Astronomers From The United States

"Eratosthenes... knew that the Sun was straight overhead in... Syene at noon on the summer solstice, but that it was 7.2 degrees south of straight overhead in , located 794 kilometers farther north. He concluded... 794 kilometers corresponded to 7.2 degrees out of the 360 degrees... around Earth's circumference, so that the circumference must be... 39,700 km..."

"Aristarchos of Samos... was able to use to figure out... the distance between the Earth and the Sun. His conclusion... the Sun was about twenty times farther... than the Moon and therefore twenty times bigger than the Moon. In other words, the Sun was... over five times bigger than the Earth in diameter. This insight prompted Aristarchos to propose the heliocentric hypothesis long before Nicolaus Copernicus... It turned out to be quite difficult to tell precisely when the Moon was 50% illuminated, and the correct Sun-Moon angle... isn't 87 degrees but about 89.85 degrees... This makes... the Sun... almost twenty times further away... and about 109 times larger than the Earth... [T]his wasn't corrected until almost two thousand years later, so when Copernicus came along... the overall scale of his Solar System model was about twenty times too small..."

"At this moment it seems as though science will never be able to raise the curtain on the mystery of creation. For the scientist who has lived by his faith in the power of reason, the story ends like a bad dream. He has scaled the mountains of ignorance; he is about to conquer the highest peak; as he pulls himself over the final rock, he is greeted by a band of theologians who have been sitting there for centuries."

"When a scientist writes about God, his colleagues assume he is either over the hill or going bonkers. In my case it should be understood from the start that I am an agnostic in religious matters. My views on this question are close to those of Darwin, who wrote, "My theology is a simple muddle. I cannot look at the Universe as the result of blind chance, yet I see no evidence of beneficent design in the details.""

"We can assume that in a relatively short time — perhaps within 100 million years — the one celled organism evolved into a colony of cells. With the further passage of time, groups of cells within those colonies assumed specialized functions of food-gathering, digestion, the structural features of an outer skin, and so on; thus began the stage of evolution leading to the complex, many-celled creatures which dominate life today. The fossil record contains no trace of these preliminary stages in the development of many-celled organisms. The first clues to the existence of relatively advanced forms of life consist of a few barely discernible tracks, presumably made in the primeval slime by soft, wriggling wormlike animals. These are found in rocks about one billion years old. These meager remains are the earliest traces of many-celled animal life on the planet."

"So far as thought may peer into the past, the epic of our solar system began with a great catastrophe. Two suns met. What had been, ceased; what was to be, arose. Fatal to both progenitors, the event dated a stupendous cosmic birth."

"In the great desert of northern Arizona the traveller, threading his way across a sage-brush and cacti plain shut in by abrupt-sided shelves of land rising here and there some hundreds of feet higher, suddenly comes upon a petrified forest."

"Are physical forces alone at work there, or has evolution begotten something more complex, something not unakin to what we know on Earth as life?"

"The whole object of science is to synthesize, and so simplify; and did we but know the uttermost of a subject we could make it singularly clear."

"Formulae are the anaesthetics of thought, not its stimulants and to make any one think is far better worth while than cramming him with ill-considered, and therefore indigestible, learning."

"That Mars is inhabited by beings of some sort or other we may consider as certain as it is uncertain what these beings may be."

"War is a survival among us from savage times and affects now chiefly the boyish and unthinking element of the nation. The wisest realize that there are better ways for practicing heroism and other and more certain ends of insuring the survival of the fittest. It is something a people outgrow. But whether they consciously practice peace or not, nature in its evolution eventually practices it for them, and after enough of the inhabitants of a globe have killed each other off, the remainder must find it more advantageous to work together for the common good."

"I may go down in history as the guy who killed Pluto."

