WHAT if the big bang never happened? Ask cosmologists this and they鈥檒l usually tell you it is a stupid question. The evidence, after all, is written in the heavens. Take the way galaxies are scattered across the sky, or witness the fading afterglow of the big bang fireball. Even the way the atoms in your body have come into being over the eons. They are all smoking guns that point to the existence 13.7 billion years ago of an ultra-hot, ultra-dense state known as the big bang.
Or are they? A small band of researchers is starting to ask the question no one is supposed to ask. Last week the dissidents met to review the evidence at the first ever Crisis in Cosmology conference in Mon莽茫o, Portugal. There they argued that cosmologists鈥� most cherished theory of the universe fails to explain certain crucial observations. If they are right, the universe could be a lot weirder than anyone imagined. But before venturing that idea, say the dissidents, it is time for some serious investigation into the big bang鈥檚 validity and its alternatives.
鈥淟ook at the facts,鈥� says Riccardo Scarpa of the European Southern Observatory in Santiago, Chile. 鈥淭he basic big bang model fails to predict what we observe in the universe in three major ways.鈥� The temperature of today鈥檚 universe, the expansion of the cosmos, and even the presence of galaxies, have all had cosmologists scrambling for fixes. 鈥淓very time the basic big bang model has failed to predict what we see, the solution has been to bolt on something new 鈥� inflation, dark matter and dark energy,鈥� Scarpa says.
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For Scarpa and his fellow dissidents, the tinkering has reached an unacceptable level. All for the sake of saving the notion that the universe flickered into being as a hot, dense state. 鈥淭his isn鈥檛 science,鈥� says Eric Lerner who is president of Lawrenceville Plasma Physics in West Orange, New Jersey, and one of the conference organisers. 鈥淏ig bang predictions are consistently wrong and are being fixed after the event.鈥� So much so, that today鈥檚 鈥渟tandard model鈥� of cosmology has become an ugly mishmash comprising the basic big bang theory, inflation and a generous helping of dark matter and dark energy.
The fact that the conference went ahead at all is an important step forward, say its organisers. Last year they wrote an open letter warning that failure to fund research into big bang alternatives was suppressing free debate in the field of cosmology (New 杏吧原创, 22 May 2004, p 20).
The trouble, says Lerner, who headed the list of more than 30 signatories, is that cosmology is bankrolled by just a few sources, and the committees that control those purse strings are dominated by supporters of the big bang. Critics of the standard model of cosmology are not just uncomfortable about the way they feel it has been cobbled together. They also point to specific observations that they believe cast doubt on cosmology鈥檚 standard model.
鈥淒ark matter is turning up in places where it shouldn鈥檛 exist鈥�
Take the most distant galaxies ever spotted, for example. According to the accepted view, when we observe ultra-distant galaxies we should see them in their youth, full of stars not long spawned from gas clouds. This is because light from these faraway galaxies has taken billions of years to reach us, and so the galaxies must appear as they were shortly after the big bang. But there is a problem. 鈥淲e don鈥檛 see young galaxies,鈥� says Lerner. 鈥淲e see old ones.鈥�
He cites recent observations of high-red-shift galaxies from NASA鈥檚 Spitzer space telescope. A galaxy鈥檚 red shift is a measure of how much the universe has expanded since it emitted its light. As the light travels through an expanding universe, its wavelength gets stretched, as if the light wave were drawn on a piece of elastic. The increase in wavelength corresponds to a shift towards the red end of the spectrum.
The Spitzer galaxies have red shifts that correspond to a time when the universe was between about 600 million and 1 billion years old. Galaxies this young should be full of newborn stars that emit blue light because they are so hot. The galaxies should not contain many older stars that are cool and red. 鈥淏ut they do,鈥� says Lerner.
Spitzer is the first telescope able to detect red stars in faraway galaxies because it is sensitive to infrared light. This means it can detect red light from stars in high-red-shift galaxies that has been pushed deep into the infrared during its journey to Earth. 鈥淚t turns out these galaxies aren鈥檛 young at all,鈥� says Lerner. 鈥淭hey have pretty much the same range of stars as present-day galaxies.鈥�
And that is bad news for the big bang. Among the stars in today鈥檚 galaxies are red giants that have taken billions of years to burn all their hydrogen and reach this bloated phase. So the Spitzer observations suggest that some of the stars in ultra-distant galaxies are older than the galaxies themselves, which plunges the standard model of cosmology into crisis.
