Paul Davies, a British-born cosmologist, theoretical physicist, and bestselling author, conducts inter-disciplinary research in the areas of physics, cosmology, and biology. Dr. Davies is the director of a new research center at Arizona State University called Beyond. The mission of the center is to explore the great questions of our existence, the origin of our universe and life, the nature of consciousness, and the mathematical laws that underpin the universe. He is particularly interested in the Big Bang Theory, one of the most influential theories of our time concerning the origins of our universe.

Matter&Beyond: You are a cosmologist and the topic obviously is fascinating. But what is the root of our connection with space? What is the root of our human fascination with the sky and stars?

It’s very interesting to speculate if human beings had developed on a planet that was totally covered in cloud and had no awareness of the sky and astronomical bodies, whether society would’ve developed very differently. It’s quite clear when you look back at human history that the “heavens,” as they used to be called, had a very major role to play in all early civilizations. We can see evidence of astronomical observatories, thousands of years ago, long before the invention of telescopes. There are monuments, for example, pyramids that were built or Stonehenge in England, which are clearly astronomical monuments of some sort. And then we think of the world’s great religions and they all have an astronomical component. Think of the role of the new moon in Islam, for example, or the Star of Bethlehem in Christianity. … I think we can trace this preoccupation with the sky and the heavens to the early days of the development of agriculture because it became really important for people to know when to plant their crops and when to harvest them and the different seasons and so on. We can imagine that, say 10,000 years ago, people studied the sky very, very carefully and they became familiar with the movement of the objects and they invented complicated mathematical formulas to chart them.

M&B: How did our fascination with space change after industrialization?

What I would say has happened in the last three or four hundred years is that actually most people have become less aware of space. We live in cities that are polluted so we don’t see outer space. We’re too busy looking at televisions or driving home from work so we never look up and see this wonderland above our heads. How many people, for example, could name even the major constellations of stars if they were ever taken outside of their cities to somewhere where they could see the dark night sky? And so astronomy has become in a way less and less significant in people’s lives.

M&B: But today astronomy and cosmology is making a comeback. There are a lot of bestseller popular science books written on space and time.

I think during the 1970s and ‘80s people became very antiscientific, perhaps as a result of a reaction to the Vietnam War. Astronomy somehow remained aloof from that. It was perceived as a subject that wasn’t dangerous, that we could study the stars, they were a long way away using benign equipment like telescopes and astronomers weren’t going to threaten anybody. And so I think exploring the universe has been seen in many ways as a sort of untainted glorious enterprise that doesn’t have this sort of threatening aspect to it. It’s still, of course, immensely popular. People still want to go to planetariums and they read books on astronomy and they like television productions on astronomical things. But I think it’s shifted now from those early days where people’s lives really revolved around the stars in a very literal sense, and those days are now gone.

M&B: You are a cosmologist, but based on the wide range of research areas at the center Beyond, I would say that you look more like a modern seeker of old times.

Since the dawn of human history people have asked the great questions of existence, how did the universe come to exist? What is the role of human beings in the great cosmic scheme of things? How will the universe end? What is it made of? Now for the greater part of human history, these questions were addressed by priests and philosophers. But in recent years, science has made progress as well. So scientists find themselves now asking those same age-old questions of existence. In my career, I have covered topics like the origin of the universe and the origin of life, the nature of time, the nature of consciousness, and the underlying laws of the universe. Inevitably these topics trespass on territory which was previously almost exclusively philosophy or religion’s. Now science has a story to tell about these great issues.

M&B: If you have to pick the most interesting question modern science is trying to answer, what would be your choice?

I suppose the most interesting thing modern science is telling us about is how the universe came into existence. When I was a student, the Big Bang Theory was just one of many ideas about the origin of the universe. But over the past 30 years it’s become much more secure so that not only do we know that there was a Big Bang about 13.7 billion years ago, but we know a great deal about the details including the conditions that prevailed in the universe back to as little as one-trillionth of a second after the Big Bang. So we’re now able to reconstruct precisely how the universe went bang and how it developed over the subsequent billions of years into what we see today. So I think that the scientific story of the genesis of a universe is fascinating—its origin, its explosive outbursts, and the long period of enrichment and complexification of matter leading eventually to the emergence of life and beings like ourselves who could look back and reflect on it all.

M&B: The Big Bang Theory is well established. Yet it’s still open to commentaries and interpretations.

It’s often said that science deals with “how?” questions and religion deals with “why?” questions and so you don’t normally go to a scientist to find meaning or purpose in the universe. Nevertheless it is clear that because science is now able to fill in so many details about the big picture, that scientists are inevitably asked to make pronouncements about meaning and purpose. As they do so, they divide about equally into two groups. One group who says, “Well, the universe is beautiful, it’s so ingenious that it looks as if it has been designed by an intelligent creator but in fact it hasn’t.” There is no meaning, no purpose in the universe. The famous quote by Steven Weinberg, the American cosmologist, goes: “The more the universe seems comprehensible, the more it also seems pointless.” Then the other half of cosmologists look at this same set of facts and they agree about the facts but they interpret them differently. They will say, “Well, it does suggest that there is a grand scheme of things, it does suggest that the universe is about something. This grand and wonderful scheme, which is so ingeniously constructed, does suggest that there is something deeper to it all.”

M&B: We find more and more scientists thinking and writing about these topics on both sides.

