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Endless Universe: Beyond the Big Bang -- Rewriting Cosmic History
Two world-renowned scientists present an audacious new vision of the cosmos that “steals the thunder from the Big Bang theory.” — Wall Street Journal
The Big Bang theory—widely regarded as the leading explanation for the origin of the universe—posits that space and time sprang into being about 14 billion years ago in a hot, expanding fireball of nearly infinite density. Over the last three decades the theory has been repeatedly revised to address such issues as how galaxies and stars first formed and why the expansion of the universe is speeding up today. Furthermore, an explanation has yet to be found for what caused the Big Bang in the first place.
In Endless Universe , Paul J. Steinhardt and Neil Turok, both distinguished theoretical physicists, present a bold new cosmology. Steinhardt and Turok “contend that what we think of as the moment of creation was simply part of an infinite cycle of titanic collisions between our universe and a parallel world” ( Discover ). They recount the remarkable developments in astronomy, particle physics, and superstring theory that form the basis for their groundbreaking “Cyclic Universe” theory. According to this theory, the Big Bang was not the beginning of time but the bridge to a past filled with endlessly repeating cycles of evolution, each accompanied by the creation of new matter and the formation of new galaxies, stars, and planets.
Endless Universe provides answers to longstanding problems with the Big Bang model, while offering a provocative new view of both the past and the future of the cosmos. It is a “theory that could solve the cosmic mystery” ( USA Today ).
The Big Bang theory—widely regarded as the leading explanation for the origin of the universe—posits that space and time sprang into being about 14 billion years ago in a hot, expanding fireball of nearly infinite density. Over the last three decades the theory has been repeatedly revised to address such issues as how galaxies and stars first formed and why the expansion of the universe is speeding up today. Furthermore, an explanation has yet to be found for what caused the Big Bang in the first place.
In Endless Universe , Paul J. Steinhardt and Neil Turok, both distinguished theoretical physicists, present a bold new cosmology. Steinhardt and Turok “contend that what we think of as the moment of creation was simply part of an infinite cycle of titanic collisions between our universe and a parallel world” ( Discover ). They recount the remarkable developments in astronomy, particle physics, and superstring theory that form the basis for their groundbreaking “Cyclic Universe” theory. According to this theory, the Big Bang was not the beginning of time but the bridge to a past filled with endlessly repeating cycles of evolution, each accompanied by the creation of new matter and the formation of new galaxies, stars, and planets.
Endless Universe provides answers to longstanding problems with the Big Bang model, while offering a provocative new view of both the past and the future of the cosmos. It is a “theory that could solve the cosmic mystery” ( USA Today ).
304 pages, Paperback
First published January 1, 2007
93 people are currently reading
2030 people want to read
About the author
Paul J. Steinhardt
5 books43 followersPaul Joseph Steinhardt (born December 25, 1952) is an American theoretical physicist whose principal research is in cosmology and condensed matter physics. He is currently the Albert Einstein Professor in Science at Princeton University where he is on the faculty of both the Departments of Physics and of Astrophysical Sciences.
Steinhardt is best known for his development of new theories of the origin, evolution and future of the universe. He is also well known for his exploration of a new form of matter, known as quasicrystals, which were thought to exist only as man-made materials until he co-discovered the first known natural quasicrystal in a museum sample.
He subsequently led a separate team that followed up that discovery with several more examples of natural quasicrystals recovered from the wilds of the Kamchatka Peninsula in far eastern Russia.
Steinhardt is best known for his development of new theories of the origin, evolution and future of the universe. He is also well known for his exploration of a new form of matter, known as quasicrystals, which were thought to exist only as man-made materials until he co-discovered the first known natural quasicrystal in a museum sample.
He subsequently led a separate team that followed up that discovery with several more examples of natural quasicrystals recovered from the wilds of the Kamchatka Peninsula in far eastern Russia.
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September 16, 2012
In James Blish's Golden Age SF novel
A Clash of Cymbals
, the concluding volume of the "Cities in Flight" tetralogy, scientists make a momentous discovery: we are not the only universe. A parallel universe, separated from ours across a fourth spatial dimension, is drawing ever closer. When the two universes collide, they will mutually annihilate and start a new cycle of the cosmic story.
I liked Blish's story as a teen, but found the basic premise hard to swallow. I am all the more astonished to discover that Paul Steinhardt and Neil Turok (hereafter, S&T), both highly respected cosmologists, have proposed a similar scenario and argued for it at length. There are a few differences, of course. In Blish's story, the other universe was made of antimatter, and the S&T one is normal matter; also, Blish has the collision occurring in 4004 A.D., while S&T more conservatively estimate that it will happen about a trillion years from now. All the same, the two versions are surprisingly similar. Even more surprisingly, no one seems to have told the two scientists about their fictional precursor. They quote Asimov's short story The Final Question with evident approval, but there's not a mention of poor old Blish.
S&T seem disappointed that hardly anyone is prepared to take them seriously, despite all the work they've done. They make some good points. "Inflation", the current mainstream theory of the very early universe, is a bit of a mess: in particular, it relies on an expansive force which only had effect right at the beginning of time, and whose nature is still obscure. Originally it was supposed to be caused by the Higgs field, but it turned out that that didn't work; now it's claimed to be something similar to the Higgs field, but distinct from it. The properties of the "inflaton" field seem rather ad hoc, and have to tuned carefully to fit the data. S&T point out that we already know about one universal expansive field, dark energy. Their theory uses dark energy to do all the expanding and smoothing that inflation is supposed to do. Each trillion year cycle of the universe ends up with space-time ironed flat by dark energy; it then collides with the parallel universe, releasing a huge amount of energy and kicking the cycle off again. Some parts of this idea seem to have been borrowed by Penrose in his recent book Cycles of Time .
S&T have detailed mathematical models for everything, and there's no doubt that it's real science. It makes concrete predictions: if inflation happened, it ought to have given rise to strong gravitational waves, whose effects we should fairly soon be in a position to detect by the way they would polarize the Cosmic Background Radiation. S&T, in contrast, predict much weaker gravitational waves. We only need to be able to measure the polarization a little more accurately to be able to distinguish the two theories. Stephen Hawking (a colleague of Turok) has apparently made one of his famous bets to the effect that these measurements will disprove the cyclic theory. Right now, however, it seems that no one knows what's going on.
So the jury's still out, but I'm afraid my reaction is the same as it was when I read Blish's novel in the early 70s: it's just too bizarre to think that there's an invisible universe alongside ours, which periodically collides with us. I gather that my reaction is pretty much the usual one. All the same, the book is responsibly written and contains a lot of interesting detail about how the world of modern cosmology works. If you're into that kind of thing, I warmly recommend it.
___________________________________________________
I wrote to Steinhardt yesterday to ask if it really was the case that he had not come across the James Blish novel. He thanked me and said that I was the first person to point out the connection. I do feel sorry for Blish. Evidently his book is utterly forgotten, a mere 50 years after it was first published.
I liked Blish's story as a teen, but found the basic premise hard to swallow. I am all the more astonished to discover that Paul Steinhardt and Neil Turok (hereafter, S&T), both highly respected cosmologists, have proposed a similar scenario and argued for it at length. There are a few differences, of course. In Blish's story, the other universe was made of antimatter, and the S&T one is normal matter; also, Blish has the collision occurring in 4004 A.D., while S&T more conservatively estimate that it will happen about a trillion years from now. All the same, the two versions are surprisingly similar. Even more surprisingly, no one seems to have told the two scientists about their fictional precursor. They quote Asimov's short story The Final Question with evident approval, but there's not a mention of poor old Blish.
S&T seem disappointed that hardly anyone is prepared to take them seriously, despite all the work they've done. They make some good points. "Inflation", the current mainstream theory of the very early universe, is a bit of a mess: in particular, it relies on an expansive force which only had effect right at the beginning of time, and whose nature is still obscure. Originally it was supposed to be caused by the Higgs field, but it turned out that that didn't work; now it's claimed to be something similar to the Higgs field, but distinct from it. The properties of the "inflaton" field seem rather ad hoc, and have to tuned carefully to fit the data. S&T point out that we already know about one universal expansive field, dark energy. Their theory uses dark energy to do all the expanding and smoothing that inflation is supposed to do. Each trillion year cycle of the universe ends up with space-time ironed flat by dark energy; it then collides with the parallel universe, releasing a huge amount of energy and kicking the cycle off again. Some parts of this idea seem to have been borrowed by Penrose in his recent book Cycles of Time .
S&T have detailed mathematical models for everything, and there's no doubt that it's real science. It makes concrete predictions: if inflation happened, it ought to have given rise to strong gravitational waves, whose effects we should fairly soon be in a position to detect by the way they would polarize the Cosmic Background Radiation. S&T, in contrast, predict much weaker gravitational waves. We only need to be able to measure the polarization a little more accurately to be able to distinguish the two theories. Stephen Hawking (a colleague of Turok) has apparently made one of his famous bets to the effect that these measurements will disprove the cyclic theory. Right now, however, it seems that no one knows what's going on.
So the jury's still out, but I'm afraid my reaction is the same as it was when I read Blish's novel in the early 70s: it's just too bizarre to think that there's an invisible universe alongside ours, which periodically collides with us. I gather that my reaction is pretty much the usual one. All the same, the book is responsibly written and contains a lot of interesting detail about how the world of modern cosmology works. If you're into that kind of thing, I warmly recommend it.