"According to Guth, he had discovered the equations of De Sitter's cosmology (1917), written in the form introduced somewhat later by Georges Lemaitre (1925), as part of his MIT Thesis, before introducing inflation as the starting point of his new cosmology. After taking care, by means of inflation of the "monopole problem". ...Guth went one step further to solve the so called "flatness problem". ...Guth finally goes on to explain how his theory of inflation solves the "horizon problem". ...we will analyze in some detail to what extent the "monopole problem", the "flatness problem" and the "horizon problem" require, or not, cosmic inflation as a problem solving "paradigm"."

"It is said that there’s no such thing as a free lunch. But the universe is the ultimate free lunch."

"The recent developments in cosmology strongly suggest that the universe may be the ultimate free lunch."

"It becomes very tempting to ask whether, in principle, it's possible to create a universe in the laboratory—or a universe in your backyard—by man-made processes."

"It turns out that the energy of a gravitational field—any gravitational field—is negative. During inflation, as the universe gets bigger and bigger and more and more matter is created, the total energy of matter goes upward by an enormous amount. Meanwhile, however, the energy of gravity becomes more and more negative. The negative gravitational energy cancels the energy in matter, so the total energy of the system remains whatever it was when inflation started—presumably something very small. ...This capability for producing matter in the universe is one crucial difference between the inflationary model and the previous model."

"We should not act like we know that the universe began with the Big Bang... we'll see that there are strong suggestions that the Big Bang was perhaps not really the beginning of existence, but really just the beginning of our local universe, often called a pocket universe."

"What the Big Bang theory tells us, is that at least our region of the universe 13.82 billion years ago, was an extremely hot, dense uniform soup of particles which in the conventional standard Big Bang model filled literally all of space—and now we certainly believe that it filled essentially all of the space that we have access to—uniformly. ...This is contrary to a popular cartoon image of the Big Bang, which is just plain wrong. The cartoon image of the Big Bang is the image of a small egg of highly dense matter that then exploded and spewed out into empty space. That is not the scientific picture of the Big Bang. ...If there was a small egg that exploded into empty space, you would certainly expect that today you would see something different if you were looking towards where the egg was, versus looking the opposite direction, but we don't see any effect like that. When we look around the sky the universe looks completely uniform, on average, in all directions, to a very high degree of accuracy... So we don't see a sign of an egg having happened anywhere. Rather, the Big Bang seems to have happened everywhere, uniformly."

"The conventional Big Bang theory does not say anything about what caused the expansion. It really is only a theory about the aftermath of a bang. In the scientific version of the Big Bang, the universe starts with everything already expanding, with no explanation of how that expansion started... So the Scientific version of the Big Bang theory is not really a theory of a bang, it's really a theory of the aftermath of a bang."

"The conventional Big Bang theory says nothing about where all the matter came from. The theory really assumes that for every particle that we see in the universe today, there was, at the very beginning, at least some precursor particle, if not the same particle, with no explanation of where all those particles came from."

"In short what I like to say is that the Big Bang says nothing about what banged, why it banged, or what happened before it banged. It really has no bang in the Big Bang. It is a bangless theory, despite its name."

"Inflation is a prequel to the conventional Big Bang theory. ...It does provide a theory of the propulsion that drove the universe into this humungous episode of expansion which we call the Big Bang."

"The miracle of physics that I'm talking about here is something that was actually known since the time of Einstein's general relativity; that gravity is not always attractive. Gravity can act repulsively. Einstein introduced this in 1916... in the form of the cosmological constant, and the original motivation of modifying the equations of general relativity to allow this was because Einstein thought that the universe was static, and he realized that ordinary gravity would cause the universe to collapse if it was static. ...The fact that general relativity can support this gravitational repulsion, still being consistent with all the principles that general relativity incorporates, is the important thing which Einstein himself did discover.."

"Inflation takes advantage of this possibility... to let gravity be the repulsive force that drove the universe into the period of expansion that we call the Big Bang. In fact, when one combines general relativity with conventional ideas, now, in particle physics there really is a pretty clear indication, I should say, not quite a prediction... that at very high energy densities one expects to find states of matter which literally turn gravity on its head and cause gravity to become repulsive."