Human beings usually are not happy just to have a technical description of how the universe works, and in particular people always want to ask the question what happened before the Big Bang? What made the Big Bang go bang? Why is there a universe in the first place, and why is the universe as it is and not something different? And these are questions right on the edge of science because science really can only deal with things that can be measured and observed. They can deal with the facts of the world, the things before us. When we come to questions about why does the world exist at all or why are there laws and where do those laws come from, it’s very difficult for science to make a contribution. Nevertheless, in the last ten or twenty years more and more scientists have been addressing those questions. The nature of physical laws is a very good example… When I was a student, you were simply told the laws of physics are what they are, we don’t know why, maybe there isn’t any reason why—that’s just the way it is. It was not the job of the scientists to ask why those laws of physics exist. The job of the scientist was to discover what the laws are and then apply them. But that has changed. There is now a feeling that maybe the nature of physical laws is something that is a proper, legitimate subject for scientific inquiry. And so there’s a whole bunch of physicists who are looking at alternative laws.

M&B: How do they theorize alternative laws?

Supposing we stipulate a different law of gravitation and see what the consequences would be. We can work out using mathematics what it would be like if gravity differed a little bit from the observed law. And then we can do the same with the other forces of nature and other features of the world. What would it be like if we lived in the universe with 23 space dimensions instead of three? We can work that out. Partly that’s a recreational exercise—it would be fun to know what it would be like in a universe with different dimensions or different forces—but also we would like to know is there anything special about the particular laws of this particular universe.

M&B: What is the result of such experiments?

There is something special and that special thing is that the particular laws that we observe in this universe are very strangely conducive to the emergence of life. They’re highly suited to life, even suspiciously so. It’s almost as if these laws have been fine-tuned for life, and so at that point disagreement sets in and some scientists say, “Well, it’s just a lucky coincidence that that is the case,” and others say, “No, there must be some other explanation for it.” But it is certainly the case that the universe we observe and the laws that underpin it, which used to just be regarded as given, as not a proper subject for inquiry, are now being studied as one set among a vast variety of possible sets, and it’s generally agreed that the particular laws that we observe are very special in their relation to the ability to bring forth life.

M&B: And you call this a “cosmic jackpot.”

My book, Cosmic Jackpot: Why Our Universe Is Just Right for Life, examines a very specific problem, the problem of why the universe seems to be just right for life. When we look at the fundamental laws of physics and the way that the universe originated in the Big Bang, there are many features that appear to be coincidences or the happy arrangement of different aspects of physical laws without which there would be no life and no observers like ourselves. And the question is, What are we to make of that? Some people say, “Well, it looks like the whole thing is a fix, it looks like the universe is being created by an Intelligent Designer.” Well, obviously all the scientists aren’t going to believe that. So instead they come up with other explanations.

M&B: There is the theory of multiverses.

According to that theory, there are many universes each of which has its own set of laws and these laws are just randomly distributed across these universes. So here and there, just by chance, the laws are going to come out just right for life. It’s no surprise that we find ourselves living in a universe where conditions are just right for life because we could hardly live in a universe which had laws of physics that did not permit life. It’s like a gigantic cosmic lottery with all of these different universes and we’ve just hit the cosmic jackpot because we’re winners of this vast lottery. So that is the popular view as to how we explain that the universe is just right for life. I think that view is progressive but I think it falls far short of providing a complete explanation of existence. I take life seriously and I take the mind seriously so I don’t think that these are just incidental phenomena in the great cosmic scheme of things. I think they’re fundamental to the workings of the universe as a whole and so what I’m trying to do here is to go beyond the rather startled debate between science and religion that’s existed for the last 30 years about the ultimate source of reality.

M&B: It just seems to me, just based on intuition, that we’re not alone here. The universe is so vast, there’s just got to be life somewhere. Does mathematics and statistics support this intuition?

A lot of people make that mistake by saying, statistically, there has to be life elsewhere, the universe is so vast, so many stars out there. It would be incredible if this was the only planet with life. It’s just simply not true. The probability of forming even the simplest enzyme, the simplest protein in known life, if you did it just by shuffling the building blocks, the amino acids that make up for that, is infinitesimal. If you took the entire volume of the universe and filled it with an amino acid soup and just kept shuffling and shuffling and shuffling, you would simply not make it. If it’s happened once, we’re it. It would not happen anywhere else. So the probability of life forming in that way by chance is twice as infinitesimal. So if that’s the way life happened, the fact we live in a vast universe makes no different whatsoever.

M&B: People who are not scientists may think that scientists are the smartest of all of us so they must be figuring out everything, they’re the smartest ones who bring the technology. They look at scientists as natural guides. Do you see a danger here?

Scientists are human beings like everybody else, and I think it’s a mistake to see scientists as generally cold, hard, soulless people who don’t care about the consequences of their work. Scientists are very passionate people and they feel passionately not only about their work but about other aspects of human life. It is also a mistake to think that scientists have any special moral authority over questions of general relevance to human beings. The vast majority of problems that we confront in the world really are only related obliquely, if at all, to science. We struggle with things like the ruin of our environment or international disputes or family concerns or education concerns. These sort of day-to-day things loom very large in people’s lives, but I’m not sure that scientists make a contribution. Science is obviously relevant to some of these things, for example, if we could find a better source of energy that doesn’t heat the planet, that would be good. So science can play a role, but individual scientists, I don’t think are any better than anybody else as moral judges.

Introduction

Human beings have wrestled with questions about the origin of our existence and the fabric of our universe for thousands of years. This questioning formed the discipline of cosmology. Dr. Natarajan explores the nature of our world and shares her perspectives about how new scientific discoveries are reshaping our understanding of the universe and our place in it. Until very recently, the universe had been considered a vast empty space. But the Dark matter theory states that the universe is not empty, but rather filled with an invisible matter. As new mysteries unfold, Dr. Natarajan points out that it is our fundamental human curiosity that leaves us no choice but to explore the universe and how we fit into its grand picture.

