A Brief History of Time (Turtleback School & Library Binding Edition)

A Brief History of Time (Turtleback School & Library Binding Edition)

by Stephen Hawking


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An anniversary edition of a now-classic survey of the origin and nature of the universe features a new introduction by the author and a new chapter on the possibility of time travel and "wormholes" in space.

Product Details

ISBN-13: 9780613074049
Publisher: Turtleback Books
Publication date: 09/28/1998
Pages: 212
Product dimensions: 6.00(w) x 8.60(h) x 0.80(d)
Lexile: 1290L (what's this?)
Age Range: 12 - 17 Years

About the Author

Stephen Hawking, who was born on the anniversary of Galileo's death in 1942, holds Isaac Newton's chair as Lucasian Professor of Mathematics at the University of Cambridge. Widely regarded as the most brilliant theoretical physicist since Einstein, he is also the author of Black Holes and Baby Universes, a collection of essays published in 1993, as well as numerous scientific papers and books.


Cambridge, England

Date of Birth:

January 8, 1942

Date of Death:

March 14, 2018

Place of Birth:

Oxford, England

Read an Excerpt

Chapter 1


A well-known scientist (some say it was Bertrand Russell) once gave a public lecture on astronomy. He described how the earth orbits around the sun and how the sun, in turn, orbits around the center of a vast collection of stars called our galaxy. At the end of the lecture, a little old lady at the back of the room got up and said: “What you have told us is rubbish. The world is really a flat plate supported on the back of a giant tortoise.” The scientist gave a superior smile before replying, “What is the tortoise standing on?” “You’re very clever, young man, very clever,” said the old lady. “But it’s turtles all the way down!”

Most people would find the picture of our universe as an infinite tower of tortoises rather ridiculous, but why do we think we know better? What do we know about the universe, and how do we know it? Where did the universe come from, and where is it going? Did the universe have a beginning, and if so, what happened before then? What is the nature of time? Will it ever come to an end? Can we go back in time? Recent breakthroughs in physics, made possible in part by fantastic new technologies, suggest answers to some of these longstanding questions. Someday these answers may seem as obvious to us as the earth orbiting the sun–or perhaps as ridiculous as a tower of tortoises. Only time (whatever that may be) will tell.

As long ago as 340 B.C. the Greek philosopher Aristotle, in his book On the Heavens, was able to put forward two good arguments for believing that the earth was a round sphere rather than a flat plate. First, he realized that eclipses of the moon were caused by the earth coming between the sun and the moon. The earth’s shadow on the moon was always round, which would be true only if the earth was spherical. If the earth had been a flat disk, the shadow would have elongated and elliptical, unless the eclipse always occurred at a time when the sun was directly under the center of the disk. Second, the Greeks knew from their travels that the North Star appeared lower in the sky when viewed in the south than it did in more northerly regions. (Since the North Star lies over the North Pole, it appears to be directly above an observer at the North Pole, but to someone looking from the equator, it appears to lie just at the horizon. From the difference in the apparent position of the North Star in Egypt and Greece, Aristotle even quoted an estimate that the distance around the earth was 400,000 stadia. It is not known exactly what length a stadium was, but it may have been about 200 yards, which would make Aristotle’s estimate about twice the currently accepted figure. The Greeks even had a third argument that the earth must be round, for why else does one first see the sails of a ship coming over the horizon, and only later see the hull?

Aristotle thought the earth was stationary and that the sun, the moon, the planets, and the stars moved in circular orbits about the earth. He believed this because he felt, for mystical reasons, that the earth was the center of the universe, and that circular motion was the most perfect. This idea was elaborated by Ptolemy in the second century A.D. into a complete cosmological model. The earth stood at the center, surrounded by eight spheres that carried the moon, the sun, the stars, and the five planets known at the time, Mercury, Venus, Mars, Jupiter, and Saturn (Fig 1.1). The planets themselves moved on smaller circles attached to their respective spheres in order to account for their rather complicated observed paths in the sky. The outermost sphere carried the so-called fixed stars, which always stay in the same positions relative to each other but which rotate together across the sky. What lay beyond the last sphere was never made very clear, but it certainly was not part of mankind’s observable universe.

