Our place in the Universe, for so long one of the core mysteries of human existence that scientists and this journal are dedicated to unravelling, just got a little clearer. Laniakea, the scientists write, is our home supercluster, the one in which the Milky Way resides. What kind of home is it? It is big — some 160 million parsecs across. Although not as big as some superclusters, it is the largest in our local neighbourhood, which is surprisingly crowded given the vast emptiness of most of the cosmological void. It is a home that has been hiding in plain sight, colossal and all around us, yet unnoticed by previous astronomical surveys. …The name Laniakea has Hawaiian roots, and roughly translated means spacious heaven. It is a beautiful address to have. And one that comes just in time for the new school year and a new curious generation."

"Scientists previously placed the Milky Way in the Virgo Supercluster, but under Tully and colleagues' definition, this region becomes just an appendage of the much larger Laniakea, which is 160 million parsecs (520 million light years) across and contains the mass of 100 million billion Suns."

"Astronomers have mapped the cosmic watershed in which our Milky Way Galaxy is a droplet. The massive structure, which the research team dubs the Laniakea Supercluster, extends more than 500 million light-years and contains 100,000 large galaxies. The work, published in the September 4th Nature, is the first to trace our local supercluster on such a large scale. It also provides a physical way to define what a supercluster actually is."

"The name Laniakea was suggested by Nawa‘a Napoleon, an associate professor of Hawaiian Language and chair of the Department of Languages, Linguistics, and Literature at Kapiolani Community College, a part of the University of Hawaii system. … The name honors Polynesian navigators who used knowledge of the heavens to voyage across the immensity of the Pacific Ocean."

"Pavo-Indus Supercluster."

"Virgo Supercluster, the region where the Milky Way resides,"

"Amazing fine tuning occurs in the laws that make this [complexity] possible. Realization of the complexity of what is accomplished makes it very difficult not to use the word 'miraculous' without taking a stand as to the ontological status of the word."

"A life-giving factor lies at the centre of the whole machinery and design of the world."

"How surprising it is that the laws of nature and the initial conditions of the universe should allow for the existence of beings who could observe it. Life as we know it would be impossible if any one of several physical quantities had slightly different values."

"The physicists are getting down to the nitty-gritty, they've really just about pared things down to the ultimate details, and the last thing they ever expected to happen is happening. God is showing through."

"When I began my career as a cosmologist some twenty years ago, I was a convinced atheist. I never in my wildest dreams imagined that one day I would be writing a book purporting to show that the central claims of Judeo-Christian theology are in fact true, that these claims are straightforward deductions of the laws of physics as we now understand them. I have been forced into these conclusions by the inexorable logic of my own special branch of physics."

"Most constants are adjusted with a deviation of one percent, which means that if the value differs by one percent everything collapses. Physicists can certainly claim that this is a fluke, but it must be acknowledged that this cosmological constant is adjusted to an accuracy of 1/10120. No one thinks that this is solely a fluke. It is the most extreme example of hyperfine regulation..."

"With so many errors and misjudgments, and with such a gross lack of understanding of the basic science we have seen exhibited by the supporters of supernatural fine-tuning, we can safely say that their motivation is more wishful thinking than truthful scientific inference. A proper analysis finds there is no evidence that the universe is fine-tuned for us."

"Wherever physicists look, they see examples of fine tuning."

"Astronomy leads us to a unique event, a universe which was created out of nothing, one with the very delicate balance needed to provide exactly the conditions required to permit life, and one which has an underlying (one might say 'supernatural') plan."

"We are, by astronomical standards, a pampered, cosseted, cherished group of creatures. … If the Universe had not been made with the most exacting precision we could never have come into existence. It is my view that these circumstances indicate the universe was created for man to live in."

"Would you not say to yourself, in whatever language supercalculating intellects use, "Some supercalculating intellect must have designed the properties of the carbon atom, otherwise the chance of my finding such an atom through the blind forces of nature would be less than 1 part in 1040000." Of course you would. … I have always been intrigued by the remarkable relation of the 7.65 Mev energy level in the nucleus of 12C to the 7.12 Mev level in 16O. If you wanted to produce carbon and oxygen in roughly equal quantities by stellar nucleosynthesis, these are the two levels you would have to fix … A common sense interpretation of the facts suggests that a super-intellect has monkeyed with physics, as well as with chemistry and biology, and that there are no blind forces worth speaking about in nature."

"The remarkable fact is that the values of these numbers seem to have been very finely adjusted to make possible the development of life."

"As we survey all the evidence, the thought insistently arises that some supernatural agency - or, rather, Agency - must be involved. Is it possible that suddenly, without intending to, we have stumbled upon scientific proof of the existence of a Supreme Being? Was it God who stepped in and so providentially crafted the cosmos for our benefit?"

"The really amazing thing is not that life on Earth is balanced on a knife-edge, but that the entire universe is balanced on a knife-edge. You see, even if you dismiss mankind as just a mere hiccup in the great scheme of things, the fact remains that the entire universe seems unreasonably suited to the existence of life — almost contrived — you might say a "put-up job"."

"The Immortal Principle was first called water by Thales. Anaximenes called it air. The Pythagoreans called it number and were thus the first to see the Immortal Principle as something nonmaterial. Heraclitus called the Immortal Principle fire and introduced change as part of the Principle. He said the world exists as a conflict and tension of opposites. He said there is a One and there is a Many and the One is the universal law which is immanent in all things. Anaxagoras was the first to identify the One as nous, meaning "mind." Parmenides made it clear for the first time that the Immortal Principle, the One, Truth, God, is separate from appearance and from opinion, and the importance of this separation and its effect upon subsequent history cannot be overstated. It's here that the classic mind, for the first time, took leave of its romantic origins and said, "The Good and the True are not necessarily the same," and goes its separate way. Anaxagoras and Parmenides had a listener named Socrates who carried their ideas into full fruition."

"This mysterious something has been called God, the Absolute, Nature, Substance, Energy, Space, Ether, Mind, Being, the Void, the Infinite — names and ideas which shift in popularity and respectability with the winds of intellectual fashion, of considering the universe intelligent or stupid, superhuman or subhuman, specific or vague. All of them might be dismissed as nonsense-noises if the notion of an underlying Ground of Being were no more than a product of intellectual speculation. But these names are often used to designate the content of a vivid and almost sensorily concrete experience — the "unitive" experience of the mystic, which, with secondary variations, is found in almost all cultures at all times. This experience is the transformed sense of self which I was discussing in the previous chapter, though in "naturalistic" terms, purified of all hocus-pocus about mind, soul, spirit, and other intellectually gaseous words."

"All that is real in me is God; all that is real in God is I. The gulf between God and me is thus bridged. Thus by knowing God, we find that the kingdom of heaven is within us."

"All knowledge that the world has ever received comes from the mind; the infinite library of the universe is in our own mind."