M&B: Dr. Natarajan, you work on dark matter in the universe. What is the theory?

It turns out that the bulk of the matter in the universe is not made of ordinary atoms that you and I or the universe that we know and experience is made of, but instead made of this mysterious particle. Ninety percent of all the matter in the universe is dark matter, and we believe this is a set of particles that was created very early in the universe. These particles do not have charge, but they have mass. Since they dominate the mass of the universe, it turns out that they really form the scaffolding in the universe around which all galaxies, stars, and so on, form. They are sort of the basis or the framework within which normal atoms actually cool to form star galaxies, and then have generated us.

M&B: What is the evidence for their existence?

The reason dark matter remains a mystery, – although there is incontrovertible evidence for the existence of dark matter – is the fact that you only detect it indirectly. What I mean by that is you detect its presence because it has mass, and since it doesn’t have any charge it doesn’t couple to any radiation. So you don’t see radiation in any wavelength in the electromagnetic spectrum: no X-rays, no gamma rays, no visible light, nothing. But since dark matter has mass, it aggregates gravitationally, so they feel gravitational pull towards each other and they cluster. It’s the clustering of the dark matter, the fact that it gets compact, that we detect the effects of dark matter.

M&B: What happens near the regions where dark matter clusters? In your research papers you use the bending of the light rays. How do you observe it?

The primary evidence is the gravitational bending of light produced by these aggregates of dark matter. The universe is really composed of a smooth distribution of dark matter, with a lot of clump regions where this dark matter has aggregated, and then enabled the formation of galaxies. The presence of these large amounts of dark matter causes light from background galaxies coming towards us to bend. The actual shapes of galaxies that are behind a big clump of dark matter, which is along our line of sight, are actually distorted when we see it. The dark matter in general is smoothly distributed everywhere in the universe. But there are these particular regions that are denser. So we can look at regions in which the dark matter is not so densely distributed, look at the shapes of undistorted shapes of galaxies, and then use that to infer how much distortion we’re actually seeing when we see a lump, and infer its existence from the distortion. Because the strength of the distortion is directly proportional to the mass, you can directly infer how much mass there is between us and those objects.

M&B: Is there evidence other than the bending of the light rays?

The other evidence eludes to the fact that dark matter actually gives the basis for the formation of stars and galaxies. If you look at the motions of stars and galaxies, you find that, unlike the solar system, if you look at the velocities of the planets in the solar system as a function of distance from the sun you find that it’s falling. So the planets in the inner regions are moving very fast; they feel the gravity of the sun much more strongly than the outer planets, which are not actually moving as fast. So if you plot the velocity from the center or from the sun outwards in the solar system, the velocities are falling. Whereas if you go to a galaxy and you do the same experiment, you look at stars at different radii and you try to see what their speeds look like. They are speeding up as you go outwards. And the only way they can do that is there is something that is sitting outside the galaxy that holds it up as it were, and has gravity. And it turns out that our current picture is that most galaxies have very extended dark matter halos. The key point is that there’s a lot of dark matter sitting outside the galaxy well beyond where we see the stars.

The other compelling lines of evidence for the existence of dark matter come from larger scale observations of the universe. One of the leftovers of the big bang or relic of the big bang is this microwave background radiation that is detected today in the universe. It was a very hot radiation that has cooled with the expansion of the universe, and we are bathed in it. I mean it’s everywhere, in every direction, and measurements of the directional dependence of the microwave background shows that it’s very uniform. But in one part it’s anisotropic, so there are cool zones and hot zones in the sky. On very small scales we see these cold and hot spots. And these and isotropy’s in the microwave background are exactly predicted by this model, the cold dark matter model, which I said you know is postulated on the very early generation of the universe and these dark matter particles.

M&B: So we know that they exist. But what is their essence? What are their properties?

This is still a mysterious kind of beast. In fact, we don’t know the nature, but it appears that it’s collisionless. It’s very counterintuitive. That’s one of the things I find fascinating about the fact that it is so counterintuitive. These particles are actually collisionless. What that means is that when two dark matter particles approach each other, they pass through each other, they don’t actually bounce off of each other, so these particles don’t collide, which means they don’t have pressure, because pressure is generated by collision. So they are pressureless particles that have mass. Gravity holds them together, but they don’t actually collide.

So a current understanding of dark matter is that it’s definitely generated very early in the universe and that it clusters very strongly and it’s distributed on very different scales in the universe, so there’s like a smooth background and there are lots of clumps on top of it and so on.

M&B: As far as the mass of Dark Matter how much mass are we talking about? If there is no clustering, something like in the volume of the earth, for example, how much total dark matter mass do we have?

Well I guess the thing is at the position of the earth and at the position of the sun from the center of our galaxy. We are not really dominated by dark matter anymore, so dark matter at that radius doesn’t constitute significant portion of the mass. We are bathed in it, but the density is quite low. It’s at the innermost part of our galaxy where the density is very, very high, so we actually expect that the inner most regions of our galaxy is a very complicated, violent place where not only do you have a black hole which we know exists. This is a black hole that is not made of dark matter. This is a black hole that has gobbled gas and grown to about a million times the mass of the sun, and which is sitting at the center and it creates a very violent place for stars because it can rip them apart and so on. And this whole system is sort of embedded in this very, very dense region full of dark matter.

M&B: How is your everyday work? Where do you get data about the light rays coming near the regions with high Dark matter density?

A: I’m a theoretical person and what that means is that I actually build models but models that are guided by observations. The theory has transformed in the past 10 to 15 years because of the amount of data that technological progress has given us.