___________________________________________________
I wrote to Steinhardt yesterday to ask if it really was the case that he had not come across the James Blish novel. He thanked me and said that I was the first person to point out the connection. I do feel sorry for Blish. Evidently his book is utterly forgotten, a mere 50 years after it was first published.
November 30, 2016
Reading for supplement about time cosmology
January 29, 2014
I picked up Endless Universe mainly because I wanted to read something about recent cosmological theory, especially dark matter and dark energy. The book provides all that and then goes further by postulating a more controversial model than the inflationary one currently in favor.
In a recent phone conversation, I mentioned this book and its authors' ideas to a friend of mine who writes about astronomy for a major scientific magazine, and I could hear her rolling her eyes. Suffice it to say, the model put forth in Endless Universe is not widely accepted by the scientific community.
I have no problem with the inflationary model's premise that the universe will expand forever until it is so diffuse that it is, for all practical purposes, empty. What I find hard to believe is that 'everything' just popped into being one day. From where? One might as well believe in creation theory.
Paul Steinhardt and Neil Turok, physicists at Princeton and Cambridge Universities respectively, have an alternative. The idea, in a nutshell, is that rather than one big bang out of nowhere/nowhen, why couldn't there be a never-ending series of bangs and contractions? This is called the cyclic model and in itself is not a new idea. In the past, the cyclic model was soundly trounced by everything from evidence that the expansion of the universe is speeding up with no end in sight to the Second Law of Thermodynamics. To deal with all this they introduce the multiverse, the idea that there are other universes along other dimensions which exert a gravitational effect on ours that could act to reverse the inflationary effect of dark energy. The bangs themselves are actually our universe whacking into the universe next door from time to time.
The book does a great job of presenting things simply, but the midsection does get a bit difficult for layfolk. ('Challenging' is the word the authors use.) In order to explain what they're explaining they throw in basic primers on string theory and quantum mechanics. I was able to plow through all that with only the sketchiest idea of what they meant, and it was enough. Some simple drawings were helpful.
One of the joys of the book is its enthusiasm. In one touching passage, the authors, both physicists by discipline, pay tribute to the trailblazers of the previous generation, such as Andrei Sakharov and Steven Weinberg.
"In the 1960s and '70s, most particle physicists judged cosmology to be too speculative and recommended that their students steer clear of it. But a few celebrated theorists... were notable exceptions... As important as the research itself was the impression it left on the younger generation of physicists. The fact that world-renowned scientists would consider this problem worthy of their attention sent the message that cosmology was ripe for exploration by particle physicists. By the early 1980s, a growing band of young particle theorists had begun to follow their pioneering trail and explore other puzzles lurking in the early universe. The two of us were part of this new generation."
It's a great read whether you agree with their ideas or not. Steinhardt and Turok provide a good overview of cosmology, including a sympathetic summary of the inflationary model. (Steinhardt is a defector from that camp, so he knows the party line well.) There were moments reading this book when I was suddenly struck by the scale of space and time being thrown around, and I felt real awe. That alone is worth the price of admission.
In a recent phone conversation, I mentioned this book and its authors' ideas to a friend of mine who writes about astronomy for a major scientific magazine, and I could hear her rolling her eyes. Suffice it to say, the model put forth in Endless Universe is not widely accepted by the scientific community.
I have no problem with the inflationary model's premise that the universe will expand forever until it is so diffuse that it is, for all practical purposes, empty. What I find hard to believe is that 'everything' just popped into being one day. From where? One might as well believe in creation theory.
Paul Steinhardt and Neil Turok, physicists at Princeton and Cambridge Universities respectively, have an alternative. The idea, in a nutshell, is that rather than one big bang out of nowhere/nowhen, why couldn't there be a never-ending series of bangs and contractions? This is called the cyclic model and in itself is not a new idea. In the past, the cyclic model was soundly trounced by everything from evidence that the expansion of the universe is speeding up with no end in sight to the Second Law of Thermodynamics. To deal with all this they introduce the multiverse, the idea that there are other universes along other dimensions which exert a gravitational effect on ours that could act to reverse the inflationary effect of dark energy. The bangs themselves are actually our universe whacking into the universe next door from time to time.
The book does a great job of presenting things simply, but the midsection does get a bit difficult for layfolk. ('Challenging' is the word the authors use.) In order to explain what they're explaining they throw in basic primers on string theory and quantum mechanics. I was able to plow through all that with only the sketchiest idea of what they meant, and it was enough. Some simple drawings were helpful.
One of the joys of the book is its enthusiasm. In one touching passage, the authors, both physicists by discipline, pay tribute to the trailblazers of the previous generation, such as Andrei Sakharov and Steven Weinberg.
"In the 1960s and '70s, most particle physicists judged cosmology to be too speculative and recommended that their students steer clear of it. But a few celebrated theorists... were notable exceptions... As important as the research itself was the impression it left on the younger generation of physicists. The fact that world-renowned scientists would consider this problem worthy of their attention sent the message that cosmology was ripe for exploration by particle physicists. By the early 1980s, a growing band of young particle theorists had begun to follow their pioneering trail and explore other puzzles lurking in the early universe. The two of us were part of this new generation."
It's a great read whether you agree with their ideas or not. Steinhardt and Turok provide a good overview of cosmology, including a sympathetic summary of the inflationary model. (Steinhardt is a defector from that camp, so he knows the party line well.) There were moments reading this book when I was suddenly struck by the scale of space and time being thrown around, and I felt real awe. That alone is worth the price of admission.
August 6, 2008
First off I should establish my bona fides for reviewing a book like this (i.e., science): I have none!
My interest in astronomy & its relatives goes back to when I was 8 and entertained the idea of becoming an astronomer. Alas, I have no head for math and only my 9th grade science teacher was any inspiration at all so I wound up in the humanities (not that I regret it, given my talents and interests I didn't make the wrong choice). I am but an amateur dilettante who can only watch from the bleachers.
My lack of credentials firmly established, this is a very interesting read. The authors are the originators of the only serious contender to the dominant theory about the origins of the universe, the inflationary big bang theory. Their version is called "the cyclic universe" theory.
They identify several areas where the IBB is deficient; the most telling being the lack of a source for inflationary energy. But perhaps I should back track a bit: The "inflation" in IBB refers to a period right after the big bang when space/time expanded at an enormous rate, far faster than it had been and did subsequently. This inflationary quirk had to be introduced to the original big bang model because, otherwise, cosmologists couldn't explain why the universe looks the way it does today. This aspect of the big bang theory has always bothered me, actually. It seems rather arbitrary to simply introduce a condition in order to make your theory work out (though there is enough circumstantial evidence to make it plausible).
The authors attempt to resolve the dilemmas faced by the IBB by postulating that our universe is but the latest in a cycle of universes that have been created, lived & died. There may be no beginning (which would have Aquinas rolling in his grave) and no end to the cycles (which last about a trillion years). Space and time existed before our universe emerged and don't have to be created ex nihilo; and previous universes may have had an influence on the structure of ours, which would explain why ours is so congenial to our lifeform. They can do this by relying on the characteristics of the latest incarnation of string theory -- M theory. This is probably the weakest part of their argument since string theory has lately come under some fierce attacks and it may turn out NOT to be the answer to "life the universe and everything" afterall (besides we all know it's 42 anyway).
I like their theory anyway. It's more elegant than the IBB and aesthetically pleasing (which, of course, is not definitive) and the authors present it very clearly.
I'd like to think their solution or one similar to it is the correct one but I'll enjoy watching how things turn out over the course of the next few years.
My interest in astronomy & its relatives goes back to when I was 8 and entertained the idea of becoming an astronomer. Alas, I have no head for math and only my 9th grade science teacher was any inspiration at all so I wound up in the humanities (not that I regret it, given my talents and interests I didn't make the wrong choice). I am but an amateur dilettante who can only watch from the bleachers.
My lack of credentials firmly established, this is a very interesting read. The authors are the originators of the only serious contender to the dominant theory about the origins of the universe, the inflationary big bang theory. Their version is called "the cyclic universe" theory.
They identify several areas where the IBB is deficient; the most telling being the lack of a source for inflationary energy. But perhaps I should back track a bit: The "inflation" in IBB refers to a period right after the big bang when space/time expanded at an enormous rate, far faster than it had been and did subsequently. This inflationary quirk had to be introduced to the original big bang model because, otherwise, cosmologists couldn't explain why the universe looks the way it does today. This aspect of the big bang theory has always bothered me, actually. It seems rather arbitrary to simply introduce a condition in order to make your theory work out (though there is enough circumstantial evidence to make it plausible).
The authors attempt to resolve the dilemmas faced by the IBB by postulating that our universe is but the latest in a cycle of universes that have been created, lived & died. There may be no beginning (which would have Aquinas rolling in his grave) and no end to the cycles (which last about a trillion years). Space and time existed before our universe emerged and don't have to be created ex nihilo; and previous universes may have had an influence on the structure of ours, which would explain why ours is so congenial to our lifeform. They can do this by relying on the characteristics of the latest incarnation of string theory -- M theory. This is probably the weakest part of their argument since string theory has lately come under some fierce attacks and it may turn out NOT to be the answer to "life the universe and everything" afterall (besides we all know it's 42 anyway).
I like their theory anyway. It's more elegant than the IBB and aesthetically pleasing (which, of course, is not definitive) and the authors present it very clearly.
I'd like to think their solution or one similar to it is the correct one but I'll enjoy watching how things turn out over the course of the next few years.