Ptolemy’s model provided a reasonably accurate system for predicting the positions of heavenly bodies in the sky. But in order to predict these positions correctly, Ptolemy had to make an assumption that the moon followed a path that sometimes brought it twice as close to the earth as at other times. And that meant that the moon ought sometimes to appear twice as big as at other times! Ptolemy recognized this flaw, but nevertheless his model was generally, although not universally, accepted. It was adopted by the Christian church as the picture of the universe that was in accordance with Scripture, for it had the great advantage that it left lots of room outside the sphere of fixed stars for heaven and hell.

A simpler model, however, was proposed in 1514 by a Polish priest, Nicholas Copernicus. (At first, perhaps for fear of being branded a heretic by his church, Copernicus circulated his model anonymously.) His idea was that the sun was stationary at the center and that the earth and the planets moved in circular orbits around the sun. Nearly a century passed before this idea was taken seriously. Then two astronomers–the German, Johannes Kepler, and the Italian, Galileo Galilei–started publicly to support the Copernican theory, despite the fact that the orbits it predicted did not quite match the ones observed. The death blow to the Aristotelian/Ptolemaic theory came in 1609. In that year, Galileo started observing the night sky with a telescope, which had just been invented. When he looked at the planet Jupiter, Galileo found that it was accompanied by several small satellites or moons that orbited around it. This implied that everything did not have to orbit directly around the earth, as Aristotle and Ptolemy had thought. (It was, of course, still possible to believe that the earth was stationary at the center of the universe and that the moons of Jupiter moved on extremely complicated paths around the earth, giving the appearance that they orbited Jupiter. However, Copernicus’s theory was much simpler.) At the same time, Johannes Kepler had modified Copernicus’s theory, suggesting that the planets moved not in circles but in ellipses (an ellipse is an elongated circle). The predictions now finally matched the observations.

As far as Kepler was concerned, elliptical orbits were merely an ad hoc hypothesis, and a rather repugnant one at that, because ellipses were clearly less perfect than circles. Having discovered almost by accident that elliptical orbits fit the observations well, he could not reconcile them with his idea that the planets were made to orbit the sun by magnetic forces. An explanation was provided only much later, in 1687, when Sir Isaac Newton published his Philosophiae Naturalis Principia Mathematica, probably the most important single work ever published in the physical sciences. In it Newton not only put forward a theory of how bodies move in space and time, but he also developed the complicated mathematics needed to analyze those motions. In addition, Newton postulated a law of universal gravitation according to which each body in the universe was attracted toward every other body by a force that was stronger the more massive the bodies and the closer they were to each other. It was this same force that caused objects to fall to the ground. (The story that Newton was inspired by an apple hitting his head is almost certainly apocryphal. All Newton himself ever said was that the idea of gravity came to him as he sat “in a contemplative mood” and “was occasioned by the fall of an apple.”) Newton went on to show that, according to his law, gravity causes the moon to move in an elliptical orbit around the earth and causes the earth and the planets to follow elliptical paths around the sun.

The Copernican model got rid of Ptolemy’s celestial spheres, and with them, the idea that the universe had a natural boundary. Since “fixed stars” did not appear to change their positions apart from a rotation across the sky caused by the earth spinning on its axis, it became natural to suppose that the fixed stars were objects like our sun but very much farther away.

Newton realized that, according to his theory of gravity, the stars should attract each other, so it seemed they could not remain essentially motionless. Would they not all fall together at some point? In a letter in 1691 to Richard Bentley, another leading thinker of his day, Newton argued that his would indeed happen if there were only a finite number of stars distributed over a finite region of space. But he reasoned that if, on the other hand, there were an infinite number of stars, distributed more or less uniformly over infinite space, this would not happen, because there would not be any central point for them to fall to.

This argument is an instance of the pitfalls that you can encounter in talking about infinity. In an infinite universe, every point can be regarded as the center, because every point has an infinite number of stars on each side of it. The correct approach, it was realized only much later, is to consider the finite situation, in which the stars all fall in on each other, and then to ask how things change if one adds more stars roughly uniformly distributed outside this region. According to Newton’s law, the extra stars would make no difference at all to the original ones on average, so the stars would fall in just as fast. We can add as many stars as we like, but they will still always collapse in on themselves. We now know it is impossible to have an infinite static model of the universe in which gravity is always attractive.