For example, the Hubbell space telescope has really transformed the kind of modeling that can be done. So I actually use data that other people have procured. They’ve cleaned it up and they give it to me. These are very distorted images of background galaxies whose shape has been distorted because of the huge amounts of dark matter that is contained in a cluster of galaxies.

M&B: The bending of the light rays is predicted by the general relativity theory. Is it what you use for your calculations?

A: It’s a beautiful theory. I think that people really have understood the iconic status of Einstein. What is most fascinating about him for me is the profound insights that he had of such despaired phenomenon. There was a way in which he was able to see connections and synthesize. You know the whole understanding that the geometry, the fate and the contents of the universe ought to be linked is a profound insight. And I think you know it’s incredible that he enabled, you know, his mind enabled him to formulate it in the way that he did, which has allowed people like me to use general relativity and the sort of elegance of general relativity because of how simple it is in fact to apply and test.

M&B: This looks like an intriguing line of work?

I want to stress that this is a particularly wonderful time for cosmology. It’s a particularly special time. I don’t want to use the sort of often abused golden age as it were, but it’s the confluence of technological progress with the kind of data that we can obtain and the level of understanding that we have built up. This is a very special time to be doing this kind of work. And while the mystery of what dark matter might be made of, you know, it may or may not get solved in my lifetime.

M&B: If you want to describe your work, what term would you use?

In a more descriptive way, I guess. What I really do is I build a story line. I build a story line for the universe. I mean, I build a story of the sequence of events of how a structure forms and assembles. The key there is that you are guided, you have a few snapshots, so you have a bit of data, but then you have to extrapolate and you make some predictions. The goal of the kind of work that I do is to make predictions, and have them be taken seriously, to either be falsified or shown to be true, and what’s exciting about this particular time is that people can falsify your theories or your models in a very short time.

M&B: Isn’t it interesting that we can actually make a story out of universe?

Well, I mean, I think that what is fascinating, and this is a personal view, what is fascinating about cosmology is the… you know it’s mystical and it’s mysterious at the same time and it’s highly abstract. It’s not intuitive because the scale that I’m working with in terms of distances, masses, and energy are just unfathomable. So there’s a real irresistible pull for certain kinds of people to do this kind of work. And I think the universe is a pretty good subject for a narrative because of the range of phenomena that occur in it. This is possibly why in all ancient civilizations there is some notion of cosmogony and this idea of fascination with where we came from. I don’t want to sound arrogant by saying that it’s the fundamental question, but you know it’s an inescapable question for anybody to ponder where we came from.

M&B: Is there a sense of awe that motivates you in your studies?

There is a sense of wonder that the universe generates and I think that you know personally for me I’m a bit of an adventurist, and I think if I can imagine myself, if I had been born 200, 300 years ago I would have been one of those explorers. And I think there are people like that amongst us always, who want to explore in different ways. I mean, there are some people who want to explore via music. And there are frontiers that they want to break through in music, and they have the creativity to do that. And I think that for a lot of us who are doing science, and cosmology in particular, there is a sense of exploration, there’s a sense of examining or grappling with things that are really at the limits of our capabilities in a way.

M&B: In some ways one of the most important fruits of the process and coming along it’s our imagination. And the human imagination is also a part of the universe.

Absolutely. It is an inescapable part of the universe and what is fascinating is the idea that we have the capability to even contemplate the origin of the universe given that we are a part of the universe.

M&B: Many people approach science in a utilitarian way and this is not what you are doing.

I think that the fact that it is not utilitarian is precisely what attracts me to it. I think it is the other side of the coin of this, which is why we probably aren’t as well funded and we ought to be better funded than we are, because this is such a fundamental human curiosity. There is enormous public interest in what we do and the level of funding that we have does not reflect that. For instance, obviously medicine is very critical. It’s critical to our existence. But the disparity in how they are funded and how the pure sciences are funded is sort of disturbing. Because I think as a culture, as a world, we can afford to indulge in understanding basic sciences partly because there are spinoffs from all the work that we do. It is unpredictable, and I think that is what’s fascinating. There are no guaranteed benefits to human kind and society today that cosmologists can bring. However, they satisfy this hunger for knowing and going beyond, you know, satisfying your hunger and thirst on a day to day basis.

Mustafa Tabanli is a producer at Ebru TV. He conducted this interview for Emmy Award winning television series Matter&Beyond.

Bio

Dr. Priya Natarajan is a Professor of Astronomy and Physics at Yale University, and an Associate at the Dark Cosmology Center, which is part of the Niels Bohr Institute at the University of Copenhagen, Denmark. Her research interests include cosmology, gravitational lensing, and black hole physics. She earned a B.A. degree in physics and mathematics at M.I.T. and her doctorate at the Institute of Astronomy, University of Cambridge in England, where she was a member of Trinity College and elected to a Title A Research Fellowship that she held from 1997 to 2003. She is currently on leave from Yale to take up her Guggenheim Fellowship. She is deeply invested in the public dissemination of science and is currently a member of the Science Advisory Board for the public television series NOVA.

http://www.astro.yale.edu/priya/

Cosmology is the study of the universe’s beginning, formation, and evolution. Humanity has devised many cosmological theories. For example, ancient Greeks thought the universe was composed of four elements: earth, wind, fire, and water. Now, despite several millennia of effort, modern cosmologists are even worse off.

About 60 years ago, Fritz Zwicky realized that clusters of galaxies consist mainly of matter in some non-luminous form, defined as matter that we cannot see with our telescopes. Now, after decades of accumulated observations, most astronomers believe that as much as 90 percent of this material may consist of objects or particles that cannot be seen. That is, most of the matter in the universe does not radiate light. Previously, people called this phenomenon missing matter. Contemporary researchers prefer dark matter, for it is the light, not the matter, that is missing.