"What it takes to produce a gravitational repulsion is a negative pressure. According to general relativity, it turns out... both pressures and energy densities can produce gravitational fields, unlike Newtonian physics, where it's only mass densities that produce gravitational fields."

"A positive pressure produces an attractive gravitational field... Positive pressures are just sort of normal pressures and attractive gravity is normal gravity, so normal pressures produce normal gravity, but it is possible to have negative pressures, and negative pressures produce repulsive gravity, and that's the secret of what makes inflation possible."

"A very plausible choice for when inflation might have happened would be when the energy scales of the universe were at the scale of grand unified theories... which unify the weak, strong and electromagnetic interactions into a single unified interaction. ..we're talking about energies which are about 1016 times the equivalent energy of a proton mass. ...the initial patch would only have to be the ridiculously small size of about 10-28 cm across to be able to lead ultimately to the creation of everything that we see on the vast scale of which we see it."

"The gravitational repulsion created by this small patch of repulsive gravity material would be, then, the driving force of the Big Bang and it would cause the region to undergo exponential expansion... there is a certain doubling time, and if you wait the same amount of time it doubles again, and if you wait the same amount of time it doubles again... and it's because these doublings build up so dramatically, it doesn't take very much time to build the whole universe. In about 100 doublings this tiny patch of 10-28 cm can become large enough, not to be the universe, but to be a small marble-sized region which will then ultimately become the observed universe, as it continues to coast outward after inflation ends."

"The discovery of the CMB cemented the notion of a big bang. But for all its elegance, the theory had thrown up some intractable problems. Soon after the CMB was discovered, Dicke went to Cornell to talk about... the flatness problem. ...the universe seemed to be flat, meaning that the ratio of actual matter density to the critical density... Omega, was very close to 1. And for today's universe to have Omega anywhere near 1, its value just one second after the big bang had to be exactly 1 to a precision of about fourteen decimal places. Nothing in the laws of physics suggested why... In Dicke's audience was a young postdoc named Alan Guth. He was a particle physicist who had no interest in cosmology. But something about the talk tickled his fancy and set him on a journey that would solve the big-bang theory's most frustrating problem."

"Most of what we know, or believe we know, about the early moments of the universe is thanks to an idea called inflation theory first propounded in 1979 by a junior particle physicist, then at Stanford, now at MIT, named Alan Guth. He was thirty-two years old and, by his own admission, had never done anything much before. He would probably never have had his great theory except that he happened to attend a lecture on the Big Bang given by none other than Robert Dicke. The lecture inspired Guth to take an interest in cosmology, and in particular in the birth of the universe."

"We now address two of the drawbacks [of the standard Big Bang theory]... the flatness problem and the horizon problem. In the early 1980's, Alan Guth resolved these two problems with his inflationary theory. His basic idea was that the universe enters a false vacuum state shortly after the Big Bang, then tunnels out and expands exponentially. We choose to discuss Guth's original model (now called classical model or old inflation) for pedagogic reasons. Guth's model has many nice qualitative features; it does not work quantitatively. Therefore, A. Linde, A. Albrecht, P. Steinhardt, and others constructed new models as remedies. It is not clear which of the new models is correct..."

"Prior to the downfall of the GUT in the mid 1980s, Alan Guth, an elementary particle theorist, was trying to explain the scarcity of the magnetic monopoles in the universe. The standard cosmological model predicted that there should be as many monopoles as there are nucleons! Since all attempts at finding a monopole had failed, Guth suggested that the universe must have had an inflation phase during which it expanded exponentially. This exponential growth was so rapid that it diluted any existing monopoles so much so that today there may be only a few in our observable universe."

"It was fortunate that Alan Guth did his work at the same time that another idea came into fashion, which was the theory that we could understand why the universe contains matter and not antimatter in terms of some asymmetry, some favoritism for matter over antimatter in the early universe; it's no good having a scheme that can inflate the universe to enormous dimension of it's not possible to create matter to fill that large universe."