November 7, 2020
A fascinating read. The two authors provide an alternative theory, a cyclic model of the Universe, to the long-standing inflationary theory. They also describe some of the flaws in the latter theory, as well as some insights with respect to the creation of this theory, how theories are discussed between scientists and how they are evaluated.
While I understand that the cyclic model competes with the inflationary theory, sometimes I felt like the authors were more focused on criticizing the other theory and maintaining a defensive attitude throughout the book. They list the possible flaws of their theory only at the very end.
The book was first published in 2007 and in the same year another cyclic model of the Universe (the Baum-Frampton model) appeared. Of course, the debate still rages on and in 2015 a new item was added to the debate - the first (alleged) observation of gravitational waves.
This is a field I am very passionate about, albeit at an amateur level, and I am glad that there is still room for discussions and that we continue to try to solve the puzzles of the Universe.
The double Klein bottle used for the cover to symbolize the cyclic model is also a neat touch.
While I understand that the cyclic model competes with the inflationary theory, sometimes I felt like the authors were more focused on criticizing the other theory and maintaining a defensive attitude throughout the book. They list the possible flaws of their theory only at the very end.
The book was first published in 2007 and in the same year another cyclic model of the Universe (the Baum-Frampton model) appeared. Of course, the debate still rages on and in 2015 a new item was added to the debate - the first (alleged) observation of gravitational waves.
This is a field I am very passionate about, albeit at an amateur level, and I am glad that there is still room for discussions and that we continue to try to solve the puzzles of the Universe.
The double Klein bottle used for the cover to symbolize the cyclic model is also a neat touch.
February 29, 2020
I really enjoyed the book. I have read Turok before, "The Universe Within" so decided to give this a try. They present their work on an alternative model of the universe to the inflationary theory. I found it challenging at times and put some time into summarizing it so that I could benefit from a more complete understanding of the cyclic model.
Inflation post big bang caused the universe to expand 10100 times in 10-30 seconds. Gas cooled, expansion slowed allowing atoms and molecules to clump and form stars and galaxies. This was the theory conceived in 1980s, but now recent observations show that dark energy took over and started to accelerate expansion again. The standard inflationary model states that the expansion will continue forever until space turns into a nearly perfect vacuum.
Flaws of inflationary model:
1) Patchwork theory with many disconnected ingredients. Ordinary matter, dark matter (accounts for most of the mass of galaxies), dark energy (invisible antigravity force causing accelerated expansion), inflationary energy which exists in the first few instants after the big bang and decays away in 10-30 s.
As an aside, dark matter was discovered through the search for missing mass which presented itself in the unpredictably fast galactic orbital speeds which could not be explained using regular matter alone. It was discovered through gravitational lensing and most phycisists believe it is a soup of neutral elementary particles which do not scatter or absorb light. Dark energy can only be detected through its repulsive gravitational effect over large distances. It can be thought of as the cosmological constant proposed by Einstein in 1917. It is the energy of the vacuum; the energy remaining when all matter and radiation are removed and its value is much smaller today than theory predicts (cosmological constant problem).
Energy density determines the expansion rate of the universe. Energy density of mater decreases as volume increases. Same for radiation, but it is also subject to doppler effect, decreasing the frequency (and energy) as the universe expands. Dark energy in contrast, remains constant. The relative proportions are always changing. At early times, radiation dominates the energy density (0-75,000 years), then followed by a matter dominated period (expansion was slow enough to allow for the formation of higher order structures like stars, planets, and galaxies), and ending in the dark energy dominated period. Attempting to extrapolate back before Act Two (one second after the Big Bang to the present day) is difficult because the the Friedmann relation dictates that the scale of the universe is zero and the density and temperature are infinite, the singularity.
There are three issues with the current picture: homogeneity, inhomogeneity, and the flatness problem. The homogeneity problem is that the universe was very uniform just one second after the big bang and extended a light year across. But light cannot travel farther in a second than a light second. The only way to explain how a uniform universe existed one second after the big bang is to assume that the matter and radiation had been produced in a nearly perfectly uniform state. Next is the so called inhomogeneity problem which states that there must be slight variations in the density to allow for matter to clump under gravity and form galaxies. The variations have to match the observations of the cosmic microwave background (CMB). The third is the flatness problem. Measurement of the CMB show that the universe is flat on large scale. This requires a perfect balance between expansion rate and energy density. Inflationary and cyclic models both try to solves these issues.
The inflationary model assumes that the big bang was the beginning of all time. To account for the flatness of the universe, inflationary energy has specially tuned properties. The dark energy takes over to explain the current period of expansion. What if the big bang was not the beginning and dark energy could be integrated more effectively into the picture?
Enter the cyclic model.
The framework of the cyclic model relies on string theory. In essence, bits of string vibrate and rotate in specific quantized motions. Each quantized state has physical properties such as mass, charge and spin and can account for all elementary particles, including gravitons. In M theory, the Horava-Witten model uses ten dimensions of space and comes close to Einstein’s goal of explaining fundamental physics in a purely geometrical way. M theory has a so called, sixth regime involving branes not strings.
The Horava-Witten picture can be simplified. Imagine two parallel sheets (really nine-dimensional sheets) separated by an extremely small tenth dimension. Although the sheets are nine-dimensional, six of the dimensions are expected to curl into a tiny ball and are important for describing the properties of matter and forces. Now the two sheets each have three dimensions (height, length, width). The observable universe lies on one of the sheets or membranes (braneworld) and it is separated from a second hidden braneworld by 10-30 cm. Apparently, colliding branes (big bang) have the right, nearly scale invariant (objects or laws are constant on different length scales) properties needed to fit the real universe.
The cyclic model has six periods:
The Big Bang. No infinities or singularities. Before the bang, space is flattened and has a smooth energy distribution because dark energy from the previous cycle has decayed.
Radiation dominated epoch. The bang creates a smooth and flat universe, no inflationary period is needed. After a millionth of a second quarks combine to form protons and neutrons. At one second, hydrogen and helium nuclei begin to form.
Matter dominated epoch. After 75,000 years matter takes over. The first atoms are formed at 380,000 years after the big bang, matter is drawn together and galaxies form. The epoch ends after around 9 billion years.
Dark energy dominated epoch. Expansion accelerates and the universe becomes empty and uniform.
Contraction epoch. Key assumption in the cycle model is that dark energy can decay after a period of around a trillion years, causing the deceleration and eventual slow contraction. Once contraction begins, the energy density rises quickly and gravitational energy is converted into a new form of high pressure dark energy and ensures that the universe remains smooth and flat during contraction.
Big crunch. Dark energy is converted into hot matter and radiation and the universe expands. The universe was smooth and flat before the bang, so it remains so afterwards. High pressure dark energy solves the homogeneity and flatness problems.
As an added bonus, the cyclic model also solves the cosmological constant problem. One possibility is that the constant begins at a relatively large value but decreases through tiny quantum jumps (tunneling through small energy barriers to states with lower and lower vacuum energy). This process takes an unimaginably long time to complete, for the constant to reach zero. “Our calculations showed that a patch of the universe would survive at least (1010)100 cycles at this last step”. The point is that the constant is much smaller than we expect because the universe is much older (much older than 14 billion years, having gone through who knows how many cycles) than we thought. This gives the constant ample time to decrease to the observed value today.
Inflation post big bang caused the universe to expand 10100 times in 10-30 seconds. Gas cooled, expansion slowed allowing atoms and molecules to clump and form stars and galaxies. This was the theory conceived in 1980s, but now recent observations show that dark energy took over and started to accelerate expansion again. The standard inflationary model states that the expansion will continue forever until space turns into a nearly perfect vacuum.
Flaws of inflationary model:
1) Patchwork theory with many disconnected ingredients. Ordinary matter, dark matter (accounts for most of the mass of galaxies), dark energy (invisible antigravity force causing accelerated expansion), inflationary energy which exists in the first few instants after the big bang and decays away in 10-30 s.
As an aside, dark matter was discovered through the search for missing mass which presented itself in the unpredictably fast galactic orbital speeds which could not be explained using regular matter alone. It was discovered through gravitational lensing and most phycisists believe it is a soup of neutral elementary particles which do not scatter or absorb light. Dark energy can only be detected through its repulsive gravitational effect over large distances. It can be thought of as the cosmological constant proposed by Einstein in 1917. It is the energy of the vacuum; the energy remaining when all matter and radiation are removed and its value is much smaller today than theory predicts (cosmological constant problem).
Energy density determines the expansion rate of the universe. Energy density of mater decreases as volume increases. Same for radiation, but it is also subject to doppler effect, decreasing the frequency (and energy) as the universe expands. Dark energy in contrast, remains constant. The relative proportions are always changing. At early times, radiation dominates the energy density (0-75,000 years), then followed by a matter dominated period (expansion was slow enough to allow for the formation of higher order structures like stars, planets, and galaxies), and ending in the dark energy dominated period. Attempting to extrapolate back before Act Two (one second after the Big Bang to the present day) is difficult because the the Friedmann relation dictates that the scale of the universe is zero and the density and temperature are infinite, the singularity.
There are three issues with the current picture: homogeneity, inhomogeneity, and the flatness problem. The homogeneity problem is that the universe was very uniform just one second after the big bang and extended a light year across. But light cannot travel farther in a second than a light second. The only way to explain how a uniform universe existed one second after the big bang is to assume that the matter and radiation had been produced in a nearly perfectly uniform state. Next is the so called inhomogeneity problem which states that there must be slight variations in the density to allow for matter to clump under gravity and form galaxies. The variations have to match the observations of the cosmic microwave background (CMB). The third is the flatness problem. Measurement of the CMB show that the universe is flat on large scale. This requires a perfect balance between expansion rate and energy density. Inflationary and cyclic models both try to solves these issues.