In this article, I discuss evidence that proves the existence of dark matter, possible candidates for dark matter, and the importance of dark matter in understanding the universe’s beginning and end according to the Big Bang theory.

Obsering the invisible

As dark matter emits no electromagnetic radiation (e.g., light, radio waves, and X-rays), it cannot be seen by a telescope. However, we can infer its existence through its gravitational effects on luminous matter. The most obvious example of this is observed when looking at the rotation rates of galaxies. Using the resulting information, scientists can calculate the speeds of stars as they rotate around a galaxy’s center (orbital speeds) in two different ways. The first way is to look at the light coming from stars in different parts of a galaxy. Through a close study of that light’s properties, they can deduce how fast and in what direction (whether toward or away from us) that star is rotating. The second way is based upon gravitational physics. Given that we know how much matter the galaxy contains, we can calculate how fast stars must be orbiting around its center. By accounting for all of the galaxy’s luminous matter (e.g., stars, gas, and dust), astronomers can calculate the star’s orbital speeds.

But there is a problem here: The two results do not agree. The only way to account for this difference is to posit the existence of a large quantity of dark matter in the galaxies. To explain the astronomical observations, this dark matter must surround the galaxy in a large spherical distribution (known as a galactic halo).

Is the gravity of the galaxies seen in this image strong enough to contain the glowing hot gas? Superposed on an optical picture of a group of galaxies is an image taken in X-ray light. The X-ray picture shows confined hot gas highlighted in false red color and provides clear evidence that the gravity exerted in groups and clusters of galaxies exceeds all of the individual component galaxies combined. The extra gravity is attributed to dark matter, the nature and abundance of which is one of the biggest mysteries in astrophysics today. Credit: Richard Mushotzky (*)

Another effect, known as gravitational lensing, gives evidence for dark matter’s existence. This effect occurs when a massive object’s gravity bends the light that is passing by. For instance, when a cluster of galaxies blocks our view of another galaxy behind it, the cluster’s gravity warps the more distant galaxy’s light into rings or arcs, depending on the geometry involved. By observing these rings, one can calculate how much mass should be present inside the galaxy to produce this pattern. Such calculations confirm that clusters contain far more mass than the luminous matter suggests.

Image of the rich galaxy cluster Abell 2218, taken with the Hubble Space Telescope. This cluster shows evidence of multiple lensing images, as well as numerous strong and weak arcs. Using information about the arcs and multiple images allows astronomers to reconstruct the mass distribution, which then gives us knowledge about the distribution of dark matter. (*)

Dark matter defined

Understanding dark matter is a key to other important issues in cosmology, such as how much mass the universe contains, how galaxies formed, and whether or not the universe will expand forever.

The posited explanations for dark matter can be grouped into three main categories:

– Dark matter could be some kind of ordinary matter that emits or reflects too little radiation for our instruments to detect. Such objects are known as massive astrophysical compact halo objects (MACHOs) and may be ultrafaint stars, large or small black holes, cold gas, or dust scattered around the universe.

– Dark matter could consist of exotic, unfamiliar particles (i.e., different from such known particles as electrons, protons, and neutrons) that we have not figured out how to observe. These are known as weakly interacting massive particles (WIMPS). Despite the many theories about them, their existence remains unconfirmed. These exotic particles are thought to have very small masses (smaller than atoms), meaning that there would have to be a huge number of them to make up the missing matter. Thus, millions of WIMPs are passing through Earth and us. They interact with ordinary matter only by means of gravity. Since the interaction is very weak, it is difficult to detect them.

Our understanding of gravity needs a major revision–but most physicists do not consider this option seriously.

Dark matter and the universe

The search for dark matter is more than trying to explain discrepancies in galactic mass calculations, for it is closely related to how the universe was formed and will end.

The Big Bang theory, which tries to explain how the universe was formed, maintains that in the beginning, everything was compressed into a single point. Then, a great explosion resulted in the universe being formed. It is still expanding. This theory is based on the fact that all galaxies, when observed with telescopes, are moving away from each other. After this explosion, matter started clumping together to form the stars and galaxies we see today.

The picture shows mankind’s deepest, most detailed visible view of the universe provided by Hubble telescope. Representing a narrow keyhole view stretching to the visible horizon of the universe, the Hubble Deep Field image covers a speck of the sky only about the width of a dime 75 feet away. Though the field is a very small sample of the, it is considered representative of the typical distribution of galaxies in space, because the universe, statistically, looks largely the same in all directions. In this picture, Hubble uncovered a bewildering assortment of at least 1,500 galaxies at various stages of evolution. (*)

One problem with this theory is explaining how the stars and galaxies were formed. If matter initially was distributed evenly in all directions, what caused it to clump together in some regions and form stars and galaxies? Gravity alone cannot cause this in a smooth universe, and so something had to supply the initial gravity that allowed galaxies to form. Physicists suggest that dark matter WIMPs accomplished this task. Since WIMPs only affect ordinary matter gravitationally, physicists say this dark matter could be the seed of galactic formation.

According to the Big Bang theory, there are three possibilities for the universe’s future. In a closed universe, gravity is strong enough to stop the expansion eventually and pull everything back to a single point. In an open universe, gravity cannot stop the expansion and so it will continue forever. In a flat universe, there is just the right amount of mass so that gravity can stop the expansion but not pull it back into one point.

The amount of dark matter that exists is crucial to determining the universe’s fate, because the Big Bang theory posits that the amount of mass in the universe determines gravity’s strength and, by extension, whether the universe will be closed, open, or flat. To quantify this, scientists define a constant, called Omega, as the ratio of the universe’s density to some critical density. A flat universe is said to have an Omega of 1, meaning that its density is equal to that of the critical density. If the density is greater than 1, the universe is closed; if it is less than 1, is be open. Without dark matter, the universe’s observed density is between 0.01 and 0.1. Therefore we live in an open universe. If a lot of dark matter were present, the universe would be closed. If there were just the right amount present, it would be flat.

Conclusion

The discovery of dark matter could affect our view of our place in the universe. If its existence were proven, our world and its inhabitants would be made of something comprising an insignificant portion of the physical universe. This probably would not affect our daily life, but would create a new scientific paradigm. In this sense, the discovery of dark matter would be as revolutionary as finding of extraterrestrial life.

Footnotes

1. Herman, R. and S. L. Larson. Is Dark Matter Theory or Fact? Scientific American (15 June 1998).
2. Rubin, V. Dark Matter in the Universe. Scientific American (March 1998).

* http://www.nasa.gov

Cosmology is the study of how the universe we live in came into being, why it looks and behaves as it does, and what its ultimate fate is. Building on the work of Albert Einstein, cosmologists have come up with a new account of the origin of the universe, the so-called big-bang cosmology. Over the past three decades a series of observational developments and refinements to the theory have led to its wider acceptance. For the present, there are no fundamental challenges to the big bang theory, although there are certainly unresolved issues with the theory itself. Astronomers are not sure, for example, how the galaxies were formed, but it is questionable whether there is a reason not to think the process did not occur within the framework of the big bang. Indeed, the predictions of the theory have survived all tests to date.

Nevertheless, we should always bear in mind that present-day science is not the last word, and perhaps Einstein’s theories, and the big-bang cosmology, will in turn be superseded.

Our present knowledge of the universe is restricted to a handful of observational facts. The expansion of the universe, indicated by the law relating the red shift in light from astronomical objects to their distance, was dis¬covered by Edwin Hubble in the early part of this century. The existence of the microwave background radiation corresponding to a temperature of 2.7K, and the cosmological abundance of helium are more recent discoveries. Together, these three observations suggest that the universe was born in a hot fireball from a very dense state-the big bang. Not just matter was created in the big bang, but space-time as well. There was nothing outside for the big bang to explode into-and this nothing means not even empty space.

Cosmologists today do not claim to know exactly what made the universe explode into existence from a state of zero volume and infinite density-a space-time singularity-but they do claim to be able to describe in great detail how a hot fireball of matter and radiation has evolved from a fraction of a second after the instant of creation over about 15 billion years to produce the cool, dark spread of empty space, dotted with galaxies made up of stars, gas, dust and planets, that we see about us now.

The laws of nature as we currently understand them allow us to trace the observed expansion of the universe back billions of years to what would be a true beginning, a moment when the universe was infinitely hot and dense. Although, theorists are now pushing back their speculations about what happened in the first 10-35 seconds after the big bang, with less confidence, the modern cosmological world view begins at a time when the universe had cooled to only 1012K, about 10-5 seconds after the instant creation. At these extreme conditions, the laws of physics as deduced here on earth can be applied to produce the story of everything that ha happened since. At a temperature of 1012K, particles and radiation would be interchangeable, as the mass equivalent of energy in the radiation would be ample to produce particles like protons, neutrons, and electrons, not out of thin air but out of thick radiation, in line with the rules E=mc2 for a particle of mass m and E=hv for radiation with frequency v (h is Planck’s constant). Here higher black body temperature of radiation corresponds to bigger v, that is bigger energy E, and therefore to more massive particle equivalents.

So, one-hundred-thousandth of a second after it began, the universe would have been a seething mass of particles and radiation, a swirling soup in which particle/antiparticle pairs were constantly being created out of energetic photons, and constantly annihilating with one another to produce other energetic photons. Overall though, the total mass/energy of the whole system was constant. For every E/c2 of mass created or destroyed an exactly equivalent E/h of radiation is destroyed or created.

Things began to get more orderly at 1011, still within the first 0.1 seconds after the big bang, as the universe expanded so that the density of radiation at any point was no longer enough to produce the more exotic particles. Only electron/positron pairs, and the massless photons and neutrino/antineutrino pairs, were light enough to have a continuing involvement in the matter/radiation balance.

About 14 seconds after the big bang, the temperature of the universe had dropped to around 3xl09K, and even electrons and positrons needed too much energy for the weakening radiation to create them. As the universe con¬tinued to expand and cool, creation became slower than annihilation, and almost all the particles and antiparticles disappeared. But for some unknown reason, a small proportion of electrons, protons and neutrons were left over. It is this early excess of matter over an¬timatter that survived to form light atomic nuclei a few minutes later, then (after about a million years) to form atoms and, still later, to be cooked to heavier elements in stars, ultimately to provide the material out of which life would arise. The reason for this predominance of matter over antimatter remains a mystery and has been a source of concern to modern cosmology. It is, nevertheless, one of the key initial conditions that determined the future development of the universe.

As the temperature dropped to 109K-about 70 times the temperature in the heart of the sun today-many protons and neutrons fused into helium nuclei, and by the end of first four minutes no free neutrons were left. Some 75% of the mass of the visible universe had been processed into protons plus electrons (ultimately to be bound into hydrogen atoms) while rather more than 25% mass of the universe had been processed into helium. The abundance of these elements in the universe is detectable today, and provides a constraint on the range of allowable models.