It is an interesting reflection on the general climate of thought before the twentieth century that no one had suggested that the universe was expanding or contracting. It was generally accepted that either the universe had existed forever in an unchanging state, or that it had been created at a finite time in the past more or less as we observe it today. In part this may have been due to people’s tendency to believe in eternal truths, as well as the comfort they found in the thought that even though they may grow old and die, the universe is eternal and unchanging.

Even those who realized that Newton’s theory of gravity showed that the universe could not be static did not think to suggest that it might be expanding. Instead, they attempted to modify the theory by making the gravitational force repulsive at very large distances. This did not significantly affect their predictions of the motions of the planets, but it allowed an infinite distribution of stars to remain in equilibrium–with the attractive forces between nearby stars balanced by the repulsive forces from those that were farther away. However, we now believe such an equilibrium would be unstable: if the stars in some region got only slightly nearer each other, the attractive forces between them would become stronger and dominate over the repulsive forces so that the stars would continue to fall toward each other. On the other hand, if the stars got a bit farther away from each other, the repulsive forces would dominate and drive them farther apart.

Another objection to an infinite static universe is normally ascribed to the German philosopher Heinrich Olbers, who wrote about this theory in 1823. In fact, various contemporaries of Newton had raised the problem, and the Olbers article was not even the first to contain plausible arguments against it. It was, however, the first to be widely noted. The difficulty is that in an infinite static universe nearly every line of sight would end on the surface of a star. Thus one would expect that the whole sky would be as bright as the sun, even at night. Olbers’s counterargument was that the light from distant stars would be dimmed by absorption by intervening matter. However, if that happened the intervening matter would eventually heat up until it glowed as brightly as the stars. The only way of avoiding the conclusion that the whole of the night sky should be as bright as the surface of the sun would be to assume that the stars had not been shining forever but had turned on at some finite time in the past. In that case the absorbing matter might not have heated up yet or the light from distant stars might not yet have reached us. And that brings us to the question of what could have caused the stars to have turned on in the first place.

The beginning of the universe had, of course, been discussed long before this. According to a number of early cosmologies and the Jewish/Christian/Muslim tradition, the universe started at a finite, and not very distant, time in the past. One argument for such a beginning was the feeling that it was necessary to have “First Cause” to explain the existence of the universe. (Within the universe, you always explained one event as being caused by some earlier event, but the existence of the universe itself could be explained in this way only if it had some beginning.) Another argument was put forward by St. Augustine in his book The City of God. He pointed out that civilization is progressing and we remember who performed this deed or developed that technique. Thus man, and so also perhaps the universe, could not have been around all that long. St. Augustine accepted a date of about 5000 B.C. for the Creation of the universe according to the book of Genesis. (It is interesting that this is not so far from the end of the last Ice Age, about 10,000 B.C., which is when archaeologists tell us that civilization really began.)

Aristotle, and most of the other Greek philosophers, on the other hand, did not like the idea of a creation because it smacked too much of divine intervention. They believed, therefore, that the human race and the world around it had existed, and would exist, forever. The ancients had already considered the argument about progress described above, and answered it by saying that there had been periodic floods or other disasters that repeatedly set the human race right back to the beginning of civilization.

Table of Contents

Foreword ..... vii
Chapter 1: Our Picture of the Universe ..... 1
Chapter 2: Space and Time ..... 15
Chapter 3: The Expanding Universe ..... 37
Chapter 4: The Uncertainty Principle ..... 55
Chapter 5: Elementary Particles and the Forces of Nature ..... 65
Chapter 6: Black Holes ..... 83
Chapter 7: Black Holes Ain't So Black ..... 103
Chapter 8: The Origin and Fate of the Universe ..... 119
Chapter 9: The Arrow of Time ..... 147
Chapter 10: Wormholes and Time Travel ..... 159
Chapter 11: The Unification of Physics ..... 171
Chapter 12: Conclusion ..... 187
Albert Einstein ..... 192
Galileo Galilei ..... 194
Isaac Newton ..... 196
Glossary ..... 199
Acknowledgments ..... 205
Index ..... 207

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A Brief History Of Time (Turtleback School & Library Binding Edition) 4.3 out of 5 based on 0 ratings. 202 reviews.
ReadingRedHead More than 1 year ago
When I started reading this book, I thought there is no way in the world I will be able to understand one of the greatest minds in physics today. How wrong I was! Dr. Hawking makes complicated theory understandable for the rest of us. This is a fascinating book that I would recommend to everyone.
CodyHunt More than 1 year ago
Throughout his book, Stephen Hawking presents his outstanding observations and beliefs of the physics of our universe. Hawking presents information on the history of the universe, motion of the universe and most exhilarating of all, black holes. He includes his perception and opinions of the universe and its past as well as the physics acting upon it as time passes He presents the writing in reasonable short chapters that help you understand him and all of his reasoning as well as the tons of background information that he has researched and drawn his observations from. I would recommend this as a read for anyone that has even a slight interest in astronomy and the cosmos. Stephen Hawking teaches you about simple and general astronomy and from that draws major theories that are constantly changing as we learn more about our universe through technological innovations. There are many pages that will have to be read multiple times before you can really understand what he is even talking about. This isn't really a book that you can skim through or you are bound to miss something vital to the theory of relativity or some function of quantum physics. Since it is so thorough, unlike some books, you WILL put it down. Chances are, you'll throw it down in frustration with Hawking, but you will be rewarded in the end when you realize how blatantly he put some of the most complex thoughts and information accessible to humans. I enjoyed Hawkings sense of humor and voice in his writing. Before I read this book, physics seemed extremely dry and boring but he adds humor and feeling and made me captivated by concepts. I felt like I was sitting in a classroom while I read this, hearing the teachers voice rambling on and on and on about something I didn't really care about until he cracked a joke that I just caught through the blur of boredom. I let out a little chuckle and grin then realize that the subject is exhilarating and fun. I had no dislike from this book, just shock and awe of a new subject that I knew very little about. Irate this book overall, four stars out five because I do not think this book is for everyone, but I loved it and believe that many people could capture some of the ideas in the writing and be surprised with an epiphany of your surroundings and how miniscule we are in the universe and how much else is out there in time and space.
Guest More than 1 year ago
Hawkings brings to life the wonder of science in a language that anyone can understand. We need more books like this.
Guest More than 1 year ago
I am 14 and I have a passion for astrophysics. I knew a lot of facts about which the book is talking about, but I had chaos in my head. Mr. Hawking brought peace and order. This book is amazing in 2 major things: 1) It guides the reader through a vast topic that is flooding with unrelated information in a smooth and orederly way. 2) He describes super-hard concepts in an amazingly simple manner so that almost everyone can understand the General Theory of Relativity having but a little understannding of physics. I reccommend this book for those that are interested in astrophysics and especially for those that simply want to get the answer to those basic standard questions (How did universe began?).
Anonymous More than 1 year ago
I am in 8th grade and got this book recommended to me by my teachers. It is an informative book but you need to have a fairly high reading level to understand some parts of it.This book also answers a lot of the questions I had. All in all, it is a good book.
Guest More than 1 year ago
Many years after its initial release, this book is still a great pleasure to read. Written in a conversational tone, much of it is probably readily understandable to most readers. However, some parts of it, especially toward the end, aren't exactly simple by any means. Any curious reader, even if not particularly interested in physics or astronomy, will find this little book to be a gem. An extra treat is a few pages at the end describing prominent events from the lives of Einstein, Galileo, and Newton. Highly recommended read.
Guest More than 1 year ago
Excellent for everyone with an interest in how we came about being here today. No need to have an advanced degree in physics or mathematics to understand this book. If you're interested enough to be reading this review, you should buy the book -- you will not be sorry.
Guest More than 1 year ago
Stephen Hawking, One of the World's most brilliant men, has published this incredible piece of literature. His writings are so precise, yet comprehendable by all. His explanation of the Big Bang theory is brilliant, as is any other theory in this book. I highly recommend that you buy this book, because it is worth it.
d_k More than 1 year ago