The inflationary model assumes that the big bang was the beginning of all time. To account for the flatness of the universe, inflationary energy has specially tuned properties. The dark energy takes over to explain the current period of expansion. What if the big bang was not the beginning and dark energy could be integrated more effectively into the picture?
Enter the cyclic model.
The framework of the cyclic model relies on string theory. In essence, bits of string vibrate and rotate in specific quantized motions. Each quantized state has physical properties such as mass, charge and spin and can account for all elementary particles, including gravitons. In M theory, the Horava-Witten model uses ten dimensions of space and comes close to Einstein’s goal of explaining fundamental physics in a purely geometrical way. M theory has a so called, sixth regime involving branes not strings.
The Horava-Witten picture can be simplified. Imagine two parallel sheets (really nine-dimensional sheets) separated by an extremely small tenth dimension. Although the sheets are nine-dimensional, six of the dimensions are expected to curl into a tiny ball and are important for describing the properties of matter and forces. Now the two sheets each have three dimensions (height, length, width). The observable universe lies on one of the sheets or membranes (braneworld) and it is separated from a second hidden braneworld by 10-30 cm. Apparently, colliding branes (big bang) have the right, nearly scale invariant (objects or laws are constant on different length scales) properties needed to fit the real universe.
The cyclic model has six periods:
The Big Bang. No infinities or singularities. Before the bang, space is flattened and has a smooth energy distribution because dark energy from the previous cycle has decayed.
Radiation dominated epoch. The bang creates a smooth and flat universe, no inflationary period is needed. After a millionth of a second quarks combine to form protons and neutrons. At one second, hydrogen and helium nuclei begin to form.
Matter dominated epoch. After 75,000 years matter takes over. The first atoms are formed at 380,000 years after the big bang, matter is drawn together and galaxies form. The epoch ends after around 9 billion years.
Dark energy dominated epoch. Expansion accelerates and the universe becomes empty and uniform.
Contraction epoch. Key assumption in the cycle model is that dark energy can decay after a period of around a trillion years, causing the deceleration and eventual slow contraction. Once contraction begins, the energy density rises quickly and gravitational energy is converted into a new form of high pressure dark energy and ensures that the universe remains smooth and flat during contraction.
Big crunch. Dark energy is converted into hot matter and radiation and the universe expands. The universe was smooth and flat before the bang, so it remains so afterwards. High pressure dark energy solves the homogeneity and flatness problems.
As an added bonus, the cyclic model also solves the cosmological constant problem. One possibility is that the constant begins at a relatively large value but decreases through tiny quantum jumps (tunneling through small energy barriers to states with lower and lower vacuum energy). This process takes an unimaginably long time to complete, for the constant to reach zero. “Our calculations showed that a patch of the universe would survive at least (1010)100 cycles at this last step”. The point is that the constant is much smaller than we expect because the universe is much older (much older than 14 billion years, having gone through who knows how many cycles) than we thought. This gives the constant ample time to decrease to the observed value today.
January 25, 2016
A very well written account of the evolving efforts to establish the theory of a cyclic universe as an alternative to inflation theory. Along the way it seems that great pains were taken to explain the operant features of the theory in terms that non-physicists could understand. I'm not sure how successful Steinhardt and Turok were in that regard, but I think they made heroic efforts to do so. I'm not sure how difficult this account of the cyclic universe might be to physicists and cosmologists, but it was a tough slog for me, and the best I can say is that I think I sort of get the gist of it. Certainly the symmetry of the cyclic model is somehow more uplifting than the uncertainties built into the inflationary model along with the depressing end of the universe predicted by the inflationary model. One feature of the overall cyclic theory that is perplexing is the apparent need for there to be two (2) interacting Branes. Why this number? Why not multiples of two or even infinite Branes? And of course, it seems as though the inflationary model comes closer to explaining the original cause of creation. The cyclic model explains the original cause of our observable universe, of course, but not the original cause of the elements that give rise to each big bang, namely the Branes themselves.
As someone who learns somewhat more easily visually, I thought that the illustrations and cartoons were fairly lame, and not particularly helpful in illustrating how things happen in either of the two models.
One of the nicest features of this book was the understated way in which these world class theorists repeatedly made clear that it will be years or decades before the world of physics and cosmology ultimately adopts the inflationary model, displaces it with the cyclic model, or finds another model altogether. They were very careful not to paint the cyclic model as a panacea for physics and cosmology.
All in all, in spite of the heavy lifting required of non-physicist readers, the book was enjoyable, informative, and in some sense even spiritually uplifting.
As someone who learns somewhat more easily visually, I thought that the illustrations and cartoons were fairly lame, and not particularly helpful in illustrating how things happen in either of the two models.
One of the nicest features of this book was the understated way in which these world class theorists repeatedly made clear that it will be years or decades before the world of physics and cosmology ultimately adopts the inflationary model, displaces it with the cyclic model, or finds another model altogether. They were very careful not to paint the cyclic model as a panacea for physics and cosmology.
All in all, in spite of the heavy lifting required of non-physicist readers, the book was enjoyable, informative, and in some sense even spiritually uplifting.
November 27, 2021
This is the part in which we enter the realm of particle cosmology. I did not know what the hell that was until this was explained to me in this book. We are all informed and aware about the whereabouts of the Big Bang. Hubble discovered that galaxies we leaving us, even faster than we first calculated. Later on, Arno Penzias and Robert Wilson discovered the CMB, then Alan Guth proposed something, an inflation model that resolved some problems but lacked the explanation of "why", later on, first COBE and later WMAP confirmed the theory and the first images of the Universe were created. If we were able to use our imagination and "reverse time" we would find that every single star, and every single galaxy no matter how big it is, would collapse into a point, that point we called the Big Bang", and in mathematical terms, a singularity.
What is exposed in this book, is something, really, really weird. By the cover I thought that this universe was the product of a hypermassive black hole or something like that. BUT, here, authors mention that our universe is the collision of two "branes". Imagine yourself pulling together two paper sheets. Then imagine some kind of dark energy pulling length and width of every sheet while you are pushing them towards each other, at the moment that contact is made, big bang occurs. And that forever and ever. Always, that's it.
Hell, they explain everything. I mean, at first I thought, well, this one is string theory, the next chapter we are talking about branes, interdimensional entities that every cycle come together and get away, every cycle comes about to a trillion years or zillion years (no idea really). There are two different points of view, the first one is the inflationary model and the cyclic model.
I dont wanna sound like a simple "I dont buy it", I mean, there's a LOT of mathematical difficulty to it. But the idea, maybe it's because we are living a transition and we are now in particle cosmology. But the idea seems more than weird, but bizarre. It is all part of a theory, called M Theory, which considers gravity into String theory.
What is exposed in this book, is something, really, really weird. By the cover I thought that this universe was the product of a hypermassive black hole or something like that. BUT, here, authors mention that our universe is the collision of two "branes". Imagine yourself pulling together two paper sheets. Then imagine some kind of dark energy pulling length and width of every sheet while you are pushing them towards each other, at the moment that contact is made, big bang occurs. And that forever and ever. Always, that's it.
Hell, they explain everything. I mean, at first I thought, well, this one is string theory, the next chapter we are talking about branes, interdimensional entities that every cycle come together and get away, every cycle comes about to a trillion years or zillion years (no idea really). There are two different points of view, the first one is the inflationary model and the cyclic model.
I dont wanna sound like a simple "I dont buy it", I mean, there's a LOT of mathematical difficulty to it. But the idea, maybe it's because we are living a transition and we are now in particle cosmology. But the idea seems more than weird, but bizarre. It is all part of a theory, called M Theory, which considers gravity into String theory.
September 14, 2010
Endless Universe was good though a bit bothersome at times.
I understand that, as competing theories, it is essential to point out the dissimilarities between the inflationary and cyclic models of the universe, but Steinhardt and Turok seemed like they were fighting their way out of a corner throughout the book — and they wrote it!
Being in a defensive stance for most of the book also made some of their arguments seem petty. On p.222 they basically claim that the inflationary model spells the end of empirical science as if there is nothing else to discover about the universe if that theory "succeeds." It's just not true.
Another issue I had was that the authors waited until almost the end of the book to elaborate on any flaws in the cyclic model, leaving me with some very obvious questions in the front of my mind throughout my reading. I know that you don't want to hand over a list of all your character flaws on a first date, but when it comes to science writing, not hearing the faults in a more natural progression was very distracting.
Also, it was one of those books that elaborates on some pretty high concepts to paint a picture of a theory, but then goes on to define what an atom is in the glossary! Most popular physics books claim that no prior knowledge is necessary, but it's never true.
If you don't know what an atom is, you probably won't understand anything covered in this book... and you are scientifically illiterate to an embarrassing degree.
The authors ended the book on a very vague "we'll see what happens" note, so I figured I'd do the same:
Endless Universe was a good read about some very interesting ideas that, frankly, I hope are right! The ekpyrotic (cyclic) model is a beautiful theory indeed, though no self-respecting scientist worth his weight in protons chooses a model based on neatness. Without resorting to the anthropic principle, it does make a lot of sense, but only space-time will tell!
I understand that, as competing theories, it is essential to point out the dissimilarities between the inflationary and cyclic models of the universe, but Steinhardt and Turok seemed like they were fighting their way out of a corner throughout the book — and they wrote it!
Being in a defensive stance for most of the book also made some of their arguments seem petty. On p.222 they basically claim that the inflationary model spells the end of empirical science as if there is nothing else to discover about the universe if that theory "succeeds." It's just not true.
Another issue I had was that the authors waited until almost the end of the book to elaborate on any flaws in the cyclic model, leaving me with some very obvious questions in the front of my mind throughout my reading. I know that you don't want to hand over a list of all your character flaws on a first date, but when it comes to science writing, not hearing the faults in a more natural progression was very distracting.
Also, it was one of those books that elaborates on some pretty high concepts to paint a picture of a theory, but then goes on to define what an atom is in the glossary! Most popular physics books claim that no prior knowledge is necessary, but it's never true.
If you don't know what an atom is, you probably won't understand anything covered in this book... and you are scientifically illiterate to an embarrassing degree.
The authors ended the book on a very vague "we'll see what happens" note, so I figured I'd do the same:
Endless Universe was a good read about some very interesting ideas that, frankly, I hope are right! The ekpyrotic (cyclic) model is a beautiful theory indeed, though no self-respecting scientist worth his weight in protons chooses a model based on neatness. Without resorting to the anthropic principle, it does make a lot of sense, but only space-time will tell!
Read
January 22, 2021Endless Universe, very huge as the cosmos but can be packed in a mustard seed.
Endless since everything started and it's on going right now.
Life has started and there is an end to it. It's reality. Death is a process that has started the day we were born and it will end if the process is completed. Some, haven't accepted it yet.
But there is something that have not yet started so there is no end to it. Is it cyclical? No. Cyclical is for the unconscious or the unaware. For the conscious, it is moving forward. That something which has not yet started or not yet ending is what we called as the future. Future is not cyclical, it should be moving forward. If future is cyclical, it will not take you anywhere.
Endless since everything started and it's on going right now.
Life has started and there is an end to it. It's reality. Death is a process that has started the day we were born and it will end if the process is completed. Some, haven't accepted it yet.
But there is something that have not yet started so there is no end to it. Is it cyclical? No. Cyclical is for the unconscious or the unaware. For the conscious, it is moving forward. That something which has not yet started or not yet ending is what we called as the future. Future is not cyclical, it should be moving forward. If future is cyclical, it will not take you anywhere.
August 31, 2010
A good review of the Cyclic Model, as presented by someone who helped develop it. I think it poses some strong arguments against the currently held inflationary model but was disappointed by the lack of mathematical explanation given. I still love this book. Even if they may turn out incorrect I love that they have challenged the conventional cosmological outlook as I think that is the nature of true science and discovery.
August 28, 2020
I have tried to read this book once before. I am not sure about the exact details.
My high approval rating comes from how these two scientists brought me closer to understanding a subject I have not done as well with as I would have preferred.
I will read this book again, very likely, but I am not sure when.
My high approval rating comes from how these two scientists brought me closer to understanding a subject I have not done as well with as I would have preferred.
I will read this book again, very likely, but I am not sure when.
July 16, 2020
Excellent read. Fascinating, complex concepts that potentially reflect the nature of reality. Probably good to have some grounding in previous concepts of The Big Bang & exposure to basic principles of particle physics, but not prerequisites. This has prompted me to read more about string theory.
September 15, 2020
I still love it, even after the discovery of gravity waves I found it interesting: while
The cyclic model put forth by Turok and steinhardt may not have been correct the criticism of inflationary cosmology still holds today
The cyclic model put forth by Turok and steinhardt may not have been correct the criticism of inflationary cosmology still holds today
June 6, 2022
My review - essentially a summary of the concepts and questioning of some of the arguments - is too long to fit, so will be reduced and is to come.
August 25, 2025
2025 Review: Didn't realize I had read this book two years earlier, so re-read and did another review,
that, interestingly, can be compared to the 2023 Review:
The writers counter a one-directional, linear expansion into infinity view of the cosmos, which seems to be the prevailing perspective these days. In contrast, the authors propose a cyclic model where the universe repeatedly expands and contracts (hence, the book’s title).
In the linear model (my preferred term, because it contrasts with cyclic), the big bang undergoes an inflation event shortly after the initial explosion, which creates a super expansion phase that smooths out the wrinkles of spacetime. This was followed by a cooling phase that had just enough perturbation to allow gravitational effects to take hold, thereby forming stars and galaxies. This matter-dominated period was followed by the Hubble expansion (galaxies move faster and faster away from our observation point) that was later explained by an anti-gravity, repulsive phenomenon called dark energy, and it is this that takes the cosmos into the infinite void.
The writers are critical of this model in a couple of respects. They say that inflationary energy was unnecessary, and that dark energy alone could account for the perceived inflationary effects, but their position got too technical for me to follow. The authors also bring in string theory to explain why the cosmos is cyclic, but I found this part of their book even more challenging to understand.
To bolster their argument somewhat, the authors note that in the early 1930s, Einstein favored an “oscillating” cosmos whereby the universe expands and contracts at regular intervals. This point of view was from Einstein’s post-cosmological constant period where he tried to incorporate the Hubble findings on cosmic expansion into his general relativity perspective, though that was apparently short lived as Einstein, the authors conceded, that the universe is flat and expands forever.
Two questions pop up regarding the Steinhardt and Turok perspectives. First, as most others do, they refer to gravity as a “pulling” force by a gravitational center. How this matches up with Einstein’s geometric view of cosmic movement is not clear: Matter-energy moves toward the largest center of concentrated energy (mass) in the “local” cosmic neighborhood. In other words, there is no “gravitational pulling.” Rather, matter-energy moves (inertially, per Newton’s first law)* on its own, in or through (this is not clear) spacetime, and gravity is a passive presence that, Wheeler-like, “tells” spacetime (and stuff in it), how and where to move. This is significant for looking at both the linear and cyclic models in this book: The big bang creates this inertial movement with a speed that is sufficiently strong to escape gravitational effects. At some point (8 billion years post big bang?), per the inverse square law, inertial movement becomes free of gravitational effects. Might this, and not dark energy, explain the Hubble expansion?
Second, it’s not clear about what the writers mean when they refer to their preferred model as “cyclic” and “oscillating.” That the cosmos repeats itself in big bang** and contraction cycles is not the issue. Rather, their model seems to have more of an “out and back” scenario: Expansionary (inflationary, then dark) energy (why wouldn’t this be the creation of inertial movement per Newton’s first law) creates outward movement, and contraction reels it back to the starting point. The oscillating reference certainly conveys an “out and back” model.
And perhaps they took some liberties in characterizing Einstein’s 1931 views as “oscillating,” whereas, in spite of all the technicalities of his theory, he believed, the authors say, theories about the universe should be “simple and comprehensible.” In this regard, Einstein’s cosmos was curved,*** and that makes an out-and-back scenario unlikely. Rather, once free of the cosmic gravitational center, inertial energy from the expansionary phase of the universe moves beyond a stasis point (outgoing direction = ingoing direction) and continues around curvature and returns to the beginning where most of the density lies,**** creating cosmic curvature. With the movement around curvature, it increasingly feels the effect of this gravitational presence, and moves toward it (“pulled,” if you will) at increased speed and strength (the inverse square law reversed)? Some of the non-contemporary accounts of the universe - versus Einstein himself and some of his articulators - convey a perspective that reflects movement around cosmic curvature.
The strongest part of this book is upfront when they contrast their overarching perspective with the prevailing linear model. Unfortunately for the lay reader, their explanation for why they differ got too thick, real fast.
*Re inertia, the term conveys inertness, or lack of movement, whereas an argument can be made that it is precisely the opposite: Energy, and bodies consisting of energy, is always in motion. Atoms are wiggling and jiggling, always. At the macro scale, everything is in motion - from the expansionary energy from the big bang and supernova explosions, to bodies at rest (e.g. in orbital situations) relative to other bodies in mot
**The writers I believe are critical of mathematical models that reduce the pre-big bang moment to singularities where time and space disappear. (“Mathematicians use the term ‘singularity’ to indicate that equations are failing….The big bang is referred to as the ‘initial singularity because Einstein’s equations of general relativity break down when temperature and energy density become infinite, as Einstein himself recognized, and their description of the expansion of the universe ceases to be valid.”) In their model they seem to allow for pre-big bang scenarios that don’t involve such singularities. In the contraction phase, matter and energy come together and, in effect, bounce off each other (is this where his string-brane theory applies?).
***Einstein’s theory of gravity “does not require that space be flat. Space can have a positive curvature, so that it bends back on itself like the surface of a sphere.” The writers also refer to the “cosmic sphere,” and “the other edge of the cosmic sphere” (which is an interesting statement as it prompts a next question about what lies beyond such an edge).
****Is there a cosmic center, a concentration of matter-energy, where big bangs occur? Or does the explosion create a hole, void of concentrated mass at its center?
2023 Review
The book identifies problems with the more or less standard account of cosmological history that runs, linearly, from the big bang, to an inflation stage (an explosion - just fractions of a second later - after the initial one), followed by a radiation-dominant (energy too hot to clump) stage, then a matter stage (gravitational clumping), and now to a dark energy dominant stage that pulls (or pushes) the cosmos into an infinite void (a flat cosmic model, with flat being a cosmos void of curvature so that outward motion continues forever). The problem with this model, Steinhardt and Turok say, is that “Inflation, once begun, would continue forever.”
According to the book, this problem, apparently, was identified by Alan Guth, the initial proponent of inflationary expansion. Inflation solved a problem for cosmology - how to account for the universe’s smoothness as identified by the uniform microwave background findings in the early ‘60s, thereby countering the variable densities for the initial big bang that allowed gravitational clumping to form once the radiation (heat) phase cooled down. Steinhardt and Turok argue that inflation is not necessary after all. Dark energy itself would have the same effect of smoothing out energy densities by pulling and stretching space. Once the reign of matter ran its course, dark energy became dominant five billion years after the big bang, creating the Hubble effect seen today in the expansion of space at ever increasing speed and accounting for the uniform state of cosmic space.
The expansion epoch is, according to the book, to be followed by a contraction phase when the universe returns to itself, followed yet again by a renewal of the same process that continues perpetually. Hence, the cyclic increase model that they term the ekphyrotic universe and this contraction phase is where I lost the trail. It could be because of the book’s discussion of string theory and extra dimensions all within the context of dark energy that “has been observationally established” (I didn’t know such a finding was that certain).
My biggest problem with this book is not the cyclic universal idea, but, rather, the contraction phase to their model. The idea that the cosmos moves cyclically, not linearly, seems graspable as the big bang expands outward from a round, ball-like point, not out one side as the linear graphic and flat cosmos implies. The basic shape is roundness, not Euclidean flatness. And the book’s skepticism about inflation makes sense as well - if the first explosion from the big bang causes differential densities (ripples), why would a second explosion that creates smoothness occur (or why would there be a second explosion at all)?
The rest of the “standard model” is in sync with the cyclic idea until it comes to contraction, where the universe curves back on itself. Nowhere in this book is there a discussion of inertial, straight-line motion in the presence of overall gravitational curvature and the role of the inverse square law that lessens gravitational effects as the universe expands. At some point, does the lessening of such effects liberate energy to continue on - much as dark energy is said to do - and with free inertial motion that is subject to overall cosmic curvature,* to return back to its originating point?** And the book seems to suggest that this is what is happening: Movement around curvature eventually increases matter-energy consolidation and, with that, contraction back to a beginning point. Some of the early cosmological writings hint of this, somewhat.
*If, with expansion, there’s dispersal of matter-energy, then traced back to the big bang beginning, would there be a concentrated density of matter-energy seen by Webb or, alternatively, would such matter-energy have been dispersed leaving a big void behind?
**It is interesting that dark energy is said to “push” outward, whereas, in contrast, a gravitational center would “pull” energy around to its starting point.
that, interestingly, can be compared to the 2023 Review:
The writers counter a one-directional, linear expansion into infinity view of the cosmos, which seems to be the prevailing perspective these days. In contrast, the authors propose a cyclic model where the universe repeatedly expands and contracts (hence, the book’s title).
In the linear model (my preferred term, because it contrasts with cyclic), the big bang undergoes an inflation event shortly after the initial explosion, which creates a super expansion phase that smooths out the wrinkles of spacetime. This was followed by a cooling phase that had just enough perturbation to allow gravitational effects to take hold, thereby forming stars and galaxies. This matter-dominated period was followed by the Hubble expansion (galaxies move faster and faster away from our observation point) that was later explained by an anti-gravity, repulsive phenomenon called dark energy, and it is this that takes the cosmos into the infinite void.
The writers are critical of this model in a couple of respects. They say that inflationary energy was unnecessary, and that dark energy alone could account for the perceived inflationary effects, but their position got too technical for me to follow. The authors also bring in string theory to explain why the cosmos is cyclic, but I found this part of their book even more challenging to understand.
To bolster their argument somewhat, the authors note that in the early 1930s, Einstein favored an “oscillating” cosmos whereby the universe expands and contracts at regular intervals. This point of view was from Einstein’s post-cosmological constant period where he tried to incorporate the Hubble findings on cosmic expansion into his general relativity perspective, though that was apparently short lived as Einstein, the authors conceded, that the universe is flat and expands forever.
Two questions pop up regarding the Steinhardt and Turok perspectives. First, as most others do, they refer to gravity as a “pulling” force by a gravitational center. How this matches up with Einstein’s geometric view of cosmic movement is not clear: Matter-energy moves toward the largest center of concentrated energy (mass) in the “local” cosmic neighborhood. In other words, there is no “gravitational pulling.” Rather, matter-energy moves (inertially, per Newton’s first law)* on its own, in or through (this is not clear) spacetime, and gravity is a passive presence that, Wheeler-like, “tells” spacetime (and stuff in it), how and where to move. This is significant for looking at both the linear and cyclic models in this book: The big bang creates this inertial movement with a speed that is sufficiently strong to escape gravitational effects. At some point (8 billion years post big bang?), per the inverse square law, inertial movement becomes free of gravitational effects. Might this, and not dark energy, explain the Hubble expansion?
Second, it’s not clear about what the writers mean when they refer to their preferred model as “cyclic” and “oscillating.” That the cosmos repeats itself in big bang** and contraction cycles is not the issue. Rather, their model seems to have more of an “out and back” scenario: Expansionary (inflationary, then dark) energy (why wouldn’t this be the creation of inertial movement per Newton’s first law) creates outward movement, and contraction reels it back to the starting point. The oscillating reference certainly conveys an “out and back” model.
And perhaps they took some liberties in characterizing Einstein’s 1931 views as “oscillating,” whereas, in spite of all the technicalities of his theory, he believed, the authors say, theories about the universe should be “simple and comprehensible.” In this regard, Einstein’s cosmos was curved,*** and that makes an out-and-back scenario unlikely. Rather, once free of the cosmic gravitational center, inertial energy from the expansionary phase of the universe moves beyond a stasis point (outgoing direction = ingoing direction) and continues around curvature and returns to the beginning where most of the density lies,**** creating cosmic curvature. With the movement around curvature, it increasingly feels the effect of this gravitational presence, and moves toward it (“pulled,” if you will) at increased speed and strength (the inverse square law reversed)? Some of the non-contemporary accounts of the universe - versus Einstein himself and some of his articulators - convey a perspective that reflects movement around cosmic curvature.
The strongest part of this book is upfront when they contrast their overarching perspective with the prevailing linear model. Unfortunately for the lay reader, their explanation for why they differ got too thick, real fast.
*Re inertia, the term conveys inertness, or lack of movement, whereas an argument can be made that it is precisely the opposite: Energy, and bodies consisting of energy, is always in motion. Atoms are wiggling and jiggling, always. At the macro scale, everything is in motion - from the expansionary energy from the big bang and supernova explosions, to bodies at rest (e.g. in orbital situations) relative to other bodies in mot
**The writers I believe are critical of mathematical models that reduce the pre-big bang moment to singularities where time and space disappear. (“Mathematicians use the term ‘singularity’ to indicate that equations are failing….The big bang is referred to as the ‘initial singularity because Einstein’s equations of general relativity break down when temperature and energy density become infinite, as Einstein himself recognized, and their description of the expansion of the universe ceases to be valid.”) In their model they seem to allow for pre-big bang scenarios that don’t involve such singularities. In the contraction phase, matter and energy come together and, in effect, bounce off each other (is this where his string-brane theory applies?).
***Einstein’s theory of gravity “does not require that space be flat. Space can have a positive curvature, so that it bends back on itself like the surface of a sphere.” The writers also refer to the “cosmic sphere,” and “the other edge of the cosmic sphere” (which is an interesting statement as it prompts a next question about what lies beyond such an edge).
****Is there a cosmic center, a concentration of matter-energy, where big bangs occur? Or does the explosion create a hole, void of concentrated mass at its center?
2023 Review
The book identifies problems with the more or less standard account of cosmological history that runs, linearly, from the big bang, to an inflation stage (an explosion - just fractions of a second later - after the initial one), followed by a radiation-dominant (energy too hot to clump) stage, then a matter stage (gravitational clumping), and now to a dark energy dominant stage that pulls (or pushes) the cosmos into an infinite void (a flat cosmic model, with flat being a cosmos void of curvature so that outward motion continues forever). The problem with this model, Steinhardt and Turok say, is that “Inflation, once begun, would continue forever.”
According to the book, this problem, apparently, was identified by Alan Guth, the initial proponent of inflationary expansion. Inflation solved a problem for cosmology - how to account for the universe’s smoothness as identified by the uniform microwave background findings in the early ‘60s, thereby countering the variable densities for the initial big bang that allowed gravitational clumping to form once the radiation (heat) phase cooled down. Steinhardt and Turok argue that inflation is not necessary after all. Dark energy itself would have the same effect of smoothing out energy densities by pulling and stretching space. Once the reign of matter ran its course, dark energy became dominant five billion years after the big bang, creating the Hubble effect seen today in the expansion of space at ever increasing speed and accounting for the uniform state of cosmic space.
The expansion epoch is, according to the book, to be followed by a contraction phase when the universe returns to itself, followed yet again by a renewal of the same process that continues perpetually. Hence, the cyclic increase model that they term the ekphyrotic universe and this contraction phase is where I lost the trail. It could be because of the book’s discussion of string theory and extra dimensions all within the context of dark energy that “has been observationally established” (I didn’t know such a finding was that certain).
My biggest problem with this book is not the cyclic universal idea, but, rather, the contraction phase to their model. The idea that the cosmos moves cyclically, not linearly, seems graspable as the big bang expands outward from a round, ball-like point, not out one side as the linear graphic and flat cosmos implies. The basic shape is roundness, not Euclidean flatness. And the book’s skepticism about inflation makes sense as well - if the first explosion from the big bang causes differential densities (ripples), why would a second explosion that creates smoothness occur (or why would there be a second explosion at all)?