Another 700,000 years later, the expanding universe cooled to the point where electrons can bind to helium and hydrogen nuclei to make atoms, at a temperature of around 5000K. This signalled the end of the last remaining links between matter and radiation on a cosmic scale. Although free electrons and atomic nuclei, being electrically charged, interact strongly with radiation, electrically neutral atoms do not. From then on, the background radiation had nothing left to do but spread thinner in the expanding and cooling universe, to become the faint hiss we now detect at temperature equivalent of 2.7K. The very high degree of uniformity of the microwave background today is a strong indication that uniform, isotropic models provide a good description of the universe.

After the first thousand million years or so, with matter firmly established and radiation playing only a minor and decreasing role, the story of the universe can be taken up in terms of gravity, left as the dominating force because of its long range and its independence of electric charge. Gravitational forces then shaped the galaxies by holding stars and planets together.

However, our grasp of the conditions that prevailed in the early universe does not translate into a full understanding of how galaxies formed. Many scientists believe that the hydrogen and helium gases that filled the universe must have been pulled into concentrations by gravity. But there are problems with this explanation: for, what could cause large, diffuse gas clouds to collapse, even with the aid of gravity, while the universe as a whole is expanding?

Having established that the universe began in a hot big bang, and being tolerably happy with a rough understanding of how galaxies formed, the truly cosmological question remaining for astronomers to puzzle over is whether the universe is open (will it expand forever) or closed (will it one day collapse into a new fireball)?

The answer lies in its density. The symbol used for the mass density of the universe is Omega. If Omega, is less than 1, the universe will expand forever, so that, eventually, all the galaxies and stars will grow dark and cold. The alternative to this ‘big chill’ is a ‘big crunch.’ If Omega is more than 1, gravity will eventually reverse the expansion, and all matter and energy will be reunited. For the present, since we are not sure how galaxies formed, the value of Omega is uncertain-most astronomers put it somewhere between 0.1 and 1.

While eternal expansion is the generally favoured hypothesis; there may be enough of the unseen matter in the universe to produce a gravitational pull capable of halting the expansion and eventually producing a recollapse. Though the case is not yet proven, one current idea is that neutrinos, once believed to be massless particles, may have a rest mass less than 1/10000 of an electron. As neutrinos are thought to be as numerous as photons, their aggregate mass could suffice to close the universe. The fact that we cannot see enough matter to close the universe does not mean that it is not there.

During the next decade, as techniques for measuring the mass of the universe improve, we may learn whether the present expansion is headed toward a big chill or a big crunch. What happens then? Just as we do not know how everything could appear from nothing in the big bang if space-time did not exist, we do not know what happens to the universe at this stage; the laws of physics are inadequate to describe such extreme conditions. If there is ever to be a solution to the mystery of the origin and end of the universe, it must await a substantial increase in our understanding of the quantum nature of gravity-the big bang account of creation has forged an unlikely marriage between cosmology, the science of the very large, and particle physics, the science of the very small.

In any event, the universe we inhabit seems to be very improbable. Random processes and statistical fluctuations on cosmological time scales could easily have made it quite inhospitable to life. Are we just lucky? Or is there some deep significance to the fact that we live in a universe just right for us?

For all its violence-including the possibility of a black hole resident at the centre of our own galaxy-the universe seems to be an ideal place for man. Everywhere we look in the universe, from far flung galaxies to the deepest recesses of the atom, we encounter order. The laws of physics can explain beautifully the analytic structure of nature, the behaviour of individual particles and fields, but tell us nothing about the collective, collaborative organization of matter: that is, how the world is put together.

Why is the world the way it is and not otherwise? This is not the type of question scientists normally ask. The customary approach to scientific inquiry is to discuss what we see, not what we might see. Nevertheless, the universe is such a remarkable place, and we, as observers, are perhaps the most remarkable feature, it seems worth while ascertaining just how probable or improbable the present arrangement is.

For example, we do not understand why the fundamental constants of nature have the values they do. Einstein captured its essence when he said: ‘What really interests me is whether God had any choice in the creation of the world.’ Very slight changes in the physical constants of nature could have made the universe unfold in a completely different manner.

Most of the features of the everyday world and the astronomical scene are determined by a few basic physical laws and constants, such as the masses of the elementary particles and the relative strengths of the basic forces that operate between them. In many cases, a rather delicate balance seems to prevail. For example, if the nuclear forces were slightly stronger then they actually are, compared with electromagnetism, the di-proton-an atomic nucleus containing just two protons and no other particle-would be stable; ordinary hydrogen would not exist, and stars would evolve very differently. If nuclear forces were slightly weaker, no chemical elements other than hydrogen would be stable, and chemistry would be dull indeed. In either case, we would not be here to ponder such matters.

Or suppose the constant of gravity were stronger and the gravitational force were, say 1030 times weaker than the electromagnetic force instead of a factor of 1040 weaker. Then we would have a small-scale, speeded-up universe, in which stars-gravitationally bound fusion redactors-had only 10-15 times the sun’s mass, and lived for about a year. This might not allow time for complex systems-such as life forms-to evolve. The question-Was the relative strength of electromagnetic force over the gravitational force there from the beginning of time or is it an accident of today? -remains intractable.