Fog-filled universe
Not surprisingly, cosmologists have panned Lerner鈥檚 theories. They put the discrepancy down to large uncertainties in estimating the ages of galaxies. But Lerner has a reply. He points to other distant objects that appear much older than they ought to be. 鈥淎t high red shift, we also observe clusters and huge superclusters of galaxies,鈥� he says, arguing that it would have taken far longer than a billion years for galaxies to clump together to form such giant structures.
His solution to the puzzle is extreme. Rather than being caused by the expanding universe, he believes that the red shift is down to some other mechanism. But at this stage it is only a guess. 鈥淚 admit I don鈥檛 know what that mechanism might be,鈥� Lerner says, 鈥渢hough I believe it is intrinsic to light.鈥�
To test his idea, he would like to see sensitive experiments on Earth capable of detecting minute changes in light. One possibility would be to modify the LIGO detector in Hanford, Washington state. LIGO is designed to detect gravitational waves, the warps in space-time created by events such as neutron star collisions. To do this it bounces perpendicular beams of laser light hundreds of times between mirrors 4 kilometres apart, looking for subtle shifts in the beams鈥� lengths. With a few tweaks, Lerner believes that LIGO could be modified to measure any intrinsic red-shifting that light might undergo.
If the experiment ever gets the go-ahead and Lerner is proved right, the implications would be immense, not least because the tapestry of cosmology as we know it would unravel. Without an expanding universe, there would be no need to invoke dark energy to account for the apparent acceleration of that expansion. Nor would there be any reason to suppose the big bang was the ultimate beginning. 鈥淚 can prove that the universe wasn鈥檛 born 13.7 billion years ago,鈥� says Lerner. 鈥淭he big bang never happened.鈥�
However, Lerner鈥檚 claims leave plenty of awkward questions. Among them is the matter of the cosmic microwave background. First detected in 1965, the vast majority of cosmologists believe that this faint, all-pervading soup of microwaves is the dying glow of the big bang, and proof of the ultimate beginning. According to big bang theory, the hot radiation that filled space after the birth of the universe has been trapped inside ever since because it has nowhere else to go. As the universe expanded over the past 13.7 billion years, the radiation has cooled to today鈥檚 temperature of less than 3 kelvin above absolute zero.
So if there was no big bang, where did the cosmic microwave background come from? Lerner believes that cosmologists have got the origin of the microwave glow all wrong. 鈥淚f you wake up in a tent and everything around you is white, you don鈥檛 conclude you鈥檝e seen the start of the universe,鈥� he says. 鈥淵ou conclude you鈥檙e in fog.鈥�
Rather than coming from the big bang, Lerner believes that the cosmic background radiation is really starlight that has been absorbed and re-radiated. It is an old idea that was widely promoted by the late cosmologist and well-known big bang sceptic Fred Hoyle. He believed that starlight was absorbed by needle-like grains of iron ejected by supernovae and then radiated as microwaves. But Hoyle never found any evidence to back up his ideas and many cosmologists dismissed them.
鈥淪ome of the stars in distant galaxies appear older than the universe itself鈥�
Lerner鈥檚 idea is similar, though he thinks that threads of electrically charged gas called plasma are responsible, rather than iron whiskers. Jets of plasma are squirted into intergalactic space by highly energetic galaxies known as quasars, and Lerner believes that such plasma filaments continually fragmented until they filled the universe like fog. This fog then scattered the infrared light radiated by dust that had in turn absorbed starlight. By doing so, Lerner believes, the infrared radiation became uniform in all directions, just as the cosmic microwave background appears to be.
All this is possible, he argues, because standard cosmology theory has overlooked processes involving plasmas. 鈥淎ll astronomers know that 99.99 per cent of matter in the universe is in the form of plasma, which is controlled by electromagnetic forces,鈥� he says. 鈥淵et all astronomers insist on believing that gravity is the only important force in the universe. It is like oceanographers ignoring hydrodynamics.鈥� To make progress, Lerner is calling for theories that include plasma phenomena as well as gravity, and for more rigorous testing of theory against observations.
Of course, Lerner鈥檚 ideas are extremely controversial and few people are convinced, but that doesn鈥檛 stop other researchers questioning the standard theory too. They have their own ideas about what is wrong with it. In Scarpa鈥檚 case, the mysterious dark matter is at fault.
