Dr. M.Rees what we still dont know.

S eeking answers Philosophers and theologians have long debated our purpose in the universe. We have always assumed that there is some higher purpose for humanity, but the universe it seems may have other ideas. In Why Are We Here? Martin Rees explains how scientists have had to revise long-held beliefs about the very nature of the universe, and in the process re-evaluate our place here. To do this, Rees presents some of the most fundamental questions about the universe and our own origins: What was the beginning? What is the nature of life? What is the future of the cosmos and the nature of reality? The answers may not be what you expect. Empty space is not so empty after all. Most of the universe is made up not of atoms, as previously thought, but of a mysterious and elusive substance called dark matter. Without it the universe simply would not exist. But working against dark matter is an even more mysterious force that threatens to tear the universe apart dark energy. Arguments about the very nature and fabric of the universe stretch back to the pre-Socratic philosophers. But the atomist theories of Ancient Greece are a far cry from what we now know. The bedrock of 20th-century science was to understand that we and everything else are made up of atoms, says Martin Rees. There are 92 types of naturally occurring atoms, allowing for billions of different combinations, forming the chemical components that underlie everything from the simplest crystals to the most complex objects that we know of human beings. Humans contain 10,000 trillion trillion atoms, linked together in a very complicated way. Building something as complex as a human being involves more than just massing together atoms. Says Max Tegmark of the Massachusetts Institute of Technology: The big difference between a dead thing like a crystal and a living thing is not what they are made of. They're both made of the same building blocks. It's rather the complexity of how they're put together. You have to keep arranging these atoms in new and different ways without repeating yourself. That's how you get this fantastic complexity which to me really is the hallmark of life, says Tegmark. It has taken nature about 4 billion years to get from the simplest life forms on primordial Earth to the complex life forms of today. We just don't know how that happened, but we do know that the staggering variety of different substances would never have been possible if the universe hadn't created the 92 different types of atoms that underlie everything that we know about.

More than 400 years ago, Giordano Bruno, an Italian monk, wrote that "In space there are numberless earths circling around other suns, which may bear upon them creatures similar or even superior to those upon our human Earth." Bruno deserves to be remembered in the millennium year -- he was burnt at the stake, in Rome, in the year 1600.

In the late 19th century, the science fiction of Jules Verne and H.G. Wells popularised the idea of alien life. Percival Lowell, a wealthy American, built his own observatory in Flagstaff, Arizona primarily to study Mars. He believed that its surface was criss-crossed by 'canals', dug by an advanced civilisation to channel water from the frozen polar caps to the 'deserts' near the Red Planet's equator.

In 1900, a French foundation offered the Guzman Prize of 100,000 francs for the first contact with an extra-terrestrial species; but prudence led them to exclude Mars -- detecting Martians was then thought to be too easy! Is there life on Mars - the idea has always fascinated us. How life began, and whether it exists elsewhere remains one of the most fascinating questions in the whole of science -- indeed, you don't need to be a scientist to wonder about this. But we still don't know the answer. We're less optimistic about Mars than our forbears were a hundred years ago. Even if there is life there, it would be nothing more than microscopic 'bugs' of the kind that existed on Earth early in its history--- there is certainly nothing on Mars like the 'Martians' of popular fictions.

Indeed, nobody now expects 'advanced life' on any of the planets or moons in our Solar System. But our Sun is just one star among billions. And in the vastness of space far beyond our own Solar System we can rule out nothing. Astronomers have discovered, just within the last five years, that many stars have their own retinue of planets. There are millions of other Solar Systems. And there would surely, among this vast number, be many planets resembling our Earth.

Could some of these planets, orbiting other stars, harbour life-forms far more interesting and exotic than anything we might find on Mars? Could they even be inhabited by beings that we could recognise as intelligent? If intelligent aliens were common, shouldn’t they have visited us already? Some people, of course, claim that aliens have indeed visited us. But the evidence for UFOs is no better than that for ghosts, and I'm personally quite unconvinced. Some astronomers cite this as evidence that aliens are rare. They note that some stars are billions of years older than our Sun, and point out that, if life were common, its emergence should have had a 'head start' on planets around these ancient stars. But the fact that we haven't been visited doesn't, in my view, imply that aliens don't exist -- the question remains open. It would be far harder to traverse the mind-boggling distances of interstellar space than to send a radio signal. That's perhaps how aliens would reveal themselves first. The nearest stars are so far away that signals would take many years in transit. For this reason alone it makes sense to 'listen' rather than transmit --- if a signal were detected, there would be time to send a measured response, but no scope for quick repartee! (Aliens equipped with large radio antennae could in any case pick up the combined output of all our TV transmitters -- if they could decode them, it's hard to think what they might conclude about 'intelligent' life on Earth!).

Attempts to search for such signals have had a hard time getting public funding (even at the level of the tax revenues from a single science fiction movie) because the topic is encumbered by 'flakey' associations with UFOs, and so forth. But there’s a serious effort in California, backed by hefty donations from some silicon-valley millionaires.

We have no idea what intelligent aliens would look like -- it would depend on the habitat that their 'home planet' offered. They could be balloon-like creatures floating in dense atmospheres; they could be the size of insects, on a big planet where gravity pulled strongly. Or they may be freely-floating is space. They could even, as some science fiction reminds us, be super-intelligent computers, created by a race of alien beings that had already died out. Even if intelligent aliens existed, they may not be transmitting any signals; and their brains and senses may be so different from ours that we couldn't recognise them. There may be a lot more life out there than we could ever detect -- absence of evidence wouldn't be evidence of absence. There are heavy odds against such searches succeeding.

But I'm enthusiastic about these searches, because of the import of any manifestly artificial signal. Even if we couldn't make much sense of it, we'd have learnt that 'intelligence' wasn't unique and had emerged elsewhere. Our cosmos would seem far more interesting; we would look at a distant star with renewed interest if we knew it was another Sun, shining on a world as intricate and complex as our own.

If we ever established contact with aliens, what could we discuss with them? I've argued in a new book that we're assured one common interest. We'd belong to the same universe of stars and planets, all made of similar atoms and governed by universal laws. We'd all trace our origins back to a single 'genesis event' -- the so-called 'big bang', which happened about 12 billion years ago.

To firm up the odds on alien life, we need to understand how life begins and evolves. An extraordinary precession of species (almost all now extinct) have swum, crawled and flown during the Earth’s 4.5 billion year history. For a billion years, primitive 'bugs' exhaled oxygen, transforming the young Earth's poisonous atmosphere and clearing the way for our eventual emergence. We know from fossils that a cornucopia of swimming and creeping things evolved during the Cambrian era 550 million years ago. The next 200 million years saw the greening of the land, offering a habitat for exotic creatures ---dragonflies as big as seagulls, millipedes a yard long, giant scorpions and squid-like sea-monsters. Then came the dinosaurs. Their sudden demise opened the way to mammals -- to the evolution of apes and us. We are the outcome of time and chance: if evolution was 're-run', there would be no humans, and we can't predict whether any other species would achieve our dominant role. So we can't lay firm odds on whether 'intelligence' would emerge on another Earth-like planet.

We know this happened on Earth, but we'd dearly like to discover a second example where even the earliest stages of life might exist. Mars remains the best place to look. Three years ago, American scientists announced evidence for fossil 'bugs' on a meteorite that had come from Mars. This claim, hyped up at a press conference attended by President Clinton himself, was dubious and premature -- NASA has been backtracking on it ever since. We'll learn more from a series of space probes that will be sent to Mars in the next decade, to study its surface, and eventually return samples to Earth. And there are longer-term plans to search elsewhere -- for instance, a submersible robot will probe the ice-covered oceans of Jupiter's moons Europa and Callisto.

All this depends on the space programme. For most of the present century, space travel was a futuristic concept, familiar from comics and corn flakes packets. But in July 1969, Neil Armstrong's 'one small step' made space travel a reality. Those of us who are now middle-aged can remember viewing 'live' the murky TV pictures of that event: it seemed a high point in a decade blighted by the arms race and the Vietnam war.

Another lasting image from the 1960s was the first photograph of the entire round Earth, taken from the Moon. Our habitat of land, oceans and clouds was revealed as a thin delicate-seeming glaze. Our home planet -- the 'third rock from the Sun' -- is very special. The beauty and vulnerability of 'spaceship Earth' contrasts with the stark and sterile moonscape on which the astronauts left their footprints.

In the 1960s, the first brief excursions to the Moon seemed just a beginning. We imagined follow-up projects: a permanent 'lunar base', rather like the one at the South Pole; or even huge 'space hotels' orbiting the Earth. Manned expeditions to Mars seemed a natural next step. But none of these has happened. The year 2001 will not resemble Arthur C. Clarke's depiction, any more than 1984 (fortunately) resembled Orwell's.

The programme, announced by President Kennedy in 1961, 'to land a man on the Moon before the end of the decade, and return him safely to earth', was lavishly funded because America wanted to beat Russia. Their pride had been badly dented in 1957, when Russia launched the first 'Sputnik', and this was a chance to recapture the lead in the space race. Reaching the Moon was an end in itself: the last lunar landing was in 1972.

Manned spaceflight now seems a rather jaded spectator-sport: the veteran senator John Glenn's recent trip in the Space Shuttle may have been a morale-booster for elderly Americans, but it didn't recapture the excitement of his pioneering flight 36 years earlier. We admired the Russian cosmonauts more for their fortitude and DIY skills than for anything else, as they coped with one malfunction after another in the decrepit Mir spacecraft.

Nationals of other countries have hitched rides into space. The British astronaut Michael Foal heroically survived the hazards of Mir, the Russian Space Station. French, Bulgarian and Mongolian astronauts have also made the trip. But none of this has recaptured public enthusiasm.

The practical case for manned spaceflight was never strong, and it gets weaker as robots and computers get more powerful. Space technology -- now funded commercially as well as by governments -- has abundantly proved its value. Thousands of small unmanned objects have been launched into orbit.

Satellites are routinely used for long distance telephones and satellite tv broadcasts. The 'global positioning satellites' allow planes or ships to navigate precisely -- and allow solo hikers or sailor to locate themselves accurately anywhere on Earth, with a pocket-sized instrument. Weather forecasts depend on pictures and data from space.

Space exploration need not involve humans. It can be better (and far more cheaply) carried out by fleets of unmanned probes, exploiting the advances that have given us mobile phones and high-powered personal computers.

Cameras and scientific instruments have beamed back pictures from the other planets of our Solar system. And the Hubble Space Telescope has imaged stars and galaxies so deep in space that their light set out on its journey towards us billions of years before our Earth and Sun were born. The cosmos is fantastically larger and more complex than could have been imagined by the ancients who first mapped the constellations.

The cosmos confronted with huge spans of time, as well as stupendous expanses of space. Life on Earth has evolved for billions of years, but our Sun has burnt up less than half its fuel, and will keep shining for another five billion years. If life isn't prematurely snuffed out, our remote progeny will surely -- in the aeons that lie ahead -- spread far beyond this planet.

We plainly can't forecast the vastly remote future. But what might happen in the first decades of the new millennium? How long will it be before people return to the Moon, and perhaps explore still further afield? The centerpiece of the current US programme is the new International Space Station: this will be in orbit a few hundred miles up, and the size of a football field. It will be the most expensive artifact ever constructed, costing its own weight in gold. Even if it is finished -- something that seems uncertain, given the immense and ever-rising costs, and prolonged delays -- it will be neither practical nor inspiring. Thirty years after men walked on the Moon, a new generation of astronauts will be going round and round the Earth, in more comfort than Mir can offer, but much more expensively. The astronauts will be able to do experiments, but most of those could be done more cheaply by robots in smaller free-flying satellites.

The Space Station would make somewhat more sense as a staging post on the way to other planets. But no such follow-up will materialise unless public enthusiasm revives, or unless some technical breakthrough renders space travel much cheaper and easier than it now seems. Present launching techniques are as extravagant as air travel would be if the plane had to be rebuilt after every flight. Spaceflight will only be affordable when it adopts the same techniques as supersonic aircraft. Tourist trips into orbit may then become routine. And wealthy adventurers may boldly go further. Future Richard Bransons, for whom round-the-world ballooning seems too tame and routine, could aim for the Moon. If Bill Gates seeks a challenge that won't make his later life seem an anticlimax, he could sponsor the first expedition to Mars.

Some people use the so-called 'insurance policy argument' to advocate a manned space programme. There is an ever-present risk (though fortunately a small one) that a comet or asteroid will hit the Earth. The craters on the Moon's surface are records of these impacts. An impact on Earth - leaving a huge undersea crater near Chicxulub in the Gulf of Mexico, probably sealed the fate of the dinosaurs 65 million years ago.

There is about one chance in 10000 that, within the next 50 years, the Earth will be hit by an asteroid large enough to cause world-wide devastation -- ocean waves hundreds of feet high, tremendous earthquakes, and changes in global weather. This chance is low - but no lower than the risk (for the average person) of being killed in an air crash. Indeed, it's higher than any other natural hazards that most Europeans or North Americans are exposed to.

The ever-present risk from nature has been augmented since humankind entered the nuclear and biotechnological age. Humanity will remain vulnerable to these (probably increasing) hazards so long as it is confined here on Earth. But once self-sustaining communities exist away from the Earth -- on the Moon, on Mars, or freely floating in space -- our species would be invulnerable to any global disaster, and whatever potential it has for the 5-billion-year future could not be snuffed out.

Whether on not humans spread beyond the Earth during the next millennium, we'll still want to know whether we are alone. It would in some ways be disappointing if searches for alien intelligence were doomed to fail. On the other hand, it would boost our 'cosmic' self-esteem. If our tiny Earth were a unique abode of intelligence, we could view it in a less humble cosmic perspective than it would merit if the Galaxy already teemed with complex life. We'd have even stronger motives to cherish this 'pale blue dot' in the cosmos, and not foreclose life's future -- a future that could be even longer than the time span over which simple life has evolved into humans. That is why we should expand our cosmic vision in the new millennium.

Sir Martin Rees, Astronomer Royal and Royal Society Research Professor at Cambridge University, is renowned for his extraordinary intuition in unraveling the complexities of the universe. He has been a leader in the quest to understand the physical processes near black holes and is responsible for major advances in our understanding of the cosmic background radiation, quasars, gamma-ray bursts, and galaxy formation. He has contributed to almost every area of cosmology and astrophysics and has been an inspiring leader, eloquent spokesperson, and patient guide for astronomers all over the world. Through his public speaking and writing he has made the Universe a more familiar place for everyone. Sir Martin Rees is one of the most eminent theoretical astrophysicists of our time. His work is characterized by deep insight into the physical processes governing the scientific problems he is studying, distilling the essence of the physical system in each case. He is among the most far-ranging of scientists, having made important contributions to our understanding of the formation of galaxies, the nature of the cosmic microwave background, quasars, black holes, gamma-ray bursts, and many other subjects. Professor Rees has had particular interest in the nature of compact objects. Neutron stars and black holes lie at the center of many astronomical phenomena, ranging from X-ray binary stars to powerful quasars at the centers of galaxies. Among his many contributions, he promoted the idea that infall onto supermassive black holes power quasars and active galactic nuclei and he used observations of the light observed from these objects to develop detailed models for the physical processes taking place close to the black hole. His explanation of rapid variability in these objects included the spectacular prediction of apparent superluminal motion in their radio emission. He predicted that massive black holes would be found at the center of our Galaxy and others. Much of his work over the past decade has been focused on the enigmatic gamma-ray bursts, which, due largely to work of Professor Rees and his colleagues, we now believe are due to explosive processes occurring in the vicinity of neutron stars. Professor Rees has also been a leader in understanding the structure and evolution of the universe. He contributed many of the foundational ideas about galaxy formation, particularly regarding the important role of gas and dissipation. In his quest to explain how the universe emerged from the cosmic ``dark ages'', he has examined how the first generations of stars, galaxies, and quasars formed and then ionized much of the universe. He made the first predictions about polarization and other detailed features of the cosmic microwave background. Both within and beyond astrophysics proper, Professor Rees has had broad impact on how we think about the universe. He has probed deeply into questions on the borders between science and philosophy, why the universe has the characteristics that it has, and how humans as sentient beings fit into this universe. Through his books, papers, and his students, he has been tremendously influential in setting the research agenda and stimulating investigations in all the many fields he has worked in. As Astronomer Royal, Professor Rees has been an international expositor of astronomy for both scientists and lay publics for decades. He is a masterful public speaker, and through his many popular books on astronomy and cosmology, has fascinated many with his erudition in describing the wonders of the universe.

Martin Rees was born in 1942, and grew up in Shropshire, a rural part of England. He studied mathematics at Trinity College Cambridge, where he obtained a bachelor’s degree in 1964. Subsequently, he became a graduate student at Cambridge, working under the supervision of Dennis Sciama. This was the time when the first firm evidence for the 'big bang' was emerging, and when the discovery of quasars, pulsars and cosmic x-ray sources were opening up the new field of 'relativistic astrophysics'. His insightful and original contributions quickly made an impact. Over his 35-year career, he has maintained a high productivity over a broad scientific field. Many of his ideas -- on topics including cosmic radio sources, black holes, galaxy formation, and gamma ray bursts -- have been vindicated by later observations. I>n 1973 he was appointed Plumian Professor of Astronomy and Experimental Philosophy at Cambridge. He held this post for 18 years, and for 10 of those years was also Director of Cambridge's Institute of Astronomy. In 1992 he was appointed to a Royal Society Research Professorship, which he still holds. At that time, he also became President of the Royal Astronomical Society, and in 1995 he acquired the honorary title of Astronomer Royal. Cambridge remains his base, where he continues to teach and to be involved in various aspects of the University. He is a Senior Fellow of King's College, and Honorary Fellow of Trinity and Jesus Colleges. He has held several visiting professorships, and given many special lectures in Europe, the U.S. and Japan. He holds honorary degrees from ten universities.He has always been an enthusiast for international collaboration in science, and has fostered this not only by his individual efforts but through membership of numerous advisory bodies and committees, especially in Europe. He was Chairman of the European Space Agency's Scientific Advisory Committee when the decision was taken to collaborate with NASA on 'Ulysses' and the Hubble Space Telescope. He has for many years been active in the British Association for the Advancement of Science and has served as its President (1994-95). He has broad cultural interests beyond science, serving, for instance, on the Board of Trustees of the British Museum, the National Endowment for Science, Technology and the Humanities (U.K.), and the Kennedy Memorial Trust (U.K.).He has written five books in the last five years: New Perspectives in Astrophysical Cosmology, Gravity's Fatal Attraction: Black Holes in the Universe, co-authored with Mitchell Begelman, Before the Beginning: Our Universe and Others, and Just Six Numbers. His latest book, Our Cosmic Habitat, will be published in October.

Cosmology and astrophysics are branches of physics in which one needs an unusual combination of breadth and depth to excel. Martin Rees is arguably the finest all-round theoretical physicist working today. I do not always agree with him—especially in areas outside physics itself—but I always want to know his opinion. As does every wise person.

—David Deutsch

I have known and admired Martin Rees since the early 1970's when we were postdocs together at Cambridge University. Even at that stage Martin's extraordinary breadth of knowledge and expertise were apparent. Pick almost any topic in astronomy or physics, and he would have a carefully evaluated position worked out. He is one of only a few great scientists who is both open-minded and healthily-skeptical. At a time in his career when he could justifiably rest on his laurels, Martin Rees is as energetic and active as ever, offering stunning insights into many emerging scientific fields.

— Paul Davies

Martin Rees one of the most influential people working in astrophysical and cosmological theory. He is simultaneously open to new ideas and suggestions and careful and rigorous in his response and criticisms. Also, it's difficult to suggest an idea about the evolution of structure in the universe or the formation of the galaxies that he hasn't thought of or played with or perhaps even written about at some time. Much of the credit for what I like to think of as the discovery that the laws of nature are special in ways that allow the universe to be very structured is due to him.

—Lee Smolin

Martin Rees is my favorite theoretical astrophysicist. He is not only incredibly knowledgeable, but he is also wonderfully helpful to his colleagues. He has contributed over 500 papers to the scientific literature, making important contributions to almost every aspect of astrophysics. He is especially well-known for his work on galaxy formation and the theory of cold dark matter, and also for his work on active galactic nuclei and the black holes that are believed to drive them.

—Alan Guth

There are two types of cosmologists active today: those who seek the physical principles driving the global properties of the Universe, and those who concentrate on the details of astrophysical objects, like galaxies, quasars, and black holes, that give complementary information about structure at smaller distances. Martin Rees is one of the few cosmologists exploring both venues, giving him a unique perspective from which to develop scientific ideas, and to synthesize known ideas for a broader audience. He always has something interesting to say.

—Lisa Randall

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