These mysteries are heightened when we reflect how surprising it is that the laws of nature and the initial conditions of the universe should allow for the existence of beings who could observe it. Life as we know it would be impossible if any of several physical quantities had slightly different values. The best known of these quantities is the energy of one of the excited states of the carbon-12 nucleus. There is an essential step in the chain of nuclear reactions that build up heavy elements in stars. In this step, two helium nuclei join together to form the unstable nucleus of beryllium-8, which sometimes before fissioning absorbs another helium nucleus, forming carbon-12 in this excited state. The carbon-12 nucleus then emits a photon and decays into the stable state of lowest energy. In subsequent nuclear reactions carbon is built up into oxygen and nitrogen and the other heavy elements necessary for life. If the energy of the excited state of carbon-12 were just a little higher, the rate of its formation would be much less, so that almost all the beryllium-8 nuclei would fission into helium nuclei before carbon could be formed. The universe would then consist almost entirely of hydrogen and helium, without the ingredients for life.

Moreover, if the proton and neutron masses were equal, then neutrons and protons could not bind to form deuterium and heavy nuclei, and nuclear burning in stars and, consequently, life would be impossible.

The most ubiquitous examples of orderliness in the universe are the stars. They represent an extreme departure from thermodynamic equilibrium because they burn brightly in a cold, dark space. The source of starlight is the nuclear furnace at the core of the star, where the chief nuclear reaction is the fusion of hydrogen to helium. This is a downhill process, leading to nuclei of greater stability, and the cost paid for achieving it is the redistribution of nuclear energy into the surrounding space in the form of heat and light. This particular orderliness, and with it most familiar examples of terrestrial organization, leads to the question: Is the present structure of the universe-which is made mainly of hydrogen and not helium or heavier elements-just luck, a coincidence? Because, if the universe were made of, say, iron (the most stable element) there would be no stars like the sun.

Also, the structure of our world depends vitally not only on the availability of free hydrogen, but also on the reasonably smooth distribution of the primeval matter. If the big bang had only coughed out black holes-the ultimate triumph of gravity-in which everything is completely obliterated and disappears, no life would have been possible.

Can all these peculiar ‘coincidences’ be understood in terms of some self-evolutionary mechanism?

In its standard form, the big bang theory assumes that all parts of the universe began expanding simultaneously. Observations confirmed this assumption and showed that the expansion is remarkably uniform in all directions. This would seem to imply a collaboration between widely separated regions of the cosmos to expand at the same rate everywhere. Such highly organized behaviour leads us to ask how all the different parts of the universe could synchronize the beginning of their expansion?

Where does the energy that makes the universe expand come from? What could be a permanent, decidedly nonzero source of energy in the universe, with cosmic consequences? Could it be vacuum-as the source of everything yet itself nothing? This is one of the hottest topics in contemporary physics and lies at the heart of perhaps the most important new concept in cosmology of the past decade. If it is correct, could the creation of being out of nothingness occur without the mediation of a Creator?

There are many such peculiar ‘coincidences’ in the universe. Is it just our luck that they have worked out that way, or is there a deeper explanation? One understanding would be that the world is the way it is because it is the creation of a Creator who wills it to be capable of fruitful process: His command, when He desires a thing, is to say to it ‘Be!’, and it is (Ya Sin, 36.82). Without an Organizer, chaos can never be transformed into cosmos. This explanation is not a temporary sop to satisfy our curiosity about phenomena for which we cannot yet work out a satisfactory physical explanation; rather, it is a step guiding us towards a better understanding of the real world.

That does not mean that these mysteries constitute a barrier beyond which science cannot pass. As in the past, we may reasonably expect that, in the future, deeper understanding will be achieved and a more profound pattern discerned at the basis of physical reality, in a new, perhaps new kind, of explanatory theory. It may be some version of supergravity or it may be the novel theory of ‘superstrings’. Or some other theory that we have not yet thought of.

However, we should bear in mind that both our growing knowledge about the universe, and the need, alongside it, to revise it continually, is clear evidence for the inconclusiveness of science and the limitation of its methods.

In addition, the finititude of man’s existence (in this very small part of a vast universe) and the limitations of his senses mean that all our efforts must be considered ‘relative.’ The results of pure and experimental sciences are a limited portion of reality as man can grasp it from his location in the universe and within the very limited time allotted to him, and not the truth itself. There is of course, a great difference between being aware of things and knowing their actual truth. The former is limited to sensible events only, while the latter lies beyond the capacity of our senses.

No inquiry into the nature of creation or any part of it can be closed and concluded. The patterns of God in creation are infinite: there will always be more of them to discover. As we strive to do so, understand more and more about nature, the scientist’s sense of wonder will not diminish but become sharper, more narrowly focused on the mysteries that still remain. The worth of science lies in its commitment to understanding the Divine handiwork. The comprehensibility of the reality around us is among the greatest of God’s favours to us. Einstein remarked this: ‘The most incomprehensible thing about the universe is that it is comprehensible.’

The Qur’an contains many scientifically accurate statements, some of them still relevant to cosmology; it does not contain any statements which are in conflict with the findings of man’s scientific research nor open to criticism from modern science. Many of its verses allude to, and urge, reflection upon the reality around us as a form of worship, as a way to draw nearer to the Creator. I shall conclude by citing (in translation) a verse which draws our attention to the fact that, in a general sense, the future will be the age of knowledge and information, and that as a natural consequence of this, it will be an age of faith and belief:

Soon We shall show them Our signs on the furthest horizons, and in their own souls, until it becomes manifest to them that this is truth. Is it not enough that your Lord witnesses all things? (Fussilat, 41.53)

USEFUL READING

• GRIBBIN, J. (1982) Cosmology today: A New Scientist Guide
• JAMES, P. et al. (1994) ‘The Evolution of the Universe’, Scientific American, October
• SIMSEK, U. (1986) Big Bang-Kainatin Dogusu, Yeni Asya, Istanbul
• NURBAKI, H. (1989) Verses from the Glorious Qur’an and the Facts of Science, Turkish Foundation for Religion Publications