Dark matter has become an essential ingredient in cosmology鈥檚 standard model. That鈥檚 because the big bang on its own fails to describe how galaxies could have congealed from the matter forged shortly after the birth of the universe. The problem is that gas and dust made from normal matter were spread too evenly for galaxies to clump together in just 13.7 billion years. Cosmologists fix this problem by adding to their brew a vast amount of invisible dark matter which provides the extra tug needed to speed up galaxy formation.
The same gravitational top-up helps to explain the rapid motion of outlying stars in galaxies. Astronomers have measured stars orbiting their galactic centres so fast that they ought to fly off into intergalactic space. But dark matter鈥檚 extra gravity would explain how the galaxies hold onto their speeding stars. Similarly, dark matter is needed to explain how clusters of galaxies can hold on to galaxies that are orbiting the cluster鈥檚 centre so fast they ought to be flung away.
But dark matter may not be the cure-all it seems, warns Scarpa. What worries him are inconsistencies with the theory. 鈥淚f you believe in dark matter, you discover there is too much of it,鈥� he says. In particular, his observations point to dark matter in places cosmologists say it shouldn鈥檛 exist. One place no one expects to see it is in globular clusters, tight knots of stars that orbit the Milky Way and many other galaxies. Unlike normal matter, the dark stuff is completely incapable of emitting light or any other form of electromagnetic radiation. This means a cloud of the stuff cannot radiate away its internal heat, a process vital for gravitational contraction, so dark matter cannot easily clump together at scales as small as those of globular clusters.
Scarpa鈥檚 observations tell a different story, however. He and his colleagues have found evidence that the stars in globular clusters are moving faster than the gravity of visible matter can explain, just as they do in larger galaxies. They have studied three globular clusters, including the Milky Way鈥檚 biggest, Omega Centauri, which contains about a million stars. In all three, they find the same wayward behaviour. So if isn鈥檛 dark matter, what is going on?
Scarpa鈥檚 team believes the answer might be a breakdown of Newton鈥檚 law of gravity, which says an object鈥檚 gravitational tug is inversely proportional to the square of your distance from it. Their observations of globular clusters suggest that Newton鈥檚 inverse square law holds true only above some critical acceleration. Below this threshold strength, gravity appears to dissipate more slowly than Newton predicts.
Exactly the same effect has been spotted in spiral galaxies and galaxy-rich clusters. It was identified more than 20 years ago by Mordehai Milgrom at the Weizmann Institute in Rehovot, Israel, who proposed a theory known as modified Newtonian dynamics (MOND) to explain it. Scarpa points out that the critical acceleration of 10-10 metres per second per second that was identified for galaxies appears to hold for globular clusters too. And his work has led him to the same conclusion as Milgrom: 鈥淭here is no need for dark matter in the universe,鈥� says Scarpa.
It is a bold claim to make. And not surprisingly, MOND has had plenty of critics over the years. One of cosmologists鈥� biggest gripes is that MOND is not compatible with Einstein鈥檚 theory of relativity, so it is not valid for objects travelling close to the speed of light or in very strong gravitational fields. In practice, this means MOND has been powerless to make predictions about pulsars, black holes and, most importantly, the big bang. But this has now been fixed by Jacob Bekenstein at the Hebrew University of Jerusalem in Israel.
Bekenstein鈥檚 relativistic version of the theory already appears to be bearing fruit. In May a team led by Constantinos Skordis of the University of Oxford showed that relativistic MOND can make cosmological predictions. The researchers have reproduced both the observed properties of the cosmic microwave background and the distribution of galaxies throughout the universe ().
Gravity in crisis
Scarpa believes that MOND is a crucial body blow for the big bang. 鈥淚t means that the law of gravity from which we derive the big bang is wrong,鈥� he says. He insists that cosmologists are interpreting astronomical observations using the wrong framework. And he urges them to go back to the drawing board and derive a cosmological model based on MOND.
For now, his plea seems to be falling mostly on deaf ears. Yet there is more evidence that there could be something wrong with the standard model of cosmology. And it is evidence that many cosmologists are finding harder to dismiss because it comes from the jewel in the crown of cosmology instruments, the Wilkinson Microwave Anisotropy Probe. 鈥淚t could be telling us something fundamental about our universe, maybe even that the simplest big bang model is wrong,鈥� says Jo茫o Magueijo of Imperial College London.