"One of the issues with the then generally accepted theory of the Big Bang was the uniformity of temperature measured in any direction out in the universe, no explosion on Earth could occur as uniformly. In the early 1980's Alan Guth postulated that the universe initially grew from a small enough volume, a fraction of the size of an atom, for temperature to have equalized, within its first billionth of a second of age, to then expand exponentially..."

"The Big Bang theory says nothing about what banged, why it banged, or what happened before it banged."

"It is, indeed an incredible fact that what the human mind, at its deepest and most profound, perceives as beautiful finds its realization in external nature.… What is intelligible is also beautiful."

"All the standard equations of mathematical physics can be separated and solved in ."

"The black holes of nature are the most perfect macroscopic objects there are in the universe: the only elements in their construction are our concepts of space and time. And since the general theory of Relativity provides only a single unique family of solutions for their descriptions, they are the simplest objects as well."

"I was very fortunate to know the great astrophysicist Subrahmanyan Chandrasekhar during his last years. Chandra, as we called him, was the first to discover that general relativity implied that stars above a certain mass would collapse into what we now call a black hole. Much later, he wrote a beautiful book describing the different solutions of the equations of general relativity that describe black holes. As I got to know him, Chandra shocked me by speaking of a deep anger toward Einstein. Chandra was upset that Einstein, after inventing general relativity, had abandoned this masterpiece, leaving it to others to struggle through it."

"Gamow was fantastic in his ideas. He was right, he was wrong. More often wrong than right. Always interesting; … and when his idea was not wrong it was not only right, it was new."

"By an incredible coincidence, Gamow and Edward Condon, who had discovered simultaneously and independently the explanation of radioactivity (one in Russia, the other in this country), came to spend the last ten years of their lives within a hundred yards of each other in Boulder."

"The physicist George Gamow was also an entertaining popularizer. He once told the story of how with his wife and their baby daughter he visited the Leaning Tower of Pisa. As they climbed the steps, they noticed an increasingly musty smell, which they first attributed to the ancient walls of the building. Then, however, they began to suspect their little girl, and by the time they reached the top it was clear that she needed immediate attention. “And from the very place,” explained Gamow, raising his arm and his voice dramatically, “where Galileo launched his experimental objects, we also propelled…”"

"It took less than an hour to make the atoms, a few hundred million years to make the stars and planets, but five billion years to make man!"

"If the expansion of the space of the universe is uniform in all directions, an observer located in anyone of the galaxies will see all other galaxies running away from him at velocities proportional to their distances from the observer."

"So I am just sitting and waiting, listening, and if something exciting comes, I just jump in."

"I feel that matter has properties which physics tells you."

"I decided to get Ph.D. in experimental physics because experimental physicists have their own room in the Institute where they can hang their coat, whereas theoretical physicists have to hang their coat at the entrance."

"With very few exceptions, philosophers do not know much science and do not understand it, which is quite natural because science lies beyond the boundaries of typical philosophical subjects such as ethics, aestetics, and gnosiology. But while in the free countries philosophers are quite harmless, in the dictatorial countries they constitute a great danger for the development of science. In Russia, state philosophers are bred in the Communist Academy in Moscow and are placed in all the educational and research institutions to prevent the professors and researchers from falling into idealistic, capitalistic heresies. The state philosophers are usually familiar with the subject of the research institution they are going to supervise, being either former schoolteachers or having taken in the academy a one-semester course on the subject in question. But they rank in the their power above the scientific directors of the institution and can veto any research project on publication which deviates from the correct ideology. One notable example of philosophical dictatorship in Russian science was the prohibition of Einstein's theory of relativity on the ground that it denied world ether, "the existence of which follows directly from the philosophy of dialectical materialism". It is interesting to note that the existence of the "world ether" was doubted long before Einstein by Engels, who in one of his letter to friend wrote "...the world ether, if it exists"."