Stephen Hawking’s A Brief History of Time is a mind-boggling series of facts and theories. From his explanation of the big bang, black holes, and relativity, everything in the book is explained thoroughly so that more simplistic minds than that of Stephen Hawking’s can understand. I really liked how he explained different factors of why our universe exists the way it does and how it would be if some factors were changed. His explanation of relativity was also quite impressive to me because of the real life examples Hawking provided to the reader. Don’t get me wrong, this book is very complex and difficult to understand. I found myself having to re-read certain sections of the book just to make sure I was understanding what I was reading. People who are interested in science, math, or physics should definitely keep an open mind about reading this book. People with minimal focus towards scientific theory or math should pass this one up. Hawking takes the time to explain every little thing with great detail. Even though this book is around 180 pages, it is not a quick read. People without much free time should not read this book. Since I am only 15, it is impossible for me to completely understand quantum mechanics or complex theories. There is a very helpful glossary in the back of the book though. I highly recommend other scientific books about space and time if one enjoyed reading this one. Stephen Hawking’s mind is to brilliant, that he can simplify complex theories and ideas so that people like me can completely understand what he is talking about. His mind soars beyond what is comprehensive about the universe that we live in. I give this book a ¿.
Guest More than 1 year ago
I read this book about 2 years ago, and i have not thought about life in the same way ever since. I think it is one of the best books ever written on particle and theoretical physics. It is extremely understandable, enjoyable, and interesting. After reading this book, i became so interested in its subject matter that i have collected an entire bookshelf full of books on related topics.
Guest More than 1 year ago
A very well done book, put in to an easy to understand format combines to make this text an outstanding piece. Strongly suggested for anyone who looks for a general but firm understanding in the underpinning of what makes our universe tick as time (whatever it may be) passes. If it kept me reading, it will with out a doubt keep you intriuged. Mr. Hawking is a man of exceptional intellect, which is reflected in this book.
Guest More than 1 year ago
It is easy reading for most everyone and the reading goes by quickly. The man proves anyone can do anything they want to regardless of any disabilities they may have.
Guest More than 1 year ago
This book was exciting to read because it presented information about the theory of relativity, time travel, black holes,quantum physics, particles and other studies, in an easy and fun to read manner. Stephen W. Hawking gave me the opportunity to study some very complicated and interesting scientific issues in a detailed and precise manner, without boring me with massive formulas, talking down to me, and without jamming me with academic regalia. The author was able to translate complicated scientific theories in a way that makes it easy for 'non-science majors' to understand. His examples are fun and helpful. The results are a much clearer understanding of the world around me, and the space/time continuum. My favorite and the most amazing example was the 'Spin' theory. How can a particle be rotated 720% before it resumes it's original look? Isn't 360% a full rotation? Read it and you will find out! The author explains this phenomenon very clearly in simple terms, with interesting stories and examples. In conclusion I recommend this book to anyone who has ever wondered about light speed, space/time curvature, the theories regarding the expansion of or the implosion of the universe, black holes, gravity, or the BIG BANG theory. This book has it all. Try it!
ryeLee More than 1 year ago
There are some extremely intelligent mathematicians and scientists we call geniuses, and rightly so. WOW! I am real glad I read this book for even a hint of understanding is amazing.
RubyPC More than 1 year ago
I love it!! It's so easy to read!!!!
Guest More than 1 year ago
All in all, this was definitely one of the better books that I have ever read. There was a lot of interesting information that really made you think, although lots of the material was quite complicated. I enjoyed parts of the book that explained the future of the universe and was glad to know that my own theories match the ones in the book. This is definitely a must read for science lover although I would recommend it for university students if you are expecting to understand all of the content.
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LisaMaria_C on LibraryThing More than 1 year ago
A friend of mine loves this book and has read it more than once. Reassuring, since like me, she doesn't hold a doctorate in the sciences! In fact, as someone who used to do a lot of science reading--I read many a astronomy book by Isaac Asimov and Carl Sagan once upon a time--most of the concepts here were very familiar. Well, until we reached the very weird land of quantum mechanics and string theory and imaginary numbers, where I admit I was pretty lost. Hawking gives the history of the science surrounding the ultimate questions of the universe starting from the arguments of Aristotle in 340 B.C. for a round earth to the very strange land of today's physics of quantum mechanics with its different colored quarks and antimatter on the micro level and the strange interstellar beasties of relativistic physics of dark matter, black holes, quasars, and neutron stars and the very weird string theory that might unite both. I do think his explanations are lucid and elegant. I can't remember a better description of Einstein's General Theory of Relativity by explaining its historic relationship to Newton and how the theory tried to answer questions about the relationship between space and time. And Hawking manages to explain some sophisticated concepts without loading the book with jargon or equations. Hawking was also great at explaining how the theory of Relativity fits--or rather doesn't fit--with Quantum Mechanics and the search for a theory that could unify them both. I'm not saying I understood everything in the book. The concepts are counter-intuitive and hard to digest, and there's only so far you can go in explaining difficult subjects in simple terms to people lacking the background. But I understood it better, and certainly got the implications Hawking spelled out. About the only stylistic quirk I had an issue with was Hawking's refusal to use the B-word. (A Briticism?). I find it a lot easier to wrap my mind around ten billion than "ten thousand million." The edition I read was written in 1996, updated from the first edition from 1988 which was a enormous bestseller. In the Foreword to that revised edition, Hawking wrote he thought that "within a few years we should know whether we can believe that we live in a universe that is completely self-contained and without beginning or end." Hawking definitely leaves me wanting to read more to find out the verdict. Worth reading, although not always easy to grasp.
benfulton on LibraryThing More than 1 year ago
I can't really say if I think this is a great book or not. To my mind, it leans too far in the direction of the layman, glossing over mathematics and detailed explanations in favor of overviews and quick touches on a lot of subjects. I suppose that's how it became "brief". But I don't think it compares to other great science books like Godel, Escher, Bach or some of Einstein's books on relativity that were also aimed at the non-expert.
KayPrime on LibraryThing More than 1 year ago
Considering that I haven't taken a physics class since high shcool, I started this book expecting to follow only a minority of the information presented. However, Hawking does an excellent job explaining complex mathematical theories in the most basic of terms.Even so, the book did require my undivided attention and still I couldn't follow every single idea. (For example: it was difficult for me to wrap my mind around imaginary time and to think in four dimensions.)I absolutely loved this book (so much, in fact, that I read it twice) and can't wait to read more from Hawking. I recommend this book to anyone interested in understanding the universe in which they live ranging from the extraordinarily vast (general theory of relativity) to the extraordinarily small (quantum mechanics) and the search for the Theory of Everything (uniting the two theories in a quantum theory of gravity).
JoseArcadio on LibraryThing More than 1 year ago
The current generation's genius and scientific pioneer, Stephen Hawking provides and entertaining and informative look into quantum mechanics and the workings of the cosmost. Although posessing a brain capacity far out of reach of most people, Hawking is able to write in a style accessible by people of all IQ's. Using clear explanation, analogies and a touch of humour Hawking is able to present the most difficult and abstract current theories in an accessible manner. Although the he writes simplistically the content is certainly mind blowing. I recommend this book for people who have had a partial scientific background and a definite interest in physics. I have read the book three times and I would be exaggerating if I said I understand it completely. Despite this it is still an excellent book and I recommend to anyone with scientific interest.
Giglio.Danny on LibraryThing More than 1 year ago
"A Brief History of Time" is undisputedly the most informative and best selling physics based novel. I was shocked at Hawking's sense of humor more than anything, as I'm sure most readers will agree. The parts of the book most difficult to understand were made bearable by the hilarious puns and references of the author. Hawking does an excellent job, more than anthing else, of explaining the importance of the "Theory of Everything", and the extent to which it would change the course of modern physics if uncovered. He conveys the value of science on society rather well in the text. I was also surprised with the amount of material covered in this relatively small text. Hawking managed to cover both kinds of relativity, as well as his most important area of discussion - Black Holes. This chapter is most famously reffered to as "Black Holes Ain't so Black", again displaying Hawking's excellent sense of humor.
chersbookitlist on LibraryThing More than 1 year ago
I love books about the origins, workings and mysteries of the universe, and books by Stephen Hawking in particular. He makes the complex and unfathomable more accessible to the layperson using very entertaining prose.
NateJordon on LibraryThing More than 1 year ago
Hawking presents a scientific and philosophical view of the universe via the most complicated theories of mathematics and science in layman's terms. That said, the book requires a second reading. There's so much intriguing information in the book's 191 pages that on a first reading, I believe it would be difficult for anyone (without advanced knowledge of astrophysics, quantum mechanics, etc.) to conceptualize all the book contains and postulates. Nonetheless, an incredible book for anyone asking such questions as: how did we get here and where are we going? among others.