The rest of the “standard model” is in sync with the cyclic idea until it comes to contraction, where the universe curves back on itself. Nowhere in this book is there a discussion of inertial, straight-line motion in the presence of overall gravitational curvature and the role of the inverse square law that lessens gravitational effects as the universe expands. At some point, does the lessening of such effects liberate energy to continue on - much as dark energy is said to do - and with free inertial motion that is subject to overall cosmic curvature,* to return back to its originating point?** And the book seems to suggest that this is what is happening: Movement around curvature eventually increases matter-energy consolidation and, with that, contraction back to a beginning point. Some of the early cosmological writings hint of this, somewhat.
*If, with expansion, there’s dispersal of matter-energy, then traced back to the big bang beginning, would there be a concentrated density of matter-energy seen by Webb or, alternatively, would such matter-energy have been dispersed leaving a big void behind?
**It is interesting that dark energy is said to “push” outward, whereas, in contrast, a gravitational center would “pull” energy around to its starting point.
September 5, 2019
I feel like I need to preface this review with some context. I have a BS in Biology, I took exactly 1 physics class in college, a bunch of chemistry classes, and that's it. I struggle to grasp cosmology and astrophysics and metaphysics. Last year, I watched that Stephen Hawking biopic and enjoyed it but I still didn't "get it". It sent me down the rabbit hole of looking at "cosmology for dummies" on YouTube, trying to understand Dark Matter, trying to understand how the hell we are holograms on the edge of a black hole. (Like, seriously?) So I made it a bit of a mission this year to try to learn more and better my understanding. I ended up at OMSI and watched a Neil Degrasse thing in the planetarium on astronomy and cosmology. I liked it, but had even more questions. I knew it was just grazing the surface and I just. didn't. get. it. The museum shop has a bunch of books on cosmology - I took pictures of them, looked at reviews, and selected a couple to invest in in hopes of getting a better understanding. This book, Endless Universe, was the first one I picked up.
It is beyond me. The principles are too advanced for me to comprehend. I would have moments of "ahhhhha" where they would explain something well, but then I'd be lost again in the next paragraph. It took me 6 months to wade my way through. I ended up just reading a couple pages a day to try to get through it because reading large chunks would send me into anxiety. Maybe I need to start in the kids section...
That being said, I can tell this book was well thought out and they do offer a compelling argument for the cyclic model. I get that piece, on a high level. The details elude me though. But I gleaned enough to definitely raise my eyebrows questioningly at the current inflationary model. This book is now over a decade old and more WMAP's have come out - I would have loved to see an afterward added that discussed advancements since original publication.
I cannot in good conscience give a glowing review merely because my comprehension level is so extraordinarily low. I did find the history of theory progressions very interesting, and the straw example of extra dimensions did stick with me.
It is beyond me. The principles are too advanced for me to comprehend. I would have moments of "ahhhhha" where they would explain something well, but then I'd be lost again in the next paragraph. It took me 6 months to wade my way through. I ended up just reading a couple pages a day to try to get through it because reading large chunks would send me into anxiety. Maybe I need to start in the kids section...
That being said, I can tell this book was well thought out and they do offer a compelling argument for the cyclic model. I get that piece, on a high level. The details elude me though. But I gleaned enough to definitely raise my eyebrows questioningly at the current inflationary model. This book is now over a decade old and more WMAP's have come out - I would have loved to see an afterward added that discussed advancements since original publication.
I cannot in good conscience give a glowing review merely because my comprehension level is so extraordinarily low. I did find the history of theory progressions very interesting, and the straw example of extra dimensions did stick with me.
September 23, 2025
This is the part in which we enter the realm of particle cosmology. I did not know what the hell that was until this was explained to me in this book. We are all informed and aware about the whereabouts of the Big Bang. Hubble discovered that galaxies we leaving us, even faster than we first calculated. Later on, Arno Penzias and Robert Wilson discovered the CMB, then Alan Guth proposed something, an inflation model that resolved some problems but lacked the explanation of "why", later on, first COBE and later WMAP confirmed the theory and the first images of the Universe were created. If we were able to use our imagination and "reverse time" we would find that every single star, and every single galaxy no matter how big it is, would collapse into a point, that point we called the Big Bang", and in mathematical terms, a singularity.
What is exposed in this book, is something, really, really weird. By the cover I thought that this universe was the product of a hypermassive black hole or something like that. BUT, here, authors mention that our universe is the collision of two "branes". Imagine yourself pulling together two paper sheets. Then imagine some kind of dark energy pulling length and width of every sheet while you are pushing them towards each other, at the moment that contact is made, big bang occurs. And that forever and ever. Always, that's it.
Hell, they explain everything. I mean, at first I thought, well, this one is string theory, the next chapter we are talking about branes, interdimensional entities that every cycle come together and get away, every cycle comes about to a trillion years or zillion years (no idea really). There are two different points of view, the first one is the inflationary model and the cyclic model.
I dont wanna sound like a simple "I dont buy it", I mean, there's a LOT of mathematical difficulty to it. But the idea, maybe it's because we are living a transition and we are now in particle cosmology. But the idea seems more than weird, but bizarre. It is all part of a theory, called M Theory, which considers gravity into String theory.
What is exposed in this book, is something, really, really weird. By the cover I thought that this universe was the product of a hypermassive black hole or something like that. BUT, here, authors mention that our universe is the collision of two "branes". Imagine yourself pulling together two paper sheets. Then imagine some kind of dark energy pulling length and width of every sheet while you are pushing them towards each other, at the moment that contact is made, big bang occurs. And that forever and ever. Always, that's it.
Hell, they explain everything. I mean, at first I thought, well, this one is string theory, the next chapter we are talking about branes, interdimensional entities that every cycle come together and get away, every cycle comes about to a trillion years or zillion years (no idea really). There are two different points of view, the first one is the inflationary model and the cyclic model.
I dont wanna sound like a simple "I dont buy it", I mean, there's a LOT of mathematical difficulty to it. But the idea, maybe it's because we are living a transition and we are now in particle cosmology. But the idea seems more than weird, but bizarre. It is all part of a theory, called M Theory, which considers gravity into String theory.
November 2, 2022
Accepting Infinity?
POSTED BY ME AT AMAZON 2008
No matter how long, deep and hard we dwell on existence of the Universe, it is impossible to avoid concept of infinity. What (or Who) is able to be eternal? If this is God, then not Universe. If Universe is such, then there is no need for God. Interestingly authors briefly muse about it in the middle of the book. Saying this and taking theology/philosophy aside I highly appreciate the huge effort taken by both scientists to present their quite stunning, and as for today, extravagant theory - theory challenging inflation. It was easier for me to comprehend Inflationary models (for example in Vilenkin's "Many Worlds in One"). Endless Cycling model is by far the most difficult one, since it is based on String Theory and assumption of extra dimensions. Part of the book evaluates supersymmetry vs. simple string theory in particle physics. Most of the time we read about advantages of Ekpyrotic (Cycling) Universe theory when compared to Inflationary models. Swinging back and forth (in a bit of chaotic and repetitive manner ) authors drill voraciously in systematic fashion all possible holes in the Guth/Linde's Inflationary as well as in Susskind's Landscape and Vilenkin's Multiverses models. And how dedicated, convinced, passionate, determined and eloquent they are!! Though certain fragments are truly exhausting (for example: how colliding branes convert one type of energy to another), numerous repetitions and attempts to emphasize how things happen, are actually often helpful. What has been planted in my head is that: extra "D" + branes + dark energy + potential energy related "spring-like" force between the branes = ekpyrosis. Be it. The final judge deciding which model represents true reality appears to be gravity. Authors list number of proposed and being in progress projects aiming at DETECTING gravitational waves. Unfortunately we will not be able to do so in the next decades, especially if it comes to very weak inflationary waves. However detection is not a single dilemma. We still cannot EXPLAIN the essence of gravity and I did not find anything related to it in this book. Physicists sometimes talk about a concept known as "Mach's Principle", but that principle has never been successfully developed and fails to explain apparent instantaneous action-at-a-distance. In the end comes the last strong punch: Cyclic Ekpyrotic model is free of Anthropic Principle dilemma!! It is very important to cosmology to have competing models and unanswered lingering questions about their validity. In general: very brave and colorful popular science book, recommended for curious and following "strange" cosmology ideas readers.
POSTED BY ME AT AMAZON 2008
No matter how long, deep and hard we dwell on existence of the Universe, it is impossible to avoid concept of infinity. What (or Who) is able to be eternal? If this is God, then not Universe. If Universe is such, then there is no need for God. Interestingly authors briefly muse about it in the middle of the book. Saying this and taking theology/philosophy aside I highly appreciate the huge effort taken by both scientists to present their quite stunning, and as for today, extravagant theory - theory challenging inflation. It was easier for me to comprehend Inflationary models (for example in Vilenkin's "Many Worlds in One"). Endless Cycling model is by far the most difficult one, since it is based on String Theory and assumption of extra dimensions. Part of the book evaluates supersymmetry vs. simple string theory in particle physics. Most of the time we read about advantages of Ekpyrotic (Cycling) Universe theory when compared to Inflationary models. Swinging back and forth (in a bit of chaotic and repetitive manner ) authors drill voraciously in systematic fashion all possible holes in the Guth/Linde's Inflationary as well as in Susskind's Landscape and Vilenkin's Multiverses models. And how dedicated, convinced, passionate, determined and eloquent they are!! Though certain fragments are truly exhausting (for example: how colliding branes convert one type of energy to another), numerous repetitions and attempts to emphasize how things happen, are actually often helpful. What has been planted in my head is that: extra "D" + branes + dark energy + potential energy related "spring-like" force between the branes = ekpyrosis. Be it. The final judge deciding which model represents true reality appears to be gravity. Authors list number of proposed and being in progress projects aiming at DETECTING gravitational waves. Unfortunately we will not be able to do so in the next decades, especially if it comes to very weak inflationary waves. However detection is not a single dilemma. We still cannot EXPLAIN the essence of gravity and I did not find anything related to it in this book. Physicists sometimes talk about a concept known as "Mach's Principle", but that principle has never been successfully developed and fails to explain apparent instantaneous action-at-a-distance. In the end comes the last strong punch: Cyclic Ekpyrotic model is free of Anthropic Principle dilemma!! It is very important to cosmology to have competing models and unanswered lingering questions about their validity. In general: very brave and colorful popular science book, recommended for curious and following "strange" cosmology ideas readers.
April 6, 2020
The book discusses the two theories of formation of Universe, the inflationary theory and the cyclic theory and analyse the plausibly as to which theory will gain traction. Written in a language, which is easy to understand but at the same time not bare of technical aspects, the book also deals with various theories of Universe which have been considered in the past by renowned scientists, including the Big Bang theory. It also analyses Einstein’s concept of cosmological constant in the context of the cyclic theory, which itself has evolved out of the ekpyrotic theory of Universe. A worth read, for the beginner as week as the well versed.
January 21, 2018
I picked up this book because the title intrigued me. Its over a decade old at this point, and if anything the assertions made here are less likely to be true than they were then, but it is fun to see how the debate about cosmology unfolds. The theory argued for here is the "cyclic model" as opposed to the "expansion model." Its a really interesting idea, but relies on M theory, which itself is very controversial.
May 13, 2018
Fantastic overview that is, unfortunately, still relevant.
An excellent review of modern cosmology, including the debate between proponents of inflation, and those of its opponents, who back the cyclic models. What is depressing and unfortunate is that cosmologists are no closer to resolving the debate more than a decade after the book was written. Oh well...the authors suggest we will know in less than 88 more years so that is something to look forward to.
An excellent review of modern cosmology, including the debate between proponents of inflation, and those of its opponents, who back the cyclic models. What is depressing and unfortunate is that cosmologists are no closer to resolving the debate more than a decade after the book was written. Oh well...the authors suggest we will know in less than 88 more years so that is something to look forward to.
November 23, 2022
An easy to read (and comprehend) alternate view to the big bang, Steinhardt and Turok's book is a timely reminder that what may come across as accepted fact in cosmology is usually simply a robust theory, and several equally robust alternate explanations are available.
Well worth the effort, even if the personal stories of their meeting and collaboration felt, at times, more like padding to meet a word length goal.
Well worth the effort, even if the personal stories of their meeting and collaboration felt, at times, more like padding to meet a word length goal.
August 21, 2019
Good read, loved one section where authors cite hinduism having though about the cyclic or endless universe many thousands of years ago!
March 7, 2020
Extremely intriguing, following this topic!!
August 9, 2021
A little out of date by now, but good.
November 4, 2022
This book thrilled me and filled me with existential dread.
June 2, 2023
Weowww that’s pretty cool
December 14, 2023
4.5 - A little repetitive here and there but well put together explaining a somewhat difficult subject.
December 20, 2025
I’m reading at least one thousand books of history in chronological order, going from the big bang through human civilization to the end of the world, and this is book #4 in that series. I began with A Brief History of Time and Cosmos as overviews, then read Steven Weinburg's The First Three Minutes: A Modern View of the Origin of the Universe to understand the prevailing theories on the nature of the big bang. This, then, is an alternate theory, and I'll say up front that this is one of the best books I've read in this entire history project of mine.
So, the big bang was always presented to me as an established and accepted theory, and those guys who think the universe may be undergoing endless cycles as pretty wonky and fringe personalities. Well, Steinhardt and Turok are those guys, and I was impressed throughout this book at how detailed and substantial their arguments are: this isn’t a crackpot theory, but a viable alternative to the big bang by established scientists—who were contributing to the traditional view before their research led them in this unexpected direction.
For one thing, even after reading Weinburg's book, great though it was, I was still fairly unaware of all the problems with the big bang and how it was assembled and rearranged piecemeal over the course of the twentieth century; when a new bit of theory or observation came along it was attached to the theory, often making for an ungainly Frankenstein’s monster with contradictory or at best mismatched parts jutting out everywhere—like Bill Peet's Whingdingdilly, for those picture book afficionados. Plus, at the end of the day it still doesn’t explain why there was a big bang in the first place or what came before it. In my experience this is usually addressed through philosophy or religion, but Steinhardt and Turok address it through the scientific evidence, completely satisfactorily to boot.
So, while explaining the standard model of the universe with great fairness, they guide us through the evolution of their concept of a cyclic universe, describing not just their own work but that of numerous colleagues and mentors. The theory that’s emerged from this is, to my view, much more elegant and comprehensive than the big bang, describing what came before it without any philosophical leaps into an absolute zero of time or God saying “Let there be light,” and integrating not just well-established phenomena like the unevenness of the cosmic background radiation into their theory, but newer concepts like dark matter, dark energy, and of course string theory, which the entire cyclic model relies on. They do fantastic work explaining these concepts to a general reader, and while I can’t repeat it all back to you I think I got over 90% of everything without much struggle. Now I want to review a summary of the entire theory enough that I can explain it in conversation, because it's a lot to mentally hold together if you're not a scientist, but it's the kind of thing I want to be able to explain just as accurately as the big bang. These two theories should be evaluated equally in the public sphere and be equally known by everybody. I feel like we're a moment akin to when vague ideas about continental drift, or even the stasis of the continents, was being gradually displaced by mounting evidence of active plate tectonics. If Steinhardt and Turok can be believed, the evidence for the cyclic universe keeps mounting as well, and fifty years from now it may well have displaced the accepted big bang model.
Either way, if you accept it or not, if you’re interested in the origin of the universe, you definitely should give the cyclic model as much attention as the big bang model, and you probably won’t find a better explanation of it than this.
The previous title in my series of 1,000 history books—going chronologically from dinosaurs to pyramids to knights to spaceships, with lots of other stuff in there too—is Steven Weinberg's The First Three Minutes: A Modern View of the Origin of the Universe, and the next one is The Complex Lives of Star Clusters by David S. Stevenson. You can also start at the beginning with Stephen Hawking’s A Brief History of Time or see the complete list here.
So, the big bang was always presented to me as an established and accepted theory, and those guys who think the universe may be undergoing endless cycles as pretty wonky and fringe personalities. Well, Steinhardt and Turok are those guys, and I was impressed throughout this book at how detailed and substantial their arguments are: this isn’t a crackpot theory, but a viable alternative to the big bang by established scientists—who were contributing to the traditional view before their research led them in this unexpected direction.
For one thing, even after reading Weinburg's book, great though it was, I was still fairly unaware of all the problems with the big bang and how it was assembled and rearranged piecemeal over the course of the twentieth century; when a new bit of theory or observation came along it was attached to the theory, often making for an ungainly Frankenstein’s monster with contradictory or at best mismatched parts jutting out everywhere—like Bill Peet's Whingdingdilly, for those picture book afficionados. Plus, at the end of the day it still doesn’t explain why there was a big bang in the first place or what came before it. In my experience this is usually addressed through philosophy or religion, but Steinhardt and Turok address it through the scientific evidence, completely satisfactorily to boot.
So, while explaining the standard model of the universe with great fairness, they guide us through the evolution of their concept of a cyclic universe, describing not just their own work but that of numerous colleagues and mentors. The theory that’s emerged from this is, to my view, much more elegant and comprehensive than the big bang, describing what came before it without any philosophical leaps into an absolute zero of time or God saying “Let there be light,” and integrating not just well-established phenomena like the unevenness of the cosmic background radiation into their theory, but newer concepts like dark matter, dark energy, and of course string theory, which the entire cyclic model relies on. They do fantastic work explaining these concepts to a general reader, and while I can’t repeat it all back to you I think I got over 90% of everything without much struggle. Now I want to review a summary of the entire theory enough that I can explain it in conversation, because it's a lot to mentally hold together if you're not a scientist, but it's the kind of thing I want to be able to explain just as accurately as the big bang. These two theories should be evaluated equally in the public sphere and be equally known by everybody. I feel like we're a moment akin to when vague ideas about continental drift, or even the stasis of the continents, was being gradually displaced by mounting evidence of active plate tectonics. If Steinhardt and Turok can be believed, the evidence for the cyclic universe keeps mounting as well, and fifty years from now it may well have displaced the accepted big bang model.
Either way, if you accept it or not, if you’re interested in the origin of the universe, you definitely should give the cyclic model as much attention as the big bang model, and you probably won’t find a better explanation of it than this.
The previous title in my series of 1,000 history books—going chronologically from dinosaurs to pyramids to knights to spaceships, with lots of other stuff in there too—is Steven Weinberg's The First Three Minutes: A Modern View of the Origin of the Universe, and the next one is The Complex Lives of Star Clusters by David S. Stevenson. You can also start at the beginning with Stephen Hawking’s A Brief History of Time or see the complete list here.
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