Since its launch in 2001, WMAP has been quietly taking the temperature of the universe from its vantage point 1.5 million kilometres out in space. The probe measures the way the temperature of the cosmic microwave background varies across the sky. Cosmologists believe that the tiny variations from one place to another are an imprint of the state of the universe about 300,000 years after the big bang, when matter began to clump together under gravity. Hotter patches correspond to denser regions, and cooler patches reflect less dense areas. These density variations began life as quantum fluctuations in the vacuum in the first split second of the universe鈥檚 existence, and were subsequently amplified by a brief period of phenomenally fast expansion called inflation.
Because the quantum fluctuations popped up at random, the hot and cold spots we see in one part of the sky should look much like those in any other part. And because the cosmic background radiation is a feature of the universe as a whole rather than any single object in it, none of the hot or cold regions should be aligned with structures in our corner of the cosmos. Yet this is exactly what some researchers are claiming from the WMAP results.
Earlier this year, Magueijo and his Imperial College colleague Kate Land reported that they had found a bizarre alignment in the cosmic microwave background. At first glance, the pattern of hot and cold spots appeared random, as expected. But when they looked more closely, they found something unexpected. It is as if you were listening to an anarchic orchestra playing some random cacophony, and yet when you picked out the violins, trombones and clarinets separately, you discovered that they are playing the same tune.
Like an orchestral movement, the WMAP results can be analysed as a blend of patterns of different spatial frequencies. When Magueijo and Land looked at the hot and cold spots this way, they noticed a striking similarity between the individual patterns. Rather than being spattered randomly across the sky, the spots in each pattern seemed to line up along the same direction. With a good eye for a newspaper headline, Magueijo dubbed this alignment the axis of evil. 鈥淚f it is true, this is an astonishing discovery,鈥� he says.
鈥淲ithout an expanding universe, the big bang was not the ultimate beginning鈥�
That鈥檚 because the result flies in the face of big bang theory, which rules out any such special or preferred direction. So could the weird effect be down to something more mundane, such as a problem with the WMAP satellite? Charles Bennett, who leads the WMAP mission at NASA鈥檚 Goddard Space Flight Center in Greenbelt, Maryland, discounts that possibility. 鈥淚 have no reason to think that any anomaly is an artefact of the instrument,鈥� he says.
Another suggestion is that heat given off by the Milky Way鈥檚 dusty disk has not been properly subtracted from the WMAP signals and mimics the axis of evil. 鈥淐ertainly there are some sloppy papers where insufficient attention has been paid to the signals from the Milky Way,鈥� warns Bennett. Others point out that the conclusions are based on only one year鈥檚 worth of WMAP signals. And researchers are eagerly awaiting the next batch, rumoured to be released in September.
Yet Magueijo and Land are convinced that the alignment in the patterns does exist. 鈥淭he big question is: what could have caused it,鈥� asks Magueijo. One possibility, he says, is that the universe is shaped like a slab, with space extending to infinity in two dimensions but spanning only about 20 billion light years in the third dimension. Or the universe might be shaped like a bagel. Another way to create a preferred direction would be to have a rotating universe, because this singles out the axis of rotation as different from all other directions.
Bennett admits he is excited by the possibility that WMAP has stumbled on something so important and fundamental about the universe. His hunch, though, is that the alignment is a fluke. 鈥淗owever, it鈥檚 always possible the universe is trying to tell us something,鈥� he says.
Clearly, such a universe would flout a fundamental assumption of all big bang models: that the universe is the same in all places and in all directions. 鈥淧eople made these assumptions because, without them, it was impossible to simplify Einstein鈥檚 equations enough to solve them for the universe,鈥� says Magueijo. And if those assumptions are wrong, it could be curtains for the standard model of cosmology.
That may not be a bad thing, according to Magueijo. 鈥淭he standard model is ugly and embarrassing,鈥� he says. 鈥淚 hope it will soon come to breaking point.鈥� But whatever replaced it would of course have to predict all the things the standard model predicts. 鈥淭his would be very hard indeed,鈥� concedes Magueijo.
Meanwhile the axis of evil is peculiar enough that Bennett and his colleague Gary Hinshaw have obtained money from NASA to carry out a five-year exhaustive examination of the WMAP signals. That should exclude the possibilities of the instrumental error and contamination once and for all. 鈥淭he alignment is probably just a fluke but I really feel compelled to investigate it,鈥� he says. 鈥淲ho knows what we will find.鈥�
Lerner and his fellow sceptics are in little doubt: 鈥淲hat we may find is a universe that is very different than the increasingly bizarre one of the big bang theory.鈥�
