May 15, 2015 03:25 PM
http://aeon.co/magazine/science/has-cosm...ve-crisis/
EXCERPT: [...] The science of cosmology has achieved wonders in recent centuries. It has enlarged the world we can see and think about by ontological orders of magnitude. [...] Art, literature, religion and philosophy ignore cosmology at their peril.
But cosmology’s hot streak has stalled. Cosmologists have looked deep into time, almost all the way back to the Big Bang itself, but they don’t know what came before it. They don’t know whether the Big Bang was the beginning, or merely one of many beginnings. Something entirely unimaginable might have preceded it. Cosmologists don’t know if the world we see around us is spatially infinite, or if there are other kinds of worlds beyond our horizon, or in other dimensions. And then the big mystery, the one that keeps the priests and the physicists up at night: no cosmologist has a clue why there is something rather than nothing.
To solve these mysteries, cosmologists must make guesses about events that are absurdly remote from us. [Alan] Guth’s theory of inflation is one such guess. It tells us that our Universe expanded, exponentially, a trillionth of a trillionth of a trillionth of a second after the Big Bang. In most models of this process, inflation’s expansive kick is eternal. It might cease in particular parts of the cosmos, as it did in our region, after only a fraction of a second, when inflation’s energy transformed into ordinary matter and radiation, which time would sculpt into galaxies. But somewhere outside our region, inflation continued, generating an infinite number of new regions, including those that are roaring into existence at this very moment.
Not all these regions are alike. Quantum mechanics puts a slot-machine spin on the cosmic conditions of every region, so that each has its own physical peculiarities. Some contain galaxies, stars, planets, and maybe even people. Others are entirely devoid of complex structures. Many are too alien to imagine. The slice of space and time we can see from Earth is 90 billion light years across. Today’s inflationary models tell us that this enormous expanse is only one small section of one tiny bubble that floats along in a frothy sea whose proportions defy comprehension. This vision of the world is wondrous, in its vastness and variety, in the sheer range of possibilities it suggests to the mind. But could it ever be proved?
[...] ‘The last 30 years is a very unusual period in the history of fundamental physics and cosmology,’ [Paul] Steinhardt told me. ‘There’s confusion, and maybe even a certain amount of fear. People are wedded to these ideas, because they grew up with them. Scientists don’t like to change ideas unless they’re forced to. They get involved with a theory. They get emotionally attached to it. When an idea is looking shaky, they go into defensive mode. If you’re working on something besides inflation, you find yourself outside the social network, and you don’t get many citations. Only a few brave souls are willing to risk that.’
I teased Steinhardt, pointing out that he hadn’t exactly been hauled before the Inquisition. Steinhardt is fully tenured, a lion of Princeton’s storied physics department. [...] Still, he feels overmatched. He told me he has asked for help from outside the field.
‘The outside community isn’t recognising the problem,’ he said. ‘This whole BICEP2 thing has made some people more aware of it. It’s been nice to have that aired out. But most people give us too much respect. They think we know what we’re doing. They take too seriously these voices that say inflation is established theory.’
I asked him who might help. What cavalry was he calling for?
‘I wish the philosophers would get involved,’ he said.
[...] During the early decades of the 20th century, astronomers built enormous mountaintop observatories, to peer at nebulae through thin alpine air, to confirm that they were indeed galaxies, separated by voids so vast that photons take millions of years to cross them. Like the ancients, cosmologists wondered whether their cosmos had always existed, or if it evolved as Kant suggested. Aristotle thought the cosmos was eternal. The Stoics disagreed, arguing that erosion would have already planed down Earth’s mountains if the world had always existed in its present state. When Medieval Christians took up the Greek cosmos, they sided with the Stoics. They needed the world to have a starting point in time, to stay faithful to the Genesis creation myth. Perhaps, then, we should not be surprised that it was a priest, a Belgian named Georges Lemaître, who gave our cosmos its beginning, which eventually came to be called the Big Bang.
[...] Steinhardt was surprised to see inflationary theorists clinking glasses when BICEP2 announced a high swirls figure. ‘They declared victory,’ he told me. ‘They said it was smoking-gun proof! Just what they expected!’
But then a few months passed and BICEP2’s interpretation started to look wobbly. In June, Linde told New Scientist that he didn’t like the way BICEP2’s swirls were being treated as a smoking gun for inflation. In July, Guth made similar statements to the Washington Post. Steinhardt was furious. He thought it was flip-flopping. He began to wonder if any data would disturb the serene certainty of inflationary theorists. ‘It was Andre Linde who used the “smoking gun” language in the first place,’ he told me. ‘Now he says it doesn’t make a difference what BICEP2 says. How can it be that not seeing gravitational waves is fine, and then seeing them is a smoking gun, and then not seeing them is fine again?’
Steinhardt told me that this flip-flopping on gravity waves is emblematic of inflation’s deeper flaws. Remember, inflation was originally designed to patch another theory’s fine-tuning issues. To produce the strange universe we see around us, you had to fine-tune the Big Bang. Inflation fixed that problem with a theoretical mechanism that briefly blew up the Universe like a balloon. But to produce a universe like ours, inflation’s initial conditions must also be precisely calibrated.
Eternal inflation is often invoked as a solution to inflation’s fine-tuning problem, because it spits out a multiverse, an infinite sea of cosmic regions, each with its own physical peculiarities. One with our peculiarities, our tuned initial conditions, is bound to show up somewhere. And even if such regions are rare, we are bound to inhabit one of them, for the simple reason that observers will only arise in regions with ‘Goldilocks’ conditions, just right to give rise to observers. In the lifeless regions, nature is not called ‘tuned’, or ‘designed’, or ‘beautiful’. She is not called Mother, because there is no one there to call her anything. But we observers should expect our region to look tuned. All observed regions of the cosmos look tuned.
[...] Theorists are trying to determine whether some conditions are more probable than others, but they haven’t succeeded yet, and there’s no guarantee they will. In the meantime, it’s hard to know whether inflation’s fine-tuning problems are genuine explanatory gaps that need exploring, or quirky outcomes of the quantum slot machine. The theory’s weaknesses can be explained away with the same glib shrug that accompanies the retort: ‘God just made it that way.’
A dominant, infinitely flexible multiverse theory could make it easy not to strain for the next leap forward. It could lead to a chilling effect on new ideas in cosmology, or worse, a creative crisis. Steinhardt thinks we’re already there. ‘Andre Linde has become associated with eternal inflation because he thinks the multiverse is a good idea,’ he told me. ‘But I invented it, too, and I think it’s a horrible idea. It’s an emperor’s new clothes story. Except in that story, it’s a child who points out that the Emperor has no clothes. In this case, it’s the tailors themselves telling us that the theory is not testable. It’s Guth and Linde.’
Steinhardt worries that science itself could be compromised. Science freed the imagination from cave shadows and shibboleths. Science let the mind run wild with radical ideas, ecstatic visions and new worlds, so long as those ideas explained what we actually see when we gaze out into nature. The Earth moves around the Sun: look how Venus wanders and you’ll see. The nebulae are distant galaxies, brimming with stars: magnify them and you’ll see. The Universe was once hot and dense, and has been expanding ever since: catch photons from its primordial flash and you’ll see. Science owes its epistemological gravitas to its stern insistence that every idea faces the firing squad of experiment. That is its philosophical backbone. That’s the methodology that gifted us the shimmering, intricate, expansive cosmos we live in today.
That doesn’t mean that theorists should shackle their imaginations to the limits of today’s instruments. Atoms and black holes were both theoretical entities before they were observed. Reality is always grander than the world we can see. The Caltech cosmologist Sean Carroll has argued, persuasively, that we shouldn’t refuse to contemplate the existence of what we cannot sense directly ‘on the grounds of some a priori principle’ such as testability. Especially not in the theoretical realm, which is speculative by nature. But nor should we be blind to where a field’s leading theory is leading us.
Inflation could turn out to be right in the end. Some of its predictions have come true. At the moment, there is no alternative theory of the early Universe that explains more. But cosmologists should be searching for one. They should not be waving away inflation’s fine-tuning problems with the multiverse. Until eternal inflation is testable and tested, successfully, again and again, cosmologists should not allow it to monopolise the collective theoretical imagination. Inflation is a speculative theory, and it should be treated as such.
Steinhardt looks out on his field, and sees a generation of theorists tinkering with models, wasting whole careers fiddling at the edges of a 30-year-old idea. ‘I know why they’re doing it,’ he says. ‘It’s easy to do. You can make hundreds of these models, and you can tweak them so they fit the data. But usually, those fixes aren’t the answer. Usually, you have to do something new.’
Steinhardt is trying to do something new. He spends most of his research time working on an alternative cosmological theory. He thinks the Big Bang might have been a reaction to a contraction, a bounce, perhaps one in a sequence of bounces that extends deep into the past and maybe into eternity. He is trying to figure out whether a bounce could have yielded a smoothed, stretched, uniform cosmos such as ours. Sometimes he feels isolated, but he knows how to chip away. His sense of possibility powers him through. He told me he thinks we might be edging up to a transformative idea. Something that could rearrange reality as we know it. Something of Copernican magnitude....
EXCERPT: [...] The science of cosmology has achieved wonders in recent centuries. It has enlarged the world we can see and think about by ontological orders of magnitude. [...] Art, literature, religion and philosophy ignore cosmology at their peril.
But cosmology’s hot streak has stalled. Cosmologists have looked deep into time, almost all the way back to the Big Bang itself, but they don’t know what came before it. They don’t know whether the Big Bang was the beginning, or merely one of many beginnings. Something entirely unimaginable might have preceded it. Cosmologists don’t know if the world we see around us is spatially infinite, or if there are other kinds of worlds beyond our horizon, or in other dimensions. And then the big mystery, the one that keeps the priests and the physicists up at night: no cosmologist has a clue why there is something rather than nothing.
To solve these mysteries, cosmologists must make guesses about events that are absurdly remote from us. [Alan] Guth’s theory of inflation is one such guess. It tells us that our Universe expanded, exponentially, a trillionth of a trillionth of a trillionth of a second after the Big Bang. In most models of this process, inflation’s expansive kick is eternal. It might cease in particular parts of the cosmos, as it did in our region, after only a fraction of a second, when inflation’s energy transformed into ordinary matter and radiation, which time would sculpt into galaxies. But somewhere outside our region, inflation continued, generating an infinite number of new regions, including those that are roaring into existence at this very moment.
Not all these regions are alike. Quantum mechanics puts a slot-machine spin on the cosmic conditions of every region, so that each has its own physical peculiarities. Some contain galaxies, stars, planets, and maybe even people. Others are entirely devoid of complex structures. Many are too alien to imagine. The slice of space and time we can see from Earth is 90 billion light years across. Today’s inflationary models tell us that this enormous expanse is only one small section of one tiny bubble that floats along in a frothy sea whose proportions defy comprehension. This vision of the world is wondrous, in its vastness and variety, in the sheer range of possibilities it suggests to the mind. But could it ever be proved?
[...] ‘The last 30 years is a very unusual period in the history of fundamental physics and cosmology,’ [Paul] Steinhardt told me. ‘There’s confusion, and maybe even a certain amount of fear. People are wedded to these ideas, because they grew up with them. Scientists don’t like to change ideas unless they’re forced to. They get involved with a theory. They get emotionally attached to it. When an idea is looking shaky, they go into defensive mode. If you’re working on something besides inflation, you find yourself outside the social network, and you don’t get many citations. Only a few brave souls are willing to risk that.’
I teased Steinhardt, pointing out that he hadn’t exactly been hauled before the Inquisition. Steinhardt is fully tenured, a lion of Princeton’s storied physics department. [...] Still, he feels overmatched. He told me he has asked for help from outside the field.
‘The outside community isn’t recognising the problem,’ he said. ‘This whole BICEP2 thing has made some people more aware of it. It’s been nice to have that aired out. But most people give us too much respect. They think we know what we’re doing. They take too seriously these voices that say inflation is established theory.’
I asked him who might help. What cavalry was he calling for?
‘I wish the philosophers would get involved,’ he said.
[...] During the early decades of the 20th century, astronomers built enormous mountaintop observatories, to peer at nebulae through thin alpine air, to confirm that they were indeed galaxies, separated by voids so vast that photons take millions of years to cross them. Like the ancients, cosmologists wondered whether their cosmos had always existed, or if it evolved as Kant suggested. Aristotle thought the cosmos was eternal. The Stoics disagreed, arguing that erosion would have already planed down Earth’s mountains if the world had always existed in its present state. When Medieval Christians took up the Greek cosmos, they sided with the Stoics. They needed the world to have a starting point in time, to stay faithful to the Genesis creation myth. Perhaps, then, we should not be surprised that it was a priest, a Belgian named Georges Lemaître, who gave our cosmos its beginning, which eventually came to be called the Big Bang.
[...] Steinhardt was surprised to see inflationary theorists clinking glasses when BICEP2 announced a high swirls figure. ‘They declared victory,’ he told me. ‘They said it was smoking-gun proof! Just what they expected!’
But then a few months passed and BICEP2’s interpretation started to look wobbly. In June, Linde told New Scientist that he didn’t like the way BICEP2’s swirls were being treated as a smoking gun for inflation. In July, Guth made similar statements to the Washington Post. Steinhardt was furious. He thought it was flip-flopping. He began to wonder if any data would disturb the serene certainty of inflationary theorists. ‘It was Andre Linde who used the “smoking gun” language in the first place,’ he told me. ‘Now he says it doesn’t make a difference what BICEP2 says. How can it be that not seeing gravitational waves is fine, and then seeing them is a smoking gun, and then not seeing them is fine again?’
Steinhardt told me that this flip-flopping on gravity waves is emblematic of inflation’s deeper flaws. Remember, inflation was originally designed to patch another theory’s fine-tuning issues. To produce the strange universe we see around us, you had to fine-tune the Big Bang. Inflation fixed that problem with a theoretical mechanism that briefly blew up the Universe like a balloon. But to produce a universe like ours, inflation’s initial conditions must also be precisely calibrated.
Eternal inflation is often invoked as a solution to inflation’s fine-tuning problem, because it spits out a multiverse, an infinite sea of cosmic regions, each with its own physical peculiarities. One with our peculiarities, our tuned initial conditions, is bound to show up somewhere. And even if such regions are rare, we are bound to inhabit one of them, for the simple reason that observers will only arise in regions with ‘Goldilocks’ conditions, just right to give rise to observers. In the lifeless regions, nature is not called ‘tuned’, or ‘designed’, or ‘beautiful’. She is not called Mother, because there is no one there to call her anything. But we observers should expect our region to look tuned. All observed regions of the cosmos look tuned.
[...] Theorists are trying to determine whether some conditions are more probable than others, but they haven’t succeeded yet, and there’s no guarantee they will. In the meantime, it’s hard to know whether inflation’s fine-tuning problems are genuine explanatory gaps that need exploring, or quirky outcomes of the quantum slot machine. The theory’s weaknesses can be explained away with the same glib shrug that accompanies the retort: ‘God just made it that way.’
A dominant, infinitely flexible multiverse theory could make it easy not to strain for the next leap forward. It could lead to a chilling effect on new ideas in cosmology, or worse, a creative crisis. Steinhardt thinks we’re already there. ‘Andre Linde has become associated with eternal inflation because he thinks the multiverse is a good idea,’ he told me. ‘But I invented it, too, and I think it’s a horrible idea. It’s an emperor’s new clothes story. Except in that story, it’s a child who points out that the Emperor has no clothes. In this case, it’s the tailors themselves telling us that the theory is not testable. It’s Guth and Linde.’
Steinhardt worries that science itself could be compromised. Science freed the imagination from cave shadows and shibboleths. Science let the mind run wild with radical ideas, ecstatic visions and new worlds, so long as those ideas explained what we actually see when we gaze out into nature. The Earth moves around the Sun: look how Venus wanders and you’ll see. The nebulae are distant galaxies, brimming with stars: magnify them and you’ll see. The Universe was once hot and dense, and has been expanding ever since: catch photons from its primordial flash and you’ll see. Science owes its epistemological gravitas to its stern insistence that every idea faces the firing squad of experiment. That is its philosophical backbone. That’s the methodology that gifted us the shimmering, intricate, expansive cosmos we live in today.
That doesn’t mean that theorists should shackle their imaginations to the limits of today’s instruments. Atoms and black holes were both theoretical entities before they were observed. Reality is always grander than the world we can see. The Caltech cosmologist Sean Carroll has argued, persuasively, that we shouldn’t refuse to contemplate the existence of what we cannot sense directly ‘on the grounds of some a priori principle’ such as testability. Especially not in the theoretical realm, which is speculative by nature. But nor should we be blind to where a field’s leading theory is leading us.
Inflation could turn out to be right in the end. Some of its predictions have come true. At the moment, there is no alternative theory of the early Universe that explains more. But cosmologists should be searching for one. They should not be waving away inflation’s fine-tuning problems with the multiverse. Until eternal inflation is testable and tested, successfully, again and again, cosmologists should not allow it to monopolise the collective theoretical imagination. Inflation is a speculative theory, and it should be treated as such.
Steinhardt looks out on his field, and sees a generation of theorists tinkering with models, wasting whole careers fiddling at the edges of a 30-year-old idea. ‘I know why they’re doing it,’ he says. ‘It’s easy to do. You can make hundreds of these models, and you can tweak them so they fit the data. But usually, those fixes aren’t the answer. Usually, you have to do something new.’
Steinhardt is trying to do something new. He spends most of his research time working on an alternative cosmological theory. He thinks the Big Bang might have been a reaction to a contraction, a bounce, perhaps one in a sequence of bounces that extends deep into the past and maybe into eternity. He is trying to figure out whether a bounce could have yielded a smoothed, stretched, uniform cosmos such as ours. Sometimes he feels isolated, but he knows how to chip away. His sense of possibility powers him through. He told me he thinks we might be edging up to a transformative idea. Something that could rearrange reality as we know it. Something of Copernican magnitude....